Glomerular Endothelium Research Articles

Production of Acetylcholine by Podocytes and its Protection from Kidney Injury in Glomerulonephritis.

One of the most important factors modulating endothelial health is acetylcholine, and while it is associated as a cholinergic neurotransmitter; it is also expressed by non-neuronal cells. However, its role in the kidney, which does not receive cholinergic innervation, remains unknown. To determine if acetylcholine is produced in the kidney, we used ChAT(BAC)-eGFP (ChAT mice) transgenic mice in which enhanced green fluorescent protein (eGFP) is expressed under the control of the endogenous choline acetyltransferase (ChAT) transcriptional regulatory elements. We then investigated the role of acetylcholine in kidney disease by inducing anti- glomerular basement membrane glomerulonephritis (anti-GBM GN) in ChAT transgenic mice. We demonstrate ChAT, the sole enzyme responsible for acetylcholine production, was expressed in glomerular podocytes and produced acetylcholine. We also show during anti-GBM GN in ChAT transgenic mice, ChAT expression was induced in the glomeruli, mainly in podocytes and protects mice from kidney injury with marked reduction of glomerular proliferation/fibrinoid necrosis (by 71%) crescent formation (by 98%), and tubular injury (by 78%). In contrast, specific knockout of podocyte ChAT worsened the severity of the disease. The mechanism of protection included reduction of inflammation, attenuation of angiogenic factors reduction, and increase of eNOS expression. In vitro and in vivo studies demonstrated available drugs like cholinesterase inhibitors and ChAT inducers increased the expression of podocyte-ChAT and acetylcholine production. These findings suggest de novo synthesis of acetylcholine by podocytes protected against inflammation and glomerular endothelium damage in anti-GBM glomerulonephritis.

Single-cell transcriptomics identifies aberrant glomerular angiogenic signalling in the early stages of WT1 kidney disease.

WT1 encodes a podocyte transcription factor whose variants can cause an untreatable glomerular disease in early childhood. Although WT1 regulates many podocyte genes, it is poorly understood which of them are initiators in disease and how they subsequently influence other cell-types in the glomerulus. We hypothesised that this could be resolved using single-cell RNA sequencing (scRNA-seq) and ligand-receptor analysis to profile glomerular cell-cell communication during the early stages of disease in mice harbouring an orthologous human mutation in WT1 (Wt1R394W/+). Podocytes were the most dysregulated cell-type in the early stages of Wt1R394W/+ disease, with disrupted angiogenic signalling between podocytes and the endothelium, including the significant downregulation of transcripts for the vascular factors Vegfa and Nrp1. These signalling changes preceded glomerular endothelial cell loss in advancing disease, a feature also observed in biopsy samples from human WT1 glomerulopathies. Addition of conditioned medium from murine Wt1R394W/+ primary podocytes to wild-type glomerular endothelial cells resulted in impaired endothelial looping and reduced vascular complexity. Despite the loss of key angiogenic molecules in Wt1R394W/+ podocytes, the pro-vascular molecule adrenomedullin was upregulated in Wt1R394W/+ podocytes and plasma and its further administration was able to rescue the impaired looping observed when glomerular endothelium was exposed to Wt1R394W/+ podocyte medium. In comparative analyses, adrenomedullin upregulation was part of a common injury signature across multiple murine and human glomerular disease datasets, whilst other gene changes were unique to WT1 disease. Collectively, our study describes a novel role for altered angiogenic signalling in the initiation of WT1 glomerulopathy. We also identify adrenomedullin as a proangiogenic factor, which despite being upregulated in early injury, offers an insufficient protective response due to the wider milieu of dampened vascular signalling that results in endothelial cell loss in later disease. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Non-voltage-gated Ca2+ channel signaling in glomerular cells in kidney health and disease.

Positioned at the head of the nephron, the renal corpuscle generates a plasma ultrafiltrate to initiate urine formation. Three major cell types within the renal corpuscle, the glomerular mesangial cells, podocytes, and glomerular capillary endothelial cells, communicate via endocrine- and paracrine-signaling mechanisms to maintain the structure and function of the glomerular capillary network and filtration barrier. Ca2+ signaling mediated by several distinct plasma membrane Ca2+ channels impacts the functions of all three cell types. The past two decades have witnessed pivotal advances in understanding of non-voltage-gated Ca2+ channel function and regulation in the renal corpuscle in health and renal disease. This review summarizes the current knowledge of the physiological and pathological impact of non-voltage-gated Ca2+ channel signaling in mesangial cells, podocytes and glomerular capillary endothelium. The main focus is on transient receptor potential and store-operated Ca2+ channels, but ionotropic N-methyl-d-aspartate receptors and purinergic receptors also are discussed. This update of Ca2+ channel functions and their cellular signaling cascades in the renal corpuscle is intended to inform the development of therapeutic strategies targeting these channels to treat kidney diseases, particularly diabetic nephropathy.

