ITGAM-mediated macrophages contribute to basement membrane damage in diabetic nephropathy and atherosclerosis.

BACKGROUND: Diabetic nephropathy (DN) and atherosclerosis (AS) are prevalent and severe complications associated with diabetes, exhibiting lesions in the basement membrane, an essential component found within the glomerulus, tubules, and arteries. These lesions contribute significantly to the progression of both diseases, however, the precise underlying mechanisms, as well as any potential shared pathogenic processes between them, remain elusive. METHODS: Our study analyzed transcriptomic profiles from DN and AS patients, sourced from the Gene Expression Omnibus database. A combination of integrated bioinformatics approaches and machine learning models were deployed to identify crucial genes connected to basement membrane lesions in both conditions. The role of integrin subunit alpha M (ITGAM) was further explored using immune infiltration analysis and genetic correlation studies. Single-cell sequencing analysis was employed to delineate the expression of ITGAM across different cell types within DN and AS tissues. RESULTS: Our analyses identified ITGAM as a key gene involved in basement membrane alterations and revealed its primary expression within macrophages in both DN and AS. ITGAM was significantly correlated with tissue immune infiltration within these diseases. Furthermore, the expression of genes encoding core components of the basement membrane was influenced by the expression level of ITGAM. CONCLUSION: Our findings suggest that macrophages may contribute to basement membrane lesions in DN and AS through the action of ITGAM. Moreover, therapeutic strategies that target ITGAM may offer potential avenues to mitigate basement membrane lesions in these two diabetes-related complications.

Acetyl-CoA synthetase 2 promotes diabetic renal tubular injury in mice by rewiring fatty acid metabolism through SIRT1/ChREBP pathway.

Diabetic nephropathy (DN) is characterized by chronic low-grade renal inflammatory responses, which greatly contribute to disease progression. Abnormal glucose metabolism disrupts renal lipid metabolism, leading to lipid accumulation, nephrotoxicity, and subsequent aseptic renal interstitial inflammation. In this study, we investigated the mechanisms underlying the renal inflammation in diabetes, driven by glucose-lipid metabolic rearrangement with a focus on the role of acetyl-CoA synthetase 2 (ACSS2) in lipid accumulation and renal tubular injury. Diabetic models were established in mice by the injection of streptozotocin and in human renal tubular epithelial HK-2 cells cultured under a high glucose (HG, 30 mmol/L) condition. We showed that the expression levels of ACSS2 were significantly increased in renal tubular epithelial cells (RTECs) from the diabetic mice and human diabetic kidney biopsy samples, and ACSS2 was co-localized with the pro-inflammatory cytokine IL-1ß in RTECs. Diabetic ACSS2-deficient mice exhibited reduced renal tubular injury and inflammatory responses. Similarly, ACSS2 knockdown or inhibition of ACSS2 by ACSS2i (10 µmol/L) in HK-2 cells significantly ameliorated HG-induced inflammation, mitochondrial stress, and fatty acid synthesis. Molecular docking revealed that ACSS2 interacted with Sirtuin 1 (SIRT1). In HG-treated HK-2 cells, we demonstrated that ACSS2 suppressed SIRT1 expression and activated fatty acid synthesis by modulating SIRT1-carbohydrate responsive element binding protein (ChREBP) activity, leading to mitochondrial oxidative stress and inflammation. We conclude that ACSS2 promotes mitochondrial oxidative stress and renal tubular inflammation in DN by regulating the SIRT1-ChREBP pathway. This highlights the potential therapeutic value of pharmacological inhibition of ACSS2 for alleviating renal inflammation and dysregulation of fatty acid metabolic homeostasis in DN. Metabolic inflammation in the renal region, driven by lipid metabolism disorder, is a key factor in renal injury in diabetic nephropathy (DN). Acetyl-CoA synthetase 2 (ACSS2) is abundantly expressed in renal tubular epithelial cells (RTECs) and highly upregulated in diabetic kidneys. Deleting ACSS2 reduces renal fatty acid accumulation and markers of renal tubular injury in diabetic mice. We demonstrate that ACSS2 deletion inhibits ChREBP-mediated fatty acid lipogenesis, mitochondrial oxidative stress, and inflammatory response in RTECs, which play a major role in the progression of diabetic renal tubular injury in the kidney. These findings support the potential use of ACSS2 inhibitors in treating patients with DN.

The ratio of neutrophils to lymphocytes effectively predicts clinical outcomes in idiopathic membranous nephropathy.

