Cyclophilin A Promotes Inflammation in Acute Kidney Injury but Not in Renal Fibrosis.

Cyclophilin A (CypA) is a highly abundant protein in the cytoplasm of most mammalian cells. Beyond its homeostatic role in protein folding, CypA is a Damage-Associated Molecular Pattern which can promote inflammation during tissue injury. However, the role of CypA in kidney disease is largely unknown. This study investigates the contribution of CypA in two different types of kidney injury: acute tubular necrosis and progressive interstitial fibrosis. CypA (Ppia) gene deficient and wild type (WT) littermate controls underwent bilateral renal ischaemia/reperfusion injury (IRI) and were killed 24h later or underwent left unilateral ureteric obstruction (UUO) and were killed 7 days later. In the IRI model, CypA-/- mice showed substantial protection against the loss of renal function and from tubular cell damage and death. This was attributed to a significant reduction in neutrophil and macrophage infiltration since CypA-/- tubular cells were not protected from oxidant-induced cell death in vitro. In the UUO model, CypA-/- mice were not protected from leukocyte infiltration or renal interstitial fibrosis. In conclusion, CypA promotes inflammation and acute kidney injury in renal IRI, but does not contribute to inflammation or interstitial fibrosis in a model of progressive kidney fibrosis.

Leea macrophylla root extract upregulates the mRNA expression for antioxidative enzymes and repairs the necrosis of pancreatic ß-cell and kidney tissues in fructose-fed Type 2 diabetic rats.

This research investigated the functional food effect of Leea macrophylla (Roxb.) ex Hornem root extract on pancreatic necrosis in Streptozotocin-induced type-2 diabetes. Prior to animal intervention, Leea macrophylla root extract (LMR) was subjected to GC-MS analysis. Across a three-week intervention of fructose-fed albino model with LMR50, LMR100 and LMR200, the fluid & food intake, body weight changes, weekly blood glucose concentrations and oral glucose tolerance (OGT) were recorded. The animals were sacrificed after intervention and serum was analyzed for insulin, ALT, AST, LDH, CK-MB, creatinine, uric acid and lipid profile and liver section was used for glycogen estimation. Changes of pancreas and kidney architecture were evaluated by histopathology. Relative mRNA for superoxide dismutase 1 (SOD1), glutathione peroxidase (GPx) and catalase (CAT) were quantitated using assay kits. Results showed that fluid and food intake, weekly blood glucose level, ALT, AST, LDH, CK-MB level were significantly (p < 0.05) decreased in LMR50 group. Conversely, the glucose tolerance ability, liver glycogen level, serum insulin, organ weight and pancreatic morphology were improved significantly in this group. Diameter of islet of Langerhans (µm), area occupied by ß-cell/ islet of Langerhans (µm2) and number of ß-cells/islet of Langerhans were amazingly improved to the NC animals. Expressions of mRNA for SOD1 and CAT from liver tissue have been found to be increased multifold while GPx was remained unchanged. The data suggests that L. macrophylla root extract could be very potential as functional food to modulate pancreatic action.

Patterns of renal involvement in a cohort of patients with inflammatory bowel disease in Egypt.

BACKGROUND AND STUDY AIM: Renal complications are frequent extraintestinal manifestations in inflammatory bowel disease (IBD). We aimed in our study to describe the spectrum of renal affection in our IBD patients. PATIENTS AND METHODS: This study is a retrospective analysis of renal biopsies done for IBD patients who developed renal diseases, at Cairo University Hospital, from June 2005 to Jan. 2016. Results : Among 896 IBD patients, 218 patients (24.3%) developed renal affection. The onset of renal disease mandated renal biopsy at 5.6 ± 7.4 years after IBD diagnosis. Nephrotic range proteinuria was the most common indication for a renal biopsy [81 (37.15%) patients]. Amyloidosis was the most common renal pathological diagnosis [56 patients (25.7%)] followed by immunoglobulin A (IgA) nephropathy [35 patients (16.1%)], focal segmental glome- rulosclerosis (FSGS) [32patients (14.7%)], crescentic glomerulonephritis (CGN) [32 patients (14.7%)], membranous nephropathy (MN) [18 patients (8.25%)], minimal change disease [17 patients (7.7%)], chronic interstitial nephritis (CIN) [10 patients (4.6%)], acute tubular necrosis (ATN) [8 patients (3.7%)], thrombotic microangiopathy (TMA) [6 patients (2.75%)], and acute interstitial nephritis (AIN)[4 patients (1.8%)]. Variable renal histopathology diagnoses did not correlate with age, duration of IBD diagnosis, or drugs used for IBD treatment. Crescentic GN was significantly correlating with ASCA, ANCA-p, and ANCA-c in serum. CONCLUSION: Amyloidosis is a common renal pathological diagnosis in our patients, and is followed by IgA nephropathy, and FSGS.

