Nitric oxide and glomerulonephritis

Berberine hydrochloride inhibits migration ability via increasing inducible NO synthase and peroxynitrite in HTR-8/SVneo cells

ETHNOPHARMACOLOGICAL RELEVANCE

Inadequate trophoblasts migration and invasion is considered as an initial event resulting in preeclampsia, which is closely related to oxidative stress. Berberine hydrochloride (BBR), extracted from the traditional medicinal plant Coptis chinensis Franch., exerts a diversity of pharmacological effects, and the crude drug has been widely taken by most Chinese women to treat nausea and vomit during pregnancy. But there is no research regarding its effects on trophoblast cell function.

AIM OF THE STUDY

This study aimed to investigate the effect of BBR on human-trophoblast-derived cell line (HTR-8/SVneo) migration ability and its mechanism.

MATERIALS AND METHODS

Cell viability was detected by CCK-8 assay. The effect of BBR on cells migration function was examined by scratch wound healing assay and transwell migration assay. Intracellular nitric oxide (NO), superoxide (O₂^-) and peroxynitrite (ONOO^-) levels were measured by flow cytometry. The expression levels of inducible NO synthase (iNOS), eNOS, p-eNOS, MnSOD, CuZnSOD, Rac1, NOX1, TLR4, nuclear factor-κB (NF-κB), p-NFκB, pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) in cells were analyzed by Western blotting. Uric acid sodium salt (UA), the scavenger of ONOO^-, PEG-SOD (a specific superoxide scavenger), L-NAME (a NOS inhibitor) and antioxidants (Vit E and DFO) were further used to characterize the pathway of BBR action.

RESULTS

5 μM BBR decreased both the migration distance and the number of migrated cells without affecting cells viability in HTR-8/SVneo cells after 24 h treatment. BBR could increase the level of NO in HTR-8/SVneo cells, and the over-production of NO might be attributable to iNOS, but not eNOS. BBR could increase intracellular O₂^- levels, and the over-production of O₂^- is closely related with Rac1 in HTR-8/SVneo cells. The excessive production of NO and O₂^- further react to form ONOO^-, and the increased ONOO^- level induced by BBR was blunted by UA. Moreover, UA improved the impaired migration function caused by BBR in HTR-8/SVneo cells. The depressed migration function stimulated by BBR in HTR-8/SVneo cells was diminished by PEG-SOD and L-NAME. Furthermore, BBR increased the expression of IL-6 in HTR-8/SVneo cells, and antioxidants (Vit E and DFO) could decrease the expression of IL-6 and iNOS induced by BBR.

CONCLUSIONS

BBR inhibits the cell migration ability through increasing inducible NO synthase and peroxynitrite in HTR-8/SVneo cells, indicating that BBR and traditional Chinese medicines containing a high proportion of BBR should be used with caution in pregnant women.

Nitric-Oxide-Mediated Signaling in Podocyte Pathophysiology

Nitric oxide (NO) is a potent signaling molecule involved in many physiological and pathophysiological processes in the kidney. NO plays a complex role in glomerular ultrafiltration, vasodilation, and inflammation. Changes in NO bioavailability in pathophysiological conditions such as hypertension or diabetes may lead to podocyte damage, proteinuria, and rapid development of chronic kidney disease (CKD). Despite the extensive data highlighting essential functions of NO in health and pathology, related signaling in glomerular cells, particularly podocytes, is understudied. Several reports indicate that NO bioavailability in glomerular cells is decreased during the development of renal pathology, while restoring NO level can be beneficial for glomerular function. At the same time, the compromised activity of nitric oxide synthase (NOS) may provoke the formation of peroxynitrite and has been linked to autoimmune diseases such as systemic lupus erythematosus. It is known that the changes in the distribution of NO sources due to shifts in NOS subunits expression or modifications of NADPH oxidases activity may be linked to or promote the development of pathology. However, there is a lack of information about the detailed mechanisms describing the production and release of NO in the glomerular cells. The interaction of NO and other reactive oxygen species in podocytes and how NO-calcium crosstalk regulates glomerular cells’ function is still largely unknown. Here, we discuss recent reports describing signaling, synthesis, and known pathophysiological mechanisms mediated by the changes in NO homeostasis in the podocyte. The understanding and further investigation of these essential mechanisms in glomerular cells will facilitate the design of novel strategies to prevent or manage health conditions that cause glomerular and kidney damage.