BACKGROUND: Systemic inflammatory indicators are important in the prognoses of various diseases. Such indicators, including the neutrophil-to-lymphocyte ratio (NLR), can be meaningful in predicting the clinical outcome in patients diagnosed with idiopathic membranous nephropathy (IMN). MATERIALS AND METHODS: 112 IMN patients diagnosed by renal biopsy were recruited retrospectively. The endpoint was defined as a combination of partial and complete remission. Statistical analysis determined the independent factors associated with clinical remission and the predictive utility of NLR. RESULTS: Within the 12-month follow-up period, 72 patients achieved clinical remission after treatment. Univariate analysis identified significant differences in serum albumin, estimated glomerular filtration rate (eGFR), proteinuria, neutrophil count, and NLR between the remission group and the non-remission group (all p < 0.05). Cox proportional hazards indicated that elevated eGFR (HR 1.022, 95% CI (1.009 - 1.035), p = 0.001), lower NLR (HR 0.345, 95% CI (0.237 - 0.501), p = 0.0001), and decreased proteinuria (HR 0.826, 95% CI (0.693 - 0.984), p = 0.032) were protective elements for remission. With an optimal cut-off value of 2.61, the pre-treatment NLR had an excellent ability to identify the remission (area under the curve (AUC), 0.785). Participants were separated into low- and high-NLR groups by using 2.61. Kaplan-Meier survival curves revealed significantly higher remission rates in the lower group (p < 0.0001). CONCLUSION: The NLR is an effective indicator for predicting clinical remission in patients with IMN.

Exosomal miR-125b-5p deriving from mesenchymal stem cells promotes tubular repair by suppression of p53 in ischemic acute kidney injury.

Mesenchymal stem cells-derived exosomes (MSC-exos) have attracted great interest as a cell-free therapy for acute kidney injury (AKI). However, the in vivo biodistribution of MSC-exos in ischemic AKI has not been established. The potential of MSC-exos in promoting tubular repair and the underlying mechanisms remain largely unknown. Methods: Transmission electron microscopy, nanoparticle tracking analysis, and western blotting were used to characterize the properties of human umbilical cord mesenchymal stem cells (hucMSCs) derived exosomes. The biodistribution of MSC-exos in murine ischemia/reperfusion (I/R) induced AKI was imaged by the IVIS spectrum imaging system. The therapeutic efficacy of MSC-exos was investigated in renal I/R injury. The cell cycle arrest, proliferation and apoptosis of tubular epithelial cells (TECs) were evaluated in vivo and in HK-2 cells. The exosomal miRNAs of MSC-exos were profiled by high-throughput miRNA sequencing. One of the most enriched miRNA in MSC-exos was knockdown by transfecting miRNA inhibitor to hucMSCs. Then we investigated whether this candidate miRNA was involved in MSC-exos-mediated tubular repair. Results:Ex vivo imaging showed that MSC-exos was efficiently homing to the ischemic kidney and predominantly accumulated in proximal tubules by virtue of the VLA-4 and LFA-1 on MSC-exos surface. MSC-exos alleviated murine ischemic AKI and decreased the renal tubules injury in a dose-dependent manner. Furthermore, MSC-exos significantly attenuated the cell cycle arrest and apoptosis of TECs both in vivo and in vitro. Mechanistically, miR-125b-5p, which was highly enriched in MSC-exos, repressed the protein expression of p53 in TECs, leading to not only the up-regulation of CDK1 and Cyclin B1 to rescue G2/M arrest, but also the modulation of Bcl-2 and Bax to inhibit TEC apoptosis. Finally, inhibiting miR-125b-5p could mitigate the protective effects of MSC-exos in I/R mice. Conclusion: MSC-exos exhibit preferential tropism to injured kidney and localize to proximal tubules in ischemic AKI. We demonstrate that MSC-exos ameliorate ischemic AKI and promote tubular repair by targeting the cell cycle arrest and apoptosis of TECs through miR-125b-5p/p53 pathway. This study provides a novel insight into the role of MSC-exos in renal tubule repair and highlights the potential of MSC-exos as a promising therapeutic strategy for AKI.

GPR43 deficiency protects against podocyte insulin resistance in diabetic nephropathy through the restoration of AMPKα activity.

