Immune-mediated mesangial cell injury—Biosynthesis and function of prostanoids

Immune-mediated mesangial cell injury—Biosynthesis and function of prostanoids. We studied the formation of cyclo-oxygenase products in a rat model of mesangial cell injury, in order to determine a possible role of prostaglandin E2 (PGE2), prostaglandin I2 (determined as 6-keto-PGF1α and thromboxane A2 (TxA2) in immune-mediated glomerular disease. Selective immune-mediated mesangial cell injury was induced by i.v. administration of a rabbit anti-rat thymocyte antiserum (ATS). Intravenous ATS leads to immune deposits in the mesangium followed by mesangiolysis and the infiltration of polymorphonuclear granulocytes and monocytes. Glomerular TxB2 formation two hours (292 ± 27 pg/mg/min) and 48 hours (396 ± 69 pg/mg/min) following antibody was significantly (P < 0.05) higher compared to animals receiving non-antibody rabbit IgG (TxB2: 2hr 143 ± 13; 48hr 171 ± 32 pg/mg/min). Treatment with cobra venom factor (CVF) and the reduction of glomerular monocyte infiltration inhibited the increase of glomerular TxB2 formation significantly. Depletion of granulocytes with a rabbit anti-rat granulocyte serum had no effect on glomerular prostanoid formation following ATS. Glomerular PGE2 and 6-keto PGF1α production was not altered following ATS. Inulin clearance in rats with immune-mediated mesangial cell injury was significantly (P < 0.001) lower at two hours (456 ± 24 µl/min/100g body wt) and 48 hours (433 ± 54 µl/min/lOO g body wt) compared to their corresponding control animals which were treated with non-antibody IgG (2 hr: 914 ± 51; 48 hr: 694 ± 79 µl/min/100g body wt). Pretreatment of rats with indomethacin (Indo) or with the thromboxane synthetase inhibitor UK 38485 prevented the decrease in inulin clearance following ATS at two hours (Indo: 800 ± 67; UK 38485: 923 ± 115) and at 48 hours (Indo: 697 ± 60; UK 38485: 654 ± 99). The data demonstrate that selective, immune-mediated mesangial cell injury in rats is associated with increased glomerular TxB2 formation. Complement and monocyte/macrophage depletion reduces TxB2 production. The fall in inulin clearance following ATS is ameliorated when the rats receive indomethacin or the Tx synthetase inhibitor UK 38485. Thus, elevated TxB2 formation might mediate the reduction in GFR in this model of glomerular immune injury

Chronic anti-Thy-1 nephritis is aggravated in the nonclipped but not in the clipped kidney of Goldblatt hypertensive rats

Chronic anti-Thy-1 nephritis is aggravated in the nonclipped but not in the clipped kidney of Goldblatt hypertensive rats.BackgroundWe have previously shown that renovascular hypertension does not inhibit healing of the acute Thy-1 nephritis. To test whether a chronic model of the Thy-1 nephritis is more susceptible to high blood pressure, the repetitive hit model was evaluated in rats with 2-kidney, 1-clip Goldblatt hypertension.MethodsSix weeks after initiation of 2-kidney, 1-clip hypertension, chronic Thy-1 glomerulonephritis was induced in hypertensive rats by four consecutive injections of rabbit antiserum in weekly intervals. Renal structure and function were examined two weeks after the last injection. Glomerular binding of rabbit IgG as well as expression of transforming growth factor-beta (TGF-β), α-smooth muscle actin (α-SMA) and cyclooxygenase (COX)-1 and -2 were evaluated by Western blotting.ResultsSimilar glomerular deposition of rabbit IgG was detected in normotensive rats and in both kidneys of Goldblatt hypertensive rats indicating similar delivery and binding of the heterologous antibody. Induction of the repetitive Thy-1 model significantly enhanced glomerular damage in the nonclipped kidney and increased albuminuria. Surprisingly, no glomerular damage developed in the clipped kidney of nephritic hypertensive rats. In contrast, increased glomerular volume and increased expression of TGF-β, α-SMA as well as COX-1 and COX-2 were found in normotensive nephritic rats and in both kidneys of nephritic hypertensive rats.ConclusionGlomerular and tubulointerstitial damage of the chronic Thy-1 model is dramatically enhanced in the nonclipped kidneys of Goldblatt hypertensive rats. In contrast, the clipped kidney is completely protected from this immunological injury despite similar activation of glomerular cells, induction of TGF-β, COX-1 and COX-2 and glomerular hypertrophy