Design and synthesis of novel aza-ursolic acid derivatives: in vitro cytotoxicity and nitric oxide release inhibitory activity

Aim: Inducible nitric oxide synthase (iNOS) is a validated target for anti-inflammatory treatment. Based on the authors' previous work, novel aza-ursolic acid derivatives were designed and synthesized and their inhibitory activities against lipopolysaccharide (LPS)-induced nitric oxide (NO) release from RAW264.7 cells was evaluated. Materials & results: 16 novel derivatives were screened for their in vitro inhibitory activity against NO release using Griess assays and the cytotoxicity was evaluated using MTT assays. The presence of furoxan joined to the A-ring of ursolic acid and N-methylpiperazine groups in the lead compound was identified for anti-inflammatory activity, and compound 21b showed 94.96% inhibition of NO release at 100 μM with an IC50 value of 8.58 μM. Conclusion: Compound 21b has potential anti-inflammatory activity with low cytotoxicity that warrants further preclinical study and evaluation.

The TNF-derived TIP peptide activates the epithelial sodium channel and ameliorates experimental nephrotoxic serum nephritis

In mice, the initial stage of nephrotoxic serum-induced nephritis (NTN) mimics antibody-mediated human glomerulonephritis. Local immune deposits generate tumor necrosis factor (TNF), which activates pro-inflammatory pathways in glomerular endothelial cells (GECs) and podocytes. Because TNF receptors mediate antibacterial defense, existing anti-TNF therapies can promote infection; however, we have previously demonstrated that different functional domains of TNF may have opposing effects. The TIP peptide mimics the lectin-like domain of TNF, and has been shown to blunt inflammation in acute lung injury without impairing TNF receptor-mediated antibacterial activity. We evaluated the impact of TIP peptide in NTN. Intraperitoneal administration of TIP peptide reduced inflammation, proteinuria, and blood urea nitrogen. The protective effect was blocked by the cyclooxygenase inhibitor indomethacin, indicating involvement of prostaglandins. Targeted glomerular delivery of TIP peptide improved pathology in moderate NTN and reduced mortality in severe NTN, indicating a local protective effect. We show that TIP peptide activates the epithelial sodium channel(ENaC), which is expressed by GEC, upon binding to the channel's α subunit. In vitro, TNF treatment of GEC activated pro-inflammatory pathways and decreased the generation of prostaglandin E2 and nitric oxide, which promote recovery from NTN. TIP peptide counteracted these effects. Despite the capacity of TIP peptide to activate ENaC, it did not increase mean arterial blood pressure in mice. In the later autologous phase of NTN, TIP peptide blunted the infiltration of Th17 cells. By countering the deleterious effects of TNF through direct actions in GEC, TIP peptide could provide a novel strategy to treat glomerular inflammation.

Indoxyl sulfate, a valuable biomarker in chronic kidney disease and dialysis

Chronic kidney disease (CKD) is an increasingly recognized disease with high global incidence and mortality. Yet, the existing diagnostic tools are not sufficient enough to predict prognosis of CKD and CKD comorbidities. Indoxyl sulfate, a typical uremic toxin, is of great importance in the development of CKD with its nephrotoxicity, cardiovascular toxicity, and bone toxicity. Some reports suggest that indoxyl sulfate directly associate with renal function loss and mortality in CKD patients. This review discusses the diagnostic value of indoxyl sulfate from its biological characteristics, pathophysiological effects, related therapies, and its diagnostic value in clinical studies.

Targeting protein-bound uremic toxins in chronic kidney disease

INTRODUCTION

Protein-bound uremic toxins such as indoxyl sulfate cannot be removed efficiently by hemodialysis. These protein-bound uremic toxins have emerged as important risk factors for the progression of chronic kidney disease (CKD) as well as cardiovascular disease (CVD).

AREAS COVERED

Indoxyl sulfate shows toxic effects on a variety of cells such as renal proximal tubular cells, glomerular mesangial cells, vascular smooth muscle cells, vascular endothelial cells, cardiomyocytes, cardiac fibroblasts, monocytes, osteoblasts and osteoclasts. This review overviews the cellular toxicity of indoxyl sulfate, its molecular mechanism and its role in the progression of CKD and CVD. Further, this review summarizes the clinical effects of AST-120 and the other strategies to reduce serum levels of indoxyl sulfate.