Rationale: Albuminuria is an early clinical feature in the progression of diabetic nephropathy (DN). Podocyte insulin resistance is a main cause of podocyte injury, playing crucial roles by contributing to albuminuria in early DN. G protein-coupled receptor 43 (GPR43) is a metabolite sensor modulating the cell signalling pathways to maintain metabolic homeostasis. However, the roles of GPR43 in podocyte insulin resistance and its potential mechanisms in the development of DN are unclear. Methods: The experiments were conducted by using kidney tissues from biopsied DN patients, streptozotocin (STZ) induced diabetic mice with or without global GPR43 gene knockout, diabetic rats treated with broad-spectrum oral antibiotics or fecal microbiota transplantation, and cell culture model of podocytes. Renal pathological injuries were evaluated by periodic acid-schiff staining and transmission electron microscopy. The expression of GPR43 with other podocyte insulin resistance related molecules was checked by immunofluorescent staining, real-time PCR, and Western blotting. Serum acetate level was examined by gas chromatographic analysis. The distribution of gut microbiota was measured by 16S ribosomal DNA sequencing with faeces. Results: Our results demonstrated that GPR43 expression was increased in kidney samples of DN patients, diabetic animal models, and high glucose-stimulated podocytes. Interestingly, deletion of GPR43 alleviated albuminuria and renal injury in diabetic mice. Pharmacological inhibition and knockdown of GPR43 expression in podocytes increased insulin-induced Akt phosphorylation through the restoration of adenosine 5'-monophosphate-activated protein kinase α (AMPKα) activity. This effect was associated with the suppression of AMPKα activity through post-transcriptional phosphorylation via the protein kinase C-phospholipase C (PKC-PLC) pathway. Antibiotic treatment-mediated gut microbiota depletion, and faecal microbiota transplantation from the healthy donor controls substantially improved podocyte insulin sensitivity and attenuated glomerular injury in diabetic rats accompanied by the downregulation of the GPR43 expression and a decrease in the level of serum acetate. Conclusion: These findings suggested that dysbiosis of gut microbiota-modulated GPR43 activation contributed to albuminuria in DN, which could be mediated by podocyte insulin resistance through the inhibition of AMPKα activity.

Urinary levels of podocyte-derived microparticles are associated with the progression of chronic kidney disease.

BACKGROUND: Podocyte-derived microparticles (MPs) could be secreted from activated or apoptotic podocytes. An increased number of podocyte-derived MPs in the urine might reflect podocyte injury in renal diseases. This study aimed to observe the change of urinary podocyte-derived MP levels in patients with chronic kidney disease (CKD) and to further explore its correlation with the progression of CKD. METHODS: A prospective, longitudinal study was conducted in eighty patients with biopsy-proven CKD. Podocyte-derived MPs (annexin V and podocalyxin positive) were detected by flow cytometry. The number of urinary podocyte-derived MPs was analyzed to evaluate the association with biochemical measurements and pathological glomerulosclerosis assessment. Patients with idiopathic membranous nephropathy (IMN) were followed up after the six-month treatment of prednisone combined with tacrolimus to evaluate the association of urinary podocyte-derived MP levels and the remission of IMN. RESULTS: The CKD patients had higher urinary podocyte-derived MP levels compared with healthy controls (HCs). Baseline urinary levels of podocyte-derived MPs were positively correlated with 24-hour proteinuria, while were inversely correlated with the percentage of global glomerulosclerosis. The urinary podocyte-derived MPs levels had good discrimination for glomerulosclerosis [area under curve (AUC), 0.66]. The urinary podocyte-derived MPs levels in IMN patients were significantly decreased accompanied with the recovery of abnormal clinical parameters after six-month treatment. CONCLUSIONS: The urinary levels of podocyte-derived MPs were closely associated with podocyte injury and glomerulosclerosis, which could be useful for monitoring disease activity in CKD patients. Urinary podocyte-derived MPs might be a non-invasive biomarker for the evaluation of early CKD progression.

Bioinformatics-based discovery of the urinary BBOX1 mRNA as a potential biomarker of diabetic kidney disease.

BACKGROUND: Diabetic kidney disease (DKD) is the leading cause of end-stage kidney disease (ESKD) in the world. Emerging evidence has shown that urinary mRNAs may serve as early diagnostic and prognostic biomarkers of DKD. In this article, we aimed to first establish a novel bioinformatics-based methodology for analyzing the "urinary kidney-specific mRNAs" and verify their potential clinical utility in DKD. METHODS: To select candidate mRNAs, a total of 127 Affymetrix microarray datasets of diabetic kidney tissues and other tissues from humans were compiled and analyzed using an integrative bioinformatics approach. Then, the urinary expression of candidate mRNAs in stage 1 study (n = 82) was verified, and the one with best performance moved on to stage 2 study (n = 80) for validation. To avoid potential detection bias, a one-step Taqman PCR assay was developed for quantification of the interested mRNA in stage 2 study. Lastly, the in situ expression of the selected mRNA was further confirmed using fluorescent in situ hybridization (FISH) assay and bioinformatics analysis. RESULTS: Our bioinformatics analysis identified sixteen mRNAs as candidates, of which urinary BBOX1 (uBBOX1) levels were significantly upregulated in the urine of patients with DKD. The expression of uBBOX1 was also increased in normoalbuminuric diabetes subjects, while remained unchanged in patients with urinary tract infection or bladder cancer. Besides, uBBOX1 levels correlated with glycemic control, albuminuria and urinary tubular injury marker levels. Similar results were obtained in stage 2 study. FISH assay further demonstrated that BBOX1 mRNA was predominantly located in renal tubular epithelial cells, while its expression in podocytes and urothelium was weak. Further bioinformatics analysis also suggested that tubular BBOX1 mRNA expression was quite stable in various types of kidney diseases. CONCLUSIONS: Our study provided a novel methodology to identify and analyze urinary kidney-specific mRNAs. uBBOX1 might serve as a promising biomarker of DKD. The performance of the selected urinary mRNAs in monitoring disease progression needs further validation.

