Aminoguanidine reduces glomerular inducible nitric oxide synthase (iNOS) and transforming growth factor-beta 1 (TGF-beta1) mRNA expression and diminishes glomerulosclerosis in NZB/W F1 mice

Inducible nitric oxide synthase and systemic lupus erythematosus: a systematic review and meta-analysis

Background

There is a growing body of evidences indicating iNOS has involved in the pathogenesis of SLE. However, the role of iNOS in SLE is inconsistency. This systematic review was designed to evaluate the association between iNOS and SLE.

Results

Six studies were included, reporting on a total of 277 patients with SLE. The meta-analysis showed that SLE patients had higher expression of iNOS at mRNA level than control subjects (SMD = 2.671, 95%CI = 0.446–4.897, z = 2.35, p = 0.019), and a similar trend was noted at the protein level (SMD = 3.602, 95%CI = 1.144–6.059, z = 2.87, p = 0.004) and positive rate of iNOS (OR = 9.515, 95%CI = 1.915–47.281, z = 2.76, p = 0.006) were significantly higher in SLE group compared with control group. No significant difference was observed on serum nitrite level between SLE patients and control subjects (SMD = 2.203, 95%CI = -0.386–4.793, z = 1.64, p = 0.095). The results did not modify from different sensitivity analysis, representing the robustness of this study. No significant publication bias was detected from Egger’s test.

Conclusions

There was a positive correlation between increasing iNOS and SLE. However, the source of iNOS is unknown. Besides NO pathway, other pathways also should be considered. More prospective random studies are needed in order to certify our results.

Aminoguanidine affects systemic and lung inflammation induced by lipopolysaccharide in rats

BACKGROUND

Nitric oxide is a mediator of potential importance in numerous physiological and inflammatory processes in the lung. Aminoguanidine (AG) has been shown to have anti-inflammation and radical scavenging properties. This study aimed to investigate the effects of AG, an iNOS inhibitor, on lipopolysaccharide (LPS)-induced systemic and lung inflammation in rats.

METHODS

Male Wistar rats were divided into control, LPS (1 mg/kg/day i.p.), and LPS groups treated with AG 50, 100 or 150 mg/kg/day i.p. for five weeks. Total nitrite concentration, total and differential white blood cells (WBC) count, oxidative stress markers, and the levels of IL-4, IFN-γ, TGF-β1, and PGE2 were assessed in the serum or bronchoalveolar lavage fluid (BALF).

RESULTS

Administration of LPS decreased IL-4 level (p < 0.01) in BALF, total thiol content, superoxide dismutase (SOD) and catalase (CAT) activities (p < 0.001) in BALF and serum, and increased total nitrite, malondialdehyde (MDA), IFN-γ, TGF-β1 and PGE2 (p < 0.001) concentrations in BALF. Pre-treatment with AG increased BALF level of IL-4 and total thiol as well as SOD and CAT activities (p < 0.05 to p < 0.001), but decreased BALF levels of total nitrite, MDA, IFN-γ, TGF-β1, and PGE2 (p < 0.01 to p < 0.001). AG treatment decreased total WBC count, lymphocytes and macrophages in BALF (p < 0.01 to p < 0.001) and improved lung pathological changes including interstitial inflammation and lymphoid infiltration (p < 0.05 to p < 0.001).

CONCLUSIONS

AG treatment reduced oxidant markers, inflammatory cytokines and lung pathological changes but increased antioxidants and anti-inflammatory cytokines. Therefore, AG may play a significant protective role against inflammation and oxidative stress that cause lung injury.

Pathophysiological mechanisms of diarrhea caused by the Vibrio cholerae O1 El Tor variant: an in vivo study in mice

Cholera is caused by infection with Vibrio cholerae. This study aimed to investigate the pathophysiology of diarrhea caused by the V. cholerae O1 El Tor variant (EL), a major epidemic strain causing severe diarrhea in several regions. In the ligated ileal loop model of EL-induced diarrhea in the ICR mice, a cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor and a calcium-activated chloride channel (CaCC) inhibitor similarly inhibited intestinal fluid secretion. In addition, barrier disruption and NF-κB-mediated inflammatory responses, e.g., iNOS and COX-2 expression, were observed in the infected ileal loops. Interestingly, intestinal fluid secretion and barrier disruption were suppressed by NF-κB and COX-2 inhibitors, whereas an iNOS inhibitor suppressed barrier disruption without affecting fluid secretion. Furthermore, EP2 and EP4 PGE2 receptor antagonists ameliorated the fluid secretion in the infected ileal loops. The amount of cholera toxin (CT) produced in the ileal loops by the EL was ∼2.4-fold of the classical biotype. The CT transcription inhibitor virstatin, a toll-like receptor-4 (TLR-4) antibody and a CT antibody suppressed the EL-induced intestinal fluid secretion, barrier disruption and COX-2 expression. The CT at levels detected during EL infection induced mild intestinal barrier disruption without inducing inflammatory responses in mouse intestine. Collectively, this study indicates that CT-induced intestinal barrier disruption and subsequent TLR-4-NF-κB-mediated COX-2 expression are involved in the pathogenesis of EL-induced diarrhea and represent promising novel therapeutic targets of cholera.

Bortezomib treatment prevents glomerulosclerosis associated with lupus nephritis in a murine model through suppressive effects on the immune and renin-angiotensin systems

OBJECTIVE

To clarify the mechanisms underlying lupus nephritis (LN) amelioration following bortezomib treatment.