EXPERT OPINION

Protein-bound uremic toxins such as indoxyl sulfate have emerged as target molecules for therapeutic intervention of not only CKD but also CVD. An oral sorbent AST-120 reduces serum level of indoxyl sulfate by adsorbing indole in the intestine. The modulation of intestinal bacteria by prebiotics/probiotics might be effective in reducing the production of indole in the intestine followed by reduced serum levels of indoxyl sulfate. An alternative approach might be antagonist which can counteract indoxyl sulfate-induced cellular effects and signaling pathways.

Differential effects of LY294002 and wortmannin on inducible nitric oxide synthase expression in glomerular mesangial cells

Nitric oxide (NO) that is produced by inducible nitric oxide synthase (iNOS) is associated with the pathophysiology of glomerulonephritis. Numerous studies have focused on the regulation of NO production by iNOS to reduce NO-mediated cytotoxicity. In the present study, we demonstrated the differential effects of two phosphatidylinositol 3-kinase (PI3K) inhibitors, LY294002 and wortmannin, on lipopolysaccharide- (LPS) and interferon (IFN)-γ-induced NO production in a glomerular mesangial cell line, MES-13 cells. At dosages without affecting cell viability of MES-13 cells, 5μM LY294002 showed a more-significant inhibitory effect on LPS/IFN-γ-induced NO production, and iNOS protein and gene expressions than did 1μM wortmannin. Akt phosphorylation in MES-13 cells declined upon the addition of wortmannin, but not upon treatment with LY294002. Suppression of PI3K expression by small interfering (si)RNA exhibited no effect on LPS/IFN-γ-stimulated NO production or iNOS protein expression in MES-13 cells. Neither LY294002 nor wortmannin reduced IFN-γ-induced STAT-1α phosphorylation. LY294002 exhibited a more-significant inhibitory effect on NF-κB luciferase activities than wortmannin in LPS/IFN-γ-stimulated MES-13 cells. Moreover, LY294002, but not wortmannin, accelerated iNOS protein degradation and reduced the iNOS dimer/monomer ratio in MES-13 cells. Although both LY294002 and wortmannin are known as PI3K inhibitors, their differential effects on iNOS expression in MES-13 cells indicate that the effects of LY294002 on inhibiting NF-κB activation and accelerating iNOS protein degradation are through a mechanism independent of PI3K.

The effect of cadmium toxicity on renal nitric oxide synthase isoenzymes

The aim of this study was to assess the cadmium (Cd) toxicity on renal nitric oxide synthase (NOS) isoenzymes. The study was carried out on 18 inbred male (Cd group: 10 and control group: 8) Wistar rats. Cd group received drinking water containing 15 mg/L Cd for 30 days; and at the end of the 30 days, plasma Cd was analysed. One kidney was snap frozen to assess the endothelial NOS (eNOS), inducible NOS (iNOS) and neuronal NOS (nNOS) expressions by Western blot analyses, and the other kidney was preserved for histopathological examination. Plasma Cd levels were significantly elevated in the Cd group. The Western blot analyses found higher levels of eNOS, iNOS and nNOS in the Cd group but only eNOS and nNOS levels were statistically significant. There was no difference in pathological assessment of the renal tissues. Cd toxicity increases NOS isoenzyme levels and may affect renal physiology.

Response of renal parenchyma and interstitium of Rana snk. esculenta to environmental pollution

The mesonephroi of two groups of Rana esculenta collected from two rice fields near Pavia, one relatively unpolluted and one polluted, were morphologically and histochemically investigated. Light and electron microscopy analyses were performed and certain enzyme activities studied (succinic dehydrogenase, SDH, alkaline phosphatase, AlkPase, acid phosphatase, AcPase, catalase, CAT, and NOS-related nicotinamide adenine dinucleotide phosphatase, NOS/NADPHd). The expression of the inducible NOS (iNOS) was evaluated through immunohistochemistry. In the renal parenchyma of the polluted group some structural modifications, mainly in the glomeruli and the proximal tubule epithelium, were observed. Peritubular inflammatory foci in most polluted samples were often found to be in combination with parasitic cysts. However, no necrotic processes were found in the renal parenchyma. Compared to controls, the histochemical studies on contaminated frogs evidenced an increase of the AcPase, NOS and CAT activities, and of the iNOS immunoexpression as well. All the results showed a good correspondence between the biomarkers responses and the environmental stress conditions. Overall, we can state that studying the sub-lethal effects of contamination in amphibians naturally exposed to toxicants has shown to be significant for the assessment of site-specific risk and potential hazards behind the phenomenon of progressive amphibian decline.

