Regulation and function of CX3CR1 and its ligand CX3CL1 in kidney disease

Regulatory B Cells Expressing Granzyme B from Tolerant Renal Transplant Patients: Highly Differentiated B Cells with a Unique Pathway with a Specific Regulatory Profile and Strong Interactions with Immune System Cells

The aim of our study was to determine whether granzyme B-expressing regulatory B cells (GZMB+ B cells) are enriched in the blood of transplant patients with renal graft tolerance. To achieve this goal, we analysed two single-cell RNA sequencing (scRNAseq) datasets: (1) peripheral blood mononuclear cells (PBMCs), including GZMB+ B cells from renal transplant patients, i.e., patients with stable graft function on conventional immunosuppressive treatment (STA, n = 3), drug-free tolerant patients (TOL, n = 3), and patients with antibody-mediated rejection (ABMR, n = 3), and (2) ex-vivo-induced GZMB+ B cells from these groups. In the patient PBMCs, we first showed that natural GZMB+ B cells were enriched in genes specific to Natural Killer (NK) cells (such as NKG7 and KLRD1) and regulatory B cells (such as GZMB, IL10, and CCL4). We performed a pseudotemporal trajectory analysis of natural GZMB+ B cells and showed that they were highly differentiated B cells with a trajectory that is very different from that of conventional memory B cells and linked to the transcription factor KLF13. By specifically analysing GZMB+ natural B cells in TOLs, we found that these cells had a very specific transcriptomic profile associated with a reduction in the expression of HLA molecules, apoptosis, and the inflammatory response (in general) in the blood and that this signature was conserved after ex vivo induction, with the induction of genes associated with migration processes, such as CCR7, CCL3, or CCL4. An analysis of receptor/ligand interactions between these GZMB+/- natural B cells and all of the immune cells present in PBMCs also demonstrated that GZMB+ B cells were the B cells that carried the most ligands and had the most interactions with other immune cells, particularly in tolerant patients. Finally, we showed that these GZMB+ B cells were able to infiltrate the graft under inflammatory conditions, thus suggesting that they can act in locations where immune events occur.

Identification of immune-associated biomarkers of diabetes nephropathy tubulointerstitial injury based on machine learning: a bioinformatics multi-chip integrated analysis

BACKGROUND

Diabetic nephropathy (DN) is a major microvascular complication of diabetes and has become the leading cause of end-stage renal disease worldwide. A considerable number of DN patients have experienced irreversible end-stage renal disease progression due to the inability to diagnose the disease early. Therefore, reliable biomarkers that are helpful for early diagnosis and treatment are identified. The migration of immune cells to the kidney is considered to be a key step in the progression of DN-related vascular injury. Therefore, finding markers in this process may be more helpful for the early diagnosis and progression prediction of DN.

METHODS

The gene chip data were retrieved from the GEO database using the search term ' diabetic nephropathy '. The ' limma ' software package was used to identify differentially expressed genes (DEGs) between DN and control samples. Gene set enrichment analysis (GSEA) was performed on genes obtained from the molecular characteristic database (MSigDB. The R package 'WGCNA' was used to identify gene modules associated with tubulointerstitial injury in DN, and it was crossed with immune-related DEGs to identify target genes. Gene ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed on differentially expressed genes using the 'ClusterProfiler' software package in R. Three methods, least absolute shrinkage and selection operator (LASSO), support vector machine recursive feature elimination (SVM-RFE) and random forest (RF), were used to select immune-related biomarkers for diagnosis. We retrieved the tubulointerstitial dataset from the Nephroseq database to construct an external validation dataset. Unsupervised clustering analysis of the expression levels of immune-related biomarkers was performed using the 'ConsensusClusterPlus 'R software package. The urine of patients who visited Dongzhimen Hospital of Beijing University of Chinese Medicine from September 2021 to March 2023 was collected, and Elisa was used to detect the mRNA expression level of immune-related biomarkers in urine. Pearson correlation analysis was used to detect the effect of immune-related biomarker expression on renal function in DN patients.

RESULTS

Four microarray datasets from the GEO database are included in the analysis : GSE30122, GSE47185, GSE99340 and GSE104954. These datasets included 63 DN patients and 55 healthy controls. A total of 9415 genes were detected in the data set. We found 153 differentially expressed immune-related genes, of which 112 genes were up-regulated, 41 genes were down-regulated, and 119 overlapping genes were identified. GO analysis showed that they were involved in various biological processes including leukocyte-mediated immunity. KEGG analysis showed that these target genes were mainly involved in the formation of phagosomes in Staphylococcus aureus infection. Among these 119 overlapping genes, machine learning results identified AGR2, CCR2, CEBPD, CISH, CX3CR1, DEFB1 and FSTL1 as potential tubulointerstitial immune-related biomarkers. External validation suggested that the above markers showed diagnostic efficacy in distinguishing DN patients from healthy controls. Clinical studies have shown that the expression of AGR2, CX3CR1 and FSTL1 in urine samples of DN patients is negatively correlated with GFR, the expression of CX3CR1 and FSTL1 in urine samples of DN is positively correlated with serum creatinine, while the expression of DEFB1 in urine samples of DN is negatively correlated with serum creatinine. In addition, the expression of CX3CR1 in DN urine samples was positively correlated with proteinuria, while the expression of DEFB1 in DN urine samples was negatively correlated with proteinuria. Finally, according to the level of proteinuria, DN patients were divided into nephrotic proteinuria group (n = 24) and subrenal proteinuria group. There were significant differences in urinary AGR2, CCR2 and DEFB1 between the two groups by unpaired t test (P < 0.05).