Deciphering the abundance of immune cells in glomerular endothelium of Alport syndrome kidneys using the deconvolution algorithm CONVdeconv

Due to the high cost of single-cell sequencing technology, understanding cell heterogeneity within tissues is crucial for elucidating the biological characteristics of complex tissues. Therefore, this study proposes a method for generating pseudo-bulk data based on single-cell sequencing data and designs a convolutional neural network model, CONVdeconv, based on attention mechanisms, for deconvoluting real bulk RNA data. Experimental validation on mouse kidney data demonstrates that the CONVdeconv model performs exceptionally well in deconvolution tasks, effectively restoring cell type proportions. Furthermore, deconvolution analysis of mouse data with Alport syndrome revealed significant differences in macrophages and T lymphocytes between disease and normal states, providing new clues and directions for a deeper understanding of the disease’s progression.

#1227 The role of P-selectin (CD62P) expression in renal tissue in the development of diabetic nephropathy

Abstract Background and Aims The prevalence of diabetic nephropathy (DN) is increasing in line with the increase in the incidence of diabetes mellitus (DM) worldwide. The latest data from the International Diabetes Federation (IDF) predicts that by 2045, more than 10.5% of adults worldwide will have diabetes. This will lead to kidney damage in 100-250 million people. DN is characterized by structural and functional changes. As a result of chronic hyperglycemia, pathogenic changes in the vascular wall develop, and the frequency of micro- and macrovascular complications associated with morbidity and mortality among patients with diabetes increases. However, the exact mechanism of vascular complications is not completely clear. Endothelial dysfunction plays a key role in triggering the development of inflammatory mechanisms that are associated with vascular complications in patients with type 2 diabetes mellitus (T2DM). Activation of the endothelium due to increased release of cytokines and expression of adhesion molecules promotes platelet activation and their adhesion to the activated endothelium. Selectins (E-selectin, L-selectin and P-selectin) play a major role in the development of microvascular complications. The aim of the study was to examine the role of P-selectin (CD62p) expression in the glomerular endothelium and peritubular capillaries in patients with different morphological classes of DN and to evaluate its effect on the development and progression of morphological changes in renal tissue. Method Was examined 49 patients with T2DM complicated by the development of DN. The average age of the patients was 66.58 ± 3.27 years. There were 35 women, 14 men. The duration of the disease was 17.70 ± 0.35 years. The duration of DN from the moment of detection of microalbuminuria to the morphological examination of the renal tissue and diagnosis was 1.65 ± 0.34 years. All patients underwent light and immunofluorescence microscopy of kidney tissue biopsies obtained by intravital puncture biopsy. Morphological changes in tissue were assessed in accordance with the latest international classification of diabetic nephropathy developed by the Scientific Committee of the Pathology Society, USA. According to light microscopy data, class IIa (mild mesangial expansion) was detected in 12 patients, class IIb (severe mesangial expansion) in 14 patients, class III (Kimmelstil–Wilson nodular lesions) in 19 patients, and class IV (advanced diabetic glomerulosclerosis) in 5 patients. In addition to light microscopy, the expression of CD62β (P-selectin) in the glomerular endothelium and in peritubular capillaries was determined in all patients. FITc-labeled monoclonal antibodies (FITC anti-human CD62p Antibody, clone AK4 Cat#304904), were used (Biolegend, USA). Results Analysis of biopsy tissue from DN patients showed that CD62p expression is detected both in the glomerular endothelium (1.6383 ± 0.4789 (95% CI: 0.9574-2.7234)) and in peritubular capillaries (1.1702 ± 0.1308 (95% CI: 0.9149–1.4250)). Using the linear regression method with the calculation of the coefficients of determination R2 (R Square), the values of the F criterion, significant regression models were obtained: Expression of CD62p in the glomerular endothelium promotes the development and progression of arteriolar hyalinosis (R2=0.213, F=12.476 p=0.001); expansion of the mesangial matrix (R2=0.362, F=26.09, p=0.0001); thickening of the basement membrane (R2=0.127, F=6.57, p=0.014); development and progression of nodular Kimmelstiel–Wilson lesions (R2=0.106, F=5.360, p=0.025). Expression of CD62p in peritubular capillaries promotes the development of interstitial sclerosis (R2=0.549, F=54.732, p=0.0001). The severity of CD62p expression in the glomerular endothelium depends on the morphological class of DN in patients (R2=0.216, F=12.684, p=0.001). Conclusion