Nickel chloride (NiCl2)-caused inflammatory responses via activation of NF-κB pathway and reduction of anti-inflammatory mediator expression in the kidney.

Nickel (Ni) or Ni compounds target a number of organs and produce multiple toxic effects. Kidney is the major organ for Ni accumulation and excretion. There are no investigations on the Ni- or Ni compounds-induced renal inflammatory responses in human beings and animals at present. Therefore, we determined NiCl2-caused alteration of inflammatory mediators, and functional damage in the broiler's kidney by the methods of biochemistry, immunohistochemistry and quantitative real-time polymerase chain reaction (qRT-PCR). Dietary NiCl2 in excess of 300 mg/kg caused the renal inflammatory responses that characterized by increasing mRNA expression levels of the pro-inflammatory mediators including tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), interleukin-1ß (IL-1ß), interleukin-6 (IL-6), interleukin-8 (IL-8) and interleukin-18 (IL-18) via the activation of nucleic factor κB (NF-κB), and decreasing mRNA expression levels of the anti-inflammatory mediators including interleukin-2 (IL-2), interleukin-4 (IL-4) and interleukin-13 (IL-13). Concurrently, NiCl2 caused degeneration, necrosis and apoptosis of the tubular cells, which was consistent with the alteration of renal function parameters including elevated alkaline phosphatase (AKP) activity, and reduced activities of sodium-potassium adenosine triphosphatase (Na(+)/K(+)-ATPase), calcium adenosine triphosphatase (Ca(2+)-ATPase), lactic dehydrogenase (LDH), succinate dehydrogenase (SDH) and acid phosphatase (ACP) in the kidney. The above-mentioned results present that the activation of NF-κB pathway and reduction of anti-inflammatory mediator expression are main mechanisms of NiCl2-caused renal inflammatory responses and that the renal function is decreased or impaired after NiCl2-treated.

Renoprotective Effect of Humic Acid on Renal Ischemia-Reperfusion Injury: An Experimental Study in Rats.

Humic acid is an antioxidant molecule used in agriculture and livestock breeding, as well as in medicine. Our aim was to investigate the potential renoprotective effects of humic acid in a renal ischemia reperfusion model. Twenty-one rats were randomly divided into three equal groups. Intraperitoneal serum or humic acid was injected at 1, 12, and 24 h. Non-ischemic group I was evaluated as sham. The left renal artery was clamped in serum (group II) and intraperitoneal humic acid (group III) to subject to left renal ischemic reperfusion procedure. Ischemia and reperfusion time was 60 min for each. Total antioxidant status, total oxidative status, oxidative stress index, and ischemia-modified albumin levels were analyzed biochemically from the serum samples. Kidneys were evaluated histopatologically and immunohistochemically. Biochemical results showed that total oxidative status, ischemia-modified albumin, and oxidative stress index levels were significantly decreased, but total antioxidant status was increased in the humic acid group (III) compared with the ischemia group (II) On histopathological examination, renal tubular dilatation, tubular cell damage and necrosis, dilatation of Bowman's capsule, hyaline casts, and tubular cell spillage were decreased in the humic acid group (III) compared with the ischemia group (II). Immunohistochemical results showed that apoptosis was deteriorated in group III. Renal ischemia reperfusion injury was attenuated by humic acid administration. These observations indicate that humic acid may have a potential therapeutic effect on renal ischemia reperfusion injury by preventing oxidative stress.

