Renal Neutrophil Research Articles

CHOP deficiency results in elevated lipopolysaccharide-induced inflammation and kidney injury

C/EBP homologous protein (CHOP) is an important mediator of endoplasmic reticulum (ER) stress-induced cell and organ injury. Here we show that lipopolysaccharide (LPS)-induced acute kidney injury (AKI) is associated with ER stress and elevated CHOP. We postulated that CHOP(-/-) mice would be protected against LPS-induced-AKI. Unexpectedly, while Toll-like receptor 4 (TLR4) expression levels were comparable in kidneys of CHOP(-/-) and wild-type (WT) mice, CHOP(-/-) mice developed more severe AKI after LPS injection. Furthermore, the severe kidney injury in CHOP(-/-) mice was associated with an exaggerated inflammatory response. Serum TNF-α levels were more elevated in LPS-treated CHOP(-/-) mice. There was a 3.5-fold higher amount of renal neutrophil infiltrates in LPS-treated CHOP(-/-) than in WT mice. Additionally, the kidneys of LPS-treated CHOP(-/-) mice had a more prominent increase in NF-κB activation and further upregulation of proinflammatory genes, i.e., c-x-c motif ligand 1 (CXCL-1), macrophage inflammatory protein-2 (MIP-2), and IL-6. Finally, proximal tubules, glomeruli, and podocytes isolated from CHOP(-/-) mice also had an exaggerated proinflammatory response to LPS. Since LPS directly increased CHOP in glomeruli and podocytes of WT mice, together these data suggest that the LPS-induced increase of CHOP in kidneys may inhibit inflammatory response in renal cells and provide protection against AKI.

Role of the transient receptor potential vanilloid type 1 channel in renal inflammation induced by lipopolysaccharide in mice.

To determine the role of the transient receptor potential vanilloid type 1 (TRPV1) channel in the regulation of renal inflammation, lipopolysaccharide (LPS, 3 mg/kg) was intraperitoneally injected into wild-type (WT) and TRPV1-null mutant (TRPV1(-/-)) mice. The kidney and serum were collected 6 or 24 h after LPS injection for morphological analysis and proinflammatory cytokine assay. LPS injection led to a similar degree of transient hypotension and bradycardia in WT and TRPV1(-/-) mice determined by a telemetry system. LPS administration caused parenchymal red blood cell congestion and fading of intact glomerular structure in TRPV1(-/-) compared with WT mice. Serum creatinine levels were higher 24 h after LPS injection in TRPV1(-/-) than in WT mice. Neutrophil and macrophage infiltration in the kidneys was greater 6 h for the former and 24 h for both after LPS injection in TRPV1(-/-) than in WT mice. Serum cytokine levels including tumor necrosis factor (TNF)-α, IL-1β, and IL-6 were higher 6 h after LPS injection in TRPV1(-/-) compared with WT mice. Likewise, renal chemokine levels including keratinocyte-derived chemokines and macrophage inflammatory protein were higher 6 h after LPS injection in TRPV1(-/-) than in WT mice. Renal VCAM-1 and ICAM-1 expression was further elevated 6 h for the former and 24 h for the latter after LPS injection in TRPV1(-/-) than in WT mice. Renal nuclear factor-κB (NF-κB) activity was further increased 6 h after LPS injection in TRPV1(-/-) compared with WT mice. Pharmacological blockade TRPV1 in WT mice showed aggravated renal and serum inflammatory responses resembling that of TRPV1(-/-) mice. Thus TRPV1 gene ablation exacerbates LPS-induced renal tissue and function injury, including aggravated renal neutrophil and macrophage infiltration, chemokine and adhesion molecule levels, and glomerular hypercellularity accompanying with further increased serum creatinine and cytokine levels. These results indicate that TRPV1 is activated during LPS challenge, which may constitute a protect mechanism against LPS-induced renal injury via reducing renal inflammatory responses.

