Novel biomarkers related to oxidative stress and immunity in chronic kidney disease.

Introduction: The incidence of chronic kidney disease (CKD) has been increasing in recent years, gradually becoming a global health crisis. Due to limited treatment options, novel molecular pathways are urgently required to advance the treatment and diagnosis of CKD. Materials and methods: The characteristics of differentially expressed genes (DEGs) in CKD patients were analyzed using Gene Expression Omnibus (GEO) database, and genes related to oxidative stress were retrieved from the Genecard database. Subsequently, a comprehensive approach was applied, including immune infiltration analysis, weighted gene co-expression network analysis (WGCNA) and protein-protein interaction (PPI) network analysis, to identify hub genes among differentially expressed immune-related oxidative stress genes (DEIOSGs). Validation of hub genes was performed using an external data set, and diagnostic potential capability was evaluated through receiver operating curve (ROC) analysis. In animal experiments, the expression of hub genes in CKD was confirmed by inducing a CKD model through a 5/6 nephrectomy procedure. Finally, the relationship between these hub genes and clinical characteristics were assessed using the Nephroseq v5 database. Results: 29 DEIOSGs were identified by comprehensive bioinformatics analysis. PPI analysis screened the hub genes NCF2, S100A9, and SELL. ROC analysis demonstrated excellent diagnostic efficacy. Further validation from other databases and animal experiments confirmed a substantial upregulation in the expression of hub genes in CKD. Additionally, clinical correlation analysis established a clear link between hub gene expression and renal function deterioration. Conclusions: Our study confirms NCF2, S100A9, and SELL as diagnostic biomarkers associated with immune response and oxidative stress in CKD, suggesting their potential as novel targets for CKD diagnosis and treatment.

Blockade of aryl hydrocarbon receptor restricts omeprazole-induced chronic kidney disease.

Chronic kidney disease (CKD) is the 16th leading cause of mortality worldwide. Clinical studies have raised that long-term use of omeprazole (OME) is associated with the morbidity of CKD. OME is commonly used in clinical practice to treat peptic ulcers and gastroesophageal reflux disease. However, the mechanism underlying renal failure following OME treatment remains mostly unknown and the rodent model of OME-induced CKD is yet to be established. We described the process of renal injury after exposure to OME in mice; the early renal injury markers were increased in renal tubular epithelial cells (RTECs). And after long-term OME treatment, the OME-induced CKD mice model was established. Herein, aryl hydrocarbon receptor (AHR) translocation appeared after exposure to OME in HK-2 cells. Then for both in vivo and in vitro, we found that Ahr-knockout (KO) and AHR small interfering RNA (siRNA) substantially alleviated the OME-induced renal function impairment and tubular cell damage. Furthermore, our data demonstrate that antagonists of AHR and CYP1A1 could attenuate OME-induced tubular cell impairment in HK-2 cells. Taken together, these data indicate that OME induces CKD through the activation of the AHR-CYP axis in RTECs. Our findings suggest that blocking the AHR-CYP1A1 pathway acts as a potential strategy for the treatment of CKD caused by OME. KEY MESSAGES: We provide an omeprazole-induced chronic kidney disease (CKD) mice model. AHR activation and translocation process was involved in renal tubular damage and promoted the occurrence of CKD. The process of omeprazole nephrotoxicity can be ameliorated by blockade of the AHR-CYP1A1 axis.

APOC1 exacerbates renal fibrosis through the activation of the NF-κB signaling pathway in IgAN.