Epidermal growth factor attenuates tubular necrosis following mercuric chloride damage by regeneration of indigenous, not bone marrow-derived cells.

To assess effects of epidermal growth factor (EGF) and pegylated granulocyte colony-stimulating factor (P-GCSF; pegfilgrastim) administration on the cellular origin of renal tubular epithelium regenerating after acute kidney injury initiated by mercuric chloride (HgCl2 ). Female mice were irradiated and male whole bone marrow (BM) was transplanted into them. Six weeks later recipient mice were assigned to one of eight groups: control, P-GCSF+, EGF+, P-GCSF+EGF+, HgCl2 , HgCl2 +P-GCSF+, HgCl2 +EGF+ and HgCl2 +P-GCSF+EGF+. Following HgCl2 , injection tubular injury scores increased and serum urea nitrogen levels reached uraemia after 3 days, but EGF-treated groups were resistant to this acute kidney injury. A four-in-one analytical technique for identification of cellular origin, tubular phenotype, basement membrane and S-phase status revealed that BM contributed 1% of proximal tubular epithelium in undamaged kidneys and 3% after HgCl2 damage, with no effects of exogenous EGF or P-GCSF. Only 0.5% proximal tubular cells were seen in S-phase in the undamaged group kidneys; this increased to 7-8% after HgCl2 damage and to 15% after addition of EGF. Most of the regenerating tubular epithelium originated from the indigenous pool. BM contributed up to 6.6% of the proximal tubular cells in S-phase after HgCl2 damage, but only to 3.3% after additional EGF. EGF administration attenuated tubular necrosis following HgCl2 damage, and the major cause of this protective effect was division of indigenous cells, whereas BM-derived cells were less responsive. P-GCSF did not influence damage or regeneration.

Neutrophil serine proteases promote IL-1ß generation and injury in necrotizing crescentic glomerulonephritis.

The pathogenesis of anti-neutrophil cytoplasmic antibody (ANCA)-associated necrotizing crescentic GN (NCGN) is incompletely understood. Dipeptidyl peptidase I (DPPI) is a cysteine protease required for the activation of neutrophil serine proteases (NSPs) cathepsin G, neutrophil elastase, and proteinase 3, which are enzymes that modulate inflammation. We used a mouse model of anti-myeloperoxidase (MPO) antibody-induced NCGN to determine whether active NSPs contribute to its pathogenesis. MPO-deficient animals immunized with murine MPO, irradiated, and transplanted with wild-type bone marrow developed NCGN. In contrast, transplantation with bone marrow that lacked DPPI or lacked both neutrophil elastase and proteinase 3 protected mice from NCGN induced by anti-MPO antibody. The kidneys of mice reconstituted with DPPI-deficient bone marrow generated significantly less IL-1ß than did those of mice reconstituted with wild-type bone marrow; similarly, in vitro, DPPI-deficient monocytes produced significantly less IL-1ß in response to anti-MPO antibody than did wild-type monocytes. This reduction in IL-1ß was NSP dependent; exogenous addition of PR3 restored IL-ß production in DPPI-deficient monocytes. Last, the IL-1 receptor antagonist anakinra protected animals against anti-MPO antibody-induced NCGN (16.7%±6.0% versus 2.4%±1.7% crescents), suggesting that IL-1ß is a critical inflammatory mediator in this model. These data suggest that the development of anti-MPO antibody-induced NCGN requires NSP-dependent IL-1ß generation and that these processes may provide therapeutic targets for ANCA-mediated diseases in humans.

Antioxidant-rich date palm fruit extract inhibits oxidative stress and nephrotoxicity induced by dimethoate in rat.