Effects of hydrogen sulphide in an experimental model of renal ischaemia–reperfusion injury

Renal ischaemia-reperfusion injury (IRI) is a major cause of acute renal failure and renal transplant dysfunction. The aim of this study was to investigate the efficacy of the endogenous gaseous signalling molecule hydrogen sulphide in protecting against renal IRI. Large White female pigs underwent laparotomy and cross-clamping of the left renal pedicle for 60 min. Animals were allocated randomly to treatment with either intravenous hydrogen sulphide (n = 6) or saline control (n = 6) 10 min before clamp release, and then underwent a right nephrectomy. Staff were blinded to treatment allocation and animals were recovered for 7 days. Hydrogen sulphide therapy resulted in a marked reduction in kidney injury with reduced serum creatinine levels on days 1-5, in a reduced area under the creatinine-time curve, and a halving of the time to achieve a creatinine level of less than 250 µmol/l, compared with the control. Hydrogen sulphide also preserved glomerular function, as shown by the urinary protein/creatinine ratio, which, compared with baseline, increased on days 1 and 3 in the control group (mean(s.e.m.) 3·22(1·43), P = 0·016 and 2·59(1·27), P = 0·031), but not in the treatment group (0·99(0·23), P = 0·190 and 1·06(0·44), P = 0·110, respectively). Mean(s.e.m.) tumour necrosis factor α levels at 6 h postreperfusion increased in the control animals (56(6) versus 115(21) pg/ml; P = 0·026), but not in the hydrogen sulphide-treated animals (61(7) versus 74(11) pg/ml; P = 0·460). Renal neutrophil infiltration at 30 min (myeloperoxidase staining) was also significantly reduced by treatment with hydrogen sulphide (P = 0·016). Hydrogen sulphide offers a promising new approach to ameliorating renal IRI with potential translation into a number of clinical settings, including renal transplantation.

Interleukin-11 protects against renal ischemia and reperfusion injury

Renal ischemia reperfusion (IR) injury causes renal tubular necrosis, apoptosis, and inflammation leading to acute and chronic kidney dysfunction. IL-11 is a multifunctional hematopoietic cytokine clinically approved to treat chemotherapy-induced thrombocytopenia. Recent studies suggest that IL-11 also has potent antiapoptotic and antinecrotic properties. In this study, we tested the hypothesis that exogenous IL-11 protects against renal IR injury and determined the mechanisms involved in renal protection. Pretreatment with human recombinant IL-11 (HR IL-11) or with long-acting site-specific polyethylene glycol (PEG)-conjugated human IL-11 analog (PEGylated IL-11) produced partial but significant protection against renal IR injury in mice. In addition, HR IL-11 or PEGylated IL-11 given 30-60 min after IR also provided renal protection in mice. Significant reductions in renal tubular necrosis and neutrophil infiltration as well as tubular apoptosis were observed in mice treated with HR IL-11 or PEGylated IL-11. Furthermore, HR IL-11 or PEGylated IL-11 decreased both necrosis and apoptosis in human proximal tubule (HK-2) cells in culture. Mechanistically, IL-11 increased nuclear translocation of hypoxia-inducible factor-1α (HIF-1α) and induced sphingosine kinase-1 (SK1) expression and activity in HK-2 cells. Moreover, selective HIF-1α inhibitors blocked IL-11-mediated induction of SK1 in HK-2 cells. Finally, HR IL-11 or PEGylated IL-11 failed to protect against renal IR injury in SK1-deficient mice. Together, our data show powerful renal protective effects of exogenous IL-11 against IR injury by reducing necrosis, inflammation, and apoptosis through induction of SK1 via HIF-1α.

A1 adenosine receptor allosteric enhancer PD-81723 protects against renal ischemia-reperfusion injury

Activation of A(1) adenosine receptors (ARs) protects against renal ischemia-reperfusion (I/R) injury by reducing necrosis, apoptosis, and inflammation. However, extrarenal side effects (bradycardia, hypotension, and sedation) may limit A(1)AR agonist therapy for ischemic acute kidney injury. Here, we hypothesized that an allosteric enhancer for A(1)AR (PD-81723) protects against renal I/R injury without the undesirable side effects of systemic A(1)AR activation by potentiating the cytoprotective effects of renal adenosine generated locally by ischemia. Pretreatment with PD-81723 produced dose-dependent protection against renal I/R injury in A(1)AR wild-type mice but not in A(1)AR-deficient mice. Significant reductions in renal tubular necrosis, neutrophil infiltration, and inflammation as well as tubular apoptosis were observed in A(1)AR wild-type mice treated with PD-81723. Furthermore, PD-81723 decreased apoptotic cell death in human proximal tubule (HK-2) cells in culture, which was attenuated by a specific A(1)AR antagonist (8-cyclopentyl-1,3-dipropylxanthine). Mechanistically, PD-81723 induced sphingosine kinase (SK)1 mRNA and protein expression in HK-2 cells and in the mouse kidney. Supporting a critical role of SK1 in A(1)AR allosteric enhancer-mediated renal protection against renal I/R injury, PD-81723 failed to protect SK1-deficient mice against renal I/R injury. Finally, proximal tubule sphingosine-1-phosphate type 1 receptors (S1P(1)Rs) are critical for PD-81723-induced renal protection, as mice selectively deficient in renal proximal tubule S1P(1)Rs (S1P(1)R(flox/flox) PEPCK(Cre/-) mice) were not protected against renal I/R injury with PD-81723 treatment. Taken together, our experiments demonstrate potent renal protection with PD-81723 against I/R injury by reducing necrosis, inflammation, and apoptosis through the induction of renal tubular SK1 and activation of proximal tubule S1P(1)Rs. Our findings imply that selectively enhancing A(1)AR activation by locally produced renal adenosine may be a clinically useful therapeutic option to attenuate ischemic acute kidney injury without systemic side effects.