METHODS

Bortezomib was administered subcutaneously every 3 days to NZB/W F1 mice, and the serum anti-double stranded (ds) deoxyribonucleic acid (DNA) antibody titers and proteinuria levels were measured. The renal samples and the splenocytes were examined histologically or used for real-time quantitative reverse transcription-polymerase chain reaction analysis after 18 weeks of treatment. Serum cytokine and anti-dsDNA antibody levels were measured using flow cytometry and enzyme-linked immunoassays every 3 weeks. Transforming growth factor (TGF)-β, angiotensin II type-1 receptor (AT1R), and type I collagen expression levels in the glomeruli were evaluated using immunohistochemistry.

RESULTS

Bortezomib reduced the serum anti-dsDNA antibody titers and the proteinuria levels. It prevented inflammatory cell infiltrations into and the deposition of immunoglobulin G within the glomeruli. Bortezomib reduced the interferon-γ, interleukin (IL)-4, and IL-10 levels in the serum and the ribonucleic acid expression levels for these cytokines within the splenocytes. Bortezomib prevented type I collagen synthesis by downregulating TGF-β and AT1R expression in the glomeruli.

CONCLUSIONS

Bortezomib exerts multiple immunosuppressive effects and thus ameliorates LN. Furthermore, bortezomib can prevent glomerulosclerosis formation in NZB/W F1 mice through suppressive effects on the renin-angiotensin system.

Therapeutic effect of artemisinin on lupus nephritis mice and its mechanisms

In this study, we investigated the therapeutic effect of artemisinin (Art) on lupus nephritis mice and its mechanisms by comparing the differences between lupus nephritis (LN) mice given Art and control mice in molecular biology, immunohistochemistry, and histopathology. The results showed that Art could remarkably relieve the symptoms, decrease the level of urine protein/24 h, and alleviate pathological renal lesions. The differences among the four groups in the expression of the NF-κBp65 protein, nuclear factor-κB (NF-κB) activity, and the expression of transforming growth factor-β1 (TGF-β1) mRNA in renal tissue suggested that Art can lower the serum levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) and inhibit the expression of the NF-κBp65 protein and NF-κB and TGF-β1 mRNA in the renal tissues of LN mice. These results proved that it is reliable and effective to use Art to treat LN mice, and its therapeutic mechanisms should closely be related to the fact that Art can obviously decrease the serum levels of TNF-α and IL-6 and down-regulate the expression of the NF-κBp65 protein and NF-κB and TGF-β1 mRNA in renal tissues.

Chinese herbal formula Qilong-Lishui granule improves puromycin aminonucleoside-induced renal injury through regulation of bone morphogenetic proteins

BACKGROUND

The Chinese herbal formula Qilong-Lishui granule (QLG) is an effective natural product for treatment of renal disorder. It was composed of six Chinese herbs according to our clinical practice in the treatment of patients with kidney disease. However, molecular and cellular mechanisms of QLG are still unclear. Therefore, the objective of the current study is to investigate molecular and cellular mechanisms of QLG in puromycin aminonucleoside (PAN)-induced nephrotic syndrome.

METHOD

Wistar rats were divided into six groups of sham operation, PAN model, PAN model with high-dosage QLG (QLG-H), PAN model with median-dosage QLG (QLG-M), PAN model with low-dosage QLG (QLG-L), and PAN model with fosinopril (FP). The PAN model was induced by jugular vein injection of PAN at a dose of 5 mg/100 g body weight. Quantities of 24 h urinary protein excretion were examined on days 5, 10, 15, 20, 25 and 30. All rats were sacrificed on day 31 for blood biochemistry, kidney histology and reverse transcriptase-polymerase chain reaction analysis.

RESULTS

PAN-induced nephrotic syndrome was successfully produced in rats. Treatment of QLG significantly reduced protein excretion and blood urea nitrogen and creatinine. QLG and FP treatments also improved protein content in blood, and reduced total cholesterol and triglyceride in blood. Moreover, QLG and FP improved the damage of interstitial induced by PAN. Furthermore, CYP and FP were able to reverse BMPRII and Smad1 mRNAs abundance caused by PAN.

CONCLUSION

QLG attenuates PAN-induced kidney injury possibly through the bone morphogenetic protein signal transduction pathway.

The biology of nitric oxide and other reactive intermediates in systemic lupus erythematosus

Formation of reactive nitrogen and oxygen intermediates (RNI and ROI) is an essential part of the innate immune response. Markers of systemic RNI production are increased in the setting of systemic lupus erythematosus (SLE) activity. Several lines of evidence suggest mechanisms through which the activity of inducible nitric oxide synthase (iNOS) is pathogenic in SLE, including the ability of peroxynitrite (ONOO(-), a product of iNOS activity) to modify proteins, lipids, and DNA. These modifications can alter enzyme activity and may increase the immunogenicity of self antigens, leading to a break in immune tolerance. In humans, observational data suggest that overexpression of iNOS and increased production of ONOO(-) lead to glomerular and vascular pathology. Therapies designed to target iNOS activity or scavenge ROI and RNI are in development and may provide the means to reduce the pathogenic consequences of ROI and RNI in SLE.

Nephritogenic anti-DNA antibodies regulate gene expression in MRL/lpr mouse glomerular mesangial cells

OBJECTIVE

Lupus-associated IgG anti-double-stranded DNA antibodies are thought to be pathogenic in the kidney due to cross-reaction with glomerular antigens, leading subsequently to immune complex formation in situ and complement activation. We undertook this study to determine if pathogenic anti-DNA antibodies may also contribute to renal damage by directly influencing mesangial gene expression.