Nitric oxide inhibits glomerular TGF-beta signaling via SMOC-1

Cytokines and nitric oxide (NO) stimulate rat mesangial cells to synthesize and secrete inflammatory mediators. To understand better the signaling pathways that contribute to this response, we exposed rat mesangial cells to the prototypic inflammatory cytokine IL-1beta and analyzed the changes in the pattern of gene expression. IL-1beta downregulated the gene encoding the matricellular glycoprotein secreted modular calcium-binding protein 1 (SMOC-1) in mesangial cells. Inflammatory cytokines attenuated SMOC-1 mRNA and protein expression through endogenous production of NO, which activated the soluble guanylyl cyclase. Silencing SMOC-1 expression with small interfering RNA decreased the formation of TGF-beta, reduced SMAD binding to DNA, and decreased mRNA expression of genes regulated by TGF-beta. In a rat model of anti-Thy-1 glomerulonephritis, glomerular SMOC-1 mRNA and protein decreased and inducible NO synthase expression increased simultaneously. Treatment of nephritic rats with the inducible NO synthase-specific inhibitor l-N(6)-(1-iminoethyl)-lysine prevented SMOC-1 downregulation. In summary, these data suggest that NO attenuates SMOC-1 expression in acute glomerular inflammation, thereby limiting TGF-beta-mediated profibrotic signaling.

Increased nitric oxide production by T- and B-cells in idiopathic nephrotic syndrome

The pathogenesis of idiopathic nephrotic syndrome (INS) remains unclear. To study the role of nitric oxide (NO) in INS, we measured intracellular NO produced by T- and B-cells using a novel fluorescent indicator. Twelve children with INS (mean age 7.3 years; group A-1: in relapse, group A-2: in remission) were enrolled in the study together with 16 children with other renal diseases (9.5 years; group B) and 42 healthy control children (7.7 years; group C). The amount of NO produced by CD3+ cells (T-cells) and CD19+ cells (B-cells) and of plasma NO(x) was measured by flow cytometry and colorimetry, respectively. The average amount of NO produced by CD3+ and CD19+ cells in group A-1 subjects was significantly higher than that produced by these cells in group A-2 and B patients and the healthy controls (group C), respectively (P < 0.01), and it decreased after the patients achieved remission (P < 0.01). Plasma NO(x) levels in group A-1 patients was also highest among the different groups (P < 0.01). There were no significant differences in intracellular NO and plasma NO(x) among group A-2, B, and C subjects (P > 0.05). A significant correlation between plasma NO(x) and urinary protein excretion was found only in group A patients and not in group B patients. We conclude that an aberrant immune system may exist not only in T-cells but also in B-cells, and NO may play some role in INS.

The profile of gene expression and role of nuclear factor kappa B on glomerular injury in rats with Thy-1 nephritis

Mesangioproliferative glomerulonephritis (MsPGN) is a disease of high incidence in humans. Rats with Thy-1 nephritis (Thy-1 N) are used as an animal model for studying MsPGN. Although several studies have demonstrated that many pathological factors could cause the injury of glomerular mesangial cells (GMCs) in Thy-1 N, changes of profile and the molecular mechanism of the disease (i.e. the role of transcription factors) at intervals remain unclear. The purpose of this study was to identify the changes in gene expression profile and to observe the role of nuclear factor kappa B (NF-kappaB) on the pathological change of renal tissue in Thy-1 N rats. Our results showed that the pathological changes of GMCs in Thy-1 N included three phases: apoptosis (40 min), necrosis (24 h) and proliferation (7 days). Concomitantly, at 40 min and on day 7, the up-regulation of 341 genes and 250 genes were observed, while 392 genes and 119 genes were down-regulated in Thy-1 N. Expression of interleukin (IL)-1beta, IL-6, proliferating cell nuclear antigen, alpha-smooth muscle actin, collagen type IV and excretion of urinary protein was increased in rats with Thy-1 N and decreased in pyrrolidine dithiocarbamate-treated rats with Thy-1 N. These data indicated that the significant changes in the gene profile were coupled with the pathological changes of Thy-1 N, and activation of NF-kappaB may contribute to the pathogenesis of GMCs apoptosis, proliferation, extracelluar matrix accumulation and proteinuria in Thy-1 N.