Artemisinin attenuates tubulointerstitial inflammation and fibrosis via the NF-κB/NLRP3 pathway in rats with 5/6 subtotal nephrectomy.

Artemisinin (Art) is isolated from Artemisia annua L. and known as the most effective antimalaria drugs. Previous studies demonstrated that it could exert an immune-regulatory effect on autoimmune diseases. In this study, we first investigated its potential role in tubulointerstitial inflammation and fibrosis in rats with 5/6 nephrectomy. Subtotal nephrectomized (SNx) rats were orally administered Art (100 mg·kg -1 ·d - 1) for 16 weeks. Blood and urine samples were collected for biochemical examination. Kidney tissues were collected for immunohistochemistry and Western blot analyses. Ang II-induced injury of the human kidney 2 (HK-2) cells was used for in vitro study. It was shown that Art could significantly attenuate the renal function decline in SNx rats compared with control. More importantly, Art treatment significantly reduced the tubulointerstitial inflammation and fibrosis, as demonstrated by the evaluation of renal pathology. Furthermore, Art inhibited the activation of NLRP3 inflammasome and NF-κB in the kidneys. In in vitro study, Art pretreatment could significantly prevent the activation of NLRP3 inflammasome and NF-κB in Ang II-treated HK-2 cells, while BAY11-7082 (an inhibitor of NF-κB) significantly inhibited Ang II-induced NLRP3 inflammasome activation. This study suggested that Art could provide renoprotective role by attenuating the tubulointerstitial inflammation and fibrosis in SNx rats by downregulating the NF-κB/NLRP3 signaling pathway.

Lipoprotein(a) accelerated the progression of atherosclerosis in patients with end-stage renal disease.

BACKGROUND: Increased plasma level of lipoprotein(a) (Lpa) is a risk factor of cardiovascular diseases. This study aimed to explore the role of Lpa in the progression of atherosclerosis in patients with end-stage renal disease (ESRD) and to investigate whether its potential mechanism is mediated by CXC chemokine ligand 16 (CXCL16) and low-density lipoprotein receptor (LDLr). METHODS: This is a retrospective clinical study. From January 2015 to April 2016, forty-six ESRD patients from Danyang First People's Hospital were investigated. The patients were grouped according to their plasma Lpa levels: control group (Lpa < 300 mg/l, n = 23) and high Lpa group (Lpa ≥ 300 mg/l, n = 23). ESRD Patients with acute infective diseases, cancer, and/or chronic active hepatitis were excluded. Biochemical indexes and lipid profiles of the patients were measured. Surgically removed tissues from the radial arteries of ESRD patients receiving arteriovenostomy were used for the preliminary evaluation of atherosclerosis. Haematoxylin-eosin (HE) and filipin staining were used to observe foam cell formation. Protein expression levels of Lpa, CXCL16, and LDLr were detected by immunohistochemistry staining and immunofluorescent staining. RESULTS: There was more foam cell formation and cholesterol accumulation in the radial arteries of the high Lpa group than in those of the control group. Furthermore, the expression levels of Lpa, CXCL16, and LDLr were significantly increased in the radial arteries of the high Lpa group. Correlation analyses showed that the protein expression levels of Lpa (r = 0.72, P < 0.01), LDLr (r = 0.54, P < 0.01), and CXCL16 (r = 0.6, P < 0.01) in the radial arteries of ESRD patients were positively correlated with the plasma Lpa levels. Further analyses showed that the co-expression of Lpa with LDLr or CXCL16 was increased in the high Lpa group. CONCLUSIONS: High plasma Lpa levels accelerated the progression of atherosclerosis in ESRD through inducing Lpa accumulation in the arteries, which was associated with LDLr and CXCL16. These two lipoproteins could both be major lipoprotein components that regulate the entry of Lpa into arterial cells.