METHODS

Complementary DNA microarray gene profiling was performed in primary mesangial cells (derived from lupus-prone MRL/lpr mice) treated with pathogenic, noncomplexed anti-DNA antibodies. Significant gene up-regulation induced by anti-DNA antibodies as determined by microarray analysis was further investigated by real-time polymerase chain reaction and methods to detect the relevant proteins. Induction of proinflammatory genes by pathogenic antibodies was confirmed by comparing gene expression in glomeruli of old versus young MRL/lpr mice, and by antibody injection in vivo.

RESULTS

Pathogenic, but not nonpathogenic, antibodies significantly induced a number of transcripts, including CXCL1/KC, LCN2, iNOS, CX3CL1/fractalkine, SERPINA3G, and IkappaBalpha ("marker genes"). Blocking of Fcgamma receptors or using Fcgamma chain-knockout mesangial cells had no effect on the gene regulation effect of the pathogenic antibody R4A, indicating a non-Fc-dependent mechanism. The glomerular expression of these marker genes increased over time with the development of glomerular antibody deposition and active nephritis in MRL/lpr mice. Moreover, injection of R4A into SCID mice in vivo significantly up-regulated glomerular marker gene expression.

CONCLUSION

These findings indicate that the renal pathogenicity of anti-DNA antibodies may be attributed in part to their ability to directly modulate gene expression in kidney mesangial cells through both Fc-dependent and non-Fc-dependent mechanisms.

The antioxidative effects of astragalus saponin I protect against development of early diabetic nephropathy

It has been known that oxidative stress plays an important role in the development of diabetic nephropathy (DN). The antioxidative effects of Astragalus saponin I (AS I) were studied in vitro and in vivo. In the presence of high glucose and H2O2, the total antioxidative capability, catalase, reduced glutathione, and superoxide dismutase level of rat mesangial cells were significantly decreased, and transforming growth factor beta1 (TGF-beta1) mRNA level, collagen IV, and laminin level were significantly increased. When compared with those in the high glucose group, these 4 indexes of cells incubated in 2.0 and/or 20 micromol/L of AS I were significantly enhanced, and levels of TGF-beta1 mRNA, collagen IV and laminin were statistically decreased. By flowcytomery, percentages of S phase of cells incubated in high glucose and H2O2 were lowered, while those in AS I were increased. Furthermore, the physical behaviors of rats treated with 12 mg/kg of AS I restored with vigor and weight gaining, while the level of HbAlC was significantly reduced. Thus, AS I has antioxidative effects and is a potential compound worth further study because it may prevent the development of DN.

Effect of nitric oxide synthase inhibition on proteinuria in glomerular immune injury

In glomerular immune injury, the inducible isoform of nitric oxide synthase (iNOS) becomes a major catalyst of NO production. Although iNOS-catalyzed NO production is sustained and can be cytotoxic, iNOS inhibition exacerbates the magnitude of proteinuria that accompanies immune injury. To investigate putative mechanisms of this effect, we assessed changes in glomerular permeability to albumin by using the following two approaches: (i) an in vivo rat model of glomerular immune injury induced by antibody against the glomerular basement membrane (GBM), in which urine albumin excretion was measured under conditions of iNOS inhibition, and (ii) an ex vivo model of isolated rat glomeruli, in which changes in glomerular capillary permeability to albumin were assessed under conditions of NOS inhibition. In rats with anti-GBM antibody-induced glomerular injury, there was an increase in urine albumin excretion. Treatment with two structurally dissimilar iNOS inhibitors at doses sufficient to decrease urine nitrate and/or nitrite exacerbated proteinuria. In these animals, urine excretion of the isoprostane 8-iso-PGF2alpha (marker of oxidative stress) was increased. In isolated glomeruli incubated with the NOS inhibitor L-NMMA, the permeability to albumin increased. This effect was reversed by the NO donor DETA NONOate and by the superoxide dismutase mimetic Tempol. We conclude that NOS-catalyzed NO production is an important mechanism in regulating glomerular permeability to protein. This mechanism involves control of the bioavailability of superoxide.

Toll-like receptor 2 mediates early inflammation by leptospiral outer membrane proteins in proximal tubule cells

Tubulointerstitial nephritis is a cardinal renal manifestation in leptospirosis and LipL32, the major lipoprotein component of leptospiral outer membrane proteins (OMPs), induces a robust inflammatory response in cultured renal proximal tubule cells through a nuclear factor-kappaB-related pathway. Here, we investigated whether Toll-like receptor (TLR), known to play a pivotal role in innate immunity, could mediate the inflammatory response induced by leptospiral OMPs in renal proximal tubule cells. TLR expression was analyzed by flow cytometry and indirect immunofluorescence in cultured mouse proximal tubule (pyruvate kinase simian virus 40-proximal straight (PKSV-PR)) cells. Reverse transcription-competitive polymerase chain reaction and enzyme-linked immunosorbent assay were undertaken to analyze the inducible effects of inducible nitric oxide synthase (iNOS) and monocyte chemoattractant protein-1 (MCP-1 also termed CCL2) by pathogenic and non-pathogenic leptospiral OMPs and recombinant lipoproteins in either PKSV-PR cells or TLR-transfected human embryonic kidney (HEK) 293 cells. Anti-TLR antibodies were used for blocking experiments. Leptospira santarosai serovar Shermani OMPs and LipL32 induced a significant increase in TLR2 but not TLR4 expression in PKSV-PR cells. The increase in iNOS and CCL2/MCP-1 mRNA expressions could be prevented by an anti-TLR2 antibody, but not by an anti-TLR4 antibody. Furthermore, leptospiral OMPs stimulated both CCL2/MCP-1 mRNA and secreted protein in transfected HEK 293 cells with a TLR2-expressing plasmid, but had no effect in cells with a TLR4-expressing plasmid. In conclusion, these findings indicate that the stimulation of iNOS and CCL2/MCP-1 caused by pathogenic leptospiral OMPs, in particular LipL32, in proximal tubule cells requires TLR2 for the early inflammatory response.