CONCLUSIONS

Our study provides new insights into the role of immune-related biomarkers in DN tubulointerstitial injury and provides potential targets for early diagnosis and treatment of DN patients. Seven different genes ( AGR2, CCR2, CEBPD, CISH, CX3CR1, DEFB1, FSTL1 ), as promising sensitive biomarkers, may affect the progression of DN by regulating immune inflammatory response. However, further comprehensive studies are needed to fully understand their exact molecular mechanisms and functional pathways in DN.

Expression and significance of Fractalkine/CX3CL1 in MPO-AAV-associated glomerulonephritis rats

OBJECTIVE

To investigate the expression and significance of Fractalkine (CX3CL1, FKN) in serum and renal tissue of myeloperoxidase and anti-neutrophil cytoplasmic antibody associated vasculitis (MPO-AAV) rats.

METHODS

Thirty Wistar-Kyoto (WKY) rats were randomly divided into: Control group, MPO-AAV group (400 µg/kg MPO mixed with Freund's complete adjuvant i.p), MPO-AAV + Anti-FKN group (400 µg/kg MPO mixed with Freund's complete adjuvant i.p), anti-FKN group (1 µg/ rat /day, i.p) after 6 weeks. MPO-AAV associated glomerulonephritis model was established by intraperitoneal injection of MPO + Freund's complete adjuvant with 10 mice in each group. The concentration of MPO-ANCA and FKN in serum was detected by Enzyme-linked immunosorbent assay (ELISA). Hematoxylin-eosin (HE) staining was used to detect pathological changes of kidney tissue. Western blot and immunofluorescence staining were used to detect the expression and localization of FKN protein in kidney tissue. Renal function test indicators: 24-hour urinary protein (UAER), blood urea nitrogen (BUN), serum creatinine (Scr). The expression levels of p65NF-κB and IL-6 was detected by Immunohistochemical assays.

RESULTS

Compared with the control group, the serum MPO-ANCA antibody expression level in the MPO-AAV group was significantly increased (P < 0.01), and the contents of UAER, BUN and Scr were significantly up-regulated at 24 h (P < 0.01). Compared with the control group, the glomeruli in the MPO-AAV group had different degrees of damage, infiltration of inflammatory cell, and membrane cell hyperplasia and renal tubule edema. Compared with the control group, rats in the MPO-AAV group had significantly higher levels of FKN in serum and renal tissues (P < 0.01), and high expression of p65NF-κB and IL-6 in renal tissues (P < 0.01) (P < 0.05), whereas anti-FKN reversed the expression of the above factors. In MPO-AAV renal tissue, FKN was mainly expressed in the cytoplasm of renal tubular epithelial cells and glomerular podocytes. In addition, the contents of 24 h UAER, BUN and Scr of renal function in MPO-AAV rats were significantly decreased (P < 0.01) and the damage of renal tissue was significantly ameliorated after the administration of antagonistic FKN.

CONCLUSION

FKN may play a key role in the pathogenesis of MPO-AAV associated glomerulonephritis.

Anti-CX3CL1 (fractalkine) monoclonal antibody attenuates lung and skin fibrosis in sclerodermatous graft-versus-host disease mouse model

BACKGROUND

Systemic sclerosis (SSc) is an autoimmune disease characterized by vascular injury and inflammation, followed by excessive fibrosis of the skin and other internal organs, including the lungs. CX3CL1 (fractalkine), a chemokine expressed on endothelial cells, supports the migration of macrophages and T cells that express its specific receptor CX3CR1 into targeted tissues. We previously reported that anti-CX3CL1 monoclonal antibody (mAb) treatment significantly inhibited transforming growth factor (TGF)-β1-induced expression of type I collagen and fibronectin 1 in human dermal fibroblasts. Additionally, anti-mouse CX3CL1 mAb efficiently suppressed skin inflammation and fibrosis in bleomycin- and growth factor-induced SSc mouse models. However, further studies using different mouse models of the complex immunopathology of SSc are required before the initiation of a clinical trial of CX3CL1 inhibitors for human SSc.