Transglutaminase-mediated stiffening of the glomerular basement membrane mitigates pressure-induced reductions in molecular sieving coefficient by reducing compression

Proteinuria, the presence of high molecular weight proteins in the urine, is a primary indicator of chronic kidney disease. Proteinuria results from increased molecular permeability of the glomerular filtration barrier combined with saturation or defects in tubular protein reabsorption. Any solute that passes into the glomerular filtrate traverses the glomerular endothelium, the glomerular basement membrane, and the podocyte slit diaphragm. Damage to any layer of the filter has reciprocal effects on other layers to increase glomerular permeability. The GBM is thought to act as a compressible ultrafilter that has increased molecular selectivity with increased pressure due to compression that reduced the porosity of the GBM with increased pressure. In multiple forms of chronic kidney disease, crosslinking enzymes are upregulated and may act to increase GBM stiffness. Here we show that enzymatically crosslinking porcine GBM with transglutaminase increases the stiffness of the GBM and mitigates pressure-dependent reductions in molecular sieving coefficient. This was modeled mathematically using a modified membrane transport model accounting for GBM compression. Changes in the mechanical properties of the GBM may contribute to proteinuria through pressure-dependent effects on GBM porosity.

Endothelial CXCR2 deficiency attenuates renal inflammation and glycocalyx shedding through NF-κB signaling in diabetic kidney disease

BackgroundThe incidence of diabetic kidney disease (DKD) continues to rapidly increase, with limited available treatment options. One of the hallmarks of DKD is persistent inflammation, but the underlying molecular mechanisms of early diabetic kidney injury remain poorly understood. C-X-C chemokine receptor 2 (CXCR2), plays an important role in the progression of inflammation-related vascular diseases and may bridge between glomerular endothelium and persistent inflammation in DKD.MethodsMultiple methods were employed to assess the expression levels of CXCR2 and its ligands, as well as renal inflammatory response and endothelial glycocalyx shedding in patients with DKD. The effects of CXCR2 on glycocalyx shedding, and persistent renal inflammation was examined in a type 2 diabetic mouse model with Cxcr2 knockout specifically in endothelial cells (DKD-Cxcr2eCKO mice), as well as in glomerular endothelial cells (GECs), cultured in high glucose conditions.ResultsCXCR2 was associated with early renal decline in DKD patients, and endothelial-specific knockout of CXCR2 significantly improved renal function in DKD mice, reduced inflammatory cell infiltration, and simultaneously decreased the expression of proinflammatory factors and chemokines in renal tissue. In DKD conditions, glycocalyx shedding was suppressed in endothelial Cxcr2 knockout mice compared to Cxcr2L/L mice. Modulating CXCR2 expression also affected high glucose-induced inflammation and glycocalyx shedding in GECs. Mechanistically, CXCR2 deficiency inhibited the activation of NF-κB signaling, thereby regulating inflammation, restoring the endothelial glycocalyx, and alleviating DKD.ConclusionsTaken together, under DKD conditions, activation of CXCR2 exacerbates inflammation through regulation of the NF-κB pathway, leading to endothelial glycocalyx shedding and deteriorating renal function. Endothelial CXCR2 deficiency has a protective role in inflammation and glycocalyx dysfunction, suggesting its potential as a promising therapeutic target for DKD treatment.

Modeling complement activation on human glomerular microvascular endothelial cells.