Protective effects of thymoquinone and methotrexate on the renal injury in collagen-induced arthritis

The goal of this investigation was to study the protective effects of thymoquinone (TQ) and methotrexate (MTX) on collagen-induced arthritis (CIA) in rats. On day 0 under ether anesthesia, the experimental groups were immunized with 0.5 mg native chick collagen II (CII) solubilized in 0.1 M acetic acid and emulsified in Freund's incomplete adjuvant. Control rats were gavaged with vehicle, whereas CII was administered intradermally. In addition, arthritis treated with TQ group received TQ (10 mg kg(-1) bw by gavage once a week for 3 weeks starting on day 0); and arthritis treated with MTX group received MTX (MTX was suspended in corn oil and administered by gavage at 1 mg kg (-1) bw once a week for 3 weeks starting on day 0). A significant decrease in the incidence and severity of arthritis by clinical and radiographic assessments was found in recipients of therapy, compared with that of controls. The MTX treatment significantly (P<0.01) decreased the elevated serum NO, urea and creatinine in arthritic rats. Likewise, TQ treatment was also able to reduce significantly (P<0.05) serum NO, urea and creatinine levels, but to lesser extent than MTX. The histopathologic abnormalities are consistent with the hydropic epithelial cell degenerations and moderate tubular dilatation in the some proximal and distal tubules. The severity of the degenerative changes in most of the shrunken glomerules and vascular congestion were also observed in arthritic animals. Preventive treatment of TQ and especially MTX significantly inhibited kidney dysfunction and this histopathologic alterations. These studies indicate that TQ can be used similar to MTX as a safe and effective therapy for CIA and may be useful in the treatment of rheumatoid arthritis.

Leptospiral membrane proteins stimulate pro-inflammatory chemokines secretion by renal tubule epithelial cells through toll-like receptor 2 and p38 mitogen activated protein kinase

BACKGROUND

Leptospiral membrane proteins extracted from pathogenic Leptospira santarosai serovar Shermani (LMPS) stimulated pro-inflammatory chemokines production in cultured mouse proximal tubule epithelial cells (PTECs) and implicated its role in the pathogenesis of leptospira-induced tubulointerstitial nephritis. PTECs express the functional TLR2 and TLR4, which have been shown to play essential roles in innate immunity. This study investigated the roles of Toll-like receptors (TLRs) and mitogen-activated protein kinases (MAPKs) signalling pathways in the pathogenesis of leptospira-induced tubulointerstitial nephritis.

METHODS

The immortalized mouse PKSV-PR late PTECs were used as the model system. The genes expression and secretion of CCL2/monocyte chemoattractant protein-1 (CCL2/MCP-1) and CXCL2/macrophage inflammatory protein-2 (CXCL2/MIP-2) were measured by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme linked immunosorbent assay (ELISA). We investigated MAPKs signalling pathways by Western blot and their reciprocal roles by specific inhibitors. A specific TLR2 neutralizing antibody was applied to evaluate the crosstalk between TLR2 and MAPKs.

RESULTS

The LMPS stimulated extracellular signal-regulated kinases (ERK1/2), c-Jun N-terminal kinases (JNKs) and p38 mitogen-activated protein kinase (p38 MAPK), initiated the nuclear transcription factor kappaB (NF-kappaB), and enhanced the secretion of CCL2/MCP-1 and CXCL2/MIP-2. The LMPS also unregulated the level of TLR2 mRNA expression in PTECs through time- and dose-dependent effects. The LMPS enhanced the secretion of CCL2/MCP-1 and CXCL8/interleukin-8 (CXCL8/IL-8) in TLR-defective human embryonic kidney (HEK) 293 cells only when transfected with a TLR2 expressing plasmid. The secretions of CCL2/MCP-1 and CXCL2/MIP-2 stimulated by LMPS were significantly reduced by incubating PTECs with SB203580, an inhibitor of p38 MAPK. Furthermore, a neutralizing anti-mouse TLR2 antibody hindered the phosphorylation of p38 and LMPS-stimulated secretion of CCL2/MCP-1 and CXCL2/MIP-2.

CONCLUSION

These findings demonstrate that activation of p38 MAPK and release of chemokines by LMPS are mediated by TLR2 in renal proximal tubule cells. These results also implicate the crucial role of innate immunity in leptospira-induced tubulointerstitial nephritis.

Effects of chronic inhibition of inducible nitric oxide synthase in hyperthyroid rats

We hypothesized that nitric oxide generated by inducible nitric oxide synthase (iNOS) may contribute to the homeostatic role of this agent in hyperthyroidism and may, therefore, participate in long-term control of blood pressure (BP). The effects of chronic iNOS inhibition by oral aminoguanidine (AG) administration on BP and morphological and renal variables in hyperthyroid rats were analyzed. The following four groups (n = 8 each) of male Wistar rats were used: control group and groups treated with AG (50 mg.kg(-1).day(-1), via drinking water), thyroxine (T4, 50 microg.rat(-1).day(-1)), or AG + T4. All treatments were maintained for 3 wk. Tail systolic BP and heart rate (HR) were recorded weekly. Finally, we measured BP (mmHg) and HR in conscious rats and morphological, plasma, and renal variables. T(4) administration produced a small BP (125 +/- 2, P < 0.05) increase vs. control (115 +/- 2) rats. AG administration to normal rats did not modify BP (109 +/- 3) or any other hemodynamic variable. However, coadministration of T4 and AG produced a marked increase in BP (140 +/- 3, P < 0.01 vs. T4). Pulse pressure and HR were increased in both T4- and T4 + AG -treated groups without differences between them. Plasma NOx (micromol/l) were increased in the T4 group (10.02 +/- 0.15, P < 0.05 vs. controls 6.1 +/- 0.10), and AG reduced this variable in T4-treated rats (6.81 +/- 0.14, P < 0.05 vs. T4) but not in normal rats (5.78 +/- 0.20). Renal and ventricular hypertrophy and proteinuria of hyperthyroid rats were unaffected by AG treatment. In conclusion, the results of the present paper indicate that iNOS activity may counterbalance the prohypertensive effects of T4.

