Search

Background: Macrophages play an important role in renal ischemia reperfusion injury, but the functional changes of macrophages under hypoxia/reoxygenation and the related mechanism are unclear and need to be further clarified. Methods: The effects of hypoxia/reoxygenation on functional characteristics of RAW264.7 macrophages were analyzed through the protein expression detection of pro-inflammatory factors TNF-α and CD80, anti-inflammatory factors ARG-1 and CD206. The functional implications of C-X3-C motif chemokine receptor 1(CX3CR1) down-regulation in hypoxic macrophages were explored using small interfering RNA technology. Significance was assessed by the parametric t-test or nonparametric Mann–Whitney test for two group comparisons, and a one-way ANOVA or the Kruskal–Wallis test for multiple group comparisons. Results: Hypoxia/reoxygenation significantly increased the protein expression of M1-related pro-inflammatory factors TNF-α, CD80 and chemokine C-X3-C motif chemokine ligand 1 (CX3CL1)/CX3CR1 and inhibited the protein expression of M2-related anti-inflammatory factors ARG-1 and CD206 in a time-dependent manner in RAW264.7 cells. However, the silencing of CX3CR1 in RAW264.7 cells using specific CX3CR1-siRNA, significantly attenuated the increase in protein expression of TNF-α (P

Kidney transplantation in mice is a complicated and challenging surgery procedure. There are very few publications demonstrating the key steps of this operation. Therefore, this article introduces the technique and points out the surgical caveats associated with this operation. In addition, important modifications in comparison to the conventional procedure are demonstrated. Firstly, a patch of the abdominal aorta is cut and prepared so that the proximal bifurcations of the renal artery, including the ureteral artery are transected together with the donor kidney en bloc. This reduces the risk of a ureter necrosis and avoids the development of a urinary tract occlusion. Secondly, a new method of the vascular anastomosis is demonstrated that allows the operator to flexibly increase or decrease the size of the anastomosis after renal transplant reperfusion has already been initiated. This avoids the development of vessel strictures and intraabdominal bleeding. Thirdly, a technique that enables the anastomosis of the delicate donor ureter and the recipient bladder that does not cause a trauma is shown. Adopting this protocol can shorten the operation time and reduces the damage to the recipient's bladder, thereby significantly increasing the operation success rate for the recipient mice.

Nephrotoxic drugs can cause acute kidney injury (AKI) and analgesic nephropathy. Diclofenac is potentially nephrotoxic and frequently prescribed for pain control. In this study, we investigated the effects of single and repetitive oral doses of diclofenac in the setting of pre-existing subclinical AKI on the further course of AKI and on long-term renal consequences. Unilateral renal ischemia–reperfusion injury (IRI) for 15 min was performed in male CD1 mice to induce subclinical AKI. Immediately after surgery, single oral doses (100 mg or 200 mg) of diclofenac were administered. In a separate experimental series, repetitive treatment with 100 mg diclofenac over three days was performed after IRI and sham surgery. Renal morphology and pro-fibrotic markers were investigated 24 h and two weeks after the single dose and three days after the repetitive dose of diclofenac treatment using histology, immunofluorescence, and qPCR. Renal function was studied in a bilateral renal IRI model. A single oral dose of 200 mg, but not 100 mg, of diclofenac after IRI aggravated acute tubular injury after 24 h and caused interstitial fibrosis and tubular atrophy two weeks later. Repetitive treatment with 100 mg diclofenac over three days aggravated renal injury and caused upregulation of the pro-fibrotic marker fibronectin in the setting of subclinical AKI, but not in sham control kidneys. In conclusion, diclofenac aggravated renal injury in pre-existing subclinical AKI in a dose and time-dependent manner and already a single dose can cause progression to chronic kidney disease (CKD) in this model.

BackgroundAcute rejection (AR) in kidney transplantation is an established risk factor that reduces the survival rate of allografts. Despite standard immunosuppression, molecules with regulatory control in the immune pathway of AR can be used as important targets for therapeutic operations to prevent rejection.MethodsWe downloaded the microarray data of 15 AR patients and 37 non-acute rejection (NAR) patients from Gene Expression Omnibus (GEO). Gene network was constructed, and genes were classified into different modules using weighted gene co-expression network analysis (WGCNA). Kyoto Encyclopedia of Genes and Genomes (KEGG) and Cytoscape were applied for the hub genes in the most related module to AR. Different cell types were explored by xCell online database and single-cell RNA sequencing. We also validated the SLAMF8 and TLR4 levels in Raw264.7 and human kidney tissues of TCMR.ResultsA total of 1,561 differentially expressed genes were filtered. WGCNA was constructed, and genes were classified into 12 modules. Among them, the green module was most closely associated with AR. These genes were significantly enriched in 20 pathway terms, such as cytokine–cytokine receptor interaction, chemokine signaling pathway, and other important regulatory processes. Intersection with GS > 0.4, MM > 0.9, the top 10 MCC values and DEGs in the green module, and six hub genes (DOCK2, NCKAP1L, IL2RG, SLAMF8, CD180, and PTPRE) were identified. Their expression levels were all confirmed to be significantly elevated in AR patients in GEO, Nephroseq, and quantitative real-time PCR (qRT-PCR). Single-cell RNA sequencing showed that AR patient had a higher percentage of native T, CD1C+_B DC, NKT, NK, and monocytes in peripheral blood mononuclear cells (PBMCs). Xcell enrichment scores of 20 cell types were significantly different (pConclusionThis study demonstrates six hub genes and functionally enriched pathways related to AR. SLAMF8 is involved in the M1 macrophages via TLR4, which contributed to AR process.

Acute rejection (AR) is closely associated with renal allograft dysfunction. Here, we utilised RNA sequencing (RNA-Seq) and bioinformatic methods to characterise the peripheral blood mononuclear cells (PBMCs) of patients with acute renal allograft rejection. Pretransplant blood samples were collected from 32 kidney allograft donors and 42 corresponding recipients with biopsies classified as T cell-mediated rejection (TCMR, n = 18), antibody-mediated rejection (ABMR, n = 5), and normal/non-specific changes (non-AR, n = 19). The patients with TCMR and ABMR were assigned to the AR group, and the patients with normal/non-specific changes (n = 19) were assigned to the non-AR group. We analysed RNA-Seq data for identifying differentially expressed genes (DEGs), and then gene ontology (GO) analysis, Reactome, and ingenuity pathway analysis (IPA), protein—protein interaction (PPI) network, and cell-type enrichment analysis were utilised for bioinformatics analysis. We identified DEGs in the PBMCs of the non-AR group when compared with the AR, ABMR, and TCMR groups. Pathway and GO analysis showed significant inflammatory responses, complement activation, interleukin-10 (IL-10) signalling pathways, classical antibody-mediated complement activation pathways, etc., which were significantly enriched in the DEGs. PPI analysis showed that IL-10, VEGFA, CXCL8, MMP9, and several histone-related genes were the hub genes with the highest degree scores. Moreover, IPA analysis showed that several proinflammatory pathways were upregulated, whereas antiinflammatory pathways were downregulated. The combination of NFSF14+TANK+ANKRD 33 B +HSPA1B was able to discriminate between AR and non-AR with an AUC of 92.3% (95% CI 82.8–100). Characterisation of PBMCs by RNA-Seq and bioinformatics analysis demonstrated gene signatures and biological pathways associated with AR. Our study may provide the foundation for the discovery of biomarkers and an in-depth understanding of acute renal allograft rejection.

Recent reports demonstrate that SARS-CoV-2 utilizes cell surface heparan sulfate as an attachment factor to facilitate the initial interaction with host cells. Heparan sulfate interacts with the receptor binding domain of SARS-CoV-2 spike glycoprotein, and blocking this interaction can decrease cell infection. We and others reported recently that the family of compounds of 2,5-dihydroxyphenylic acid interferes with the binding of the positively charged groove in growth factor molecules to negatively charged cell surface heparan sulfate. We hypothesized that Calcium Dobesilate (CaD)—calcium salt of 2,5-dihydroxyphenylic acid—may also interfere with the binding of SARS-CoV-2 spike protein to heparan sulfate. Using lentiviral SARS-CoV-2 spike protein pseudotyped particles we show that CaD could significantly reduce pseudovirus uptake into endothelial cells. On the contrary, CaD did not affect cell infection with VSVG-expressing lentivirus. CaD could also prevent retention of SARS-CoV-2 spike protein in ex vivo perfused mouse kidney. Using microfluidic culture of endothelial cells under flow, we show that CaD prevents spike protein interaction with heparan sulfate glycocalyx. Since CaD has no adverse side effects and is approved in humans for other medical indications, our findings can rapidly translate into clinical studies.