Atypical hemolytic uremic syndrome (aHUS) is a rare kidney disease caused by dysregulation of the complement alternative pathway. The complement dysregulation specifically leads to damage to the glomerular endothelium. To further understand aHUS pathophysiology, we validated an ex vivo model for measuring complement deposition on both control and patient human glomerular microvascular endothelial cells (GMVECs). Endothelial cells were incubated with human test sera and stained with an anti-C5b-9 antibody to visualize and quantify complement depositions on the cells with immunofluorescence microscopy. First, we showed that zymosan-activated sera resulted in increased endothelial C5b-9 depositions compared to normal human serum (NHS). The levels of C5b-9 depositions were similar between conditionally immortalized (ci)GMVECs and primary control GMVECs. The protocol with ciGMVECs was further validated and we additionally generated ciGMVECs from an aHUS patient. The increased C5b-9 deposition on control ciGMVECs by zymosan-activated serum could be dose-dependently inhibited by adding the C5 inhibitor eculizumab. Next, sera from five aHUS patients were tested on control ciGMVECs. Sera from acute disease phases of all patients showed increased endothelial C5b-9 deposition levels compared to NHS. The remission samples showed normalized C5b-9 depositions, whether remission was reached with or without complement blockage by eculizumab. We also monitored the glomerular endothelial complement deposition of an aHUS patient with a hybrid complement factor H (CFH)/CFH-related 1 gene during follow-up. This patient had already chronic kidney failure and an ongoing deterioration of kidney function despite absence of markers indicating an aHUS flare. Increased C5b-9 depositions on ciGMVECs were observed in all samples obtained throughout different diseases phases, except for the samples with eculizumab levels above target. We then tested the samples on the patient's own ciGMVECs. The C5b-9 deposition pattern was comparable and these aHUS patient ciGMVECs also responded similar to NHS as control ciGMVECs. In conclusion, we demonstrate a robust and reliable model to adequately measure C5b-9-based complement deposition on human control and patient ciGMVECs. This model can be used to study the pathophysiological mechanisms of aHUS or other diseases associated with endothelial complement activation ex vivo.

Endothelial cell plasticity in kidney fibrosis and disease.

Renal endothelial cells demonstrate an impressive remodeling potential during angiogenic sprouting, vessel repair or while transitioning into mesenchymal cells. These different processes may play important roles in both renal disease progression or regeneration while underlying signaling pathways of different endothelial cell plasticity routes partly overlap. Angiogenesis contributes to wound healing after kidney injury and pharmaceutical modulation of angiogenesis may home a great therapeutic potential. Yet, it is not clear whether any differentiated endothelial cell can proliferate or whether regenerative processes are largely controlled by resident or circulating endothelial progenitor cells. In the glomerular compartment for example, a distinct endothelial progenitor cell population may remodel the glomerular endothelium after injury. Endothelial-to-mesenchymal transition (EndoMT) in the kidney is vastly documented and often associated with endothelial dysfunction, fibrosis, and kidney disease progression. Especially the role of EndoMT in renal fibrosis is controversial. Studies on EndoMT in vivo determined possible conclusions on the pathophysiological role of EndoMT in the kidney, but whether endothelial cells really contribute to kidney fibrosis and if not what other cellular and functional outcomes derive from EndoMT in kidney disease is unclear. Sequencing data, however, suggest no participation of endothelial cells in extracellular matrix deposition. Thus, more in-depth classification of cellular markers and the fate of EndoMT cells in the kidney is needed. In this review, we describe different signaling pathways of endothelial plasticity, outline methodological approaches and evidence for functional and structural implications of angiogenesis and EndoMT in the kidney, and eventually discuss controversial aspects in the literature.

Removal of the endothelial surface layer via hyaluronidase does not modulate monocyte and neutrophil interactions with the glomerular endothelium.

The endothelial surface layer (ESL), a layer of macromolecules on the surface of endothelial cells, can both impede and facilitate leukocyte recruitment. However, its role in monocyte and neutrophil recruitment in glomerular capillaries is unknown. We used multiphoton intravital microscopy to examine monocyte and neutrophil behavior in the glomerulus following ESL disruption with hyaluronidase. Constitutive retention and migration of monocytes and neutrophils within the glomerular microvasculature was unaltered by hyaluronidase. Consistent with this, inhibition of the hyaluronan-binding molecule CD44 also failed to modulate glomerular trafficking of these immune cells. To investigate the contribution of the ESL during acute inflammation, we induced glomerulonephritis via in situ immune complex deposition. This resulted in increases in glomerular retention of monocytes and neutrophils but did not induce marked reduction in the glomerular ESL. Furthermore, hyaluronidase treatment did not modify the prolonged retention of monocytes and neutrophils in the acutely inflamed glomerular microvasculature. These observations indicate that, despite evidence that the ESL has the capacity to inhibit leukocyte-endothelial cell interactions while also containing adhesive ligands for immune cells, neither of these functions modulate trafficking of monocytes and neutrophils in steady-state or acutely-inflamed glomeruli.