Nitric oxide and glomerulonephritis

Glomerulonephritis is a common clinical condition that is caused by immune-mediated injury to the kidney and is characterized by dysfunction of the glomerular capillary filtration barrier. Nitric oxide (NO), a ubiquitous molecule with many biological functions throughout the body, has been evaluated as an inflammatory mediator in these circumstances. NO may induce glomerular injury directly or may act via stimulation of a host of other inflammatory mediators. A variety of experimental models of glomerulonephritis have been studied including those induced by infusion of antibodies to the Thy1.1 antigen or glomerular basement membrane, Heymann nephritis, and autoimmune nephritis. In virtually all of these cases there is evidence of increased NO production. Excessive production of NO by inducible nitric oxide synthase (iNOS), derived from infiltrating immune cells or resident glomerular cells, nearly always is associated with increased glomerular injury. Interventions that inhibit this enzyme result in less proteinuria and diminished glomerular damage. In contrast, NO derived from endothelial nitric oxide synthase (eNOS) may limit glomerular disease by preserving endothelial cell integrity. There are only a limited number of studies that have evaluated the impact of NO in patients with glomerulonephritis. Although the bulk of evidence supports a role of NO as a pro-inflammatory mediator in glomerulonephritis, additional work is needed to show an association between altered NO production and the severity and outcome of disease in patients with this disease. It is hoped that better understanding of the role of NO in glomerulonephritis will lead to the development of therapies to ameliorate the disease.

Involvement of inducible nitric oxide synthase in renal failure after mild hemorrhage

The role of iNOS in rats after mild hemorrhaging was examined in this study. A mild hemorrhage (17% of total blood) induced a decrease of systemic blood pressure and heart rate, transiently followed by gradual recovery. The hemorrhage caused expression of renal iNOS mRNA and an increase in systemic NO products at 1 h after bleeding. Serum creatinine and serum urea nitrogen (UN) increased progressively up to 5 h after bleeding. Light microscopic findings showed that some inflammatory monocytes, mainly consisting of neutrophil, often existed in the glomerular capillaries, eosinophilic changes were observed in the cytoplasm at the proximal tubules, and urinary casts existed in the uriniferous space at 5 h after bleeding. The selective iNOS inhibitor, S-methylisothiourea (MTU), suppressed hemorrhagic expression of renal iNOS mRNA and systemic NO products, suppressed the increases of serum creatinine and UN, and improved renal histological aggravations induced by hemorrhaging. We speculated that MTU caused the negative circuit to suppress the renal failure through a decrease of NO generation. These results in the present study showed that iNOS expression induced by mild hemorrhaging at the early phase did participate in the development of renal failure.

Role of inducible nitric oxide synthase in pig liver transplantation

BACKGROUND

Previously, we clarified the role of inducible nitric oxide synthase (iNOS) and the protective effect of an iNOS inhibitor in warm ischemia and reperfusion model. In this study, we investigated whether the same effects would be obtained by iNOS inhibitor in liver transplantation model.

MATERIAL AND METHODS

Orthotopic liver transplantation was performed in pigs in the usual manner after about 6 h of cold preservation in University of Wisconsin solution. Aminoguanidine hemisulfate (AG) was used as the iNOS inhibitor and AG was administered intraportally at the dose of 10 mg/kg just after reperfusion. Two experimental groups were subjected, control group (n = 10), and AG group (n = 10). We investigated changes of serum nitrite/nitrate (NOx) and aspartate aminotransferase (AST). Expression of iNOS was examined by immunohistochemistry, including a double immunofluorescnce technique in combination with cofocal laser scanning microscopy.

RESULTS

Serum NOx and AST were significantly lower in the AG group. Histological hepatic damage and thrombocyte thrombi were attenuated in the AG group. Expression of iNOS was recognized strongly at Kupffer cells and neutrophils in the centrilobular region of liver after reperfusion by cofocal laser scanning microscopy. Moreover, iNOS staining was attenuated in AG group compared with control group.

CONCLUSIONS

These results indicate that hepatic ischemia and reperfusion injury in liver transplantation might be triggered by iNOS expression of Kupffer cells and neutrophils, and attenuated by administration of an iNOS inhibitor. Moreover, AG showed down regulation of iNOS expression after reperfusion.