Activation of the CXCL16/CXCR6 pathway promotes lipid deposition in fatty livers of apolipoprotein E knockout mice and HepG2 cells.

Non-alcoholic fatty liver disease (NAFLD), characterised by early lipid accumulation and subsequent inflammation in the liver, is becoming a worldwide challenge due to its increasing prevalence in developing and developed countries. This study aimed to investigate the role of CXC chemokine ligand 16 (CXCL16) and its receptor CXC chemokine receptor 6 (CXCR6) in NAFLD under inflammation. We used IL-1ß stimulation in human hepatoblastoma cell line (HepG2) for in vitro studies and casein injection in apolipoprotein E knockout mice in vivo to induce inflammatory stress. The effects of inflammation on cholesterol accumulation were examined by histochemical staining and a quantitative intracellular cholesterol assay. The gene and protein expression of molecules involved in CXCL16/CXCR6 pathway and extracellular matrix (ECM) were examined by real-time polymerase chain reaction (PCR) and Western blotting. The fluorescence intensity of reactive oxygen species (ROS) was assessed by flow cytometry. Results showed that significantly elevated levels of serum amyloid protein A in casein-injected mice confirmed the successful induction of inflamed NAFLD model. Inflammation significantly increased lipid accumulation in livers compared with the high-fat diet group and the controls. Furthermore, inflammation increased the expression of CXCL16, CXCR6, and adisintegrin and metalloproteinase domain-containing protein 10 (ADAM10) in livers, accompanied with increased ECM expression and ROS production. These effects were further confirmed by in vitro studies. Interestingly, CXCL16 gene knockdown in HepG2 cells induced by CXCL16 siRNA resulted in decreased lipid accumulation, ECM excretion, and ROS production. These findings demonstrated that inflammation-mediated activation of CXCL16/CXCR6 is involved in the progression of NAFLD.

CCN3 suppresses TGF-ß1-induced extracellular matrix accumulation in human mesangial cells in vitro.

Glomerular sclerosis is characterized by mesangial cell proliferation and progressive extracellular matrix (ECM) accumulation. CCN3 belongs to the CCN family of matrix proteins; increasing evidence suggests that CCN3 is an endogenous negative regulator of the ECM and fibrosis. However, the exact role of CCN3 in the accumulation of ECM remains unknown. The aim of the present study was to investigate the effects of CCN3 on TGF-ß1-induced production of ECM in human mesangial cells (HMCs) in vitro. Treatment with TGF-ß1 (0.5-2.0 ng/mL) suppressed the mRNA and protein expression of CCN3 in HMCs in dose- and time-dependent manners. Furthermore, treatment with TGF-ß1 significantly increased the expression of the two markers of renal fibrosis, fibronectin (FN) and type I collagen (COLI), in HMCs. Moreover, treatment with TGF-ß1 significantly decreased the expression of metalloproteinase (MMP)-2 and MMP-9, and markedly increased the expression of tissue inhibitor of metalloproteinase (TIMP)-1 in HMCs. Pretreatment of HMCs with exogenous CCN3 (5-500 ng/mL) or overexpression of CCN3 significantly attenuated TGF-ß1-induced changes in FN, COLI, MMP-2, MMP-9 and TIMP-1 in HMCs. These results suggest that CCN3 suppresses TGF-ß1-induced accumulation of ECM in HMCs. CCN3 may have potential as a novel therapeutic target for alleviating glomerulosclerosis.

The Emerging Roles of Microparticles in Diabetic Nephropathy.

Microparticles (MPs) are a type of extracellular vesicles (EVs) shed from the outward budding of plasma membranes during cell apoptosis and/or activation. These microsized particles then release specific contents (e.g., lipids, proteins, microRNAs) which are active participants in a wide range of both physiological and pathological processes at the molecular level, e.g., coagulation and angiogenesis, inflammation, immune responses. Research limitations, such as confusing nomenclature and overlapping classification, have impeded our comprehension of these tiny molecules. Diabetic nephropathy (DN) is currently the greatest contributor to end-stage renal diseases (ESRD) worldwide, and its public health impact will continue to grow due to the persistent increase in the prevalence of diabetes mellitus (DM). MPs have recently been considered as potentially involved in DN onset and progression, and this review juxtaposes some of the research updates about the possible mechanisms from several relevant aspects and insights into the therapeutic perspectives of MPs in clinical management and pharmacological treatment of DN patients.