Age-dependent Role of Microvascular Endothelial and Polymorphonuclear Cells in Lipopolysaccharide-induced Acute Kidney Injury

The incidence of acute kidney injury following severe sepsis is higher in the elderly. We hypothesized that microvascular endothelium is "primed" by aging and that sepsis represents a "second hit," resulting in more severe microvascular complications. Three- and 18-months-old mice were intraperitoneally injected with 1,500 EU/g body weight lipopolysaccharide and sacrificed after 8 h. Flow cytometry and myeloperoxidase ELISA determined neutrophils in plasma. Quantitative reverse transcription polymerase chain reaction was used to analyze messenger ribonucleic acid levels of cell adhesion molecules P-selectin and E-selectin, vascular cell adhesion protein-1, intercellular adhesion molecule-1, angiopoietin receptor TIE-2, and angiopoietins Ang1 and Ang2. In kidney tissue we assessed neutrophil influx and E-selectin protein expression. Neutrophils were depleted with the monoclonal antibody NIMP. At basal conditions, microvascular endothelial cell activation status was similar in both groups, except for a higher Ang-2 expression (P < 0.05) in the kidney of aged mice. Lipopolysaccharide-induced increase in neutrophil count was higher in old (3.3-fold change) compared with young mice (2.2-fold change). Messenger ribonucleic acid analysis showed higher upregulation of P- and E-selectin (P = 0.0004, P = 0.0007) after lipopolysaccharide administration in kidneys of elderly mice, which was confirmed at the protein level for E-selectin. Renal neutrophil influx in lipopolysaccharide-treated aged mice was increased (2.5-fold induction in aged and 2.1-fold in young, P < 0.0001). Polymorphonuclear cell depletion exaggerated the lipopolysaccharide-induced kidney injury. Ang-2 is increased in older mice, which might cause priming of the endothelial cells. Endothelium responded by a more extensive increase in expression of P- and E-selectin in older mice and increased polymorphonuclear cell influx.

Renal neutrophil gelatinase associated lipocalin expression in lipopolysaccharide-induced acute kidney injury in the rat

BackgroundNeutrophil gelatinase associated lipocalin (NGAL) is a highly predictive biomarker of acute kidney injury. To understand the role of NGAL in renal injury during sepsis, we investigated the temporal changes and biological sources of NGAL in a rat model of acute kidney injury, and explored the relationship between renal inflammation, humoral NGAL and NGAL expression during endotoxemia.MethodsTo induce acute renal injury, rats were treated with lipopolysaccharide (LPS, 3.5 mg/kg, ip), and the location of NGAL mRNA was evaluated by in situ hybridization. Quantitative RT-PCR was also used to determine the dynamic changes in NGAL, tumor necrosis factor α (TNFα) and interleukin (IL)-6 mRNA expression 1, 3, 6, 12, and 24 hours following LPS treatment. The correlation among NGAL, TNFα and IL-6 was analyzed. Urinary and plasma NGAL (u/pNGAL) levels were measured, and the relationship between humoral NGAL and NGAL expression in the kidney was investigated.ResultsRenal function was affected 3–12 hours after LPS. NGAL mRNA was significantly upregulated in tubular epithelia at the same time (P < 0.001). The course of NGAL mRNA upregulation occurred in parallel with renal damage. There was a transient increase in TNFα and IL-6 mRNA levels within 3 hours following LPS administration, and a strong correlation between TNFα and NGAL mRNA (r = 0.995, P <0.001) but not with IL-6 mRNA. Both pNGAL and uNGAL levels were markedly increased compared with those in the control group (P < 0.001); however, only uNGAL levels were correlated with NGAL mRNA (r = 0.850, P <0.001).ConclusionsNGAL upregulation is sensitive to LPS-induced renal TNFα increase and injury, which are observed in the tubular epithelia. Urinary NGAL levels accurately reflect changes in NGAL in the kidney.