Introduction: IgA nephropathy (IgAN) is the most common disease leading to end-stage renal disease, and tubular fibrosis represents an important risk factor for disease progression. However, research on early molecular diagnostic indicators of tubular fibrosis and the mechanisms underlying disease progression is still lacking. Methods: The GSE93798 dataset was downloaded from the GEO database. DEGs were screened and analyzed for GO and KEGG enrichment in IgAN. The least absolute shrinkage and selection operator (LASSO) and support vector machine recursive feature elimination (SVM-RFE) algorithms were applied to screen for hub secretory genes. The expression and diagnostic efficacy of hub genes were confirmed by the GSE35487 dataset. ELISA was applied to detect the expression of APOC1 in serum. The expression and localization of hub genes in IgAN were verified by the expression of IHC and IF in human kidney tissues, and the correlation of expression with clinical data was verified in the Nephroseq database. Finally, cellular experiments clarified the role of hub genes in the signaling pathway. Results: A total of 339 DEGs were identified in IgAN, of which 237 were upregulated and 102 downregulated. The KEGG signaling pathway is enriched in the ECM-receptor interaction and AGE-RAGE signaling pathway. APOC1, ALB, CCL8, CXCL2, SRPX2, and TGFBI identified six hub secretory genes using the LASSO and SVM-RFE algorithms. In vivo and in vitro experiments demonstrated that APOC1 expression was elevated in IgAN. The serum concentration of APOC1 was 1.232 ± 0.1812 µg/ml in IgAN patients, whereas it was 0.3956 ± 0.1233 µg/ml in healthy individuals. APOC1 exhibited high diagnostic efficacy for IgAN (AUC of 99.091%, specificity of 95.455%, and sensitivity of 99.141%) in the GSE93798 dataset. APOC1 expression negatively correlated with eGFR (R 2 = 0.2285, p = 0.0385) and positively correlated with serum creatinine (R 2 = 0.41, p = 0.000567) in IgAN. APOC1 exacerbated renal fibrosis, possibly in part by activating the NF-κB pathway in IgAN. Conclusion: APOC1 was identified as the core secretory gene of IgAN, which was closely associated with blood creatinine and eGFR and had significant efficacy in the diagnosis of IgAN. Mechanistic studies revealed that the knockdown of APOC1 could improve IgAN renal fibrosis by inhibiting the NF pathway, which may be a potential therapeutic target for improving renal fibrosis in IgAN.

APOC1 as a novel diagnostic biomarker for DN based on machine learning algorithms and experiment.

Introduction: Diabetic nephropathy is the leading cause of end-stage renal disease, which imposes a huge economic burden on individuals and society, but effective and reliable diagnostic markers are still not available. Methods: Differentially expressed genes (DEGs) were characterized and functional enrichment analysis was performed in DN patients. Meanwhile, a weighted gene co-expression network (WGCNA) was also constructed. For further, algorithms Lasso and SVM-RFE were applied to screening the DN core secreted genes. Lastly, WB, IHC, IF, and Elias experiments were applied to demonstrate the hub gene expression in DN, and the research results were confirmed in mouse models and clinical specimens. Results: 17 hub secretion genes were identified in this research by analyzing the DEGs, the important module genes in WGCNA, and the secretion genes. 6 hub secretory genes (APOC1, CCL21, INHBA, RNASE6, TGFBI, VEGFC) were obtained by Lasso and SVM-RFE algorithms. APOC1 was discovered to exhibit elevated expression in renal tissue of a DN mouse model, and APOC1 is probably a core secretory gene in DN. Clinical data demonstrate that APOC1 expression is associated significantly with proteinuria and GFR in DN patients. APOC1 expression in the serum of DN patients was 1.358±0.1292µg/ml, compared to 0.3683±0.08119µg/ml in the healthy population. APOC1 was significantly elevated in the sera of DN patients and the difference was statistical significant (P > 0.001). The ROC curve of APOC1 in DN gave an AUC = 92.5%, sensitivity = 95%, and specificity = 97% (P < 0.001). Conclusions: Our research indicates that APOC1 might be a novel diagnostic biomarker for diabetic nephropathy for the first time and suggest that APOC1 may be available as a candidate intervention target for DN.

Identification and validation of P4HB as a novel autophagy-related biomarker in diabetic nephropathy.