The endothelial glycocalyx and its regulated shedding are important to vascular health. Endo-β-D-glucuronidase heparanase-1 (HPSE1) is the only enzyme that can shed heparan sulfate. However, the mechanisms are not well understood. We show that HPSE1 activity aggravated Toll-like receptor 4 (TLR4)-mediated response of endothelial cells to LPS. On the contrary, overexpression of its endogenous inhibitor, heparanase-2 (HPSE2) was protective. The microfluidic chip flow model confirmed that HPSE2 prevented heparan sulfate shedding by HPSE1. Furthermore, heparan sulfate did not interfere with cluster of differentiation-14 (CD14)-dependent LPS binding, but instead reduced the presentation of the LPS to TLR4. HPSE2 reduced LPS-mediated TLR4 activation, subsequent cell signalling, and cytokine expression. HPSE2-overexpressing endothelial cells remained protected against LPS-mediated loss of cell-cell contacts. In vivo, expression of HPSE2 in plasma and kidney medullary capillaries was decreased in mouse sepsis model. We next applied purified HPSE2 in mice and observed decreases in TNFα and IL-6 plasma concentrations after intravenous LPS injections. Our data demonstrate the important role of heparan sulfate and the glycocalyx in endothelial cell activation and suggest a protective role of HPSE2 in microvascular inflammation. HPSE2 offers new options for protection against HPSE1-mediated endothelial damage and preventing microvascular disease.

Tristetraprolin (TTP) is an RNA-binding protein and an essential factor of posttranscriptional repression of cytokine biosynthesis in macrophages. Its activity is temporally inhibited by LPS-induced p38MAPK/MAPKAPK2/3–mediated phosphorylation, leading to a rapid increase in cytokine expression. We compared TTP expression and cytokine production in mouse bone marrow–derived macrophages of different genotypes: wild type, MAPKAP kinase 2 (MK2) deletion (MK2 knockout [KO]), MK2/3 double deletion (MK2/3 double KO [DKO]), TTP-S52A-S178A (TTPaa) knock-in, as well as combined MK2 KO/TTPaa and MK2/3 DKO/TTPaa. The comparisons reveal that MK2/3 are the only LPS-induced kinases for S52 and S178 of TTP and the role of MK2 and MK3 in the regulation of TNF biosynthesis is not restricted to phosphorylation of TTP at S52/S178 but includes independent processes, which could involve other TTP phosphorylations (such as S316) or other substrates of MK2/3 or p38MAPK. Furthermore, we found differences in the dependence of various cytokines on the cooperation between MK2/3 deletion and TTP mutation ex vivo. In the cecal ligation and puncture model of systemic inflammation, a dramatic decrease of cytokine production in MK2/3 DKO, TTPaa, and DKO/TTPaa mice compared with wild-type animals is observed, thus confirming the role of the MK2/3/TTP signaling axis in cytokine production also in vivo. These findings improve our understanding of this signaling axis and could be of future relevance in the treatment of inflammation.

GPI-anchored uPAR is the receptor for the extracellular serine protease urokinase-type plasminogen activator (uPA). Though uPAR role in inflammatory processes is documented, underlying mechanisms are not fully understood. In this study we demonstrate that uPAR is a part of Toll-like receptor 4 (TLR4) interactome. Downregulation of uPAR expression resulted in diminished LPS-induced TLR4 signaling, less activation of NFκB, and decreased secretion of inflammatory mediators in myeloid and non-myeloid cells in vitro. In vivo uPAR−/− mice demonstrated better survival, strongly diminished inflammatory response and better organ functions in cecal ligation and puncture mouse polymicrobial sepsis model. Mechanistically, GPI-uPAR and soluble uPAR colocalized with TLR4 on the cell membrane and interacted with scavenger receptor CD36. Our data show that uPAR can interfere with innate immunity response via TLR4 and this mechanism represents a potentially important target in inflammation and sepsis therapy.

GPI-anchored uPAR is the receptor for the extracellular serine protease urokinase-type plasminogen activator (uPA). Binding of uPA to uPAR localizes proteolytic cascade activation at the cell surface and can induce intracellular signaling. As uPAR possesses no transmembrane domain, it relies on uPAR cross-talk with various membrane receptors. Though uPAR role in inflammatory processes is well documented, underlying mechanisms are not fully understood. In this study we demonstrate that uPAR is a part of Toll-like receptor 4 (TLR4) interactome. GPI-uPAR and soluble uPAR colocalized with TLR4 on the cell membrane and interacted with scavenger receptor CD36. We show that downregulation of uPAR expression resulted in diminished LPS-induced TLR4 signaling, less activation of NFκB, and decreased secretion of inflammatory mediators in myeloid and non-myeloid cells in vitro. In vivo uPAR−/− mice demonstrated strongly diminished inflammatory response and better organ functions in cecal ligation and puncture mouse polymicrobial sepsis model. Our data show that uPAR can interfere with innate immunity response via TLR4 and this mechanism represents a potentially important target in inflammation and sepsis therapy.

Background and Aims Much literature evidence points towards an essential role of mitochondrial quality control mechanisms in acute kidney injury progression. Renal ischemic-reperfusion injury (IRI) results in metabolic adaptation of proximal tubule epithelial cells, a site of high mitochondrial turnover (1). Moreover, exacerbation of renal injury has been demonstrated following IRI in both PTEN-induced kinase 1 (PINK1) knockout and Parkin knockout mice (2). The identification of a single point mutation (m.547A>T) within the mitochondrial genome of a large pedigree of patients with maternally-inherited tubulointerstitial kidney disease, highlights the importance of mitochondrial integrity in human renal pathophysiology (3). USP30 is a mitochondrial associated deubiquitylating enzyme that acts on the mitochondrial import receptor subunit TOM20 to repress PINK1/Parkin-mediated mitophagy and modulate mitochondrial protein transport (4,5). Within kidney, USP30 expression is predominantly tubular and accordingly, USP30 inhibition may provide a mechanism to protect against IRI. MTX008 is a selective small molecule inhibitor of USP30. Prophylactic administration of MTX008 15 mg/kg (p.o.) BID has shown robust and reproducible efficacy in a mouse model of IRI-induced kidney fibrosis (6). Here we present data showing that dosing MTX008 15 mg/kg (p.o.) BID in a therapeutic paradigm, also results in efficacy in the same IRI-induced kidney fibrosis model. Method On Day 0 (zero) C57BL/6 mice were anaesthetized, and their left renal pedicle was clamped transiently for 45 min, causing circulatory arrest in the kidney with consecutive IRI. Mice were then administered either vehicle or MTX008 15 mg/kg (p.o.) BID for 21 days, with first treatment starting five hours following IRI surgery (i.e. therapeutics dosing). Mice were monitored and kidneys harvested at Day +21. Kidney sections were quantitatively assessed for relative cellular morphology, fibrosis and macrophage infiltration using blinded histological scoring methods. Results Body weight was similar between groups and remained constant throughout the observation periods. Masson trichrome staining revealed significantly less tubular atrophy in MTX008 treated animals on Day +21. Similarly, fibronectin expression and macrophage infiltration in the cortex was also significantly reduced in MTX008 treated mice on Day +21. Conclusion MTX008, a novel selective small molecule inhibitor of USP30 has shown efficacy in a model of IR-induced CKD when dosed therapeutically. Initiating treatment after the establishment of IRI has shown significant benefits towards reduced progression to CKD with less tubular atrophy and renal fibrosis. Mission Therapeutics is investigating MTX008 in a variety of preclinical renal injury models with a view to developing this novel molecule towards the clinic. Therapeutic dosing opens a new and attractive opportunity for the treatment of AKI and sets our UPS30 inhibitor apart from other molecules currently in development.