METHODS

To assess the preclinical utility and functional mechanism of anti-CX3CL1 mAb therapy in skin and lung fibrosis, a sclerodermatous chronic graft-versus-host disease (Scl-cGVHD) mouse model was analyzed with immunohistochemical staining for characteristic infiltrating cells and RNA sequencing assays.

RESULTS

On day 42 after bone marrow transplantation, Scl-cGVHD mice showed increased serum CX3CL1 level. Intraperitoneal administration of anti-CX3CL1 mAb inhibited the development of fibrosis in the skin and lungs of Scl-cGVHD model, and did not result in any apparent adverse events. The therapeutic effects were correlated with the number of tissue-infiltrating inflammatory cells and α-smooth muscle actin (α-SMA)-positive myofibroblasts. RNA sequencing analysis of the fibrotic skin demonstrated that cGVHD-dependent induction of gene sets associated with macrophage-related inflammation and fibrosis was significantly downregulated by mAb treatment. In the process of fibrosis, mAb treatment reduced cGVHD-induced infiltration of macrophages and T cells in the skin and lungs, especially those expressing CX3CR1.

CONCLUSIONS

Together with our previous findings in other SSc mouse models, the current results indicated that anti-CX3CL1 mAb therapy could be a rational therapeutic approach for fibrotic disorders, such as human SSc and Scl-cGVHD.

Cytotoxic Tph subset with low B-cell helper functions and its involvement in systemic lupus erythematosus

T peripheral helper (Tph) cells are thought to contribute to extra-follicular B cell activation and play a pathogenic role in autoimmune diseases. However, the role of Tph subsets is not fully elucidated. Here, we investigate the immunological functions of Tph subsets and their involvement in systemic lupus erythematosus (SLE). We have defined four Tph subsets (Tph1: CXCR3+CCR6-, Tph2: CXCR3-CCR6-, Tph17: CXCR3-CCR6+, and Tph1-17: CXCR3+CCR6+) and performed RNA sequencing after cell sorting. Tph1 and Tph17 subsets express substantial levels of IL21, indicating B cell helper functions. However, Tph2 and Tph1-17 subsets express low IL21. Interestingly, we have found Tph2 subset express high levels of CX3CR1, GZMB, PRF1, GLNY, S1PR5, TBX21, EOMES, ZNF863, and RUNX3, indicating a feature of CD4+ cytotoxic T lymphocytes. In SLE patients, the frequency of Tph1 and Tph2 subsets are significantly increased and positively correlated with SLE disease activity indexes. Tph1 cells expansion has been observed in patients with cutaneous and musculoskeletal manifestations. On the other hand, Tph2 cell expansion has been found in patients with lupus nephritis in addition to the above manifestations. Our findings imply that Tph1 and Tph2 subsets exert distinct immunological functions and are contributed to the complexity of clinical manifestations in SLE.

Roles of Chemokines in Intervertebral Disk Degeneration

PURPOSE OF REVIEW

Intervertebral disc degeneration is the primary etiology of low back pain and radicular pain. This review examines the roles of crucial chemokines in different stages of degenerative disc disease, along with interventions targeting chemokine function to mitigate disc degeneration.

RECENT FINDINGS

The release of chemokines from degenerated discs facilitates the infiltration and activation of immune cells, thereby intensifying the inflammatory cascade response. The migration of immune cells into the venous lumen is concomitant with the emergence of microvascular tissue and nerve fibers. Furthermore, the presence of neurogenic factors secreted by disc cells and immune cells stimulates the activation of pain-related cation channels in the dorsal root ganglion, potentially exacerbating discogenic and neurogenic pain and intensifying the degenerative cascade response mediated by chemokines. Gaining a deeper comprehension of the functions of chemokines and immune cells in these processes involving catabolism, angiogenesis, and injury detection could offer novel therapeutic avenues for managing symptomatic disc disease.

MDIC3: Matrix decomposition to infer cell-cell communication

Crosstalk among cells is vital for maintaining the biological function and intactness of systems. Most existing methods for investigating cell-cell communications are based on ligand-receptor (L-R) expression, and they focus on the study between two cells. Thus, the final communication inference results are particularly sensitive to the completeness and accuracy of the prior biological knowledge. Because existing L-R research focuses mainly on humans, most existing methods can only examine cell-cell communication for humans. As far as we know, there is currently no effective method to overcome this species limitation. Here, we propose MDIC3 (matrix decomposition to infer cell-cell communication), an unsupervised tool to investigate cell-cell communication in any species, and the results are not limited by specific L-R pairs or signaling pathways. By comparing it with existing methods for the inference of cell-cell communication, MDIC3 obtained better performance in both humans and mice.

Identification and validation of immune and cuproptosis - related genes for diabetic nephropathy by WGCNA and machine learning

Background

As the leading cause of chronic kidney disease, diabetic kidney disease (DKD) is an enormous burden for all healthcare systems around the world. However, its early diagnosis has no effective methods.