Mammalian N-glycan branching protects against innate immune self-recognition and inflammation in autoimmune disease pathogenesis

Autoimmune diseases are prevalent and often life-threatening syndromes, yet the pathogenic triggers and mechanisms involved remain mostly unresolved. Protein asparagine linked- (N-) glycosylation produces glycan structures that substantially differ among the extracellular compartments of evolutionarily divergent organisms. Alpha-mannosidase-II (alphaM-II) deficiency diminishes complex-type N-glycan branching in vertebrates and induces an autoimmune disease in mice similar to human systemic lupus erythematosus. We found that disease pathogenesis provoking glomerulonephritis and kidney failure was nonhematopoietic in origin, independent of complement C3 and the adaptive immune system, mitigated by intravenous administration of immunoglobulin-G, and linked to chronic activation of the innate immune system. N-glycans produced in alphaM-II deficiency bear immune-stimulatory mannose-dependent ligands for innate immune lectin receptors, disrupting the phylogenic basis of this glycomic recognition mechanism. Thus, mammalian N-glycan branching safeguards against the formation of an endogenous immunologic signal of nonself that can provoke a sterile inflammatory response in the pathogenesis of autoimmune disease.

Gene expression profile and overexpression of apoptosis-related genes (NGFI-B and Gadd 45 gamma) in early phase of Thy-1 nephritis model

Mesangioproliferative glomerulonephritis (MPGN) is a disease of high incidence in humans. Rat Thy-1 nephritis (Thy-1 N), namely, anti-thymocyte serum (ATS)-induced nephritis, is considered to be an animal model for studying MPGN. Although previous studies have demonstrated that glomerular mesangial cell (GMCs) injury might be a feature of Thy-1 N, the mechanism of the disease (i.e., GMC apoptosis) remains unclear. We have examined the pathologic changes of GMCs and the gene expression profile of renal tissues in Thy-1 N. The pathologic changes of Thy-1 N include three phages: GMC apoptosis (40 min), necrosis (2 h), and proliferation (5 days). Many TUNEL-positive cells are found 40 min after administration of ATS. Concomitantly, 341 genes are up-regulated, whereas 392 genes are down-regulated, as shown by microarrays analysis. The mRNA and protein of two of the up-regulated genes (nerve growth factor induced protein I-B, NGFI-B; growth arrest- and DNA-damage-inducible protein 45 gamma, Gadd 45 gamma) in the GMC apoptotic phase of Thy-1 N are markedly elevated, as observed by real-time polymerase chain reaction and immunohistochemistry. Our data indicate that pathologic changes of Thy-1 N are involved in the abnormal gene profile. The overexpression of the NGFI-B and Gadd 45 gamma genes may be associated with GMC apoptosis of Thy-1 N.

The complement C5b-9 complexes induced injury of glomerular mesangial cells in rats with Thy-1 nephritis by increasing nitric oxide synthesis

Thy-1 nephritis (Thy-1 N), namely, anti-Thy-1 or anti-thymocyte serum (ATS) induced nephritis (ATSN), is a typical model of human mesangioproliferative glomerulonephritis. The pathologic changes of glomerular mesangial cells (GMCs) in Thy-1 N are complement-dependent, especially C5b-9 complexes, but the role of C5b-9 in the mechanism of Thy-1 N has not been defined. Because previous studies have demonstrated that sublytic C5b-9 can increase production of several inflammatory mediators from resident glomerular cells, we utilized the isolated human membrane-bound C5b-9 complexes to stimulate the cultured rat GMCs and examined whether the GMCs can also induce the synthesis of nitric oxide (NO) in vitro. Simultaneously, the effects of antiserum against rat C5b-9 and NG-monomethyl-L-arginine (L-NMMA, NO inhibitor), including interfering with the formation of C5b-9, reducing NO production and GMCs injury were observed. The results showed that sublytic C5b-9 can increase synthesis of inducible NO from the stimulated GMCs, and that the anti-C5b-9 antiserum can obviously inhibit the pathologic changes in Thy-1 N, while L-NMMA can decrease the GMCs damage although the effect is not so significant as that of the anti-C5b-9 antiserum. These findings indicate that the synthesis of NO by GMCs can be promoted by sublytic C5b-9, and that lesions of GMCs in rats with Thy-1 N are prevented by either inhibiting C5b-9 formation or NO elevation in advance. The pathologic changes of GMCs in Thy-1 N are indeed complement C5b-9-dependent, and the glomerular injury can be mediated in part through elevation of NO from the GMCs after the sublytic C5b-9 stimulation.