Glomerular expression of p27Kip1 in diabetic db/db mouse: Role of hyperglycemia

Glomerular expression of p27Kip1 in diabetic db/db mouse: Role of hyperglycemia Early diabetic nephropathy is characterized by glomerular hypertrophy. Previous studies in vitro have demonstrated that mesangial cells exposed to high glucose are arrested in the G1-phase of the cell cycle and express increased levels of the cyclin-dependent kinase inhibitor p27Kip1. The present study was performed to investigate the renal expression of p27Kip1 in db/db mice, a model of diabetes mellitus type II. Glomerular p27Kip1 protein, but not mRNA expression, was strongly enhanced in diabetic db/db mice compared with non-diabetic db/+ littermates. Immunohistochemical studies revealed that this stimulated expression was mainly restricted to the nuclei of mesangial cells and podocytes, but glomerular endothelial cells occasionally also stained positively. Quantification of p27Kip1 positive glomerular cells showed a significant increase of these cells in db/db mice compared with non-diabetic db/+ animals. Although tubular cells revealed a positive staining for p27Kip1 protein, there was no difference between db/+ and db/db mice. Immunoprecipitation experiments revealed that p27Kip1 protein associates with Cdk2 and Cdk4, but not with Cdk6. To test for the influence of hyperglycemia on cell cycle arrest and p27Kip1 expression, mesangial cells were isolated from db/+ and db/db mice. There was a similar basal proliferation when these cells were grown in normal glucose-containing medium (100 mg/dl). However, raising the glucose concentration to 275 to 450 mg/dl induced cell cycle arrest in db/+ as well as db/db mesangial cells. Increasing the medium osmolarity with D-mannitol failed to induce p27Kip1 expression in mesangial cells. Transfection of cells with p27Kip1 antisense, but not missense, phosphorothioate oligonucleotides facilitated cell cycle progression equally well in db/+ and db/db mesangial cells. Furthermore, p27Kip1 expression was comparable in both cell lines in normal glucose, but increased in high glucose medium. Our studies demonstrate that p27Kip1 expression is enhanced in diabetic db/db animals. This induction appears to be due to hyperglycemia. Expression of p27Kip1 may be important in cell cycle arrest and hypertrophy of mesangial cells during early diabetic nephropathy

Expression of the chemokines MCP-1/CCL2 and RANTES/CCL5 is differentially regulated by infiltrating inflammatory cells

Expression of the chemokines MCP-1/CCL2 and RANTES/CCL5 is differentially regulated by infiltrating inflammatory cells.BackgroundChemokines are involved in the regulation of the cellular renal infiltrate in glomerulonephritis; however, it is unclear to which degree resident glomerular cells or infiltrating leukocytes contribute to the formation of chemokines in glomerular inflammatory lesions. We therefore examined whether monocytes/macrophages play a role in the expression of the C-C chemokines MCP-1/CCL2 and RANTES/CCL5 in renal tissue in a lipopolysaccharide (LPS)-induced model of inflammation, where previously we have shown increased glomerular RANTES expression and glomerular infiltration of ED-1-positive cells.MethodsInflammatory lesions were induced by an intraperitoneal injection of LPS. The infiltration of monocytes into the glomerulus was reduced by two experimental approaches. First, rats were depleted of monocytes by the use of specific monocyte-antisera or by cytotoxic drugs. Second, the infiltration of monocytes into the kidney was reduced by using intercellular adhesion molecule-1 (ICAM-1) knockout mice.ResultsBoth experimental approaches demonstrated a significant reduction in the number of infiltrating monocytes/macrophages after lipopolysaccharide injection. This reduction in the infiltration of inflammatory cells was associated with significantly reduced RANTES/CCL5 mRNA expression. However, MCP-1/CCL2 mRNA expression was not inhibited after the LPS injection by monocyte/macrophage depletion. Also, the increase in nuclear factor-κB (NF-κB) binding activity after the LPS injection was not reduced in pretreated animals. The experiments therefore demonstrate that infiltrating monocytes/macrophages contribute to increased RANTES/CCL5 mRNA expression in inflammatory renal lesions, whereas MCP-1/CCL2 mRNA expression and NF-κB activation were not reduced by monocyte/macrophage depletion.ConclusionMCP-1/CCL2 released from renal tissue upon stimulation plays a major role in the regulation of monocyte/macrophage infiltration, which contributes significantly to increased renal RANTES/CCL5 expression. This cross-talk between resident renal cells and monocytes/macrophages is therefore likely to boost the number of infiltrating inflammatory cells