Effect of mycophenolate mofetil on severity of nephritis and nitric oxide production in lupus-prone MRL/lpr mice

Mycophenolate mofetil (MMF), an immunosuppressive drug commonly used in organ transplantation, is increasingly being used to treat autoimmune diseases including systemic lupus erythematosus (SLE). Excessive production of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) has been implicated in the pathogenesis of lupus nephritis. We evaluated the effect of MMF on the severity of nephritis and the production of NO in lupus-prone MRL/lpr mice. Eight-week-old female MRL/lpr mice (n = 20) were treated with MMF (100 mg/kg/day) by oral gavage for 12 weeks. Control mice (n = 20) received vehicle on the same schedule. The mice were killed after 12 weeks of treatment. Treatment with MMF significantly decreased the amount of proteinuria, prolonged survival and reduced the histological severity of glomerulonephritis. Urinary nitrite/nitrate excretion in the MMF-treated mice was significantly reduced during the first 8 weeks of treatment. However, by the end of the 12 weeks' treatment period, there was no significant difference between vehicle and MMF-treated mice in terms of urinary nitrite/nitrate excretion, intra-renal production of NO, expression of iNOS protein and induction of iNOS mRNA. We conclude that MMF is effective in attenuating the severity of nephritis in MRL/lpr mice. The beneficial effects of MMF on lupus nephritis during the early phase of the disease might be partly attributed to the inhibition of NO production. The inhibitory effect of MMF on NO production diminishes as the disease progresses. MMF probably has additional, as yet undefined mode of actions to fully account for its beneficial effects on lupus nephritis.

Nitric oxide production in renal cells by immune complexes: Role of kinases and nuclear factor-kappaB

BACKGROUND

Interaction of deposited immune complexes (IC) with Fc receptors (FcR) on tissue cells elicits the release of inflammatory mediators leading to tissue damage. Nitric oxide (NO) radicals generated by inducible NO synthase (iNOS) are important mediators in inflammatory processes. To analyze the role of NO in IC-mediated glomerular inflammation, we studied the in vitro and in vivo expression of iNOS in renal cells [resident mesangial cells (MC), and infiltrating monocytes] induced by IC, and the possible intermediate steps between FcR occupancy and iNOS induction.

METHODS

MC and monocytes were stimulated with IgG- and IgA-containing IC, and NO production (nitrite accumulation), iNOS transcription (luciferase assay) and their expression was measured by RT-PCR and Western blot. The involvement of FcR, transcription factor nuclear factor-kappaB (NF-kappaB), and protein kinases was assessed by using Fc fragments and specific inhibitors. Immune glomerulonephritis was induced in rats, and iNOS expression and NF-kappaB activation were analyzed.

RESULTS

In MC and monocytes, IC enhanced iNOS transcription/expression and NO generation, which were attenuated by specific inhibitors of NF-kappaB. In addition, mitogen-activated protein kinase (MAPK) inhibitors decreased NO production, but did not interfere with NF-kappaB activity, suggesting that both pathways may converge downstream in the induction of iNOS. In experimental immune glomerulonephritis, increased iNOS expression correlated with proteinuria levels, and appeared colocalized with NF-kappaB in glomerular and infiltrating cells. Treatment of animals and cells with Fc fragments prevented iNOS induction and NF-kappaB activation by IC.

CONCLUSIONS

These results indicate that IC, through activation of FcR, induce iNOS expression in renal resident and recruited cells by mechanisms involving MAPK and NF-kappaB, and support the idea of the important role of local NO generation in IC-mediated glomerular injury.

Evidence for the existence of two distinct functions for the inducible NO synthase in the rat kidney: effect of aminoguanidine in rats with 5/6 ablation

The functional role of the NO synthase (NOS) isoforms in the normal or diseased kidney is uncertain. This study examined the renal expression of the endothelial (eNOS), neuronal (nNOS), and inducible (iNOS) isoforms by both immunohistochemistry and Western blot analyses in sham-operated rats (S) and in rats subjected to 5/6 nephrectomy (Nx). Primary antibodies from two different sources were used to detect iNOS. Additional S and Nx rats were chronically treated with aminoguanidine (AG), a selective iNOS inhibitor. All three isoforms were clearly expressed in S kidney. Their renal abundance, evaluated by Western blot analysis, fell in Nx rats. With the use of anti-iNOS antibodies from two distinct sources, the immunohistochemical analysis showed the presence of what appeared to be two distinct iNOS fractions: a "tubular" fraction, present in S and with decreased intensity in Nx; and an "interstitial" fraction, observed only in inflamed areas of Nx rats. AG treatment greatly attenuated renal injury in Nx rats by a direct antiinflammatory effect, likely related to iNOS inhibition, rather than to amelioration of renal hemodynamics or to reduced protein glycation. These observations suggest that: (1) the functional role of the renal iNOS isoform may vary dramatically under different physiologic conditions; (2) caution should be taken in the interpretation of immunohistochemical iNOS data, because antibodies from different sources may detect different iNOS fractions; and (3) AG treatment may become useful in the treatment of human progressive nephropathies, even those not associated with diabetes or aging.

The Leptospira outer membrane protein LipL32 induces tubulointerstitial nephritis-mediated gene expression in mouse proximal tubule cells

Tubulointerstitial nephritis is a main renal manifestation caused by pathogenic leptospira that accumulate mostly in the proximal tubules, thereby inducing tubular injury and tubulointerstitial nephritis. To elucidate the role of leptospira outer membrane proteins in tubulointerstitial nephritis, outer membrane proteins from pathogenic Leptospira shermani and nonpathogenic Leptospira patoc extracted by Triton X-114 were administered to cultured mouse proximal tubule cells. A dose-dependent increase of monocyte chemoattractant protein-1 (MCP-1), RANTES, nitrite, and tumor necrosis factor-alpha (TNF-alpha) in the culture supernatant was observed 48 h after incubating Leptospira shermani outer membrane proteins with mouse proximal tubule cells. RT competitive-PCR experiments showed that Leptospira shermani outer membrane proteins (0.2 microg/ml) increased the expression of MCP-1, nitric oxide synthase (iNOS), RANTES, and TNF-alpha mRNA by 3.0-, 9.4-, 2.5-, and 2.5-fold, respectively, when compared with untreated cells. Outer membrane proteins extract from avirulent Leptospira patoc did not induce significant effects. The pathogenic outer membrane proteins extract contain a major component of a 32-kD lipoprotein (LipL32), which is absent in the nonpathogenic leptospira outer membrane. An antibody raised against LipL32 prevented the stimulatory effect of Leptospira shermani outer membrane proteins extract on MCP-1 and iNOS mRNA expression in cultured proximal tubule cells, whereas recombinant LipL32 significantly stimulated the expression of MCP-1 and iNOS mRNAs and augmented nuclear binding of nuclear factor-kappaB (NF-kappaB) and AP-1 transcription factors in proximal tubule cells. An antibody raised against LipL32 also blunted the effects induced by the recombinant LipL32. This study demonstrates that LipL32 is a major component of pathogenic leptospira outer membrane proteins involved in the pathogenesis of tubulointerstitial nephritis.