Feature selection and classification of urinary mRNA microarray data by iterative random forest to diagnose renal fibrosis: a two-stage study.

Renal fibrosis is a common pathological pathway of progressive chronic kidney disease (CKD). However, kidney function parameters are suboptimal for detecting early fibrosis, and therefore, novel biomarkers are urgently needed. We designed a 2-stage study and constructed a targeted microarray to detect urinary mRNAs of CKD patients with renal biopsy and healthy participants. We analysed the microarray data by an iterative random forest method to select candidate biomarkers and produce a more accurate classifier of renal fibrosis. Seventy-six and 49 participants were enrolled into stage I and stage II studies, respectively. By the iterative random forest method, we identified a four-mRNA signature in urinary sediment, including TGFß1, MMP9, TIMP2, and vimentin, as important features of tubulointerstitial fibrosis (TIF). All four mRNAs significantly correlated with TIF scores and discriminated TIF with high sensitivity, which was further validated in the stage-II study. The combined classifiers showed excellent sensitivity and outperformed serum creatinine and estimated glomerular filtration rate measurements in diagnosing TIF. Another four mRNAs significantly correlated with glomerulosclerosis. These findings showed that urinary mRNAs can serve as sensitive biomarkers of renal fibrosis, and the random forest classifier containing urinary mRNAs showed favourable performance in diagnosing early renal fibrosis.

Activation of the CXCL16/CXCR6 Pathway by Inflammation Contributes to Atherosclerosis in Patients with End-stage Renal Disease.

Background: Chronic inflammation plays a critical role in the progression of atherosclerosis (AS). This study aimed to determine the effects of the CXC chemokine ligand 16 (CXCL16)/CXC chemokine receptor 6 (CXCR6) pathway on cholesterol accumulation in the radial arteries of end-stage renal disease (ESRD) patients with concomitant microinflammation and to further investigate the potential effects of the purinergic receptor P2X ligand-gated ion channel 7 (P2X7R). Methods: Forty-three ESRD patients were divided into the control group (n=17) and the inflamed group (n=26) based on plasma C-reactive protein (CRP) levels. Biochemical indexes and lipid profiles of the patients were determined. Surgically removed tissues from the radial arteries of patients receiving arteriovenostomy were used for preliminary evaluation of AS. Haematoxylin-eosin (HE) and Filipin staining were performed to assess foam cell formation. CXCL16/CXCR6 pathway-related protein expression, P2X7R protein expression and the expression of monocyte chemotactic protein-1 (MCP-1), tumour necrosis factor-α (TNF-α), and CD68 were detected by immunohistochemical and immunofluorescence staining. Results: Inflammation increased both MCP-1 and TNF-α expression and macrophage infiltration in radial arteries. Additionally, foam cell formation significantly increased in the radial arteries of the inflamed group compared to that of the controls. Further analysis showed that protein expression of CXCL16, CXCR6, disintegrin and metalloproteinase-10 (ADAM10) in the radial arteries of the inflamed group was significantly increased. Furthermore, CXCL16 expression was positively correlated with P2X7R expression in the radial arteries of ESRD patients. Conclusions: Inflammation contributed to foam cell formation in the radial arteries of ESRD patients via activation of the CXCL16/CXCR6 pathway, which may be regulated by P2X7R.

TLR2-MyD88-NF-κB pathway is involved in tubulointerstitial inflammation caused by proteinuria.

Proteinuria is an important risk factor for chronic kidney diseases (CKD). Several studies have suggested that proteinuria initiates tubulointerstitial inflammation, while the mechanisms have not been fully understood. In this study, we hypothesized whether the activation of the TLR2-MyD88-NF-κB pathway is involved in tubulointerstitial inflammation induced by proteinuria. We observed expression of TLR2, MyD88, NF-κB, as well as TNF-α and IL-6 detected by immunohistostaining, Western blotting and real-time PCR in albumin-overloaded (AO) nephropathy rats. In vitro, we observed these markers in HK-2 cells stimulated by albumin. We used TLR2 siRNA or the NF-κB inhibitor BAY 11-7082 to observe the influence of TNF-α and IL-6 expression caused by albumin overload. Finally, we studied these markers in non-IgA mesangioproliferative glomerulonephritis (MsPGN) patients with different levels of proteinuria. It was demonstrated that expression of TLR2, MyD88 and NF-κB were significantly increased in AO rats and in non-IgA MsPGN patients with high levels of proteinuria, and TNF-α and IL-6 expressions were increased after NF-κB activation. Furthermore, TNF-α and IL-6 expression was positively correlated with the level of proteinuria. Albumin-overload induced TNF-α and IL-6 secretions by the TLR2-MyD88-NF-κB pathway activation, which could be attenuated by the TLR2 siRNA or BAY 11-7082 in HK-2 cells. In summary, we demonstrated that proteinuria may exhibit an endogenous danger-associated molecular pattern (DAMP) that induces tubulointerstitial inflammation via the TLR2-MyD88-NF-κB pathway activation.