Translocation of outer membrane vesicles from enterohemorrhagic Escherichia coli O157 across the intestinal epithelial barrier.

Outer membrane vesicles (OMVs) carrying virulence factors of enterohemorrhagic Escherichia coli (EHEC) are assumed to play a role in the pathogenesis of life-threatening hemolytic uremic syndrome (HUS). However, it is unknown if and how OMVs, which are produced in the intestinal lumen, cross the intestinal epithelial barrier (IEB) to reach the renal glomerular endothelium, the major target in HUS. We investigated the ability of EHEC O157 OMVs to translocate across the IEB using a model of polarized Caco-2 cells grown on Transwell inserts and characterized important aspects of this process. Using unlabeled or fluorescently labeled OMVs, tests of the intestinal barrier integrity, inhibitors of endocytosis, cell viability assay, and microscopic techniques, we demonstrated that EHEC O157 OMVs translocated across the IEB. OMV translocation involved both paracellular and transcellular pathways and was significantly increased under simulated inflammatory conditions. In addition, translocation was not dependent on OMV-associated virulence factors and did not affect viability of intestinal epithelial cells. Importantly, translocation of EHEC O157 OMVs was confirmed in human colonoids thereby supporting physiological relevance of OMVs in the pathogenesis of HUS.

Determining ACE-2 Level and Some Relevant Biochemical Parameters and studying the effect of Gender in Iraqi Diabetic Patients with Glomeruli and Renal Tubules Fibrosis as Early Prediction Marker

Diabetic kidney disease is an illness of the glomerulus that interferes with the glomerular filtration barrier (GFB), which is worked to enable kidney to selective purification of water and solutes in addition to limiting the movement of large macromolecules such as albumin. In the glomerular endothelium, mesangial cells, foot cells, and the brush border of the proximal tubules, ACE-2 is expressed and that the kidneys represent the highest-expressing region of this enzyme. Thus, the current study aimed to evaluate ACE-2 level in this case compared to healthy condition. The study Conducted with 120 male and female ranging in age (30-65) years old. Ninety patients with type 2 diabetes subdivided into three groups on the basis of ACR criteria including normoalbuminuria, microalbuminuria, macroalbuminuria (30 patients for each group) and 30 healthy people served as the control group, all visited Baghdad Teaching Hospital / Medical City and Al-Yarmouk Teaching Hospital, at the period between December 2021 and May 2022. ACE-2 levels were determined using the ELISA technique. Urea results showed significant differences between diabetic nephropathy in patient and control group in female cases but no significant differences in male patients with diabetic nephropathy and control group. Similar results were obtained in K ion. Also the results revealed significant differences in Na ion, ACR, eGFR, Urea, FBS, creatinine between diabetic nephropathy groups and healthy group.ACE-2 represents a good marker for early prediction in diabetic nephropathy case. ROC data analysis support the importance of ACE-2 in diagnosis of the studied disease case.

Genetic susceptibility to diabetic kidney disease is linked to promoter variants of XOR.

The lifetime risk of kidney disease in people with diabetes is 10-30%, implicating genetic predisposition in the cause of diabetic kidney disease (DKD). Here we identify an expression quantitative trait loci (QTLs) in the cis-acting regulatory region of the xanthine dehydrogenase, or xanthine oxidoreductase (Xor), a binding site for C/EBPβ, to be associated with diabetes-induced podocyte loss in DKD in male mice. We examine mouse inbred strains that are susceptible (DBA/2J) and resistant (C57BL/6J) to DKD, as well as a panel of recombinant inbred BXD mice, to map QTLs. We also uncover promoter XOR orthologue variants in humans associated with high risk of DKD. We introduced the risk variant into the 5'-regulatory region of XOR in DKD-resistant mice, which resulted in increased Xor activity associated with podocyte depletion, albuminuria, oxidative stress and damage restricted to the glomerular endothelium, which increase further with type 1 diabetes, high-fat diet and ageing. Therefore, differential regulation of Xor contributes to phenotypic consequences with diabetes and ageing.

