IgA nephropathy: gut microbiome regulates the production of hypoglycosilated IgA1via the TLR4 signaling pathway.

BACKGROUND: IgA nephropathy (IgAN) is a major cause of primary glomerulonephritis characterized by mesangial deposits of galactose-deficient IgA1 (Gd-IgA1). Toll-like receptors (TLRs), particularly TLR4 are involved in the pathogenesis of IgAN. The role of gut microbiota on IgAN patients was recently investigated. However, whether gut microbial modifications of Gd-IgA1 through TLR4 play a role in IgAN remains unclear. METHODS: We recruited subjects into four groups, including 48 patients with untreated IgAN, 22 treated IgAN patients (IgANIT), 22 primary membranous nephropathy (MN), and 31 healthy controls (HCs). Fecal samples were collected to analyze changes in gut microbiome. Gd-IgA1 levels, expression of TLR4, B-cell stimulators, and intestinal barrier function were evaluated in all subjects. C57BL/6 mice were treated with a broad-spectrum antibiotic cocktail to deplete the gut microbiota and then gavaged with fecal microbiota transplanted fromclinical subjects of every group. Gd-IgA1 and TLR4 pathway were detected in peripheral blood mononuclear cells (PBMCs) from IgAN and HCs co-incubated with Lipopolysaccharide (LPS) and TLR4 inhibitor. RESULTS: Compared with other three groups, different compositions and decreased diversity demonstrated gut dysbiosis in un-treated IgAN, especially the enrichment of Escherichia -Shigella. Elevated Gd-IgA1 levels were found in un-treated IgAN patients and correlated with gut dysbiosis, TLR4, B-cell stimulators, indexes of intestinal barrier damage, and proinflammatory cytokines. In vivo, mice colonized with gut microbiota from IgAN and IgANIT patients, copied the IgAN phenotype with the activation of TLR4/MyD88/NF-κB pathway, B-cell stimulators in the intestine, and complied with enhanced proinflammatory cytokines. In vitro, LPS activated TLR4/MyD88/NF-κB pathway, B-cell stimulators and proinflammatory cytokines in the PBMCs from IgAN patients, which resulted in overproduction of Gd-IgA1 and inhibited by TLR4 inhibitor. CONCLUSIONS: Our results illustrated that gut-kidney axis was involved in the pathogenesis of IgAN. Gut dysbiosis could stimulate the overproduction of Gd-IgA1 by TLR4 signaling pathway production and B-cell stimulators.

Identification of Hub Gene and Transcription Factor Related to Chronic Allograft Nephropathy Based on WGCNA Analysis.

INTRODUCTION: Kidney transplantation (KT) has surpassed dialysis as the optimal therapy for end-stage kidney disease. Yet, most patients could suffer from a slow but continuous deterioration of kidney function leading to graft loss mostly due to chronic allograft nephropathy (CAN) after KT. The dysregulated gene expression for CAN is still poorly understood. METHODS: To explore the pathogenesis of genomics in CAN, we analyzed the differentially expressed genes (DEGs) of kidney transcriptome between CAN and nonrejecting patients by downloading gene expression microarrays from the Gene Expression Omnibus database. Then, we used weighted gene coexpression network analysis (WGCNA) to analyze the coexpression of DEGs to explore key modules, hub genes, and transcription factors in CAN. Functional enrichment analysis of key modules was performed to explore pathogenesis. ROC curve analysis was used to validate hub genes. RESULTS: As a result, 3 key modules and 15 hub genes were identified by WGCNA analysis. Three key modules had 21 mutual Gene Ontology term enrichment functions. Extracellular structure organization, extracellular matrix organization, and extracellular region were identified as significant functions in CAN. Furthermore, transcription factor 12 was identified as the key transcription factor regulating key modules. All 15 hub genes, Yip1 interacting factor homolog B, membrane trafficking protein, toll like receptor 8, neutrophil cytosolic factor 4, glutathione peroxidase 8, mesenteric estrogen dependent adipogenesis, decorin, serpin family F member 1, integrin subunit beta like 1, SRY-box transcription factor 15, trophinin associated protein, SRY-box transcription factor 1, metallothionein 3, lysosomal protein transmembrane, FERM domain containing kindlin 3, and cathepsin S, had a great diagnostic performance (AUC > 0.7). CONCLUSION: This study updates information and provides a new perspective for understanding the pathogenesis of CAN by bioinformatics means. More research is needed to validate and explore the results we have found to reveal the mechanisms underlying CAN.