Modelling of electron-transfer kinetics in magnesium electrolytes: Influence of the solvent on the battery performance

Regarding energy density, safety, cost, and sustainability rechargeable magnesium batteries are a very promising next-generation energy storage technology. However, the processes in the electrolyte and at the electrode surface are not yet properly understood. The bivalency of the magnesium cations leads to strong coulomb interactions with the anion as well as with the solvent. It was found that magnesium salts are prone to form ion pairs and bigger clusters – especially at high concentrations, which may adversely affect the transport in the electrolyte and the plating behaviour at the electrode.[1] Consequently, a good solvation is important for the dissociation of the magnesium salts, which is in turn crucial for a high ionic conductivity of the electrolyte. At the same time, the desolvation of double charged magnesium cations usually goes along with high energeticbarriers, which can have a crucial impact on the deposition process. This can lead to significantly higher overpotentials for magnesium deposition compared to magnesium dissolution. In our contribution we will present a newly developed kinetic model for electrochemical reactions at metal electrodes, which explicitly couples desolvation to electron transfer and, furthermore, qualitatively considers effects of the electrochemical double layer. By including this kinetics into our general transport model [2] the impact of five different solvents on the battery performance is studied for the state-of-the-art, chloride-free Mg[B(hfip)4]2 electrolyte salt [3]. The parametrization of the model is mainly based on DFT calculations [4]and the simulation results are validated and supported by experimental measurements. It becomes apparent that the desolvation of one coordination site of the solvated cation is limiting the overall magnesium deposition. Consequently, the thermodynamics of this initial desolvation, which are determined by the solvent, play a crucial role for the battery performance. However, the impact of the electrochemical double layer is equally important to reproduce the non-intuitive qualitative trends observed in the experiments with different solvents. All in all, the combination of different modelling techniques with experimental measurements providesimportant insights into the operation of magnesium batteries

Gluon polarization in the nucleon from quasi-real photoproduction of high-pT hadron pairs

We present a determination of the gluon polarization Delta G/G in the nucleon, based on the helicity asymmetry of quasi-real photoproduction events, Q^2<1(GeV/c)^2, with a pair of large transverse-momentum hadrons in the final state. The data were obtained by the COMPASS experiment at CERN using a 160 GeV polarized muon beam scattered on a polarized 6-LiD target. The helicity asymmetry for the selected events is = 0.002 +- 0.019(stat.) +- 0.003(syst.). From this value, we obtain in a leading-order QCD analysis Delta G/G=0.024 +- 0.089(stat.) +- 0.057(syst.) at x_g = 0.095 and mu^2 =~ 3 (GeV}/c)^2.Comment: 10 pages, 3 figure

Measurement of the Spin Structure of the Deuteron in the DIS Region

We present a new measurement of the longitudinal spin asymmetry A_1^d and the spin-dependent structure function g_1^d of the deuteron in the range 1 GeV^2 < Q^2 < 100 GeV^2 and 0.004< x <0.7. The data were obtained by the COMPASS experiment at CERN using a 160 GeV polarised muon beam and a large polarised 6-LiD target. The results are in agreement with those from previous experiments and improve considerably the statistical accuracy in the region 0.004 < x < 0.03.Comment: 10 pages, 6 figures, subm. to PLB, revised: author list, Fig. 4, details adde

The COMPASS Experiment at CERN

The COMPASS experiment makes use of the CERN SPS high-intensitymuon and hadron beams for the investigation of the nucleon spin structure and the spectroscopy of hadrons. One or more outgoing particles are detected in coincidence with the incoming muon or hadron. A large polarized target inside a superconducting solenoid is used for the measurements with the muon beam. Outgoing particles are detected by a two-stage, large angle and large momentum range spectrometer. The setup is built using several types of tracking detectors, according to the expected incident rate, required space resolution and the solid angle to be covered. Particle identification is achieved using a RICH counter and both hadron and electromagnetic calorimeters. The setup has been successfully operated from 2002 onwards using a muon beam. Data with a hadron beam were also collected in 2004. This article describes the main features and performances of the spectrometer in 2004; a short summary of the 2006 upgrade is also given.Comment: 84 papes, 74 figure

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results