Coaxial cell printing of a human glomerular model: an in vitro glomerular filtration barrier and its pathophysiology

Much effort has been expended in emulating the kidney’s glomerular unit because of its limitless potential in the field of drug screening and nephrotoxicity testing in clinics. Herein, we fabricate a functional bilayer glomerular microvessel-on-a-chip that recapitulates the specific arrangement of the glomerular endothelial cell, podocyte layers, and the intervening glomerular basement membrane (GBM) in a single step. Our perfusable chip allows for the co-culture of monolayer glomerular endothelium and podocyte epithelium, which display mature functional markers of glomerular cells, and their proper interactions produce GBM proteins, which are the major components of the GBM in vivo. Furthermore, we test the selective permeability capacity, a representative hallmark function of the glomerular filtration barrier. Lastly, we evaluate the response of our glomerular model to Adriamycin- and hyperglycemia-induced injury to evaluate its applicability for drug screening and glomerular disease modeling.

Basic Research Protocol: Exome Sequencing in Adults With Loin Pain Hematuria Syndrome: A Pilot Study.

Loin pain hematuria syndrome (LPHS) is a poorly understood clinical syndrome characterized by hematuria and either unilateral or bilateral severe kidney pain in the absence of identifiable urological disease. Loin pain hematuria syndrome imposes a significant health and economic impact with a loss of productivity and quality of life in a young population. Owing to an incomplete understanding of its pathophysiology, treatment has been limited to nonspecific pain management. Nearly 60 years after its initial description, we are no further ahead in understanding the molecular pathways involved in LPHS. To outline the study design for exome sequencing in adults with LPHS and their families. In this single-center case series, 24 patients with LPHS and 2 additional first-degree family members per participant will be recruited. DNA extracted from venous blood samples will undergo exome sequencing on the Illumina NovaSeq 6000 System at 100× depth and will be assessed for pathogenic variants in genes associated with hematuria (number of genes in: glomerular endothelium [n = 10] and basement membrane [n = 8]), and pain pathways (number of genes in: pain transduction [n = 17], conduction [n = 8], synaptic transmission [n = 37], and modulation [n = 27]). We will further examine identified potentially pathogenic variants that co-segregate with LPHS features among affected families. This pilot study may identify new directions for an investigation into the molecular mechanisms underlying LPHS.

3D vascularised proximal tubules-on-a-multiplexed chip model for enhanced cell phenotypes.

Modelling proximal tubule physiology and pharmacology is essential to understand tubular biology and guide drug discovery. To date, multiple models have been developed; however, their relevance to human disease has yet to be evaluated. Here, we report a 3D vascularized proximal tubule-on-a-multiplexed chip (3DvasPT-MC) device composed of co-localized cylindrical conduits lined with confluent epithelium and endothelium, embedded within a permeable matrix, and independently addressed by a closed-loop perfusion system. Each multiplexed chip contains six 3DvasPT models. We performed RNA-seq and compared the transcriptomic profile of proximal tubule epithelial cells (PTECs) and human glomerular endothelial cells (HGECs) seeded in our 3D vasPT-MCs and on 2D transwell controls with and without a gelatin-fibrin coating. Our results reveal that the transcriptional profile of PTECs is highly dependent on both the matrix and flow, while HGECs exhibit greater phenotypic plasticity and are affected by the matrix, PTECs, and flow. PTECs grown on non-coated Transwells display an enrichment of inflammatory markers, including TNF-a, IL-6, and CXCL6, resembling damaged tubules. However, this inflammatory response is not observed for 3D proximal tubules, which exhibit expression of kidney signature genes, including drug and solute transporters, akin to native tubular tissue. Likewise, the transcriptome of HGEC vessels resembled that of sc-RNAseq from glomerular endothelium when seeded on this matrix and subjected to flow. Our 3D vascularized tubule on chip model has utility for both renal physiology and pharmacology.

ABCA1 deficiency-mediated glomerular cholesterol accumulation exacerbates glomerular endothelial injury and dysfunction in diabetic kidney disease

BackgroundHyperglycemia and dyslipidemia are two major characteristics of diabetes. In this study, the effects of glomerular cholesterol accumulation primarily due to ABCA1 deficiency on glomerular endothelial injury in diabetic kidney disease (DKD) and the possible mechanisms were investigated. MethodsThe effects of ABCA1 deficiency on glomerular lipid deposition and kidney injury were examined in a type 2 diabetic mouse model with ABCA1 deficiency in glomerular endothelial cells (DM-ABCA1−/− mice) and human renal glomerular endothelial cells (HRGECs) cultured in high glucose and high cholesterol conditions, which simulated type 2 diabetes in vitro. ResultsABCA1 deficiency in glomerular endothelial cells exacerbated renal lipid deposition and kidney injuries in type 2 diabetic mice and manifested as increased creatinine levels, more severe proteinuria, mesangial matrix expansion and fusion of foot processes, and more pronounced renal inflammatory injury and cell death. In HRGECs cultured under high glucose and high cholesterol conditions, ABCA1 deficiency increased the deposition of cellular cholesterol, contributed to inflammation and apoptosis, damaged the endothelial glycocalyx barrier, and induced endoplasmic reticulum stress (ERS). Conversely, ABCA1 overexpression enhancing cholesterol efflux or inhibition of ERS in vitro, significantly protected against glomerular endothelial injury stimulated by high glucose and high cholesterol. ConclusionsThese findings establish a pathogenic role of ABCA1 deficiency in glomerular endothelium injury and dysfunction and imply that ABCA1 may represent a potential effective therapeutic target for early diabetic kidney disease.