Attenuation of cisplatin-induced renal injury by inhibition of soluble epoxide hydrolase involves nuclear factor κB signaling.

Acute kidney injury is associated with a significant inflammatory response that has been the target of renoprotection strategies. Epoxyeicosatrienoic acids (EETs) are anti-inflammatory cytochrome P450-derived eicosanoids that are abundantly produced in the kidney and metabolized by soluble epoxide hydrolase (sEH; Ephx2) to less active dihydroxyeicosatrienoic acids. Genetic disruption of Ephx2 and chemical inhibition of sEH were used to test whether the anti-inflammatory effects of EETs, and other lipid epoxide substrates of sEH, afford protection against cisplatin-induced nephrotoxicity. EET hydrolysis was significantly reduced in Ephx2(-/-) mice and was associated with an attenuation of cisplatin-induced increases in serum urea nitrogen and creatinine levels. Histological evidence of renal tubular damage and neutrophil infiltration was also reduced in the Ephx2(-/-) mice. Likewise, cisplatin had no effect on renal function, neutrophil infiltration, or tubular structure and integrity in mice treated with the potent sEH inhibitor 1-adamantan-1-yl-3-(1-methylsulfonyl-piperidin-4-yl-urea) (AR9273). Consistent with the ability of EETs to interfere with nuclear factor-κB (NF-κB) signaling, the observed renoprotection was associated with attenuation of renal NF-κB activity and corresponding decreases in the expression of tumor necrosis factor (TNF) α, TNF receptor (TNFR) 1, TNFR2, and intercellular adhesive molecule-1 before the detection of tubular injury. These data suggest that EETs or other fatty acid epoxides can attenuate cisplatin-induced kidney injury and sEH inhibition is a novel renoprotective strategy.

D-Allose Ameliorates Cisplatin-Induced Nephrotoxicity in Mice

Cisplatin (cis-diamminedichloroplatinum II) is a potent antineoplastic agent widely used to treat various forms of cancer. However, its therapeutic use is limited because of dose-dependent nephrotoxicity. Inflammatory mechanisms may play an important role in the pathogenesis of cisplatin nephrotoxicity. D-allose is an aldo-hexose present in nature that recently has been demonstrated to inhibit production of inflammatory mediators in septic kidneys. The purpose of this study was to determine the protective effects of D-allose on cisplatin-induced nephrotoxicity. Cisplatin (20 mg/kg) was administered by intraperitoneal injection to mice in the cisplatin group and the cisplatin plus D-allose group, as was normal saline to control group mice. D-allose was intraperitoneally administered immediately after cisplatin injection. Serum and renal tumor necrosis factor (TNF)-alpha concentrations, renal monocyte chemoattractant protein-1 (MCP-1; a chemotactic factor for monocytes), renal function, histological changes and renal cortex neutrophil infiltration were determined 72 h after cisplatin injection. The serum TNF-alpha concentration in the cisplatin plus D-allose (400 mg/kg body weight) group significantly decreased in comparison with that in the cisplatin group. The renal TNF-alpha and MCP-1 concentrations in the cisplatin plus D-allose group significantly decreased in comparison with those in the cisplatin group. Neutrophil infiltration in the cisplatin plus D-allose group was significantly lower than that in the cisplatin group. Cisplatin-induced renal dysfunction and renal tubular injury scores were attenuated by D-allose treatment. These results reveal that D-allose attenuates cisplatin-induced nephrotoxicity by suppressing renal inflammation. Hence, D-allose may become a new therapeutic candidate for treatment of cisplatin-induced nephrotoxicity.