Methods

First, gene expression data in GEO database were extracted, and the differential genes of diabetic tubulopathy were obtained. Immune-related genesets were generated by WGCNA and immune cell infiltration analyses. Then, differentially expressed immune-related cuproptosis genes (DEICGs) were derived by the intersection of differential genes and genes related to cuproptosis and immune. To investigate the functions of DEICGs, volcano plots and GO term enrichment analysis was performed. Machine learning and protein-protein interaction (PPI) network analysis helped to finally screen out hub genes. The diagnostic efficacy of them was evaluated by GSEA analysis, receiver operating characteristic (ROC) curve, single-cell RNA sequencing and the Nephroseq website. The expression of hub genes at the animal level by STZ -induced and db/db DKD mouse models was further verified.

Results

Finally, three hub genes, including FSTL1, CX3CR1 and AGR2 that were up-regulated in both the test set GSE30122 and the validation set GSE30529, were screened. The areas under the curve (AUCs) of ROC curves of hub genes were 0.911, 0.935 and 0.922, respectively, and 0.946 when taking as a whole. Correlation analysis showed that the expression level of three hub genes demonstrated their negative relationship with GFR, while those of FSTL1 displayed a positive correlation with the level of serum creatinine. GSEA was enriched in inflammatory and immune-related pathways. Single-nucleus RNA sequencing indicated the main distribution of FSTL1 in podocyte and mesangial cells, the high expression of CX3CR1 in leukocytes and the main localization of AGR2 in the loop of Henle. In mouse models, all three hub genes were increased in both STZ-induced and db/db DKD models.

Conclusion

Machine learning was combined with WGCNA, immune cell infiltration and PPI analyses to identify three hub genes associated with cuproptosis, immunity and diabetic nephropathy, which all have great potential as diagnostic markers for DKD and even predict disease progression.

ProBDNF contributed to patrolling monocyte infiltration and renal damage in systemic lupus erythematosus

Monocyte aberrations have been increasingly recognized as contributors to renal damage in systemic lupus erythematosus (SLE), however, recognition of the underlying mechanisms and modulating strategies is at an early stage. Our studies have demonstrated that brain-derived neurotrophic factor precursor (proBDNF) drives the progress of SLE by perturbing antibody-secreting B cells, and proBDNF facilitates pro-inflammatory responses in monocytes. By utilizing peripheral blood from patients with SLE, GEO database and spontaneous MRL/lpr lupus mice, we demonstrated in the present study that CX3CR1+ patrolling monocytes (PMo) numbers were decreased in SLE. ProBDNF was specifically expressed in CX3CR1+ PMo and was closely correlated with disease activity and the degree of renal injury in SLE patients. In MRL/lpr mice, elevated proBDNF was found in circulating PMo and the kidney, and blockade of proBDNF restored the balance of circulating and kidney-infiltrating PMo. This blockade also led to the reversal of pro-inflammatory responses in monocytes and a noticeable improvement in renal damage in lupus mice. Overall, the results indicate that the upregulation of proBDNF in PMo plays a crucial role in their infiltration into the kidney, thereby contributing to nephritis in SLE. Targeting of proBDNF offers a potential therapeutic role in modulating monocyte-driven renal damage in SLE.

A double-edged sword: interactions of CX3CL1/CX3CR1 and gut microbiota in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic chronic disease initiated by an abnormal immune response to self and can affect multiple organs. SLE is characterized by the production of autoantibodies and the deposition of immune complexes. In regard to the clinical observations assessed by rheumatologists, several chemokines and cytokines also contribute to disease progression. One such chemokine and adhesion molecule is CX3CL1 (otherwise known as fractalkine). CX3CL1 is involved in cell trafficking and inflammation through recognition by its receptor, CX3CR1. The CX3CL1 protein consists of a chemokine domain and a mucin-like stalk that allows it to function both as a chemoattractant and as an adhesion molecule. In inflammation and specifically lupus, the literature displays contradictory evidence for the functions of CX3CL1/CX3CR1 interactions. In addition, the gut microbiota has been shown to play an important role in the pathogenesis of SLE. This review highlights current studies that illustrate the interactions of the gut microbiota and CX3CR1 in SLE.

Microglia in Central Control of Metabolism

Beyond their role as brain immune cells, microglia act as metabolic sensors in response to changes in nutrient availability, thus playing a role in energy homeostasis. This review highlights the evidence and challenges of studying the role of microglia in metabolism regulation.