Activation of mTORC1 disrupted LDL receptor pathway: a potential new mechanism for the progression of non-alcoholic fatty liver disease.

Our previous studies demonstrated that inflammation exacerbates the progression of non-alcoholic fatty liver disease (NAFLD) by disrupting cholesterol homeostasis. This study aimed to investigate the role of mammalian target of rapamycin complex 1 (mTORC1) in NAFLD under conditions of inflammation. Chronic inflammation was induced by using subcutaneous injections of 10% casein in apolipoprotein E knockout (ApoE KO) mice in vivo and interleukin-1ß stimulation of the HepG2 hepatoblastoma cell line in vitro. Results demonstrated that inflammation increased lipid accumulation in HepG2 cells and in livers of apolipoprotein E knockout mice. These effects were correlated with an increase in low density lipoprotein receptor (LDLR) gene transcription, which was mediated through the up-regulation of sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP), SREBP-2, and through enhanced translocation of the SCAP/SREBP-2 complex from endoplasmic reticulum (ER) to Golgi. In addition, our data indicated that inflammation down-regulated the expression of proprotein convertase subtilisin kexin 9 (PCSK9) and prevented the degradation of LDLR protein via posttranscriptional mechanisms. Further analysis showed that inflammation increased the protein phosphorylation of mTOR, eukaryotic initiation factor 4E-binding protein 1, and p70 S6 kinase. Interestingly, blocking mTORC1 activity inhibited the translocation of SCAP/SREBP-2 complex from the ER to the Golgi and decreased the expression of LDLR, SCAP, and SREBP-2. These effects were accompanied by an increase in the expression of PCSK9 and accelerated LDLR degradation. Our findings demonstrated that increased mTORC1 activity exacerbated the progression of NAFLD by disrupting LDLR expression via transcriptional and posttranscriptional mechanisms.

FTY720 inhibits tubulointerstitial inflammation in albumin overload-induced nephropathy of rats via the Sphk1 pathway.

AIM: FTY720, a new immunomodulatory drug with low cytotoxicity, is currently used to treat multiple sclerosis. In this study, we investigated the effects of FTY720 on inflammatory cell infiltration in albumin overload-induced nephropathy of rats. METHODS: Male Wistar rats were subjected to right-side nephrectomy and divided into 3 groups. One week after the surgery, albumin overload (AO) group was treated with BSA (5 g·kg(-1)·d(-1), ip) for 9 weeks; AO+FTY720 group was given BSA (5 g·kg(-1)·d(-1), ip) plus FTY720 (0.5 g·kg(-1)·d(-1), ip) for 9 weeks; and control group received daily ip injection of equivalent volume of saline. All rats were killed 9 weeks after nephrectomy. RESULTS: AO rats exhibited gradually increased urinary protein excretion accompanied by elevated urinary N-acetyl-ß-O-glucosaminidase activity, and both reached their peak values at week 7. Furthermore, AO significantly increased lymphocytes and monocytes in circulation and the inflammatory cells recruited to tubulointerstitium, and the expression of inflammatory cytokines MCP-1, TNF-α and IL-6, as well as sphingosine 1-phosphate (S1P) receptors S1pr1 and S1pr3, and S1P-synthesizing enzyme sphingosine kinase 1 (Sphk1) in the kidney. Concomitant administration of FTY720 significantly attenuated all the AO-induced pathological changes. CONCLUSION: FTY720 alleviates tubulointerstitium inflammation in an AO rat model of nephropathy via down-regulation of the Sphk1 pathway.

Activation of the Nlrp3 inflammasome by mitochondrial reactive oxygen species: a novel mechanism of albumin-induced tubulointerstitial inflammation.