[Activation of intestinal mucosal TLR4/NF-κB pathway is associated with renal damage in mice with pseudo-sterile IgA nephropathy].

Objective To investigate the effect of intestinal mucosal Toll-like receptor 4/nuclear factor κB (TLR4/NF-κB) signaling pathway on renal damage in pseudo-sterile IgA nephropathy (IgAN) mice. Methods C57BL/6 mice were randomly divided into experimental group (pseudosterile mouse model group), control group (IgAN mouse model group), pseudosterile mouse blank group, and normal mouse blank group. Pseudosterile mice were established by intragastric administration of quadruple antibiotics once a day for 14 days. The pseudosterile IgAN mouse model was set up by combination of oral bovine serum albumin (BSA) administration and staphylococcal enterotoxin B (SEB) injection. The pathological changes of renal tissue were observed by immunofluorescence staining and PAS staining, and the intestinal mucosa barrier damage indicators lipopolysaccharide(LPS), soluble intercellular adhesion molecule 1(sICAM-1) and D-lactate(D-LAC) were analyzed by ELISA. Biochemical analysis was used to test 24 hour urine protein, serum creatinine and blood urea nitrogen. The mRNA and protein levels of Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88) and nuclear factor κB (NF-κB) were detected by reverse transcription PCR and Western blot analysis. Results The kidney damage of pseudosterile IgAN mice was more severe than that of IgAN mice, and the expressions of intestinal mucosal barrier damage markers (LPS, sICAM-1 and D-LAC) were significantly increased in pseudosterile IgAN mice. In addition, the expressions of TLR4, MyD88, and NF-κB level were all up-regulated in the intestinal tissues of IgAN pseudosterile mice. Conclusion Intestinal flora disturbance leads to intestinal mucosal barrier damage and induces activation of TLR4 signaling pathway to mediate renal injury in IgAN.

Gut Microbiota Correlates With Clinical Responsiveness to Erythropoietin in Hemodialysis Patients With Anemia.

The main treatment for renal anemia in end-stage renal disease (ESRD) patients on hemodialysis is erythropoiesis (EPO). EPO hyporesponsiveness (EH) in dialysis patients is a common clinical problem, which is poorly understood. Recent searches reported that gut microbiota was closely related to the occurrence and development of ESRD. This study aims to explore the changes in gut microbiota between ESRD patients with different responsiveness to EPO treatment. We compared the gut microbiota from 44 poor-response (PR) and 48 good-response (GR) hemodialysis patients treated with EPO using 16S rDNA sequencing analysis. The results showed that PR patients displayed a characteristic composition of the gut microbiome that clearly differed from that of GR patients. Nine genera (Neisseria, Streptococcus, Porphyromonas, Fusobacterium, Prevotella_7, Rothia, Leptotrichia, Prevotella, Actinomyces) we identified by Lasso regression and ROC curves could excellently predict EH. In contrast, five genera (Faecalibacterium, Citrobacter, Bifidobacterium, Escherichia-Shigella, Bacteroides) identified by the same means presented a protective effect against EH. Analyzing the correlation between these biomarkers and clinical indicators, we found that gut microbiota may affect response to EPO through nutritional status and parathyroid function. These findings suggest that gut microbiota is altered in hemodialysis patients with EH, giving new clues to the pathogenesis of renal anemia.