Background and Aims Diclofenac is frequently used for pain control. In a previous study, we showed that already a single oral dose of diclofenac could reduce renal perfusion in healthy individuals. To investigate the influence of oral diclofenac administration on renal inflammation in the setting of pre-existing renal damage, we used a mouse model of subclinical acute kidney injury (AKI) induced by renal ischemia-reperfusion injury (IRI) followed by diclofenac administration. Method Male CD1 mice (7-8 weeks old) underwent unilateral renal pedicle clamping for 15min to induce subclinical AKI. After reperfusion mice received a single oral dose of 100 or 200mg/kg diclofenac via oral gavage. Vehicle treated mice with unilateral IRI served as control. At day 1, mice were placed into metabolic cages to collect urine. Histology was performed on day 1 and 14 for renal morphology. Inflammation and fibrosis were investigated by immunohistochemistry and qPCR. Results Diclofenac treated mice showed reduced urine production. Morphologically, signs of AKI were more pronounced in diclofenac treated kidneys which also showed more Cox-2 positive tubuli in the cortex. On mRNA expression level the pro-inflammatory markers IL-6 and CXCL2, the chemoattractant for neutrophils, were elevated in the diclofenac group. Early upregulation of the pro-fibrotic markers CTGF and PAI-1 was detected already on d1 after IRI in the diclofenac group and tubular atrophy was pronounced after two weeks. Conclusion Already, a single oral dose of diclofenac causes aggravation of renal inflammation and progressive renal fibrosis in the setting of pre-existing subclinical acute kidney injury.

Peritoneal dialysis (PD) employs hypertonic glucose to remove excess water and uremic waste. Peritoneal membrane failure limits its long-term use. T-cell cytokines promote this decline. T-cell differentiation is critically determined by the microenvironment. We here study how PD-range hypertonic glucose regulates T-cell polarization and IL-17 production. In the human peritoneal cavity, CD3+ cell numbers increased in PD. Single cell RNA sequencing detected expression of T helper (Th) 17 signature genes RORC and IL23R. In vitro, PD-range glucose stimulated spontaneous and amplified cytokine-induced Th17 polarization. Osmotic controls l-glucose and d-mannose demonstrate that induction of IL-17A is a substance-independent, tonicity dose-dependent process. PD-range glucose upregulated glycolysis and increased the proportion of dysfunctional mitochondria. Blockade of reactive-oxygen species (ROS) prevented IL-17A induction in response to PD-range glucose. Peritoneal mesothelium cultured with IL-17A or IL17F produced pro-inflammatory cytokines IL-6, CCL2, and CX3CL1. In PD patients, peritoneal IL-17A positively correlated with CX3CL1 concentrations. PD-range glucose-stimulated, but neither identically treated Il17a-/- Il17f-/- nor T cells cultured with the ROS scavenger N-acetylcysteine enhanced mesothelial CX3CL1 expression. Our data delineate PD-range hypertonic glucose as a novel inducer of Th17 polarization in a mitochondrial-ROS-dependent manner. Modulation of tonicity-mediated effects of PD solutions may improve membrane survival.

Background Peritoneal membrane (PM) damage during peritoneal dialysis (PD) is mediated largely by high glucose (HG)-induced pro-inflammatory and neo-angiogenic processes, resulting in PM fibrosis and ultrafiltration failure. We recently demonstrated a crucial role for protein kinase C (PKC) isoform α in mesothelial cells. Methods In this study we investigate the role of PKCβ in PM damage in vitro using primary mouse peritoneal macrophages (MPMΦ), human macrophages (HMΦ) and immortalized mouse peritoneal mesothelial cells (MPMCs), as well as in vivo using a chronic PD mouse model. Results We demonstrate that PKCβ is the predominant classical PKC isoform expressed in primary MPMΦ and its expression is up-regulated in vitro under HG conditions. After in vitro lipopolysaccharides stimulation PKCβ-/- MPMΦ demonstrates increased levels of interleukin 6 (IL-6), tumour necrosis factor α, and monocyte chemoattractant protein-1 and drastically decrease IL-10 release compared with wild-type (WT) cells. In vivo, catheter-delivered treatment with HG PD fluid for 5 weeks induces PKCβ up-regulation in omentum of WT mice and results in inflammatory response and PM damage characterized by fibrosis and neo-angiogenesis. In comparison to WT mice, all pathological changes are strongly aggravated in PKCβ-/- animals. Underlying molecular mechanisms involve a pro-inflammatory M1 polarization shift of MPMΦ and up-regulation of PKCα in MPMCs of PKCβ-/- mice. Finally, we demonstrate PKCβ involvement in HG-induced polarization processes in HMΦ. Conclusions PKCβ as the dominant PKC isoform in MPMΦ is up-regulated by HG PD fluid and exerts anti-inflammatory effects during PD through regulation of MPMΦ M1/M2 polarization and control of the dominant mesothelial PKC isoform α.

Chronic renal allograft dysfunction (CAD) is a major limiting factor of long-term graft survival. It is characterized by interstitial fibrosis and tubular atrophy. The underlying pathomechanisms are incompletely understood. MicroRNAs are powerful regulators of gene expression and may have an impact on various diseases by direct mRNA decay or translational inhibition. A murine model of allogenic kidney transplantation was used resulting in CAD at 6 weeks after kidney transplantation. We identified fibrosis-associated miR-21a-5p by whole miRNAome expression analysis to be among the most highly upregulated miRNAs. In vitro in renal fibroblasts, miR-21a-5p was transcriptionally activated by interleukin 6–induced signal transducer and activator of transcription 3. Co-culture of LPS-activated macrophages with renal fibroblasts increased expression levels of miR-21a-5p and markers of fibrosis and inflammation. In addition, mature miR-21a-5p was secreted by macrophages in small vesicles, which were internalized by renal fibroblasts, thereby promoting profibrotic and proinflammatory effects. Notch2 receptor was identified as a potential target of miR-21a-5p and validated by luciferase gene reporter assays. Therapeutic silencing of miR-21a-5p in mice after allogenic kidney transplantation resulted in an amelioration of CAD, as indicated by a reduction in fibrosis development, inflammatory cell influx, tissue injury and BANFF lesion scoring. In a life-supporting model, miR-21a-5p antagonism had beneficial effects on kidney function. miR-21a-5p silencing may therefore be a viable therapeutic option in the treatment of patients following kidney transplantation to halt the development of CAD.

Background: Ischemia reperfusion injury (IRI) plays a major role in solid organ transplantation. The length of warm ischemia time is critical for the extent of tissue damage in renal IRI. In this experimental study we hypothesized that local release of labile heme in renal tissue is triggered by the duration of warm ischemia (15 vs. 45 min IRI) and mediates complement activation, cytokine release, and inflammation. Methods: To induce IRI, renal pedicle clamping was performed in male C57BL/6 mice for short (15 min) or prolonged (45 min) time periods. Two and 24 h after experimental ischemia tissue injury labile heme levels in the kidney were determined with an apo-horseradish peroxidase assay. Moreover, renal injury, cytokines, and C5a and C3a receptor (C5aR, C3aR) expression were determined by histology, immunohistochemistry and qPCR, respectively. In addition, in vitro studies stimulating bone marrow-derived macrophages with LPS and the combination of LPS and heme were performed and cytokine expression was measured. Results: Inflammation and local tissue injury correlated with the duration of warm ischemia time. Labile heme concentrations in renal tissue were significantly higher after prolonged (45 min) as compared to short (15 min) IRI. Notably, expression of the inducible heme-degrading enzyme heme oxygenase-1 (HO-1) was up-regulated in kidneys after prolonged, but not after short IRI. C5aR, the pro-inflammatory cytokines IL-6 and TNF-alpha as well as pERK were up-regulated after prolonged, but not after short ischemia times. Consecutively, neutrophil infiltration and up-regulation of pro-fibrotic cytokines such as CTGF and PAI were more pronounced in prolonged IRI in comparison to short IRI. In vitro stimulation of macrophages with LPS revealed that IL-6 expression was enhanced in the presence of heme. Finally, administration of the heme scavenger human serum albumin (HSA) reduced the expression of pro-inflammatory cytokines, C3a receptor and improved tubular function indicated by enhanced alpha 1 microglobulin (A1M) absorption after IRI. Conclusions: Our data show that prolonged duration of warm ischemia time increased labile heme levels in the kidney, which correlates with IRI-dependent inflammation and up-regulation of anaphylatoxin receptor expression.