Albuminuria is not only an important marker of chronic kidney disease but also a crucial contributor to tubulointerstitial inflammation (TIF). In this study, we determined whether activation of the Nlrp3 inflammasome is involved in albuminuria induced-TIF and the underlying mechanisms of inflammasome activation by mitochondrial reactive oxygen species (mROS). We established an albumin-overload induced rat nephropathy model characterised by albuminuria, renal infiltration of inflammatory cells, tubular dilation and atrophy. The renal expression levels of the Nlrp3 inflammasome, IL-1ß and IL-18 were significantly increased in this animal model. In vitro, albumin time- and dose-dependently increased the expression levels of the Nlrp3 inflammasome, IL-1ß and IL18. Moreover, the silencing of the Nlrp3 gene or the use of the caspase-1 inhibitor Z-VAD-fmk significantly attenuated the albumin-induced increase in IL-1ß and IL-18 expression in HK2 cells. In addition, mROS generation was elevated by albumin stimulation, whereas the ROS scavenger N-acetyl-l-cysteine (NAC) inhibited Nlrp3 expression and the release of IL-1ß and IL-18. In kidney biopsy specimens obtained from patients with IgA nephropathy, Nlrp3 expression was localised to the proximal tubular epithelial cells, and this result is closely correlated with the extent of proteinuria and TIF. In summary, this study demonstrates that albuminuria may serve as an endogenous danger-associated molecular pattern (DAMP) that stimulates TIF via the mROS-mediated activation of the cytoplasmic Nlrp3 inflammasome.

Enalapril inhibits tubulointerstitial inflammation and NLRP3 inflammasome expression in BSA-overload nephropathy of rats.

AIM: Proteinuria is not only a common marker of renal disease, but also involved in renal tubulointerstitial inflammation and fibrosis. The aim of this study was to investigate the mechanisms underlying the protective effects of enalapril, an ACEI, against nephropathy in rats. METHODS: Wistar rats underwent unilateral right nephrectomy, and then were treated with BSA (5 g·kg(-1)·d(-1), ip), or BSA plus enalapril (0.5 g·kg(-1)·d(-1), po) for 9 weeks. The renal lesions were evaluated using histology and immunohistochemistry. The expression of NLRP3, caspase-1, IL-1ß and IL-18 was analyzed using immunohistochemistry, RT-PCR and Western blot. RESULTS: BSA-overload resulted in severe proteinuria, which peaked at week 7, and interstitial inflammation with prominent infiltration of CD68(+) cells (macrophages) and CD3(+) cells (T lymphocytes), particularly of CD20(+) cells (B lymphocytes). BSA-overload markedly increased the expression of NLRP3, caspase-1, IL-1ß and IL-18 in the proximal tubular epithelial cells, and in inflammatory cells as well. Furthermore, the expression of IL-1ß or IL-18 was significantly correlated with proteinuria (IL-1ß: r=0.757; IL-18: r=0.834). These abnormalities in BSA-overload rats were significantly attenuated by concurrent administration of enalapril. CONCLUSION: Enalapril exerts protective effects against BSA-overload nephropathy in rats via suppressing NLRP3 inflammasome expression and tubulointerstitial inflammation.

Activation of mTOR contributes to foam cell formation in the radial arteries of patients with end-stage renal disease.

BACKGROUND: Our previous in-vivo and in-vitro studies demonstrated that inflammation accelerated the progression of atherosclerosis via the dysregulation of the low-density lipoprotein receptor (LDLr) pathway. The current study aimed to investigate the effects and their underlying mechanisms of inflammation on lipid accumulation in the radial arteries of endstage renal disease (ESRD) patients with arteriovenostomy. METHODS: 30 ESRD patients with arteriovenostomy were included. The patients were divided into two groups based on their plasma levels of C-reactive protein: a control (n = 16) and an inflamed group (n = 14). The expression of tumor necrosis factor-alpha (TNF-alpha) and monocyte chemotactic protein-1 of the radial arteries were increased in the inflamed group. Foam cell formation and lipid droplet accumulation were examined by hematoxylin and eosin (H & E) and Oil Red O staining. Intracellular cholesterol trafficking-related proteins were examined by immunohistochemistry and immunofluorescent staining. RESULTS: There was significant lipid accumulation in the radial arteries of the inflamed group compared with the control. Further analysis demonstrated that this accumulation was correlated with the increased protein expression of LDLr, sterol regulatory element-binding protein-2 (SREBP-2), and SREBP cleavageactivating protein (SCAP). Confocal microscopy showed that inflammation enhanced the translocation of SCAP escorting SREBP-2 from the endoplasmic reticulum to the Golgi, thereby activating LDLr gene transcription. Interestingly, upregulated LDLr expression was positively associated with the increased protein expression of mammalian target of rapamycin (mTOR), which had enhanced coexpression with SREBP-2. This finding suggests that the activation of mTOR may be involved in LDLr pathway disruption through the upregulation of SREBP-2 expression. CONCLUSION: Inflammation contributed to foam cell formation in the radial arteries of ESRD patients via the dysregulation of the LDLr pathway, which could be modulated by the activation of the mTOR pathway.