Peripheral CD4 T-cell depletion is not sufficient to prevent ischemic acute renal failure

BACKGROUND: Ischemia reperfusion injury leading to acute renal failure (ARF) and delayed graft function is an important problem in organ transplantation. CD4+ T cells, essential for transplant rejection, may mediate ischemic ARF. We have demonstrated that the caspase-1 mediated production of IL-18 is pathogenic in ischemic ARF in mice. A potential source of IL-18 in ischemic ARF is the CD4+ T cell. We therefore examined the effect CD4+ T cell depletion on the development of ischemic ARF and the activation of IL-18. METHODS: Functional and histological correlates were examined in two groups of mice with ischemic ARF: 1) CD4 T-cell depleted with the antibody GK1.5, and 2) T-cell receptor alpha-chain deficient (TCRalpha -/-) mice. TCRalpha -/- mice lack the alpha chain of the T-cell receptor and therefore lack functional CD4+ and CD8+ T cells. RESULTS: Flow cytometry of lymph nodes and immunohistochemistry of kidneys demonstrated complete depletion of CD4+ T cells in mice with ischemic ARF treated with GK 1.5. CD4+ T-cell depletion did not confer functional (serum creatinine, BUN and FITC-labeled inulin clearance) or histological protection against ischemic ARF. Likewise, TCRalpha -/- mice were not protected against ischemic ARF. Renal caspase-1 activity and IL-18 protein were similar in CD4+ T-cell depleted and wild-type postischemic reperfusion. CONCLUSIONS: Ischemic ARF can occur in the absence of classical T-cell function. The evaluation of other inflammatory mediators (e.g., macrophages or NK cells) as a source of IL-18 and mediator of ischemic ARF warrants further investigation.     

Urinary prostacyclin metabolites in patients with IgA nephropathy

Background. Urinary 6-keto-prostaglandin F_1α (6kPGF) is an index of renal prostacyclin (PGI₂) synthesis, while urinary 2,3-dinor-6-keto-prostaglandin F_1α (23d6kPGF) reflects extrarenal PGI₂ synthesis. We therefore examined the relationship between the urinary excretion of PGI₂ metabolites and the deterioration of renal function and histopathological findings. Methods. We measured these PGI₂ metabolites in 24-h collected urine from 32 patients with IgA nephropathy (IgAN) and 24 normal controls. Results. The urinary 6kPGF excretion in all patients (790 ± 395 pg/mg creatinine [Cr]) did not differ significantly from that in the normal controls (896 ± 351 pg/mgCr), but it was decreased in the patients with histopathological deterioration (661 ± 281 pg/mgCr). There were no such findings for 23d6kPGF. In the IgAN patients, the urinary 6kPGF excretion demonstrated a positive correlation to the 1/creatinine slope, which indicated deterioration of renal function (r = 0.43; P < 0.03). Conclusions. Renal PGI₂ production is reduced in IgAN patients with histopathological deterioration, and 24-h urinary 6kPGF excretion may be an effective marker to evaluate the renal injury. Received: June 22, 1998 / Accepted: December 19, 1999     

Ischemic acute renal failure following nephrectomy impairs long-term renal function

Uninephrectomy is associated with increased glomerular filtration rate in both the donated and the remaining contralateral kidney. The long-term effects of ischemic acute renal failure (ARF) following uninephrectomy are unknown. This study examined renal function, histology and proteinuria 52 weeks after an episode of reversible ischemic ARF. Ischemic ARF was induced in uninephrectomised mice by renal pedicle clamping. At 52 weeks inulin clearance (muL/min/g) was 7.2+/-0.2 in sham, 5.0+/-0.1 in uninephrectomy (P<0.01 vs. sham) and 3.9+/-0.1 in uninephrectomy + ischemia (P<0.01 vs. sham, P<0.05 vs. uninephrectomy). Thus, mice subjected to uninephrectomy alone demonstrated compensatory hyperfiltration following reduction in renal mass. This response was prevented by ischemic ARF. At 52 weeks there was no difference in urine protein/creatinine, mean arterial pressure or scores of glomerulosclerosis or interstitial fibrosis. In conclusion, ischemic ARF following uninephrectomy in mice impairs long-term renal function.     

Natriuretic and renoprotective effect of chronic oral neutral endopeptidase inhibition in acute renal failure