The endothelial glycocalyx and its regulated shedding are important to vascular health. Endo-β-D-glucuronidase heparanase-1 (HPSE1) is the only enzyme that can shed heparan sulfate. However, the mechanisms are not well understood. We show that HPSE1 activity aggravated Toll-like receptor 4 (TLR4)-mediated response of endothelial cells to LPS. On the contrary, overexpression of its endogenous inhibitor, heparanase-2 (HPSE2) was protective. The microfluidic chip flow model confirmed that HPSE2 prevented heparan sulfate shedding by HPSE1. Furthermore, heparan sulfate did not interfere with cluster of differentiation-14 (CD14)-dependent LPS binding, but instead reduced the presentation of the LPS to TLR4. HPSE2 reduced LPS-mediated TLR4 activation, subsequent cell signalling, and cytokine expression. HPSE2-overexpressing endothelial cells remained protected against LPS-mediated loss of cell-cell contacts. In vivo, expression of HPSE2 in plasma and kidney medullary capillaries was decreased in mouse sepsis model. We next applied purified HPSE2 in mice and observed decreases in TNFα and IL-6 plasma concentrations after intravenous LPS injections. Our data demonstrate the important role of heparan sulfate and the glycocalyx in endothelial cell activation and suggest a protective role of HPSE2 in microvascular inflammation. HPSE2 offers new options for protection against HPSE1-mediated endothelial damage and preventing microvascular disease.

ObjectiveThe endothelial glycocalyx and the regulation of its shedding are important to vascular health. Endo-β-D-glucuronidase heparanase-1 (HPSE1) is the only enzyme that can shed heparan sulfate. However, the mechanisms are not well understood.Approach and resultsTo investigate HPSE1 and its endogenous inhibitor, heparanase-2 (HPSE2), we used cell culture, lentiviral protein overexpression, a microfluidic chip model of cell culture under shear stress conditions, and lipopolysaccharide (LPS) injections in mice. We show that HPSE1 activity aggravated Toll-like receptor 4 (TLR4)-mediated response of endothelial cells to LPS. On the contrary, HPSE2 overexpression was protective. The microfluidic chip flow model confirmed that HPSE2 prevented heparan sulfate shedding by HPSE1. Furthermore, heparan sulfate did not interfere with cluster of differentiation-14 (CD14)-dependent LPS binding, but instead reduced the presentation of the LPS-CD14 complex to TLR4. HPSE2 reduced LPS-mediated TLR4 activation by LPS, subsequent cell signaling, and cytokine expression. Moreover, HPSE2-overexpressing endothelial cells remained protected against LPS-mediated loss of cell-cell contacts. In vivo, expression of HPSE2 in plasma and kidney medullary capillaries was decreased in mouse sepsis model. We next applied purified HPSE2 in mice and observed decreases in TNFα and IL-6 plasma concentrations after intravenous LPS injections.ConclusionsOur data demonstrate the important role of heparan sulfate and the glycocalyx in endothelial cell activation and suggest a protective role of HPSE2 in microvascular inflammation. HPSE2 offers new options for protection against HPSE1-mediated endothelial damage and preventing microvascular disease. Graphical abstractNon standard abbreviations

Inhibiting vascular endothelial growth factor (VEGF) is a therapeutic option in diabetic microangiopathy. However, VEGF is needed at physiological concentrations to maintain glomerular integrity; complete VEGF blockade has deleterious effects on glomerular structure and function. Anti-VEGF therapy in diabetes raises the challenge of reducing VEGF-induced pathology without accelerating endothelial cell injury. Heparan sulfate (HS) can act as a co-receptor for VEGF. Calcium dobesilate (CaD) is a small molecule with vasoprotective properties that has been used for the treatment of diabetic microangiopathy. Preliminary evidence suggests that CaD interferes with HS binding sites of fibroblast growth factor. We therefore tested the hypotheses that (1) CaD inhibits VEGF signaling in endothelial cells, (2) that this effect is mediated via interference between CaD and HS, and (3) that CaD ameliorates diabetic nephropathy in a streptozotocin-induced diabetic mouse model by VEGF inhibition. We found that CaD significantly inhibited VEGF165-induced endothelial cell migration, proliferation, and permeability. CaD significantly inhibited VEGF165-induced phosphorylation of VEGFR-2 and suppressed the activity of VEGFR-2 mediated signaling cascades. The effects of CaD in vitro were abrogated by heparin, suggesting the involvement of heparin-like domain in the interaction with CaD. In addition, VEGF121, an isoform which does not bind to heparin, was not inhibited by CaD. By applying proximity ligation assays to endothelial cells, we show inhibition of interaction in situ between HS and VEGF and between VEGF and VEGFR-2. Moreover, CaD reduced VEGF signaling in diabetic kidneys and ameliorated diabetic nephropathy and neuropathy, suggesting CaD as a VEGF inhibitor without the negative effects of complete VEGF blockade and therefore could be useful as a strategy in treating diabetic nephropathy.

Peritoneal dialysis (PD) is limited by glucose-mediated peritoneal membrane (PM) fibrosis, angiogenesis, and ultrafiltration failure. Influencing PM integrity by pharmacologically targeting sodium-dependent glucose transporter (SGLT)-mediated glucose uptake has not been studied. In this study, wildtype C57Bl/6N mice were treated with high-glucose dialysate via an intraperitoneal catheter, with or without addition of selective SGLT2 inhibitor dapagliflozin. PM structural changes, ultrafiltration capacity, and peritoneal equilibration testing (PET) status for glucose, urea, and creatinine were analyzed. Expression of SGLT and facilitative glucose transporters (GLUT) was analyzed by real-time PCR, immunofluorescence, and immunohistochemistry. Peritoneal effluents were analyzed for cellular and cytokine composition. We found that peritoneal SGLT2 was expressed in mesothelial cells and in skeletal muscle. Dapagliflozin significantly reduced effluent transforming growth factor (TGF-&beta, ) concentrations, peritoneal thickening, and fibrosis, as well as microvessel density, resulting in improved ultrafiltration, despite the fact that it did not affect development of high-glucose transporter status. In vitro, dapagliflozin reduced monocyte chemoattractant protein-1 release under high-glucose conditions in human and murine peritoneal mesothelial cells. Proinflammatory cytokine release in macrophages was reduced only when cultured in high-glucose conditions with an additional inflammatory stimulus. In summary, dapagliflozin improved structural and functional peritoneal health in the context of high-glucose PD.

Peritoneal dialysis (PD) is limited by chronic fibrotic remodeling of the peritoneal wall, a transforming growth factor-β (TGF-β)-mediated process. The fractalkine (CX3CL1) receptor CX3CR1 is expressed on macrophages and monocytes, where it is a marker of TGFβ expression. Detection of its ligand CX3CL1 on the peritoneal mesothelium led us to hypothesize a pathophysiologic role of CX3CL1-CX3CR1 interaction in peritoneal fibrosis. We found that CX3CL1 was expressed on peritoneal mesothelial cells from PD patients and in a murine PD model. CX3CR1, mostly expressed on macrophages in the peritoneal wall, promoted fibrosis induced by chronic dialysate exposure in the mouse model. Our data suggest a positive feedback loop whereby direct interaction with CX3CR1-expressing macrophages promotes mesothelial expression of CX3CL1 and TGFβ expression. In turn, TGFβ upregulates CX3CR1 in murine and human monocytic cells. Upstream, macrophage cytokines including interleukin-1β (IL-1β) promote mesothelial CX3CR1 and TGFβ expression, providing a starting point for CX3CL1-CX3CR1 interaction. IL-1β expression was enhanced by exposure to dialysate both in vitro and in the mouse models. Our data suggest that macrophage-mesothelial cell crosstalk through CX3CR1-CX3CL1 interaction enhances mesothelial TGFβ production, promoting peritoneal fibrosis in response to dialysate exposure. This interaction could be a novel therapeutic target in PD-associated chronic peritoneal fibrosis.