Recent investigations have proved the crucial role of nutritional antioxidants to prevent the damage caused by toxic compounds. In this study, the antioxidant effect of date palm fruit extract on dimethoate-induced oxidative stress and nephrotoxicity in rat is investigated and compared with the effect of the well-known antioxidant vitamin C. Male Wistar rats were randomly divided into six groups of ten each: a control group (C), a group that received dimethoate (20 mg/kg body weight) (D), a group given Deglet Nour extract (DNE), a group treated with DNE 30 min before the administration of dimethoate (DNE + D), a group which received VitC (100 mg/kg body weight) plus dimethoate (Vit C + D), and a group given dimethoate for the first month and DNE 30 min after administration of dimethoate, during the second month (D + DNE). These components were daily administered by gavage for 2 months. After completing the treatment period, blood samples from rats were collected under inhaled diethyl ether anesthesia for serum urea, uric acid, and creatinine levels, while the rat kidneys were obtained for enzyme assays and histology. Oral administration of dimethoate in rats induced a marked renal failure characterized by a significant increase in serum creatinine and urea levels (p < 0.01) in addition to a significant decrease in serum uric acid (p < 0.05). Interestingly, these drastic modifications were accompanied by a marked enhancement of lipid peroxidation in kidney, indicating a significant induction of oxidative damage (p < 0.01) and dysfunctions of enzymatic antioxidant defenses. These biochemical alterations were also accompanied by histological changes in kidney revealed by a narrowed Bowman's space, tubular degeneration, tubular cell desquamation, and tubular dilatation of proximal tubules. Treatment with date palm fruit extract (Deglet Nour) and also with vitamin C significantly (p < 0.05) reversed the serum renal markers to their near-normal levels when compared with dimethoate-treated rats. In addition, Deglet Nour extract and vitamin C significantly reduced lipid peroxidation, restored the antioxidant defense enzymes in the kidney, and improved the histopathology changes. The present findings indicate that in vivo date palm fruit may be useful for the prevention of oxidative stress-induced nephrotoxicity.

ERK pathway mediates P2X7 expression and cell death in renal interstitial fibroblasts exposed to necrotic renal epithelial cells.

We recently reported that necrotic renal proximal epithelial cells (RPTC) stimulate the expression of P2X7 receptor in renal fibroblasts and that P2X7 receptor mediates deleterious epithelial-fibroblast cross talk. The present study was carried out to investigate the signaling mechanism of necrotic RPTC-induced P2X7 expression in cultured renal interstitial fibroblasts (NRK-49F). Exposure of NRK-49F to necrotic RPTC supernatant (RPTC-Sup) induced a time- and dose-dependent phosphorylation of several signaling pathways including extracellular signal-regulated kinases (ERK1/2), p38, c-Jun N-terminal kinases (JNKs), and AKT in NRK-49F. Pharmacological inhibition of ERK1/2, but not p38, JNK, and AKT pathways, blocked RPTC-Sup-induced P2X7 expression and renal interstitial fibroblast death. Knockdown of ERK1/2 or MEK1, a direct upstream activator of ERK1/2, also reduced RPTC-Sup-induced P2X7 expression and cell death of renal fibroblasts. Conversely, overexpression of MEK1 enhanced these responses. Upon necrotic RPTC exposure, phosphorylation of Elk1, a transcriptional factor targeted by ERK1/2, was increased in NRK-49F, and knockdown of Elk1 by siRNA remarkably reduced RPTC-Sup-induced P2X7 expression as well as renal fibroblast death. Furthermore, silencing of MEK1 inhibited Elk1 phosphorylation in response to necrotic RPTC, whereas overexpression of MEK1 increased Elk1 phosphorylation. Taken together, these data reveal that necrotic RPTC induces P2X7 expression in renal fibroblasts through activation of the MEK1-ERK1/2-Elk1 signaling pathway.

Identification and regulation of reticulon 4B (Nogo-B) in renal tubular epithelial cells.