Modulation of renal disease in MRL/lpr mice by pharmacologic inhibition of inducible nitric oxide synthase

BACKGROUND

MRL-MPJFaslpr (MRL/lpr) mice spontaneously develop lupus-like disease characterized by immune complex glomerulonephritis and overproduction of nitric oxide (NO). Blocking NO production pharmacologically by a non-specific nitric oxide synthase (NOS) inhibitor ameliorated renal disease in MRL/lpr mice while genetically deficient inducible NOS (iNOS) mice developed proliferative glomerulonephritis similar to wild-type controls.

METHODS

To clarify the role of iNOS in the pathogenesis of nephritis in MRL/lpr mice, we treated mice with two different NOS inhibitors. Either NG-monomethyl-l-arginine (L-NMMA), a nonspecific NOS inhibitor, or l-N6-(1-iminoethyl)lysine (L-NIL), an iNOS specific inhibitor, was administered in the drinking water from 10 through 22 weeks of age with disease progression monitored over time. Control mice received water alone.

RESULTS

Both L-NMMA and L-NIL blocked NO production effectively in MRL/lpr mice. As expected, neither L-NNMA nor L-NIL had an effect on antibody production, immune complex deposition or complement activation. Although both NOS inhibitors decreased protein excretion, L-NMMA was more effective than L-NIL. Pathologic renal disease was significantly decreased at 19 weeks in both treatment groups. At 22 weeks the L-NIL treated mice, but not the L-NMMA mice, had significantly reduced renal disease scores compared to controls.

CONCLUSION

These results indicate that specific inhibition of iNOS blocks the development of pathologic renal disease in MRL/lpr mice.

High glucose increases inducible NO production in cultured rat mesangial cells. Possible role in fibronectin production

BACKGROUND/AIM

Increased nitric oxide (NO) generation and action have been suggested to be associated with glomerular hyperfiltration and increased vascular permeability early in diabetes. However, previous studies have primarily focused on the constitutive nitric oxide synthase (cNOS) pathway present in endothelial cells, and the role of the inducible NOS (iNOS) pathway in diabetic nephropathy has remained unclear. This study examined whether high glucose modulates NO synthesis by the iNOS pathway in rat mesangial cells. In addition, the effect of inhibition of the iNOS pathway on fibronectin production was determined to examine the role of the iNOS pathway in high glucose-induced extracellular expansion by mesangial cells.

METHODS

NO synthesis by the iNOS pathway was evaluated by nitrite and iNOS mRNA and protein productions. The effects of protein kinase C (PKC) inhibitor and aldose reductase inhibitor on the iNOS mRNA expression and aminoguanidine, a relatively specific inhibitor of the iNOS on fibronectin protein production were examined.

RESULTS

High 30 mM glucose concentration led to significant increases in nitrite production of rat mesangial cells upon stimulation with lipopolysaccharide (LPS) plus interferon-gamma (IFN-gamma) compared with control 5.6 mM glucose concentration. Mesangial iNOS mRNA expression and protein production also increased significantly in response to high glucose. The addition of calphostin C, a PKC inhibitor, and 6-bromo-1,3-dioxo-1H-benz[d,e]isoquinoline-2(3H)-acetic acid, an aldose reductase inhibitor, significantly suppressed the enhancement of iNOS mRNA expression in high glucose concentration. High glucose also significantly increased fibronectin protein production of mesangial cells upon stimulation with LPS plus IFN-gamma compared to control glucose. Aminoguanidine reversed this high glucose-induced fibronectin production at dose inhibiting iNOS mRNA expression.

CONCLUSIONS

These results indicate that high glucose enhances cytokine-induced NO production by rat mesangial cells, and that the activation of PKC and aldose reductase pathway may play a role in this enhancement. In addition, high glucose-induced NO production by the iNOS pathway may promote extracellular matrix accumulation by mesangial cells under certain condition.

Nitric oxide and mechanisms of redox signalling: matrix and matrix-metabolizing enzymes as prime nitric oxide targets

One of the greatest biomedical breakthroughs of the twentieth century was the discovery of endothelium-derived relaxing factor and its identification as nitric oxide (NO). NO has received special attention ever since: besides its potent vasodilatory and vasoprotective effects, NO was identified as a key player in innate immunity and was found to act as an unconventional type of neurotransmitter. This article focuses on mechanisms of NO signalling that form the basis of functional cell responses to accommodate changes in the cellular microenvironment. Redox-based regulation of signal transduction and, on a more long-term scale, changes in gene expression will be exemplified by NO-modulation of matrix components and matrix-metabolizing enzymes. It seems to be a safe bet that ongoing analyses of NO signalling and gene expression will provide a wealth of promising therapeutic targets in human diseases.

Hypothesis: can glucose-insulin-potassium regimen in combination with polyunsaturated fatty acids suppress lupus and other inflammatory conditions?