Kidney injury molecule‐1 and N‐acetyl‐ß‐d‐glucosaminidase in chronic heart failure: possible biomarkers of cardiorenal syndrome

Patients with chronic heart failure are often characterized by impaired renal function, also referred to as cardiorenal syndrome (CRS). The aim of this study was to assess whether novel markers of kidney injury are elevated in chronic heart failure and CRS. The new renal biomarkers kidney injury molecule-1 (KIM-1), N-acetyl-ß-d-glucosaminidase (NAG) and neutrophil gelatinase-associated lipocalin (NGAL) were assessed from urine samples of 173 individuals. Patients with chronic heart failure (n= 150) were characterized by decreased ejection fraction (32 ± 9% vs. controls 62 ± 4%, P < 0.001) and increased plasma N-terminal pro-brain natriuretic peptide (median 1460 pg/mL, interquartile range (IQR) 630-3000 pg/mL vs. controls 56, IQR 25-64l pg/mL, P < 0.001). Urinary analysis showed that KIM-1 was significantly elevated in heart failure patients compared with healthy controls (1100, IQR 620-1920 vs. 550, IQR 320-740 ng/g urinary creatinine, P < 0.001). Further, KIM-1 increased significantly with decreasing left ventricular function (r = -0.37, P < 0.001) and severity of New York Heart Association (NYHA)-class (r = 0.5, P < 0.001). N-acetyl-ß-d-glucosaminidase showed a weaker response but correlated significantly with left ventricular dysfunction (r = -0.18, P= 0.015) and more severe clinical condition (r = 0.22, P= 0.04). In contrast, NGAL showed no significant correlation. Kidney injury molecule-1 and NAG were also predictors of all-cause mortality and the composite of all-cause mortality and rehospitalization for heart failure (all P < 0.05). Kidney injury molecule-1 and NAG are elevated in symptomatic heart failure. This finding may be present in patients with apparently normal kidney function and indicates tubular injury in chronic heart failure. Kidney injury molecule-1 and NAG are potential markers of CRS with additional prognostic value.

Diannexin Protects against Renal Ischemia Reperfusion Injury and Targets Phosphatidylserines in Ischemic Tissue

Renal ischemia/reperfusion injury (IRI) frequently complicates shock, renal transplantation and cardiac and aortic surgery, and has prognostic significance. The translocation of phosphatidylserines to cell surfaces is an important pro-inflammatory signal for cell-stress after IRI. We hypothesized that shielding of exposed phosphatidylserines by the annexin A5 (ANXA5) homodimer Diannexin protects against renal IRI. Protective effects of Diannexin on the kidney were studied in a mouse model of mild renal IRI. Diannexin treatment before renal IRI decreased proximal tubule damage and leukocyte influx, decreased transcription and expression of renal injury markers Neutrophil Gelatinase Associated Lipocalin and Kidney Injury Molecule-1 and improved renal function. A mouse model of ischemic hind limb exercise was used to assess Diannexin biodistribution and targeting. When comparing its biodistribution and elimination to ANXA5, Diannexin was found to have a distinct distribution pattern and longer blood half-life. Diannexin targeted specifically to the ischemic muscle and its affinity exceeded that of ANXA5. Targeting of both proteins was inhibited by pre-treatment with unlabeled ANXA5, suggesting that Diannexin targets specifically to ischemic tissues via phosphatidylserine-binding. This study emphasizes the importance of phosphatidylserine translocation in the pathophysiology of IRI. We show for the first time that Diannexin protects against renal IRI, making it a promising therapeutic tool to prevent IRI in a clinical setting. Our results indicate that Diannexin is a potential new imaging agent for the study of phosphatidylserine-exposing organs in vivo.

Use of Doppler ultrasound renal resistive index and neutrophil gelatinase-associated lipocalin in prediction of acute kidney injury in patients with septic shock

Acute kidney injury (AKI) is common in septic shock and there is no good marker to predict it. Neutrophil gelatinase-associated lipocalin (NGAL) is a novel renal biomarker showing promising results in prediction of AKI in patients across different clinical settings. Another potential marker is the resistive index (RI) of renal interlobar artery (calculated as (peak systolic velocity - end diastolic velocity)/peak systolic velocity), which has been shown to be useful in identifying those who will develop AKI in patients with septic shock. The aim of this study is to evaluate the usefulness of RI and NGAL in the early detection of AKI.