Nogo-B is a member of the reticulon family of proteins that has been implicated in diverse forms of vascular injury. Although Nogo-B is expressed in renal tissues, its localization and function in the kidney have not been examined. Here, we report that Nogo-B is expressed specifically in the epithelial cells of the distal nephron segments in the murine kidney. After unilateral ureteral obstruction (UUO) and ischemia/reperfusion, Nogo-B gene and protein levels increased dramatically in the kidney. This increase was driven in part by injury-induced de novo expression in proximal tubules. Examination of Nogo-B immunostaining in human biopsy specimens from patients with acute tubular necrosis showed similar increases in Nogo-B in cortical tubules. Mice genetically deficient in Nogo-A/B were indistinguishable from wild-type (WT) mice based on histological appearance and serum analyses. After UUO, there was a significant delay in recruitment of macrophages to the kidney in the Nogo-A/B-deficient mice. However, measurements of fibrosis, inflammatory gene expression, and histological damage were not significantly different from WT mice. Thus, Nogo-B is highly expressed in murine kidneys in response to experimental injuries and may serve as a marker of diverse forms of renal injury in tissues from mice and humans. Furthermore, Nogo-B may regulate macrophage recruitment after UUO, although it does not greatly affect the degree of tissue injury or fibrosis in this model.

Selective renal overexpression of human heat shock protein 27 reduces renal ischemia-reperfusion injury in mice.

We have previously shown that exogenous and endogenous A(1) adenosine receptor (A(1)AR) activation protected against renal ischemia-reperfusion (IR) injury in mice by induction and phosphorylation of heat shock protein 27 (HSP27). With global overexpression of HSP27 in mice, however, there was a paradoxical increase in systemic inflammation with increased renal injury after an ischemic insult due to increased NK1.1 cytotoxicity. In this study, we hypothesized that selective renal expression of HSP27 in mice would improve renal function and reduce injury after IR. Mice were subjected to renal IR injury 2 days after intrarenal injection of saline or a lentiviral construct encoding enhanced green fluorescent protein (EGFP) or human HSP27 coexpressing EGFP (EGFP-huHSP27). Mice with kidney-specific reconstitution of huHSP27 had significantly lower plasma creatinine, renal necrosis, apoptosis, and inflammation as demonstrated by decreased proinflammatory cytokine mRNA induction and neutrophil infiltration. In addition, there was better preservation of the proximal tubule epithelial filamentous (F)-actin cytoskeleton in the huHSP27-reconstituted groups than in the control groups. Furthermore, huHSP27 overexpression led to increased colocalization with F-actin in renal proximal tubules. Taken together, these findings have important clinical implications, as they imply that kidney-specific expression of HSP27 through lentiviral delivery is a viable therapeutic option in attenuating the effects of renal IR.

Proteinase 3-antineutrophil cytoplasmic antibody-(PR3-ANCA) positive necrotizing glomerulonephritis after restarting sulphasalazine treatment.

A 59-year-old woman with ulcerative colitis developed red eyes, pleural effusion, eosinophilia and urinary abnormalities after restarting of sulphasalazine treatment. Light microscopy of a kidney biopsy revealed segmental necrotizing glomerulonephritis without deposition of immunoglobulin or complement. Proteinase 3-antineutrophil cytoplasmic antibody (PR3-ANCA) titer was elevated at 183 ELISA units (EU) in sera (normal range less than 10 EU), myeloperoxidase-ANCA was negative. PR3-ANCA titer was 250 and 1,070 EU in pleural effusions on right and left side, respectively. Although cessation of sulphasalazine treatment resulted in improvements in fever, red eyes, chest pain, titer of C-reactive protein and volume of the pleural effusions, we initiated steroid therapy, because PR3-ANCA titer rose to 320 EU, eosinophil count increased to 1,100 cells/microl, and the pleural effusion remained. One month after steroid therapy, the pleural effusion disappeared, and PR3-ANCA titer normalized 3 months later. This case suggests that sulphasalazine can induce PR3-ANCA-positive necrotizing glomerulonephritis.

IFN-inducible protein 10 (CXCL10) regulates tubular cell proliferation in renal ischemia-reperfusion injury.