Activation of protein kinase C (PKC) has been implicated in the pathogenesis of diabetic nephropathy with proteinuria and peritubular extracellular matrix production. We have previously shown that the PKC isoforms α and β mediate different cellular effects. PKC-β contributes to hyperglycemia-induced renal matrix production, whereby PKC-α is involved in the development of albuminuria. We further tested this hypothesis by deletion of both isoforms and used a PKC inhibitor. We analyzed the phenotype of nondiabetic and streptozotocin (STZ)-induced diabetic homozygous PKC-α/β double-knockout mice (PKC-α/β−/−). After 8 weeks of diabetes mellitus, the high-glucose–induced renal and glomerular hypertrophy as well as transforming growth factor-β1) and extracellular matrix production were diminished in the PKC-α/β−/− mice compared with wild-type controls. Urinary albumin/creatinine ratio also was significantly reduced, however, it was not completely abolished in diabetic PKC-α/β−/− mice. Treatment with CGP41252, which inhibits PKC-α and PKC-β, is able to prevent the development of albuminuria and to reduce existing albuminuria in type 1 (STZ model) or type 2 (db/db model) diabetic mice. These results support our hypothesis that PKC-α and PKC-β contribute to the pathogenesis of diabetic nephropathy, and that dual inhibition of the classical PKC isoforms is a suitable therapeutic strategy in the prevention and treatment of diabetic nephropathy.

Renal ischemia-reperfusion contributes to reduced renal allograft survival. The peptide Bβ(15-42), a breakdown product of fibrin, attenuates inflammation induced by ischemia-reperfusion in the heart by competitively blocking the binding of leukocytes to endothelial VE-cadherin, but whether it could improve outcomes in renal transplantation is unknown. Here, we tested the ability of Bβ(15-42) to ameliorate the effects of renal ischemic injury during allogenic kidney transplantation in mice. In our renal transplantation model (C57BL/6 into BALB/c mice), treatment with Bβ(15-42) at the time of allograft reperfusion resulted in significantly improved survival of recipients during the 28-day follow-up (60% versus 10%). Bβ(15-42) treatment decreased leukocyte infiltration, expression of endothelial adhesion molecules, and proinflammatory cytokines. Treatment significantly attenuated allogenic T cell activation and reduced cellular rejection. Moreover, Bβ(15-42) significantly reduced tubular epithelial damage and apoptosis, which we reproduced in vitro. These data suggest that Bβ(15-42) may have therapeutic potential in transplant surgery by protecting grafts from ischemia-reperfusion injury.

Introduction: Endothelial activation leading to vascular barrier breakdown plays an essential role in the pathophysiology of multiple-organ dysfunction syndrome (MODS) in sepsis. Increasing evidence suggests that the function of the vessel-protective factor Angiopoietin-1 (Ang-1), a ligand of the endothelial-specific Tie2 receptor, is inhibited by its antagonist Angiopoietin-2 (Ang-2) during sepsis. In order to reverse the effects of the sepsis-induced suppression of Ang-1 and elevation of Ang-2 we aimed to investigate whether an intravenous injection of recombinant human (rh) Ang-1 protects against MODS in murine sepsis.Methods: Polymicrobiological abdominal sepsis was induced by cecal ligation and puncture (CLP). Mice were treated with either 1 mu g of intravenous rhAng-1 or control buffer immediately after CLP induction and every 8 h thereafter. Sham-operated animals served as time-matched controls.Results: Compared to buffer-treated controls, rhAng-1 treated septic mice showed significant improvements in several hematologic and biochemical indicators of MODS. Moreover, rhAng-1 stabilized endothelial barrier function, as evidenced by inhibition of protein leakage from lung capillaries into the alveolar compartment. Histological analysis revealed that rhAng-1 treatment attenuated leukocyte infiltration in lungs and kidneys of septic mice, probably due to reduced endothelial adhesion molecule expression in rhAng-1 treated mice. Finally, the protective effects of rhAng-1 treatment were reflected by an improved survival time in a lethal CLP model.Conclusions: In a clinically relevant murine sepsis model, intravenous rhAng-1 treatment alone is sufficient to significantly improve a variety of sepsis-associated organ dysfunctions and survival time, most likely by preserving endothelial barrier function. Further studies are needed to pave the road for clinical application of this therapy concept. (C) 2011 Elsevier Ltd. All rights reserved.

A synthetic 7-mer, HHHRHSF, was recently identified by screening a phage display library for binding to the Tie-2 receptor. A polyethylene-oxide clustered version of this peptide, termed vasculotide (VT), was reported to activate Tie-2 and promote angiogenesis in a mouse model of diabetic ulcer. We hypothesized that VT administration would defend endothelial barrier function against sepsis-associated mediators of permeability, prevent lung vascular leakage arising in endotoxemia, and improve mortality in endotoxemic mice. In confluent human microvascular endothelial cells, VT prevented endotoxin-induced (lipopolysaccharides, LPS O111:B4) gap formation, loss of monolayer resistance, and translocation of labeled albumin. In 8-wk-old male C57Bl6/J mice given a ∼70% lethal dose of endotoxin (15 mg/kg ip), VT prevented lung vascular leakage and reversed the attenuation of lung vascular endothelial cadherin induced by endotoxemia. These protective effects of VT were associated with activation of Tie-2 and its downstream mediator, Akt. Echocardiographic studies showed only a nonsignificant trend toward improved myocardial performance associated with VT. Finally, we evaluated survival in this mouse model. Pretreatment with VT improved survival by 41.4% ( n = 15/group, P = 0.02) and post-LPS administration of VT improved survival by 33.3% ( n = 15/group, P = 0.051). VT-mediated protection from LPS lethality was lost in Tie-2 heterozygous mice, in agreement with VT's proposed receptor specificity. We conclude that this synthetic Tie-2 agonist, completely unrelated to endogenous Tie-2 ligands, is sufficient to activate the receptor and its downstream pathways in vivo and that the Tie-2 receptor may be an important target for therapeutic evaluation in conditions of pathological vascular leakage.

Central mechanisms leading to ischemia induced allograft rejection are apoptosis and inflammation, processes highly regulated by the urokinase-type plasminogen activator (uPA) and its specific receptor (uPAR). Recently, up-regulation of uPA and uPAR has been shown to correlate with allograft rejection in human biopsies. However, the causal connection of uPA/uPAR in mediating transplant rejection and underlying molecular mechanisms remain poorly understood. In this study, we evaluated the role of uPA/uPAR in a mice model for kidney ischemia reperfusion (IR) injury and for acute kidney allograft rejection. uPAR but not uPA deficiency protected from IR injury. In the allogenic kidney transplant model, uPAR but not uPA deficiency of the allograft caused superior recipient survival and strongly attenuated loss of renal function. uPAR-deficient allografts showed reduced generation of reactive oxygen species and apoptosis. Moreover, neutrophil and monocyte/macrophage infiltration was strongly attenuated and up-regulation of the adhesion molecule ICAM-1 was completely abrogated in uPAR-deficient allografts. Inadequate ICAM-1 up-regulation in uPAR−/− primary aortic endothelial cells after C5a and TNF-α stimulation was confirmed by in vitro experiments. Our results demonstrate that the local renal uPAR plays an important role in the apoptotic and inflammatory responses mediating IR-injury and transplant rejection.