Diabetic nephropathy (DN), a frequent microvascular complication of diabetes, has been recognized as a primary cause of chronic kidney disease (CKD) and end-stage renal disease (ESRD). Previous studies found that autophagy of renal tubular epithelial cells plays an important role in DN pathogenesis. Our research aimed to investigate the differentially expressed autophagy-related genes (DEARGs) between DN and healthy renal tubule samples and identify a novel autophagy-related biomarker associated with tubulointerstitial injury in DN. In this study, gene expression profiles of renal tubules from 10 DN patients and 24 healthy controls in the GSE30122 dataset were analyzed, and 43 DEARGs were identified by bioinformatics analysis. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis and correlation analysis were performed on DEARGs, and the hub gene prolyl 4-hydroxylase subunit beta (P4HB) was screened by protein-protein interaction and verified by utilizing other datasets and stimulating HK-2 cells under high glucose concentration. We found that the expression of P4HB in renal tubules was correlated with renal function. In summary, our research provided novel insights for comprehension of DN molecular mechanisms and identified P4HB as a novel autophagy-related biomarker of DN.

Hydroxychloroquine alleviates renal interstitial fibrosis by inhibiting the PI3K/Akt signaling pathway.

Renal fibrosis is the ultimate presentation of chronic kidney disease, which progresses to end-stage renal disease. Hydroxychloroquine (HCQ) has been adapted for the treatment of autoimmune diseases; however, the potential mechanism underlying the role of HCQ in renal fibrosis remains unclear. C57BL/6 J mice were randomly divided into three groups (sham group, UUO group, and UUO + HCQ group (20 mg/kg)). HE and Masson staining were performed to assess kidney tissue damage and fibrosis, and western blotting was performed to assess the expression of epithelial-mesenchymal transition (EMT), extracellular matrix (ECM), PI3K/AKT, and NF-κB-related proteins. PCR and TUNEL were adopted to detect inflammatory factors and cell apoptosis. HK-2 cells treated with TGF-ß1 were used for the in vitro experiments. HCQ may potentially have therapeutic effects on renal fibrosis mediated through 122 target genes, and the Kyoto Encyclopedia of Genes and Genomes pathways of these genes were enriched for PI3K/AKT signaling based on network pharmacology. UUO mice that received HCQ demonstrated significantly less tubular damage than the UUO mice. HCQ treatment additionally blunted EMT in UUO kidneys and TGF-ß1-treated renal tubular epithelial cells, and alleviated ECM deposition in kidney tissue. Furthermore, HCQ treatment reduced UUO-induced inflammation and apoptosis. Mechanistically, HCQ treatment suppressed the activation of the PI3K/Akt and NF-kB pathways. This study demonstrated that HCQ ameliorated renal fibrosis by inhibiting the PI3K/AKT and NF-κB signaling pathways to attenuate inflammatory factors and the apoptotic function of renal tubular epithelial cells, thus providing renewed theoretical evidence for HCQ treatment of renal fibrosis.

IDO1 as a new immune biomarker for diabetic nephropathy and its correlation with immune cell infiltration.

INTRODUCTION: Indoleamine 2,3-dioxygenase 1(IDO1) has complicated roles in immune-inflammatory response regulation, but its correlation with immune cell infiltration in diabetic nephropathy (DN) remains unknown. METHODS: Gene expression data were extracted from the GEO database. Differentially expressed genes (DEGs) were identified and functional correlation analysis was performed. The immune hub gene was screened using Maximal Clique Centrality, and verified in DN model mice via western blotting, immunohistochemistry, and immunofluorescence analysis. CIBERSORTx was used to assign values to immune cell infiltration in DN and determine a correlation with the hub gene. The prognostic significance of the hub gene was then validated. RESULTS: The 330 screened DEGs from the GEO dataset were most enriched in GO functions and KEGG pathways associated with immune inflammation. IDO1 was identified as a hub immune gene, with upregulated expression in DN model mice. IDO1 expression was positively correlated with M1 macrophages (R = 0.58, P < 0.001) and monocytes (R = 0.44, P = 0.049), and was negatively correlated with resting memory CD4 T cells (R = -0.51, P = 0.019). IDO1 expression was upregulated in peritoneal macrophages after high glucose stimulation, and inflammatory factor production was reversed by IDO1 inhibition. Higher IDO1 expression was associated with worse prognosis in DN patients via multivariate survival analysis (P < 0.001). CONCLUSIONS: IDO1 was identified as a diagnostic and prognostic biomarker for DN and shown to play a vital role in immune cell infiltration in DN, ascertained using microarray data and CIBERSORTx for the first time.