Although renal tubular cell proliferation after acute tubular necrosis is an important and essential response in the recovery of renal dysfunction in acute renal failure, the precise factors and mechanisms of tubular cell regeneration remain unclear. Here, we describe our studies using a neutralizing antibody (Ab) against interferon-inducible protein of 10 kDa (IP-10; CXCL10) that indicate a role for CXCL10 in tubular cell proliferation after renal ischemia-reperfusion injury. Tissue necrosis and interstitial infiltrating numbers were comparable between anti-CXCL10 Ab-treated and control mice treated with IgG at the 24 and 48 h time points after reperfusion. In contrast, the numbers of Ki67-positive proliferating tubular cells were significantly increased in anti-CXCL10 Ab-treated mice 48 h after reperfusion. In accordance with the in vivo findings,in vitro studies using murine tubular epithelial cells indicated an antiproliferative effect of CXCL10 upon the intensity of cell proliferation and the number of Ki67-positive cells. These data suggest that CXCL10 plays a role in the regulation of tubular cell proliferation following renal ischemia-reperfusion injury.

Renal parenchymal oxygenation and hypoxia adaptation in acute kidney injury.

The pathogenesis of acute kidney injury (AKI), formally termed acute tubular necrosis, is complex and, phenotypically, may range from functional dysregulation without overt morphological features to literal tubular destruction. Hypoxia results from imbalanced oxygen supply and consumption. Increasing evidence supports the view that regional renal hypoxia occurs in AKI irrespective of the underlying condition, even under circumstances basically believed to reflect 'direct' tubulotoxicity. However, at present, it is remains unclear whether hypoxia per se or, rather, re-oxygenation (possibly through reactive oxygen species) causes AKI. Data regarding renal hypoxia in the clinical situation of AKI are lacking and our current concepts regarding renal oxygenation during acute renal failure are presumptive and largely derived from experimental studies. There is robust experimental evidence that AKI is often associated with altered intrarenal microcirculation and oxygenation. Furthermore, renal parenchymal oxygen deprivation seems to participate in the pathogenesis of experimental AKI, induced by exogenous nephrotoxins (such as contrast media, non-steroidal anti-inflammatory drugs or amphotericin), sepsis, pigment and obstructive nephropathies. Sub-lethal cellular hypoxia engenders adaptational responses through hypoxia-inducible factors (HIF). Forthcoming technologies to modulate the HIF system form a novel potential therapeutic approach for AKI.

Detection of evolving acute tubular necrosis with renal 23Na MRI: studies in rats.

The clinical detection of evolving acute tubular necrosis (ATN) and differentiating it from other causes of renal failure are currently limited. The maintenance of the corticomedullary sodium gradient, an indicator of normal kidney function, is presumably lost early in the course of ATN. Herein, sodium magnetic resonance imaging (23Na MRI) was applied to study the early alteration in renal sodium distribution in rat kidneys 6 h after the induction of ATN. Three-dimensional gradient echo sodium images were recorded at 4.7 T with high spatial resolution. ATN was produced by the administration of radiologic contrast medium, combined with inhibition of nitric oxide and prostaglandin synthesis. The sodium images revealed that the sham-controlled kidney exhibited a linear increase in sodium concentration along the corticomedullary axis of 30+/-2 mmol/l/mm, resulting in an inner medulla to cortex sodium ratio of 4.3+/-0.3 (n=5). In the ATN kidney, however, the cortico-outer medullary sodium gradient was reduced by 21% (P<0.01, n=7) and the inner medulla to cortex sodium ratio was decreased by 40% (P<0.001, n=7). Small, though significant, increments in plasma creatinine at this time inversely correlated with the decline in the corticomedullary sodium gradient. Histological findings demonstrated outer medullary ATN involving 4% of medullary thick ascending limbs. Hence, 23Na MRI non-invasively quantified changes in the corticomedullary sodium gradient in the ATN kidney when morphologic tubular injury was still focal and very limited. MRI detection of corticomedullary sodium gradient abnormalities may serve to identify evolving ATN at its early phases.

ApoSense: a novel technology for functional molecular imaging of cell death in models of acute renal tubular necrosis.