In systemic lupus erythematosus, plasma concentrations of tumor necrosis factor alpha (TNF alpha) and other pro-inflammatory cytokines are elevated and those of transforming growth factor beta (TGF beta) are decreased. TNF alpha prevents lupus nephropathy whereas increased concentration of TGF beta causes glomerulosclerosis. Insulin inhibits TNF alpha and enhances TGF beta production, augments nitric oxide synthesis and blocks superoxide anion generation. Polyunsaturated fatty acids (PUFAs) also have actions similar to insulin. Hence, it is suggested that a combination of insulin (in the form of glucose-insulin-potassium) and PUFAs may be of benefit in lupus and other inflammatory conditions.

Mycophenolate mofetil reduces renal cortical inducible nitric oxide synthase mRNA expression and diminishes glomerulosclerosis in MRL/lpr mice

Overexpression of inducible nitric oxide synthase (iNOS) has been implicated in the pathogenesis of lupus glomerulonephritis. Mycophenolate mofetil (MMF), a novel immunosuppressive agent, is currently used in organ transplantation and under evaluation for treatment of autoimmune disorders. Mycophenolic acid, the active metabolite of MMF, has been shown to suppress cytokine-induced nitric oxide production in vitro. The aim of this study was to evaluate the effect of MMF on the expression of renal cortical iNOS mRNA and protection against glomerulonephritis in MRL/lpr mice. Three-month-old MRL/lpr mice (n = 6) displaying clinical symptoms of glomerulonephritis were treated for 3 months with MMF (90 mg/kg/day) dissolved in a vehicle. Controls were age- and sex-matched mice (n = 6) that received the vehicle alone. By reverse-transcription competitive polymerase chain reaction, we found that the renal cortical iNOS/beta-actin mRNA ratio was reduced by 30.8% (P <.05) in MMF-treated mice. Furthermore, MMF significantly reduced urinary nitrite production and degree of glomerulosclerosis. The glomerular volume was reduced by 17.5% (P <.001). Proteinuria was also significantly reduced in the MMF-treated group. However, by electrophoretic mobility shift assay, the nuclear binding of nuclear factor-kappaB (NF-kappaB) was not affected by MMF treatment. We conclude that in addition to its immunosuppressive action, MMF may reduce renal cortical iNOS mRNA expression and diminish glomerulosclerosis in MRL/lpr mice independent of modulation of the NF-kappaB pathway.

Leptospira outer membrane protein activates NF-kappaB and downstream genes expressed in medullary thick ascending limb cells

Tubulointerstitial nephritis is the main manifestation of acute renal damage caused by leptospirosis, but the mechanism remains unexplored. Patients infected with LEPTOSPIRA: shermani in Taiwan disclosed tubular dysfunction particularly in the medullary thick ascending limb of loop of Henle (mTAL), and the related renal damage seems to be underestimated. To elucidate the mechanism of tubular damage, outer membrane protein extract from LEPTOSPIRA: was administered to a model of cultured mTAL cells derived from normal mice. The addition of outer membrane protein extract from L. shermani to cultured mTAL cells induced a significant nuclear DNA binding of the NF-kappa B transcription factor by electrophoresis mobility shift assay. Forty-eight h after adding the outer membrane protein extract (0.2 microg/ml) to the cultured cells, the expression of inducible nitric oxide mRNA increased by 4.2-fold, monocyte chemoattractant protein-1 by 3-fold, and tumor necrosis factor-alpha by 2.4-fold when compared with untreated cells examined by reverse transcription competitive-PCR. Supernatant nitrite, monocyte chemoattractant protein-1, and tumor necrosis factor-alpha protein levels also increased by 1.8-, 7.1-, and 5-fold, respectively. An antiserum raised against L. shermani largely prevented these effects. Outer membrane protein extract from L. bratislava induced fewer effects than L. shermani, and the avirulent nonpathogenic L. biflexa serovar patoc did not induce significant effects in the mTAL cells. In conclusion, L. shermani infection may cause mTAL cell damage and inflammation through the NF-kappa B-associated pathway. Findings of this study may be important in understanding the pathogenesis of tubulointerstitial nephritis caused by these organisms.

Prospective measure of serum 3-nitrotyrosine levels in systemic lupus erythematosus: correlation with disease activity

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease. Overproduction of nitric oxide (NO) has been implicated in its pathogenesis. Several retrospective studies have indicated a correlation between serum nitrate and nitrite (NOx) and disease activity. This measure of NO production can be falsely elevated by exogenous dietary and medication sources of NOx and variably reduced by serum thiols. These variables can make NOx a less reliable tool for studying the role of NO in SLE. Peroxynitrite, a by-product of NO and superoxide, nitrates tyrosine moieties. The resulting 3-nitrotyrosine (3NT) serves as a long-term indicator of NO-mediated protein modifications that is not affected by exogenous sources of NOx or serum thiols. We hypothesized that for these reasons serum 3NT levels would correlate with lupus disease activity more significantly than serum NOx. To address this hypothesis, we prospectively evaluated lupus disease activity, serum protein 3NT levels, and NOx levels in a cohort of lupus patients at 3-month intervals. Serum 3NT correlated with disease activity among African-Americans, while NOx correlated with disease activity among Caucasians. Subjects with active lupus nephritis had higher levels of serum 3NT than those without renal disease. Immunohistochemical analysis of renal biopsies from subjects with active proliferative lupus nephritis revealed renal expression of inducible NO synthase. The results of this study suggest that overproduction of NO may play a pathogenic role in SLE and lupus nephritis. Serum 3NT may be a useful, new tool for studying the contributions of NO to the pathogenesis of SLE.