Interventional effects of activating SUR2B/Kir6.1-type KATP channels on renal cells injury and its mechanisms

Objective: To investigate the interventional effects of a new SUR2B/Kir6.1-type KATP Channel opener iptakalim on injury renal cells (the renal glomerular endothelial, mesangial and tubular epithelial cells) and its mechanisms. Methods: ①Experimental protocol: control: the cells were treated with with 0 mg/L uric acid for 24 h; model: the cells were treated with with 1 200 mg/L uric acid for 24 h; pretreatment with iptakalim: the cells were pretreated with 0.01,0.1,1,10,100 μmol/L iptakalim for 24 h prior to treatment with 1 200 mg/L uric acid for 24 h; pretreatment with glibenclamide: the cells were preincubated with/without 10 μmol/L glibenclamide for 1 h and then treated with 10 μmol/L iptakalim for 24 h followed by incubation with 1 200 mg/L uric acid for another 24 h. ②The cell viability was measured by MTT assay and flow cytometry; the protein expressions of Kir6.1 and SUR2B and nuclear translocation were detected by immunostaining; the protein expressions of Kir6.1 and SUR2B were determined by Western blot analysis; adhesion of mononuclear cells to endothelial cells were tested by fluorimetric assay; the content of MCP-1 was measured by enzyme linked-immunosorbent assay (ELISA). Results: The renal glomerular endothelial, mesangial and tubular epithelial cells were exposed to 1 200 mg/L uric acid for 24 h. Compared with the control group, 1 200 mg/L uric acid decreased the cell survival rates significantly (P＜0.01, P＜0.01, P＜0.01). Compared with the model group, pretreatment with 0.1, 1, 10, 100 μmol/L iptakalim could remarkably alleviate cellular damages of glomerular endothelium, mesangium cells induced by uric acid (P＜0.05, P＜0.01, P＜0.01, P＜0.01). The KATP channel blocker could clearly reduce survival rates of the renal glomerular endothelial, mesangial cells(P＜0.01) and markedly reverse the inhibitory effects of iptakalim on cell death (P＜0.05, P＜0.01), no obvious difference in comparison with the model group (P＞0.05). Compared with the model group, pretreatment with 10, 100 μmol/L iptakalim could notably attenuate cellular damages of tubular epithelial cells induced by uric acid (P＜0.05, P＜0.05). The KATP channel blocker could obviously damage the tubular epithelial cells (P＜0.01), no obvious difference in comparison with the model group (P＞0.05). Compared with control group, exposure of renal tubular epithelial, mesangial and glomerular endothelial cells to 1 200 mg/L uric acid for 24 h caused a significant increase in the protein expressions of Kir6.1 and SUR2B(P＜0.05). Compared with the model group, the overexpressions of Kir6.1 and SUR2B were suppressed in presence of iptakalim at a concentration of 10 μmol/L (P＜0.05). These decreases in the expressions of Kir6.1 and SUR2B were prevented by the KATP channel blocker, no obvious difference in comparison with the model group (P＞0.05). Compare with the control group, monocytic adhesion to renal glomerular endothelial cells was notably promoted by 1 200 mg/L uric acid for 24 h (P＜0.01). Pretreatment with 10 μmol/L iptakalim for 24 h significantly reduced the monocytic adhesion in comparison with the model group (P＜0.05). It was showed that the inhibitory effects of iptakalim were antagonized by the KATP channel blocker, no obvious difference in comparison with the model group (P＞0.05). After stimulating glomerular endothelial cells with 1 200 mg/L uric acid for 24 hours, the secretion of MCP-1 was significantly increased compared to the control group (P＜0.05). Compare with the model group, preincubation with 10 μmol/L iptakalim significantly decreased MCP-1 production (P＜0.05). KATP channel blocker suppressed the downregulation of MCP-1 protein synthesis induced by iptakalim. After stimulation with uric acid, translocation of NF-κB from cytoplasms to nuclei of renal glomerular endothelial cells were observed, while that of NF-κB was suppressed in presence of iptakalim at the concentration of 10 μmol/L. This inhibition of NF-κB translocation was clearly prevented by KATP channel blocker. Conclusion: These results suggests that a new SUR2B/Kir6.1-type KATP channel opener iptakalim plays interventional roles in renal cells damages caused by uirc acid and its mechanism is involved in activating KATPchannels .