Objective: Erythropoietin (EPO) has cytoprotective effects apart from its hematopoietic effects. We studied the effects of different EPO molecules on podocyte signaling in vitro and on podocyte survival in an experimental model of diabetic kidney injury (db/db mouse). Methods: We elucidated intracellular signaling by epoetin-β, darbepoetin-α, and the continuous erythropoietin receptor activator (CERA) in immortalized murine podocyte cultures. Moreover, we treated db/db micewith placebo or with CERA in a chronic (14-week) randomized controlled study. We also studied non-diabetic db/m mice as controls. Results: We could clearly demonstrate phosphorylation of the JAK/PI3K pathway and Akt signaling in podocytes by epoetin-β, darbepoetin-α and CERA. In the long-term animal study we found significantly reduced podocyte numbers in placebo-treated db/db mice compared to db/m control mice (7.4 ± 0.2 vs. 10.2 ± 0.9 per glomerular field; p < 0.05). Chronic CERA treatment ameliorated podocyte loss in kidneys of diabetic animals (8.5 ± 0.5 per glomerular field; p < 0.05 vs. placebo-treated db/db mice). Conclusion: EPO activates pro-survival intracellular pathways in podocytes in vitro, and ameliorates diabetes-induced podocyte loss in vivo. Chronic EPO administration may be a feasible way to protect podocyte from diabetic injury.

Chronic exposure to commercial glucose-based peritoneal dialysis fluids during peritoneal dialysis induces peritoneal membrane damage leading to ultrafiltration failure. In this study the role of protein kinase C (PKC) α in peritoneal membrane damage was investigated in a mouse model of peritoneal dialysis. We used 2 different approaches: blockade of biological activity of PKCα by intraperitoneal application of the conventional PKC inhibitor Go6976 in C57BL/6 wild-type mice and PKCα-deficient mice on a 129/Sv genetic background. Daily administration of peritoneal dialysis fluid for 5 weeks induced peritoneal upregulation and activation of PKCα accompanied by epithelial-to-mesenchymal transition of peritoneal mesothelial cells, peritoneal membrane fibrosis, neoangiogenesis, and macrophage and T cell infiltration, paralleled by reduced ultrafiltration capacity. All pathological changes were prevented by PKCα blockade or deficiency. Moreover, treatment with Go6976 and PKCα deficiency resulted in strong reduction of proinflammatory, profibrotic, and proangiogenic mediators. In cell culture experiments, both treatment with Go6976 and PKCα deficiency prevented peritoneal dialysis fluid–induced release of MCP-1 from mouse peritoneal mesothelial cells and ameliorated transforming growth factor-β1–induced epithelial-to-mesenchymal transition and peritoneal dialysis fluid–induced MCP-1 release in human peritoneal mesothelial cells. Thus, PKCα plays a crucial role in the pathophysiology of peritoneal membrane dysfunction induced by peritoneal dialysis fluids, and we suggest that its therapeutic inhibition might be a valuable treatment option for peritoneal dialysis patients.

Epidemiologic studies show a correlation between the dietary intake of food polyphenols and beneficial health effects. Several in vitro studies indicate that the anti-inflammatory potential of polyphenols is, at least in part, mediated by a modulation of the enzymes of the arachidonic acid cascade, such as the prostaglandin forming cyclooxygenases (COXs). Evidence that this mode of action can be transferred to the situation in vivo is scarce. This study characterized effects of a subset of polyphenols on COX–2 expression and activity in vitro and compared the potency with known drugs. Next, the in vivo relevance of the observed in vitro effects was tested. Enzyme assays and incubations of polyphenols with the cancer cell line HCA–7 and lipopolysaccharide (LPS) stimulated primary monocytes support the hypothesis that polyphenols can effect COX–2 expression and activity in vitro. The effects were most pronounced in the monocyte assay for wogonin, apigenin, resveratrol and genistein with IC50 values of 1.5 μM, 2.6 μM, 2.8 μM and 7.4 μM. However, these values are 100- to 1000-fold higher in comparison to those of the known pharmaceuticals celecoxib, indomethacin and dexamethasone. In an animal model of LPS induced sepsis, pretreatment with polyphenols (i. p. 100 mg/kg bw) did not result in decreased plasma or tissue prostaglandin levels, whereas the positive control celecoxib effectively attenuated LPS induced prostaglandin formation. These data suggest that despite the moderate potency in vitro, an effect of polyphenols on COX–2 during acute inflammation is unlikely, even if a high dose of polyphenols is ingested.

The present study aimed to comprehensively investigate the changes in oxylipins during murine sepsis induced by lipopolysaccharide (LPS) or cecal ligation and puncture (CLP). Twenty-four hours after induction of sepsis in male C57BL/6 mice by LPS or CLP, plasma and liver, lung, kidney and heart tissues were sampled. Oxylipin levels in plasma and tissue were quantified by means of LC–MS. Moreover, clinical chemistry parameters were determined in plasma and interleukin levels (MCP-1 and IL-6) were determined in kidney and liver. Elevation of liver function plasma parameters at 24 h revealed that both models were successful in the induction of sepsis. LPS induced sepsis resulted in a dramatic increase of plasma PGE2 (2,100 % change in comparison to control) and other cyclooxygenase metabolites, whereas this effect was less pronounced in CLP induced sepsis (97 % increase of PGE2). Plasma epoxy-fatty acids (FAs) and hydroxy-FAs and most of the dihydroxy-FAs were elevated in both models of sepsis. Changes of tissue oxylipin concentrations were organ dependent. Only few changes were detected in the lung and liver tissue, epoxy-FAs were elevated in the kidney. In the heart tissue a trend towards lower levels of hydroxy-FAs and epoxy-FAs was observed. Both murine models of sepsis are characterized by changes of oxylipins formed in all branches of the arachidonic acid (AA) cascade. The more pronounced effects in the LPS model make this model more suitable for the investigation of the AA cascade and its pharmacological modulation in sepsis.

Ischemia followed by reperfusion contributes to the initial damage to allografts after kidney transplantation (ktx). In this study we tested the hypothesis that a tetrapeptide EA-230 (AQGV), might improve survival and attenuate loss of kidney function in a mouse model of renal ischemia/reperfusion injury (IRI) and ischemia-induced delayed graft function after allogenic kidney transplantation. IRI was induced in male C57Bl/6N mice by transient bilateral renal pedicle clamping for 35 min. Treatment with EA-230 (20-50mg/kg twice daily i.p. for four consecutive days) was initiated 24 hours after IRI when acute kidney injury (AKI) was already established. The treatment resulted in markedly improved survival in a dose dependent manner. Acute tubular injury two days after IRI was diminished and tubular epithelial cell proliferation was significantly enhanced by EA-230 treatment. Furthermore, CTGF up-regulation, a marker of post-ischemic fibrosis, at four weeks after IRI was significantly less in EA-230 treated renal tissue. To learn more about these effects, we measured renal blood flow (RBF) and glomerular filtration rate (GFR) at 28 hours after IRI. EA-230 improved both GFR and RBF significantly. Next, EA-230 treatment was tested in a model of ischemia-induced delayed graft function after allogenic kidney transplantation. The recipients were treated with EA-230 (50 mg/kg) twice daily i.p. which improved renal function and allograft survival by attenuating ischemic allograft damage. In conclusion, EA-230 is a novel and promising therapeutic agent for treating acute kidney injury and preventing IRI-induced post-transplant ischemic allograft injury. Its beneficial effect is associated with improved renal perfusion after IRI and enhanced regeneration of tubular epithelial cells.

Complement and FcgammaR effector pathways are central triggers of immune inflammation; however, the exact mechanisms for their cooperation with effector cells and their nature remain elusive. In this study we show that in the lung Arthus reaction, the initial contact between immune complexes and alveolar macrophages (AM) results in plasma complement-independent C5a production that causes decreased levels of inhibitory FcgammaRIIB, increased levels of activating FcgammaRIII, and highly induced FcgammaR-mediated TNF-alpha and CXCR2 ligand production. Blockade of C5aR completely reversed such changes. Strikingly, studies of pertussis toxin inhibition show the essential role of G(i)-type G protein signaling in C5aR-mediated control of the regulatory FcgammaR system in vitro, and analysis of the various C5aR-, FcgammaR-, and G(i)-deficient mice verifies the importance of Galpha(i2)-associated C5aR and the FcgammaRIII-FcgammaRIIB receptor pair in lung inflammation in vivo. Moreover, adoptive transfer experiments of C5aR- and FcgammaRIII-positive cells into C5aR- and FcgammaRIII-deficient mice establish AM as responsible effector cells. AM lacking either C5aR or FcgammaRIII do not possess any such inducibility of immune complex disease, whereas reconstitution with FcgammaRIIB-negative AM results in an enhanced pathology. These data suggest that AM function as a cellular link of C5a production and C5aR activation that uses a Galpha(i2)-dependent signal for modulating the two opposing FcgammaR, FcgammaRIIB and FcgammaRIII, in the initiation of the inflammatory cascade in the lung Arthus reaction.