Genetic variants of interferon-response factor 5 are associated with the incidence of chronic kidney disease: the D.E.S.I.R. study

Inflammation has been associated with renal diseases. The Interferon Regulatory Factor (IRF)-5 is a key transcription factor in the pro-inflammatory polarization of M1-like macrophages. GWAS have reported that the IRF5 locus is associated with autoimmune diseases and with the estimated glomerular filtration rate (eGFR). We study whether allelic variations in IRF5 are associated with the incidence of chronic kidney disease (CKD) in a general population. We genotyped eleven IRF5 SNPs in the French D.E.S.I.R. cohort from the general population (n = 4820). Associations of SNPs with baseline renal parameters were assessed. Data were analyzed for three endpoints during a 9-year follow-up, incidence of:at least stage 3 CKD, the KDIGO criterion "certain drop in eGFR", and incidence of micro/macro albuminuria. In the cross-sectional analysis, rs10954213 and rs10954214 were associated with eGFR and rs1874328 with urinary albumin/creatinine ratio (ACR). Rs3807306, rs11761199, rs78658945, rs1874328, rs10954213 and rs11770589 were associated with the incidence of stage 3 CKD in multi-adjusted models. Rs4731532, rs3807306, and rs11761199 were associated with the incidence of CKD defined by the KDIGO. Rs4731532, rs3807306, rs11761199 and rs79288514 were associated with the incidence of micro/macro albuminuria. Our results support the hypothesis of the importance of IRF5 mediated macrophage polarization in the etiology of CKD.

In vivo longitudinal 920 nm two-photon intravital kidney imaging of a dynamic 2,8-DHA crystal formation and tubular deterioration in the adenine-induced chronic kidney disease mouse model

Chronic kidney disease (CKD) is one of the most common renal diseases manifested by gradual loss of kidney function with no symptoms in the early stage. The underlying mechanism in the pathogenesis of CKD with various causes such as high blood pressure, diabetes, high cholesterol, and kidney infection is not well understood. In vivo longitudinal repetitive cellular-level observation of the kidney of the CKD animal model can provide novel insights to diagnose and treat the CKD by visualizing the dynamically changing pathophysiology of CKD with its progression over time. In this study, using two-photon intravital microscopy with a single 920 nm fixed-wavelength fs-pulsed laser, we longitudinally and repetitively observed the kidney of an adenine diet-induced CKD mouse model for 30 days. Interestingly, we could successfully visualize the 2,8-dihydroxyadenine (2,8-DHA) crystal formation with a second-harmonics generation (SHG) signal and the morphological deterioration of renal tubules with autofluorescence using a single 920 nm two-photon excitation. The longitudinal in vivo two-photon imaging results of increasing 2,8-DHA crystals and decreasing tubular area ratio visualized by SHG and autofluorescence signal, respectively, were highly correlated with the CKD progression monitored by a blood test showing increased cystatin C and blood urea nitrogen (BUN) levels over time. This result suggests the potential of label-free second-harmonics generation crystal imaging as a novel optical technique for in vivo CKD progression monitoring.

Identification of a novel immune landscape signature as effective diagnostic markers related to immune cell infiltration in diabetic nephropathy

Background

The study aimed to identify core biomarkers related to diagnosis and immune microenvironment regulation and explore the immune molecular mechanism of diabetic nephropathy (DN) through bioinformatics analysis.

Methods

GSE30529, GSE99325, and GSE104954 were merged with removing batch effects, and different expression genes (DEGs) were screened at a criterion |log2FC| &gt;0.5 and adjusted P &lt;0.05. KEGG, GO, and GSEA analyses were performed. Hub genes were screened by conducting PPI networks and calculating node genes using five algorithms with CytoHubba, followed by LASSO and ROC analysis to accurately identify diagnostic biomarkers. In addition, two different GEO datasets, GSE175759 and GSE47184, and an experiment cohort with 30 controls and 40 DN patients detected by IHC, were used to validate the biomarkers. Moreover, ssGSEA was performed to analyze the immune microenvironment in DN. Wilcoxon test and LASSO regression were used to determine the core immune signatures. The correlation between biomarkers and crucial immune signatures was calculated by Spearman analysis. Finally, cMap was used to explore potential drugs treating renal tubule injury in DN patients.

Results

A total of 509 DEGs, including 338 upregulated and 171 downregulated genes, were screened out. “chemokine signaling pathway” and “cell adhesion molecules” were enriched in both GSEA and KEGG analysis. CCR2, CX3CR1, and SELP, especially for the combination model of the three genes, were identified as core biomarkers with high diagnostic capabilities with striking AUC, sensitivity, and specificity in both merged and validated datasets and IHC validation. Immune infiltration analysis showed a notable infiltration advantage for APC co-stimulation, CD8+ T cells, checkpoint, cytolytic activity, macrophages, MHC class I, and parainflammation in the DN group. In addition, the correlation analysis showed that CCR2, CX3CR1, and SELP were strongly and positively correlated with checkpoint, cytolytic activity, macrophages, MHC class I, and parainflammation in the DN group. Finally, dilazep was screened out as an underlying compound for DN analyzed by CMap.