Low-Dose X-Ray Increases Paracellular Permeability of Human Renal Glomerular Endothelial Cells.

Objective Glomerular endothelium functions as a filtration barrier of metabolites in the kidney. Although X-ray irradiation modulated the permeability of the vascular endothelium, the response of human renal glomerular endothelial cells (HRGECs) to low-dose X-ray irradiation has not been investigated. We evaluated the impacts of low-dose X-ray irradiation on HRGECs and revealed the underlying mechanism. Methods HRGECs were exposed to X-ray with doses of 0, 0.1, 0.5, 1.0, and 2.0 Gy. The proliferation, viability, and apoptosis of HRGECs were examined by MTT assay, trypan blue staining assay, and TUNEL staining, respectively. The paracellular permeability was assessed by paracellular permeability assay. The expression of VE-cadherin was investigated via immunofluorescence assay. Western blot and qRT-PCR detected the expression levels of VE-cadherin and CLDN5. Besides, the expression levels of pVE-cadherin (pY658), TGF-β, TGF-βRI, Src, p-Src, Smad2, p-Smad2, Smad3, p-Smad3, SNAIL, SLUG, and apoptosis-related proteins were tested by Western blot. Results The proliferation, viability, and apoptosis of HRGECs were not affected by low-dose (<2.0 Gy) X-ray irradiation. X-ray irradiation dose-dependently reduced the level of VE-cadherin, and VE-cadherin and CLDN5 levels were reduced with X-ray irradiation. The levels of pY658, p-Src, p-Smad2, and p-Smad3 were upregulated with the increase in X-ray dose. Besides, the paracellular permeability of HRGECs was increased by even low-dose (<2.0 Gy) X-ray irradiation. Therefore, low-dose X-ray irradiation reduced the cumulative content of VE-cadherin and increased the level of pY658 via activation of the TGF-β signaling pathway. Conclusion Even though low-dose X-ray exposure had no impact on proliferation, viability, and apoptosis of HRGECs, it increased the paracellular permeability by deterioration and downregulation of VE-cadherin through stimulating the TGF-β signaling pathway. This study built the framework for kidney response to low-dose irradiation exposure.

Add-On Cyclic Angiotensin-(1-7) with Cyclophosphamide Arrests Progressive Kidney Disease in Rats with ANCA Associated Glomerulonephritis.

Rapidly progressive crescentic glomerulonephritis associated with anti-neutrophil cytoplasmic antibodies (ANCA-GN) is a major cause of renal failure. Current immunosuppressive therapies are associated with severe side effects, intensifying the need for new therapeutic strategies. The activation of Mas receptor/Angiotensin-(1-7) axis exerted renoprotection in chronic kidney disease. Here, we investigated the effect of adding the lanthionine-stabilized cyclic form of angiotensin-1-7 [cAng-(1-7)] to cyclophosphamide in a rat model of ANCA-GN. At the onset of proteinuria, Wistar Kyoto rats with ANCA-GN received vehicle or a single bolus of cyclophosphamide, with or without daily cAng-(1-7). Treatment with cAng-(1-7) plus cyclophosphamide reduced proteinuria by 85% vs. vehicle, and by 60% vs. cyclophosphamide, and dramatically limited glomerular crescents to less than 10%. The addition of cAng-(1-7) to cyclophosphamide protected against glomerular inflammation and endothelial rarefaction and restored the normal distribution of parietal epithelial cells. Ultrastructural analysis revealed a preserved GBM, glomerular endothelium and podocyte structure, demonstrating that combination therapy provided an additional layer of renoprotection. This study demonstrates that adding cAng-(1-7) to a partially effective dose of cyclophosphamide arrests the progression of renal disease in rats with ANCA-GN, suggesting that cAng-(1-7) could be a novel clinical approach for sparing immunosuppressants.