Reno-Protective Effect of Low Protein Diet Supplemented With α-Ketoacid Through Gut Microbiota and Fecal Metabolism in 5/6 Nephrectomized Mice.

Background: Low protein supplemented with α-ketoacid diet (LKD) was recommended to be an essential intervention to delay the progression of chronic kidney disease (CKD) in patients who were not yet on dialysis. Aberrant gut microbiota and metabolism have been reported to be highly associated with CKD. However, the effect of LKD on gut microbiota and related fecal metabolism in CKD remains unclear. Methods: Mice were fed with normal protein diet (NPD group), low protein diet (LPD group), and low protein diet supplemented with α-ketoacid (LKD group) after 5/6 nephrectomy. At the end of the study, blood, kidney tissues, and feces were collected for biochemical analyses, histological, 16S rRNA sequence of gut microbiome, and untargeted fecal metabolomic analyses. Results: Both LKD and LPD alleviate renal failure and fibrosis, and inflammatory statement in 5/6 nephrectomized mice, especially the LKD. In terms of gut microbiome, LKD significantly improved the dysbiosis induced by 5/6Nx, representing increased α-diversity and decreased F/B ratio. Compared with NPD, LKD significantly increased the abundance of g_Parasutterella, s_Parabacteroides_sp_CT06, f_Erysipelotrichaceae, g_Akkermansia, g_Gordonibacter, g_Faecalitalea, and s_Mucispirillum_sp_69, and decreased s_Lachnospiraceae_bacterium_28-4 and g_Lachnoclostridium. Moreover, 5/6Nx and LKD significantly altered fecal metabolome. Then, multi-omics analysis revealed that specific metabolites involved in glycerophospholipid, purine, vitamin B6, sphingolipid, phenylalanine, tyrosine and tryptophan biosynthesis, and microbes associated with LKD were correlated with the amelioration of CKD. Conclusion: LKD had a better effect than LPD on delaying renal failure in 5/6 nephrectomy-induced CKD, which may be due to the regulation of affecting the gut microbiome and fecal metabolic profiles.

Berberine inhibits intestinal epithelial barrier dysfunction in colon caused by peritoneal dialysis fluid by improving cell migration.

ETHNOPHARMACOLOGICAL RELEVANCE: Berberine is generally extracted from Rhizoma Coptidis (Coptis chinensis Franch), a traditional Chinese medicine, which can be used in the treatment of intestinal diseases, respiratory infections and cardiovascular diseases. Berberine is especially effective for the treatment of gastrointestinal disorders such as diarrhea because of the effect of heat-clearing and detoxifying in traditional Chinese medicine theory. AIM OF THE STUDY: This study aimed to examine the protective effect of berberine (BBR) on the damaged colonic epithelial barrier caused by peritoneal dialysis fluid (PDF). METHODS: The damage to intestinal epithelial barrier was examined by intraperitoneally injecting 4.25% dextrose-containing PDF in mice and establishing a long-term PD model in rats with renal failure. Then, the therapeutic potential of berberine on PD-related colonic injuries was examined. T84 colonic epithelial cells were used to test the effect of PDF and berberine in vitro. The damaging effect of PDF and the protective effect of berberine were evaluated by histology staining, histofluorescence and transmission electron microscopy. The migration of colonic epithelial cell and actin-related protein 2 (Arp2) were tested by wound healing assay and Western blot to determine the possible mechanism in vitro. RESULTS: PD administration induced intestinal epithelial barrier dysfunction in the colon, and berberine alleviated the injury by increasing the tight junction and adhesion junction protein, both in vivo and in vitro. Berberine could also improve the morphology of microvillus. In the wound healing assay, berberine exhibited the ability to promote cell migration, indicating that berberine could probably recover the function of intestinal epithelial cells when the intestinal epithelial barrier was damaged by the PDF. CONCLUSIONS: The present study demonstrates that berberine can ameliorate intestinal epithelial barrier dysfunction in the colon caused by long-term PDF through improving cell migration.