Conclusions

CCR2, CX3CR1, and SELP are underlying diagnostic biomarkers for DN, especially in their combination. APC co-stimulation, CD8+ T cells, checkpoint, cytolytic activity, macrophages, MHC class I, and parainflammation may participate in the occurrence and development of DN. At last, dilazep may be a promising drug for treating DN.

Mass Cytometry Reveals the Imbalanced Immune State in the Peripheral Blood of Patients with Essential Hypertension

Mounting evidence has confirmed that essential hypertension (EH) is closely related to low-grade inflammation, but there is still a lack of in-depth understanding of the state of immune cells in the circulating blood of patients with EH. We analyzed whether hypertensive peripheral blood immune cell balance was destroyed. The peripheral blood mononuclear cells (PBMCs) of all subjects were analyzed using time-of-flight cytometry (CyTOF) based on 42 kinds of metal-binding antibodies. CD45⁺ cells were categorized into 32 kinds of subsets. Compared with the health control (HC) group, the percentage of total dendritic cells, two kinds of myeloid dendritic cell subsets, one intermediate/nonclassical monocyte subset and one CD4⁺ central memory T cell subset in the EH group, was significantly higher; the percentage of low-density neutrophils, four kinds of classical monocyte subsets, one CD14^lowCD16^- monocyte subset, one naive CD4⁺ and one naive CD8⁺ T cell subsets, one CD4⁺ effector and one CD4⁺ central memory T cell subsets, one CD8⁺ effector memory T cell subset, and one terminally differentiated γδ T cell subset, decreased significantly in EH. What is more, the expression of many important antigens was enhanced in CD45⁺ immune cells, granulocytes, and B cells in patients with EH. In conclusion, the altered number and antigen expression of immune cells reflect the imbalanced immune state of the peripheral blood in patients with EH.

Localization of natriuretic peptide receptors A, B, and C in healthy and diseased mouse kidneys

The natriuretic peptides (NPs) ANP (atrial natriuretic peptide) and BNP (B-type natriuretic peptide) mediate their widespread effects by activating the natriuretic peptide receptor-A (NPR-A), while C-type natriuretic peptide (CNP) acts via natriuretic peptide receptor-B (NPR-B). NPs are removed from the circulation by internalization via the natriuretic peptide clearance receptor natriuretic peptide receptor-C (NPR-C). In addition to their well-known functions, for instance on blood pressure, all three NPs confer significant cardioprotection and renoprotection. Since neither the NP-mediated renal functions nor the renal target cells of renoprotection are completely understood, we performed systematic localization studies of NP receptors using in situ hybridization (RNAscope) in mouse kidneys. NPR-A mRNA is highly expressed in glomeruli (mainly podocytes), renal arterioles, endothelial cells of peritubular capillaries, and PDGFR-receptor β positive (PDGFR-β) interstitial cells. No NPR-A mRNA was detected by RNAscope in the tubular system. In contrast, NPR-B expression is highest in proximal tubules. NPR-C is located in glomeruli (mainly podocytes), in endothelial cells and PDGFR-β positive cells. To test for a possible regulation of NPRs in kidney diseases, their distribution was studied in adenine nephropathy. Signal intensity of NPR-A and NPR-B mRNA was reduced while their spatial distribution was unaltered compared with healthy kidneys. In contrast, NPR-C mRNA signal was markedly enhanced in cell clusters of myofibroblasts in fibrotic areas of adenine kidneys. In conclusion, the primary renal targets of ANP and BNP are glomerular, vascular, and interstitial cells but not the tubular compartment, while the CNP receptor NPR-B is highly expressed in proximal tubules. Further studies are needed to clarify the function and interplay of this specific receptor expression pattern.

CX3CL1 Worsens Cardiorenal Dysfunction and Serves as a Therapeutic Target of Canagliflozin for Cardiorenal Syndrome

The prognosis of cardiorenal dysfunction induced by diabetes mellitus (DM), which belongs to cardiorenal syndrome type 5, is poor and its pathogenesis remains elusive. We have reported that CX3CL1 exacerbated heart failure and direct inhibition of CX3CL1 improved cardiac function. Emerging evidence supports that CX3CL1 is involved in renal impairment. Here we attempt to clarify whether CX3CL1 might be a therapeutic target for cardiorenal dysfunction in diabetes. We found that cardiac and renal CX3CL1 protein levels were significantly increased in both streptozotocin-induced diabetic mice and in non-obese diabetic mice, and that hyperglycemia led to persistent CX3CL1 expression in the heart and kidneys even after it was controlled by insulin. In cultured cardiac and renal cells, soluble CX3CL1 accelerated mitochondrial-dependent apoptosis via activation of the RhoA/ROCK1-Bax signaling pathway and promoted fibrosis through cellular phenotypic trans-differentiation mediated by the TGF-β/Smad pathway. In the two diabetic mouse models, knockout of CX3CL1 receptor CX3CR1 or treatment with an CX3CL1 neutralizing antibody significantly improved cardiorenal dysfunction by inhibiting apoptosis, mitochondrial dysfunction, and fibrosis. Moreover, sodium glucose cotransporter 2 inhibitor canagliflozin significantly downregulated cardiac and renal CX3CL1 expression and improved cardiorenal dysfunction. These findings indicate that CX3CL1 could be a new therapeutic target for diabetes-induced cardiorenal dysfunction.