The Effect of PACAP38 on MyD88-Mediated Signal Transduction in Ischemia-/Hypoxia-Induced Acute Kidney Injury

Background/Aims: Toll-like receptor 4 (TLR4) and its adaptor protein MyD88 play an important role in ischemia/reperfusion (I/R) injury in the kidney, and pituitary adenylate cyclase-activating polypeptide (PACAP) could ameliorate renal I/R injury. Methods: Primary cultures of proximal tubule epithelial cells (PTEC) were prepared from wild-type and MyD88^–/– mice, and subjected to hypoxia in vitro. Acute kidney injury (AKI) was induced by I/R in vivo in wild-type mice only. Results: Hypoxia resulted in significant increases in cytokine production and apoptosis/necrosis in wild-type PTEC, but these responses were markedly blunted in MyD88^–/– PTEC. Treatment with PACAP38 before or after hypoxia further suppressed the hypoxia-induced cytokine responses and apoptosis in both MyD88^+/+ and MyD88^–/– PTEC cultures. PACAP38 significantly inhibited TLR4/MyD88/TRAF6 as well as TRIF and IRF3 expression in mouse kidney and PTEC, and inhibited the secretion and mRNA expression of cytokines in kidneys from mice after I/R, paralleling the cytokine responses in vitro. Moreover, treatment with PACAP38 protected mice from renal failure, histological damage, neutrophil influx and tubule cell apoptosis after I/R. Conclusion: Our data reveal that the TLR4-mediated cytokine responses to hypoxia are primarily dependent on MyD88 signaling and highlight the pivotal role of MyD88-dependent mechanisms in the coordination of the innate immune responses to ischemic/hypoxic acute renal tubular injury. The renoprotective effect of PACAP in AKI involves both MyD88-dependent and -independent pathways.

Parenteral iron formulations differentially affect MCP-1, HO-1, and NGAL gene expression and renal responses to injury

Despite their prooxidant effects, ferric iron compounds are routinely administered to patients with renal disease to correct Fe deficiency. This study assessed relative degrees to which three clinically employed Fe formulations [Fe sucrose (FeS); Fe gluconate (FeG); ferumoxytol (FMX)] impact renal redox- sensitive signaling, cytotoxicity, and responses to superimposed stress [endotoxin; glycerol-induced acute renal failure (ARF)]. Cultured human proximal tubule (HK-2) cells, isolated proximal tubule segments (PTS), or mice were exposed to variable, but equal, amounts of FeS, FeG, or FMX. Oxidant-stimulated signaling was assessed by heme oxygenase-1 (HO-1) or monocyte chemoattractant protein (MCP)-1 mRNA induction. Cell injury was gauged by MTT assay (HK-2 cells), %LDH release (PTS), or renal cortical neutrophil gelatinase-associated lipoprotein (NGAL) protein/mRNA levels. Endotoxin sensitivity and ARF severity were assessed by TNF-alpha and blood urea nitrogen concentrations, respectively. FeS and FeG induced lethal cell injury (in HK-2 cells, PTS), increased HO-1 and MCP-1 mRNAs (HK-2 cells; in vivo), and markedly raised plasma ( approximately 10 times), and renal cortical ( approximately 3 times) NGAL protein levels. Both renal and extrarenal (e.g., hepatic) NGAL production likely contributed to these results, based on assessments of tissue and HK-2 cell NGAL mRNA. FeS pretreatment exacerbated endotoxemia. However, it conferred marked protection against the glycerol model of ARF (halving azotemia). FMX appeared to be "bioneutral," as it exerted none of the above noted FeS/FeG effects. We conclude that 1) parenteral iron formulations that stimulate redox signaling can evoke cyto/nephrotoxicity; 2) secondary adaptive responses to this injury (e.g., HO-1/NGAL induction) can initiate a renal tubular cytoresistant state; this suggests a potential new clinical application for intravenous Fe therapy; and 3) FMX is bioneutral regarding these responses. The clinical implication(s) of the latter, vis a vis the treatment of Fe deficiency in renal disease patients, remains to be defined.