Morphological and genetic characterization of a cultivated Cordyceps sinensis fungus and its polysaccharide component possessing antioxidant property in H22 tumor-bearing mice

Cordyceps sinensis, one of the most precious traditional Chinese medicines, possesses the antitumor activity, antioxidant activity and the capability of modulating the immune system. In the present study, a fungus strain G1 isolated from wild C. sinensis was identified and initially characterized. A phylogenetic tree was generated based on the sequences of the internal transcribed spacer (ITS) region of related fungi. The analysis of ITS sequence showed that fungus G1 was clustered together with C. sinensis, Tolypocladium cylindrosporum and Tolypocladium inflatum in the phylogenetic tree. Both the morphological character and the ITS sequence analysis establish that fungus G1 is one of the anamorph strains of C. sinensis and belongs to Tolypocladium genus. Furthermore, the polysaccharide (PS) extracted from fungus G1 and its antioxidant activity on H22-bearing mice was investigated. H22 cells were hypodermically injected into the right oxter of each mouse after the ICR mice were treated with PS by means of gavage for 7 days. Then the same administration process continued for 9 days. At the end of the experiments, the tumor weight of each mouse was measured. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) level in mouse liver, brain and serum, as well as glutathione peroxidase (GSH-Px) activity in mouse liver and brain were assayed. The results showed that the H22 tumor growth was significantly inhibited by PS. Moreover, PS significantly enhanced SOD activity of liver, brain and serum as well as GSH-Px activity of liver and brain in tumor-bearing mice. PS also significantly reduced the level of MDA in liver and brain of tumor-bearing mice.

Coeliac disease and risk of renal disease-a general population cohort study

BACKGROUND

Coeliac disease (CD) may be a risk factor for renal disease.

METHODS

We investigated the risk of any form of glomerulonephritis (GN) (acute, chronic and non-specified), chronic glomerulonephritis (CGN) and renal replacement therapy including dialysis treatment and kidney transplantation (KT) in patients with CD in a general population-based cohort study. We used Cox regression to assess the risk of renal disease in 14,336 patients who had received a diagnosis of CD (1964-2003) and 69,875 reference individuals matched for age, calendar year, sex and county. Patients were identified using the Swedish Hospital Discharge Registry. Follow-up began 1 year after study entry.

RESULTS

CD was associated with an increased risk of any form of GN (hazard ratio (HR) = 1.64; 95% confidence intervals (CI) = 1.01-2.66; P = 0.046; 89 events), CGN (HR = 2.65; 95% CI = 1.34-5.24; P = 0.005; 39 events), dialysis (HR = 3.48; 95% CI = 2.26-5.37; P < 0.001; 102 positive events) and KT (HR = 3.15; 95% CI = 1.29-7.71; P = 0.012; 22 events).

CONCLUSION

We suggest that immune characteristics associated with CD increase the risk of chronic renal disease. Individuals with CD may also be at a moderately increased risk of any form of GN.