Human Endothelial Progenitor Cells Protect the Kidney against Ischemia-Reperfusion Injury via the NLRP3 Inflammasome in Mice

Ischemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI) and progression to chronic kidney disease (CKD). However, no effective therapeutic intervention has been established for ischemic AKI. Endothelial progenitor cells (EPCs) have major roles in the maintenance of vascular integrity and the repair of endothelial damage; they also serve as therapeutic agents in various kidney diseases. Thus, we examined whether EPCs have a renoprotective effect in an IRI mouse model. Mice were assigned to sham, EPC, IRI-only, and EPC-treated IRI groups. EPCs originating from human peripheral blood were cultured. The EPCs were administered 5 min before reperfusion, and all mice were killed 72 h after IRI. Blood urea nitrogen, serum creatinine, and tissue injury were significantly increased in IRI mice; EPCs significantly improved the manifestations of IRI. Apoptotic cell death and oxidative stress were significantly reduced in EPC-treated IRI mice. Administration of EPCs decreased the expression levels of NLRP3, cleaved caspase-1, p-NF-κB, and p-p38. Furthermore, the expression levels of F4/80, ICAM-1, RORγt, and IL-17RA were significantly reduced in EPC-treated IRI mice. Finally, the levels of EMT-associated factors (TGF-β, α-SMA, Snail, and Twist) were significantly reduced in EPC-treated IRI mice. This study shows that inflammasome-mediated inflammation accompanied by immune modulation and fibrosis is a potential target of EPCs as a treatment for IRI-induced AKI and the prevention of progression to CKD.

The Promoter of the Immune-Modulating Gene TIR-Containing Protein C of the Uropathogenic Escherichia coli Strain CFT073 Reacts to the Pathogen's Environment

The TIR-containing protein C (TcpC) of the uropathogenic Escherichia coli strain CFT073 modulates innate immunity by interfering with the Toll-like receptor and NALP3 inflammasome signaling cascade. During a urinary tract infection the pathogen encounters epithelial and innate immune cells and replicates by several orders of magnitude. We therefore analyzed whether these cell types and also the density of the pathogen would induce the recently defined promoter of the CFT073 tcpC gene to, in time, dampen innate immune responses. Using reporter constructs we found that the uroepithelial cell line T24/83 and the monocytic cell line THP-1 induced the tcpC promoter. Differentiation of monocytic THP-1 cells to macrophages increased their potential to switch on the promoter. Cell-associated CFT073 displayed the highest promoter activity. Since potassium represents the most abundant intracellular ion and is secreted to induce the NLRP3 inflammasome, we tested its ability to activate the tcpC promoter. Potassium induced the promoter with high efficiency. Sodium, which is enriched in the renal cortex generating an antibacterial hypersalinity, also induced the tcpC promoter. Finally, the bacterial density modulated the tcpC promoter activity. In the search for promoter-regulating proteins, we found that the DNA-binding protein H-NS dampens the promoter activity. Taken together, different cell types and salts, present in the kidney, are able to induce the tcpC promoter and might explain the mechanism of TcpC induction during a kidney infection with uropathogenic E. coli strains.

MicroRNA (miR)-590-3p alleviates high-glucose induced renal tubular epithelial cell damage by targeting C-X3-C motif chemokine ligand 1 (CX3CL1) in diabetic nephropathy

We attempted to analyze the clinical value of microRNA (miR)-590-3p in diabetic nephropathy (DN) patients and its role in high glucose (HG)-induced renal tubular epithelial cell (HK-2) injury. Serum levels of miR-590-3p were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Spearman correlation coefficient analysis of the correlation between miR-590-3p and clinical indicators. The diagnostic value of miR-590-3p was analyzed by the receiver operating characteristic (ROC) curve. Then, the DN cell model induced by HG in HK-2 cells was established. Enzyme-linked immunosorbent assay (ELISA), flow cytometry, and CCK-8 assay were employed to assess cell inflammation, oxidative stress, apoptosis, and proliferation. Dual-luciferase reporter assay confirmed the target of miR-590-3p. Serum miR-590-3p was reduced in patients of DN, which was positively correlated with eGFR and negatively associated with albuminuria. Furthermore, miR-590-3p also can diagnose patients of DN from healthy subjects or patients of T2DM. Furthermore, miR-590-3p was decreased in a concentration- and time-dependent manner during HG-induction. miR-590-3p overexpression bated HG-induced inhibition effect on cell proliferation and promotion effects on apoptosis, oxidative stress, and inflammation. C-X3-C motif chemokine ligand1 (CX3CL1) is the target of miR-590-3p, whose levels were enhanced in DN patients and are negatively regulated by miR-590-3p. Our discoveries offered new insights that reduced miR-590-3p as a potential biomarker for the diagnosis of DN, and elevated miR-590-3p can alleviate renal tubular injury by HG-induced through targeting CX3XL1, which may be a novel target for improving the development of DN.