Oxidative Stress and Neutrophil Function in Cats with Chronic Renal Failure

Oxidative stress is an important component in the progression of chronic renal failure (CRF) and neutrophil function may be impaired by oxidative stress. Cats with CRF have increased oxidative stress and decreased neutrophil function compared with control cats. Twenty cats with previously diagnosed renal failure were compared with 10 age-matched control cats. A biochemical profile, CBC, urinalysis, antioxidant capacity, superoxide dismutase (SOD) enzyme activity, reduced to oxidized glutathione ratio (GSH : GSSG), and neutrophil phagocytosis and oxidative burst were measured. Statistical comparisons (2-tailed t-test) were reported as mean +/- standard deviation. The CRF cats had significantly higher serum blood urea nitrogen, creatinine, and phosphorus concentrations than control cats, and significantly lower PCV and urine specific gravity than control cats. The GSH : GSSG ratio was significantly higher in the CRF group (177.6 +/- 197, 61.7 +/- 33; P < .02) whereas the antioxidant capacity was significantly less in the CRF group (0.56 +/- 0.21, 0.81 +/- 0.13 Trolox units; P < .005). SOD activity was the same in control and CRF cats. Neutrophil oxidative burst after Escherichia coli phagocytosis, measured as an increase in mean fluorescence intensity, was significantly higher in CRF cats than controls (732 +/- 253, 524 +/- 54; P < .05). The higher GSH : GSSG ratio and lower antioxidant capacity in CRF cats is consistent with activation of antioxidant defense mechanisms. It remains to be determined if supplementation with antioxidants such as SOD beyond the level of control cats would be of benefit in cats with CRF.

Evaluación de nuevos donadores de óxido nítrico en el trasplante renal experimental

Introduction and objectives Given the importance of minimizing renal damage due to ischemia/reperfusion in organ transplants, we evaluated prophylactic treatments to control inflammatory response, using distinct nitric oxide donors. Methods We used experimental models of ischemia/reperfusion and kidney transplants using LA-803, LA-807, LA-810 donors and molsidomine. Renal function, neutrophil infiltration, oxidative stress, pro- and anti-inflammatory cytokines, nitric oxide, leukocyte-endothelium interaction and nuclear transcription were studied. Results LA-803 demonstrated the greatest effectiveness in controlling inflammatory response and was selected to continue the study. We found a decrease in inflammatory response, oxidative stress and neutrophil infiltration and lesser endothelial damage with preservation of organ function. Conclusions We believe that the use of specific nitric oxide donors could be highly useful in organ transplantation, increasing cellular viability and organ function post-transplantation.

Abstract 5267: The Annexin A5 Homodimer Diannexin Protects Against Ischemia Reperfusion Injury Through Phosphatidylserine Binding

Renal ischemia/reperfusion injury (IRI) frequently complicates cardiac and aortic surgery and has prognostic significance. The translocation of phosphatidylserines (PS) to cell surfaces is an important pro-inflammatory signal for cell-stress after IRI. We hypothesized that shielding of exposed PS by the annexin A5 homodimer Diannexin protects against renal IRI. Mice (n =8 – 10) underwent 20 min bilateral clamping of the renal pedicle, followed by 3 or 8 days of reperfusion. Either 200 ug/kg Diannexin or vehicle was injected i.v. 20 min prior to ischemia. Renal injury peaked on day 3 post-op. When compared to vehicle, Diannexin treatment reduced the IRI-induced glucosuria, prevented the increase in urine flow, reduced the proximal tubule damage and reduced the expression and/or transcription of the renal injury markers Neutrophil Gelatinase Associated Lipocalin (NGAL) and Kidney Injury Molecule-1 (KIM-1; see table ). Reduced KIM-1 expression persisted on day 8 after Diannexin treatment [0.23±0.02 vs. 0.36±0.06; p&lt;0.05]. To confirm PS as the target for Diannexin, mice (n=2– 6) underwent unilateral IRI of the hind limb. Upon reperfusion, 4.5 ug Tc-99m-Diannexin was injected i.v. . Diannexin targeted specifically to the ischemic limb when compared to the control limb [4.0±0.60 vs. 0.2±0.02 %ID/g; p&lt;0.001]. Targeting could be reduced by a preceding injection of 500 ug unlabeled annexin A5 [1.5±0.3 vs. 0.7±0.2 %ID/g], suggesting that Diannexin targets to ischemic tissues via PS binding. This study indicates the importance of PS exposition in IRI. We conclude that Diannexin protects against renal IRI by binding to PS, making it a promising tool to prevent IRI in a clinical setting. Table: effects of Diannexin on functional, histological and injury marker parameters after renal IRI