Contribution of conjugated linoleic acid to the suppression of inducible nitric oxide synthase expression and transcription factor activation in stimulated mouse mesangial cells

That both infiltrating macrophages and resident mesangial cells express inducible nitric oxide synthase (iNOS) and produce nitric oxide (NO) excessively is crucial to the progress of glomerulonephritis. Although several reports have mentioned the protective impacts of conjugated linoleic acid (CLA) in stimulated macrophages, the role of CLA in glomerular mesangial cells is unknown. The aim of the present study was to explore the ability of CLA to regulate iNOS expression and NO production in stimulated glomerular mesangial cells. Additionally, we evaluated the effect of CLA on activation of transcription factors which mediate iNOS expression. Exogenous CLA dose-dependently diminished iNOS mRNA and protein expression as well as NO production in lipopolysaccharide (LPS) plus interferon-gamma (IFN-gamma)-stimulated SV-40-transformed mouse mesangial cells. Electrophoretic mobility shift assay experiments demonstrated that CLA (100 microM) dramatically reduced activation of nuclear factor-kappaB (NF-kappaB), activator protein-1 (AP-1) and cAMP response element binding protein (CREB) induced by LPS/IFN-gamma. Moreover, addition of 100 microM CLA significantly diminished LPS-IFN-gamma-induced protein degradation of inhibitor kappaB-alpha (IkappaB-alpha) and the protein expression of phosphorylated IkappaB-alpha in the cytosolic fraction as well as nuclear p65 expression (P < 0.05). In summary, inhibition of NF-kappaB, AP-1 and CREB activation by CLA may be associated with the molecular basis for which CLA suppresses iNOS expression and NO production in stimulated mesangial cells.

Nitric oxide preserves the glomerular protein permeability barrier by antagonizing superoxide

BACKGROUND

The interaction of nitric oxide with superoxide (O2-) is a major O2- scavenging mechanism that can minimize O2 (-)-mediated oxidative stress. Glomeruli produce both nitric oxide and O2- and generation of both radicals is increased in various forms of glomerular disease. O2- increases glomerular capillary permeability to albumin (P(alb)). The present studies tested the hypothesis that nitric oxide opposes this effect, thereby preserving the glomerular protein permeability barrier.

METHODS

P(alb) was determined in isolated rat glomeruli by measuring the change in glomerular volume in response to an experimental oncotic gradient. Changes in P(alb) in response to O2- generated by tumor necrosis factor-alpha (TNF-alpha) or xanthine/xanthine oxidase (X/XO) was assessed under conditions of nitric oxide depletion and repletion.

RESULTS

Incubation of rat glomeruli with the nitric oxide synthase (NOS) inhibitor L-N(G)-monomethyl arginine (L-NMMA) increased P(alb.) This effect was reversed by the nitric oxide donor diethylenetriamine NONOate (DETA-NONOate) and by the superoxide dismutase (SOD) mimetic Tempol. O2- generated after incubation with TNF-alpha or X/XO increased P(alb). This effect was blocked by DETA-NONOate.

CONCLUSION

We demonstrate that nitric oxide protects the glomerular filtration barrier from injury caused by O2- and suggest that inhibition of nitric oxide synthesis could enhance O2(-)-mediated oxidative injury under pathologic conditions.

Vasodilator-Stimulated Phosphoprotein–Deficient Mice Demonstrate Increased Platelet Activation but Improved Renal Endothelial Preservation and Regeneration in Passive Nephrotoxic Nephritis

Vasodilator-stimulated phosphoprotein (VASP), an actin cytoskeletal protein, is expressed in various cell types including renal cells. In vitro studies provide evidence for a role of VASP regarding platelet activation, cell adhesion, migration, and capillary formation. The in vivo role of VASP was investigated in experimental inflammatory renal disease. Kidneys of healthy VASP deficient (-/-) and wild-type (wt) mice were compared regarding morphology and functional parameters. Passive nephrotoxic nephritis was induced in 28 VASP -/- and 28 wt mice; kidneys were harvested; and tissues were analyzed by morphometric, immunohistochemical, and electron microscopic techniques on days 3, 7, 14, and 28. The time course of disease in VASP -/- mice differed substantially and biphasically from that in wt controls. Early on, VASP -/- mice demonstrated increased platelet influx associated with augmented glomerular and tubulointerstitial inflammation and sclerosis. Whereas renal disease continuously worsened up to day 28 in wt controls, renal disease in VASP -/- mice hardly progressed after day 3 as assessed by various injury indices. This long-term improvement of renal histology in VASP -/- compared with wt mice was associated with remarkable capillary preservation/regeneration up to day 28 mediated via an increased proliferative and a reduced apoptotic activity of VASP-negative peritubular endothelial cells. Despite an enhanced injury response early on, VASP -/- mice are protected from long-term progression of nephrotoxic nephritis, which is associated with improved renal endothelial cell preservation and regeneration.