IgG Fc receptors (FcgammaRs, especially FcgammaRIII) and complement (in particular, C5a anaphylatoxin) are critical effectors of the acute inflammatory response to immune complexes (ICs). However, it is unknown whether and how these two key components can interact with each other in vivo. We use here a mouse model of the acute pulmonary IC hypersensitivity reaction to analyze their potential interaction. FcgammaRIII and C5aR are coexpressed on alveolar macrophages (AMs), and both FcgammaRIII and C5aR mutant mice display impaired immune responses. We find that recombinant human C5a (rhC5a) can control inverse expression of various FcgammaRs, and costimulation of ICs with rhC5a results in strong enhancement of FcgammaRIII-triggered cellular activation in vitro and in vivo. Moreover, we show here that early IC-induced bioactive C5a, and its interaction with C5aR, causes induction of activating FcgammaRIII and suppression of inhibitory FcgammaRII on AMs that appears crucial for efficient cytokine production and neutrophil recruitment in lung pathology. Therefore, C5a, which is a potent chemoattractant, has a broader critical function in regulating the inhibitory/activating FcgammaRII/III receptor pair to connect complement and FcgammaR effector pathways in immune inflammation.

Acute kidney injury (AKI) increases the risk of morbidity and mortality after major surgery and transplantation. We investigated the effect of PKC-ε deficiency on AKI and ischemic allograft damage after kidney transplantation. PKC-ε-deficient and wild type (WT) control mice were subjected to 35 min of renal pedicle clamping to induce AKI. PKC-ε deficiency was associated with a marked improvement in survival and an attenuated loss of kidney function. Furthermore, functional MRI experiments revealed better renal perfusion in PKC-ε-deficient mice than in WT mice one day after IRI. Acute tubular necrosis and neutrophil infiltration were markedly reduced in PKC-ε-deficient mice. To determine whether this resistance to ischemia-reperfusion injury resulted from changes in local renal cells or infiltrating leukocytes, we studied a life-supporting renal transplant model of ischemic graft injury. We transplanted kidneys from H2b PKC-ε-deficient mice (129/SV) and their corresponding WT littermates into major histocompatibility complex-incompatible H2d recipients (BALB/c) and induced ischemic graft injury by prolonged cold ischemia time. Recipients of WT allografts developed severe renal failure and died within 10 days of transplantation. Recipients of PKC-ε-deficient allografts had better renal function and survival; they had less generation of ROS and upregulation of proinflammatory proteins (i.e., ICAM-1, inducible nitric oxide synthase, and TNF-α) and showed less tubular epithelial cell apoptosis and inflammation in their allografts. These data suggest that local renal PKC-ε expression mediates proapoptotic and proinflammatory signaling and that an inhibitor of PKC-ε signaling could be used to prevent hypoxia-induced AKI.

Complement factor C5a is a potent proinflammatory mediator that contributes to the pathogenesis of numerous inflammatory diseases. Here, we describe the discovery of NOX-D20, a PEGylated biostable mirror-image mixed (l-)RNA/DNA aptamer (Spiegelmer) that binds to mouse and human C5a with picomolar affinity. In vitro, NOX-D20 inhibited C5a-induced chemotaxis of a CD88-expressing cell line and efficiently antagonized the activation of primary human polymorphonuclear leukocytes (PMN) by C5a. Binding of NOX-D20 to the C5a moiety of human C5 did not interfere with the formation of the terminal membrane attack complex (MAC). In sepsis, for which a specific interventional therapy is currently lacking, complement activation and elevated levels of C5a are suggested to contribute to multiorgan failure and mortality. In the model of polymicrobial sepsis induced by cecal ligation and puncture (CLP), NOX-D20 attenuated inflammation and organ damage, prevented the breakdown of the vascular endothelial barrier, and improved survival. Our study suggests NOX-D20 as a new therapeutic candidate for the treatment of sepsis.

Protein kinase C (PKC)-θ is involved in T cell activation via regulating the avidity of the β2 integrin LFA-1 in the immunological synapse. LFA-1 also mediates leukocyte adhesion. To investigate the role of PKC-θ in neutrophil adhesion, we performed intravital microscopy in cremaster venules of mice reconstituted with bone marrow from LysM-GFP+ (wild-type [WT]) and PKC-θ gene-deficient (Prkcq−/−) mice. Following stimulation with CXCL1, both WT and Prkcq−/− cells became adherent. Although most WT neutrophils remained adherent for at least 180 s, 50% of Prkcq−/− neutrophils were detached after 105 s and most by 180 s. Upon CXCL1 injection, rolling of all WT neutrophils stopped for 90 s, but rolling of Prkcq−/− neutrophils started 30 s after CXCL1 stimulation. A similar neutrophil adhesion defect was seen in vitro, and spreading of Prkcq−/− neutrophils was delayed. Prkcq−/− neutrophil recruitment was impaired in fMLP-induced transmigration into the cremaster muscle, thioglycollate-induced peritonitis, and LPS-induced lung injury. We conclude that PKC-θ mediates integrin-dependent neutrophil functions and is required to sustain neutrophil adhesion in postcapillary venules in vivo. These findings suggest that the role of PKC-θ in outside–in signaling following engagement of neutrophil integrins is relevant for inflammation in vivo.

Extracellular adenosine formed by 5'-ectonucleotidase (CD73) is involved in tubulo-glomerular feedback in the kidney but is also known to be an important immune modulator. Since CD73(-/-)mutant mice exhibit a vascular proinflammatory phenotype, we asked whether long term lack of CD73 causes inflammation related kidney pathologies. CD73(-/-)mice (13 weeks old) showed significantly increased low molecule proteinuria compared to C57BL6 wild type controls (4.8 ≥ 0.52 vs. 2.9 ± 0.54 mg/24 h, p

Background: C57BL/6 and 129/Sv are the 2 most com- monly used strains of mice in renal ischemia-reper- fusion injury (IRI) studies, yet there are currently no studies that contrast differences in the degree of renal injury after ischemia-reperfusion. Methods: To evaluate renal IRI in male C57BL/6 and 129/Sv mice, we performed unilateral clamping of the left renal pedicle for 45 minutes and compared the de- gree of renal tissue damage and function. To measure function and tissue damage we examined: glomerular filtration rate (GFR; by inulin clearance), renal blood flow (RBF; by p-aminohippurate (PAH) clearance), renal morphology, immunohistochemistry for infiltrating leu- kocytes, and fibrogenic markers by Sirius red staining. Results: After unilateral IRI, 129/sv mice had signifi- cantly less GFR and RBF disfunction at both day 14 (d14) and d28. 129/sv mice also had significantly less acute tubular necrosis on d1 and fewer infiltrating leu- kocytes on d28, as well as less collagen deposition on d28 than C57BL/6 mice. Conclusions: C57BL/6 mice were much more sensitive to damage caused by renal IRI than are 129/Sv mice.