Renal Dendritic Cells Ameliorate Nephrotoxic Acute Kidney Injury

Inflammation contributes to the pathogenesis of acute kidney injury. Dendritic cells (DCs) are immune sentinels with the ability to induce immunity or tolerance, but whether they mediate acute kidney injury is unknown. Here, we studied the distribution of DCs within the kidney and the role of DCs in cisplatin-induced acute kidney injury using a mouse model in which DCs express both green fluorescence protein and the diphtheria toxin receptor. DCs were present throughout the tubulointerstitium but not in glomeruli. We used diphtheria toxin to deplete DCs to study their functional significance in cisplatin nephrotoxicity. Mice depleted of DCs before or coincident with cisplatin treatment but not at later stages experienced more severe renal dysfunction, tubular injury, neutrophil infiltration and greater mortality than nondepleted mice. We used bone marrow chimeric mice to confirm that the depletion of CD11c-expressing hematopoietic cells was responsible for the enhanced renal injury. Finally, mixed bone marrow chimeras demonstrated that the worsening of cisplatin nephrotoxicity in DC-depleted mice was not a result of the dying or dead DCs themselves. After cisplatin treatment, expression of MHC class II decreased and expression of inducible co-stimulator ligand increased on renal DCs. These data demonstrate that resident DCs reduce cisplatin nephrotoxicity and its associated inflammation.

Mac-1 (CD11b/CD18) links inflammation and thrombosis after glomerular injury.

Inflammation and thrombosis coexist in several disorders. Although it is recognized that leukocytes may induce a procoagulant state at sites of inflammation, the critical molecular determinants of this process remain largely unknown. To examine mechanisms of inflammation-induced thrombosis, we developed a murine model of thrombotic glomerulonephritis (TGN), a known cause of acute renal failure in patients. This model, induced by lipopolysaccharide and antibody to the glomerular basement membrane, led to rapid glomerular neutrophil recruitment, thrombotic glomerular lesions with endothelial cell injury, and renal dysfunction. In mice immunodepleted of neutrophils or lacking the leukocyte-specific integrin Mac-1, neutrophil recruitment, endothelial injury, glomerular thrombosis, and acute renal failure were markedly attenuated despite the robust generation of renal cytokines. Neutrophil elastase is a likely effector of Mac-1 because its activity was reduced in Mac-1-deficient mice and the phenotype in mice deficient in Mac-1 or neutrophil elastase was similar. Platelets accumulated in glomerular capillaries within 4 hours of TGN before evidence of thrombosis. Platelet immunodepletion before TGN markedly exacerbated hematuria (hemorrhage), inflammation, and injury, whereas thrombocytopenic Mac-1-deficient mice remained resistant to disease, indicating that initial glomerular platelet deposition protects the vessel wall from neutrophil-mediated sequelae. The subsequent thrombosis relied on the interaction of Mac-1 on recruited neutrophils with glycoprotein Ibalpha on platelets as antibody-mediated disruption of this interaction attenuated TGN without affecting renal neutrophil accumulation. These observations establish Mac-1 on neutrophils as a critical molecular link between inflammation and thrombosis and suggest it as an attractive target for antithrombotic therapy.

Mice that overexpress human heat shock protein 27 have increased renal injury following ischemia reperfusion

We previously showed that activation of the A1 adenosine receptor protected the kidney against ischemia-reperfusion injury by induction and phosphorylation of heat shock protein 27 (HSP27). Here, we used mice that overexpress human HSP27 (huHSP27) to determine if kidneys from these mice were protected against injury. Proximal tubule cells cultured from the transgenic mice had increased resistance to peroxide-induced necrosis compared to cells from wild-type mice. However, after renal ischemic injury, HSP27 transgenic mice had decreased renal function compared to wild-type mice, along with increased renal expression of mRNAs of pro-inflammatory cytokines (TNF-alpha, ICAM-1, MCP-1) and increased plasma and kidney keratinocyte-derived cytokine. Following ischemic injury, neutrophils infiltrated the kidneys earlier in the transgenic mice. Flow cytometric analysis of lymphocyte subsets showed that those isolated from the kidneys of transgenic mice had increased CD3(+), CD4(+), CD8(+), and NK1.1(+) cells 3 h after injury. When splenocytes or NK1.1(+) cells were isolated from transgenic mice and adoptively transferred into wild-type mice there was increased renal injury. Further, depletion of lymphocytes by splenectomy or neutralization of NK1.1(+) cells resulted in improved renal function in the transgenic mice following reperfusion. Our study shows that induction of HSP27 in renal tubular cells protects against necrosis in vitro, but its systemic increase counteracts this protection by exacerbating renal and systemic inflammation in vivo.