PURPOSE: Acute renal tubular necrosis (ATN), a common cause of acute renal failure, is a dynamic, rapidly evolving clinical condition associated with apoptotic and necrotic tubular cell death. Its early identification is critical, but current detection methods relying upon clinical assessment, such as kidney biopsy and functional assays, are insufficient. We have developed a family of small molecule compounds, ApoSense, that is capable, upon systemic administration, of selectively targeting and accumulating within apoptotic/necrotic cells and is suitable for attachment of different markers for clinical imaging. The purpose of this study was to test the applicability of these molecules as a diagnostic imaging agent for the detection of renal tubular cell injury following renal ischemia. METHODS: Using both fluorescent and radiolabeled derivatives of one of the ApoSense compounds, didansyl cystine, we evaluated cell death in three experimental, clinically relevant animal models of ATN: renal ischemia/reperfusion, radiocontrast-induced distal tubular necrosis, and cecal ligature and perforation-induced sepsis. RESULTS: ApoSense showed high sensitivity and specificity in targeting injured renal tubular epithelial cells in vivo in all three models used. Uptake of ApoSense in the ischemic kidney was higher than in the non-ischemic one, and the specificity of ApoSense targeting was demonstrated by its localization to regions of apoptotic/necrotic cell death, detected morphologically and by TUNEL staining. CONCLUSION: ApoSense technology should have significant clinical utility for real-time, noninvasive detection of renal parenchymal damage of various types and evaluation of its distribution and magnitude; it may facilitate the assessment of efficacy of therapeutic interventions in a broad spectrum of disease states.

Endocytic delivery of lipocalin-siderophore-iron complex rescues the kidney from ischemia-reperfusion injury.

Neutrophil gelatinase-associated lipocalin (Ngal), also known as siderocalin, forms a complex with iron-binding siderophores (Ngal:siderophore:Fe). This complex converts renal progenitors into epithelial tubules. In this study, we tested the hypothesis that Ngal:siderophore:Fe protects adult kidney epithelial cells or accelerates their recovery from damage. Using a mouse model of severe renal failure, ischemia-reperfusion injury, we show that a single dose of Ngal (10 microg), introduced during the initial phase of the disease, dramatically protects the kidney and mitigates azotemia. Ngal activity depends on delivery of the protein and its siderophore to the proximal tubule. Iron must also be delivered, since blockade of the siderophore with gallium inhibits the rescue from ischemia. The Ngal:siderophore:Fe complex upregulates heme oxygenase-1, a protective enzyme, preserves proximal tubule N-cadherin, and inhibits cell death. Because mouse urine contains an Ngal-dependent siderophore-like activity, endogenous Ngal might also play a protective role. Indeed, Ngal is highly accumulated in the human kidney cortical tubules and in the blood and urine after nephrotoxic and ischemic injury. We reveal what we believe to be a novel pathway of iron traffic that is activated in human and mouse renal diseases, and it provides a unique method for their treatment.

Comparisons of models of cortical necrosis with segmental infarction.

Sodium and water excretion were studied by standard clearance techniques in three experimental models where renal mass was reduced by superficial cortical necrosis (CN) or ischemic segmental infarction (SI). During hydropenia either CN or SI were able to conserve and regulate sodium to a very similar degree. After expansion of extracellular volume, CN reabsorbed less sodium and water than SI. In free-water clearance (CH2O) experiments, the 'apparent distal' sodium delivery was higher in CN than in SI, suggesting a decreased sodium and water reabsorption in the proximal tubules of juxtamedullary nephrons (JM). Both kidneys had similar CH2O when factored for inulin clearance but when CH2O was corrected for 'apparent distal' sodium delivery it was lower in CN than in SI, demonstrating an incapacity of JM to dilute urine. CN also showed less capacity to reabsorb free water than SI. Thus, the use of CN and SI within the same animal was useful to study functional differences between superficial and juxtamedullary nephrons. The present study also suggests that the kidney with superficial CN was unable to perform maximal urine dilution and concentration.