Aims Multipotent mesenchymal stem cells (MSCs) have regenerative properties and are recognized as putative players in the pathogenesis of cardiovascular diseases. The underlying molecular mechanisms remain, however, sparsely explored. Our study was designed to elucidate a probable role for the multifunctional urokinase (uPA)/urokinase receptor (uPAR) system in MSC regulation. Though uPAR has been implicated in a broad spectrum of pathophysiological processes, nothing is known about uPAR in MSCs. Methods and results uPAR was required to mobilize MSCs from the bone marrow (BM) of mice stimulated with granulocyte colony-stimulating factor (G-CSF) in vivo . An insignificant amount of MSCs was mobilized in uPAR−/− C57BL/6J mice, whereas in wild-type animals G-CSF induced an eight-fold increase of mobilized MSCs. uPAR−/− mice revealed up-regulated expression of G-CSF and stromal cell-derived factor 1 (CXCR4) receptors in BM. uPAR down-regulation leads to inhibition of human MSC migration, as shown in different migration assays. uPAR down- or up-regulation resulted in inhibition or stimulation of MSC differentiation into vascular smooth muscle cells (VSMCs) correspondingly, as monitored by changes in cell morphology and expression of specific marker proteins. Injection of fluorescently labelled MSCs in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice after femoral artery wire injury demonstrated impaired engraftment of uPAR-deficient MSCs at the place of injury. Conclusions These data suggest a multifaceted function of uPAR in MSC biology contributing to vascular repair. uPAR might guide and control the trafficking of MSCs to the vascular wall in response to injury or ischaemia and their differentiation towards functional VSMCs at the site of arterial injury.

Background Microalbuminuria is an early lesion during the development of diabetic nephropathy. The loss of high molecular weight proteins in the urine is usually associated with decreased expression of slit diaphragm proteins. Nephrin, is the major component of the glomerular slit diaphragm and loss of nephrin has been well described in rodent models of experimental diabetes as well as in human diabetic nephropathy. Methodology/principal findings In this manuscript we analyzed the role of PKC-alpha (PKCalpha) on endocytosis of nephrin in podocytes. We found that treatment of diabetic mice with a PKCalpha-inhibitor (GO6976) leads to preserved nephrin expression and reduced proteinuria. In vitro, we found that high glucose stimulation would induce PKCalpha protein expression in murine and human podocytes. We can demonstrate that PKCalpha mediates nephrin endocytosis in podocytes and that overexpression of PKCalpha leads to an augmented endocytosis response. After PKC-activation, we demonstrate an inducible association of PKCalpha, PICK1 and nephrin in podocytes. Moreover, we can demonstrate a strong induction of PKCalpha in podocytes of patients with diabetic nephropathy. Conclusions/significance We therefore conclude that activation of PKCalpha is a pathomechanistic key event during the development of diabetic nephropathy. PKCalpha is involved in reduction of nephrin surface expression and therefore PKCalpha inhibition might be a novel target molecule for anti-proteinuric therapy.

Background Recent studies in mice experimental models with acute ischaemic injury revealed that erythropoietin (EPO) has numerous tissue-protective effects in the heart, brain and kidneys. We therefore explored the tissue-protective properties of chronic EPO treatment in an experimental model of the db/db mouse with diabetic heart injury. Material and methods We randomly treated 11 db/db mice with placebo (saline), 0·4 μg of the continuous erythropoietin receptor activator (CERA) per week (n = 11) or 1·2 μg CERA per week (n = 11) for 14 weeks, and analysed cardiac tissue. The lower CERA dose was a non-haematologically effective dose, whereas the second increased the haematocrit. Results Compared with mice in the placebo group, CERA-treated mice had a reduction in TGF-β1 and collagen I expression in cardiac tissue (P

Deregulated apoptosis of MCs (mesangial cells) is associated with a number of kidney diseases including end-stage diabetic nephropathy. Cell death by apoptosis is a tightly orchestrated event, whose mechanisms are not completely defined. In the present study we show that the uPA (urokinase-type plasminogen activator)/uPAR (uPA receptor) system can initiate both cell survival and pro-apoptotic signals in human MCs in response to different apoptotic stimuli. uPA abrogated MC apoptosis induced by serum withdrawal conditions and enhanced apoptosis initiated in MCs by high glucose. Effects of uPA were independent of its proteolytic activity and required uPAR for both pro- and anti-apoptotic effects. Studies on the uPAR interactome provide evidence that the opposing effects of uPA were directed via different uPAR-interacting transmembrane partners. Exposure of MCs to RGD (Arg-Gly-Asp) peptide led to abrogation of the anti-apoptotic effect of uPA, which implies involvement of integrins in this process. A pro-apoptotic effect of uPA under high-glucose conditions was mediated via association of uPAR and the cation-independent M6P (mannose-6-phosphate)/IGF2R (insulin-like growth factor 2 receptor). Both receptors were co-precipitated and co-localized in MCs. Studies on the underlying signalling indicate that the ERK1/2 (extracellular-signal-regulated kinase 1/2), Akt and BAD (Bcl-2/Bcl-XL-antagonist, causing cell death) protein were involved in regulation of apoptosis by uPA in MCs. M6P/IGF2R mediated BAD perinuclear localization during apoptosis initiated by uPA and high glucose. In conclusion, we provide evidence that, in MCs, the uPA/uPAR system regulates survival/apoptosis processes in a stimulus-specific fashion via a mitochondria-dependent mechanism and that BAD protein serves as a downstream molecule.

This study explored the tissue-protective properties of the continuous erythropoietin receptor activator (CERA) in an experimental model of (nonischemic) diabetic kidney injury (i.e., the db/db mouse). Mice were randomly treated with placebo (n = 25), low-dosage CERA (n = 25), and high-dosage CERA (n = 25). Also studied were 25 nondiabetic db/m mice. Hematocrit was comparable in placebo and low-dosage CERA-treated mice but increased significantly with high-dosage CERA (P < 0.01 versus both). Significantly reduced expression of TGF-beta, vascular endothelial growth factor, and collagen IV was found in glomeruli and the tubulointerstitial area with CERA treatment, and these beneficial molecular effects were clearly dosage dependent (both P < 0.05 versus placebo). Similarly, CERA treatment caused a dosage-dependent increase in p-Akt, nephrin, and perlecan tissue expression (all P < 0.05 versus placebo). However, the accelerated mesangial expansion that was observed in placebo-treated db/db mice (versus db/m controls) was significantly reduced only in low-dosage CERA-treated mice (P < 0.01). Moreover, albuminuria was significantly reduced in low- but not high-dosage CERA-treated mice compared with placebo treatment (P < 0.05). In an ancillary study, phlebotomy was performed in high-dosage CERA-treated db/db mice to keep hematocrit within normal (baseline) levels. This procedure resulted in significantly (P < 0.05) less albuminuria as compared with high-dosage CERA-treated mice without phlebotomy, thus preserving the tissue-protective potential of CERA. Long-term CERA treatment has beneficial dosage-dependent effects on molecular pathways of diabetic kidney damage. Low-dosage CERA does not affect hematocrit and therefore may be a feasible method of tissue protection in this setting.

Immune complex (IC) deposition induces an acute inflammatory response with tissue injury. IC-induced inflammation is mediated by inflammatory cell infiltration, a process highly regulated by the cell surface-specific receptor (uPAR), a binding partner for the urokinase-type plasminogen activator (uPA). We assessed the role of the uPA/uPAR system in IC-induced inflammation using the pulmonary reverse passive Arthus reaction in mice lacking uPA and uPAR compared with their corresponding wild-type controls. Both uPA-deficient C57BL/6J (uPA−/−) and uPAR-deficient mice on a mixed C57BL/6J (75%) × 129 (25%) background (uPAR−/−) demonstrated a marked reduction of the inflammatory response due to decreased production of proinflammatory mediators TNF-α and Glu-Leu-Arg (ELR)-CXC chemokine MIP-2. In uPAR−/− animals, the reduction of inflammatory response was more pronounced because of decreased migratory capacity of polymorphonuclear leukocytes. We show that the uPA/uPAR system is activated in lung of wild-type mice, particularly in resident alveolar macrophages (AM), early in IC-induced alveolitis. This activation is necessary for an adequate C5a anaphylatoxin receptor signaling on AM that, in turn, modulates the functional balance of the activating/inhibitory IgG FcγRs responsible for proinflammatory mediator release. These data provide the first evidence that the uPA/uPAR plays an important immunoregulatory role in the initiation of the reverse passive Arthus reaction in the lung by setting the threshold for C5a anaphylatoxin receptor/FcγR activation on AM. The findings indicate an important link between the uPA/uPAR system and the two main components involved in the IC inflammation, namely, complement and FcγRs.