A calorie-restricted diet enriched with tree nuts and peanuts reduces the expression of CX3CR1 in peripheral blood mononuclear cells in patients with coronary artery disease

Background: The modification of the gut microbiome has been proposed to alter immune response which is a key driver in low-grade inflammation as well as metabolic markers. This study was conducted to determine the effects of a low-calorie diet with and without nuts on some gut bacterial abundance, metabolic markers, and gene expression in peripheral blood mononuclear cells (PBMCs) in stable coronary artery disease patients with overweight or obesity. Methods: Overweight or obese patients with stable coronary artery disease of both genders were randomly allocated to a nut-free calorie-restricted diet as 25% of energy deficit (CRD) or a CRD enriched with 39-60 gr/d of mixed nuts (CRDEN) for 8 weeks (32 patients in CRD and 35 patients in CRDEN). Mixed nuts consisted of equal amounts of unsalted pistachios, almonds, and peanuts. Microbiota analysis was performed by quantitative real-time polymerase chain reaction method on feces collected before and after the intervention, using primers targeting 16S ribosomal DNA of 4 different bacterial genera, including Bacteroides, Prevotella, Bifidobacterium, and Lactobacillus. We examined the plasma concentrations of glucose, insulin, adiponectin as well as expression of toll-like receptor-4 (TLR4) and fractalkine receptor (CX3CR1) in PBMCs. Results: A significant reduction in expression of CX3CR1 (p=0.04) and a tendency to lower expression of TLR4 in PBMCs (p=0.06) was observed in the CRDEN group at the end of the study compared to the CRD group. The abundance of fecal Prevotella also tended to increase in CRDEN compared to the CRD group (p=0.06). Plasma insulin and adiponectin had no significant changes. There was a positive correlation between fecal Prevotella abundance and plasma adiponectin at baseline (r=0.315, p=0.015) and the end of the study (r=0.380, p=0.003). Conclusion: Our results suggest that the inclusion of mixed tree nuts and peanuts in a low-calorie diet for 8 weeks led to a lower CX3CR expression in PBMCs in a cohort of overweight or obese patients with stable CAD. This finding provides another beneficial effect of diet supplemented with nuts on factors associated with inflammation. Trial registration: this clinical study has been registered at the clinical trial registration center (clinicaltrial.gov): NCT04078919 on September 6, 2019.

Ectodomain shedding by ADAM proteases as a central regulator in kidney physiology and disease

Besides its involvement in blood and bone physiology, the kidney's main function is to filter substances and thereby regulate the electrolyte composition of body fluids, acid-base balance and toxin removal. Depending on underlying conditions, the nephron must undergo remodeling and cellular adaptations. The proteolytic removal of cell surface proteins via ectodomain shedding by A Disintegrin and Metalloproteases (ADAMs) is of importance for the regulation of cell-cell and cell-matrix adhesion of renal cells. ADAM10 controls glomerular and tubule development in a Notch1 signaling-dependent manner and regulates brush border composition. ADAM17 regulates the renin angiotensin system and is together with ADAM10 involved in calcium phosphate homeostasis. In kidney disease ADAMs, especially ADAM17 contribute to inflammation through their involvement in IL-6 trans-signaling, Notch-, epithelial growth factor receptor-, and tumor necrosis factor α signaling. ADAMs are interesting drug targets to reduce the inflammatory burden, defective cell adhesion and impaired signaling pathways in kidney diseases.

Defining therapeutic targets for renal fibrosis: Exploiting the biology of pathogenesis

Renal fibrosis is a failed wound-healing process of the kidney tissue after chronic, sustained injury, which is a common pathway and pathological marker of virtually every type of chronic kidney disease (CKD), regardless of cause. However, there is a lack of effective treatment specifically targeting against renal fibrosis per se to date. The main pathological feature of renal fibrosis is the massive activation and proliferation of renal fibroblasts and the excessive synthesis and secretion of extracellular matrix (ECM) deposited in the renal interstitium, leading to structural damage, impairment of renal function, and eventually end-stage renal disease. In this review, we summarize recent advancements regarding the participation and interaction of many types of kidney residents and infiltrated cells during renal fibrosis, attempt to comprehensively discuss the mechanism of renal fibrosis from the cellular level and conclude by highlighting novel therapeutic targets and approaches for development of new treatments for patients with renal fibrosis.