Neutral endopeptidase (NEP: EC 3.4.24.11) is involved in the degradation of peptides such as atrial natriuretic peptide, angiotensin II (AngII), and endothelin-1 (ET-1). In this study we propose that NEP inhibition provides protection in glycerol-induced acute renal failure (ARF). Renal vascular responses were evaluated in ARF rats where ARF was induced by injecting 50% glycerol in candoxatril, a NEP inhibitor (30 mg/kg, orally; for 3 weeks) pretreated rats. AngII and U46619 (a TxA₂ mimetic) vasoconstriction was increased (2- to 4-fold) in ARF while ET-1 vasoconstriction was surprisingly reduced (23 ± 3%; p < 0.05). In ARF, candoxatril paradoxically enhanced ET-1 response (60 ± 20%; p < 0.05) but reduced AngII vasoconstriction (51 ± 11%; p < 0.05) without affecting U46619 response. However, candoxatril treatment was without effect on plasma ET-1 and TxB₂ levels in ARF. Candoxatril reduced plasma AngII by 34 ± 4% (p < 0.05) in ARF which was ～3.5-fold higher compared to control. Candoxatril doubled the nitrite excretion in control but was without effect on proteinuria or nitrite excretion in ARF. Candoxatril enhanced Na⁺ and creatinine excretion in ARF by 73 ± 9% and 33 ± 2%, respectively. These results suggest that NEP inhibition may confer protection in glycerol-induced ARF by stimulating renal function but without a consistent effect on renal production and renal vascular responses to endogenous vasoconstrictors.     

Prostaglandin production and platelet reactivity of small-diameter grafts

This article examines the relationship of platelet deposition to thromboxane and prostacyclin (PGI₂) production in arterial autografts (n = 8), para-anastomotic native artery (n = 40), nonseeded control (n = 6), and endothelial cell-seeded (n = 17) small-diameter Dacron grafts implanted in the carotid and femoral arteries of dogs. Platelet deposition was measured by a dual-isotope subtraction platelet-imaging technique that expresses platelet deposition as percent indium excess (%IE). PGI₂ and thromboxane assays were performed with the use of an immunoreactive assay. The %IE in the nonseeded grafts was significantly higher than in the seeded prostheses (p < 0.001). Arterial autografts accumulated significantly less platelets than did seeded grafts (p < 0.05) or nonseeded grafts (p < 0.001). The thromboxane A₂ (TXA₂) production in nonseeded grafts was significantly higher than in seeded grafts (p < 0.001), arterial autografts (p < 0.001), or in para-anastomotic native artery (p < 0.001). The PGI₂ production by the arterial autografts was significantly higher than by the nonseeded grafts (p < 0.005), seeded grafts (p < 0.001), or para-anastomotic native artery (p < 0.025). The PGF_1α/TXB₂ ratio was significantly higher in the arterial autografts when compared with the nonseeded grafts (p < 0.001), endothelial cell-seeded grafts (p < 0.001), or para-anastomotic native artery (p < 0.025). We conclude that platelet deposition can be significantly decreased by endothelial cell seeding of small-diameter grafts. The transmural production of TXA₂ by native arteries and prosthetic grafts may have an important influence on platelet deposition and patency. The balance between the production of TXA₂ and PGI₂ in the graft wall may be the best determinant of platelet deposition and possibly of long-term patency. (J VASC SURG 1984;1:774-781.)     

Thromboxane receptor mediates renal vasoconstriction and contributes to acute renal failure in endotoxemic mice

Sepsis is a major cause of acute renal failure (ARF) and death. Thromboxane A2 (TxA(2)) may mediate decreases of renal blood flow (RBF) and/or GFR associated with LPS-induced sepsis. This study tested whether TxA(2) receptor blockade, with the use of TxA(2) receptor knockout (TP-KO) mice or a selective TP receptor antagonist (SQ29,548), would alleviate LPS-induced renal vasoconstriction and ARF. Under basal conditions, anesthetized TP-KO mice displayed a lower mean arterial pressure than wild-type (WT) mice (102 versus 94 mmHg; P < 0.05). RBF, renal vascular resistance (RVR), GFR, and urine flow did not differ among groups under basal conditions, suggesting little tonic influence of TxA(2) on renal TP receptors in health. In endotoxemic WT mice, 14 h after LPS (Escherichia coli LPS 8.5 mg/kg intraperitoneally), mean arterial pressure was reduced to 85 mmHg (P < 0.001), as were RBF (5.0 versus 9.3 ml/min per g kidney wt; P < 0.001) and GFR (0.38 versus 1.03 ml/min per g kidney wt; P < 0.001). Heart rate and RVR (71 versus 47 mmHg/ml per min; P < 0.05) increased. The decreases in RBF and GFR after LPS were attenuated in TP-KO mice versus WT mice (both P < 0.05). In both TP-KO and TP antagonist-treated mice, RVR remained stable in response to LPS versus WT mice that did not receive LPS. Delayed TP-antagonist treatment (12 h after LPS injection) ameliorated RBF and RVR but did not restore GFR. In other WT animals, TP-antagonist treatment for 2 h before intravenous LPS abolished the early renal vasoconstriction and alleviated the decrease in GFR. These results demonstrate that renal vasoconstriction during endotoxemic shock induced by LPS is mediated by TP receptors as indicated by pharmacologic blockade and genetic disruption of TP receptors.     

Assessment and interpretation of the tubular threshold for phosphate in infants and children

Studies in the last decade demonstrated that in children tubular maximum phosphate reabsorption per glomerular filtration rate (TmP/GFR) is identical to TP/GFR; TP indicating tubular phosphate reabsorption under basal conditions, without phosphate load. TP/GFR is calculated from the formula TP/GFR=S_P–U_P×S_CrU_Cr, based on simultaneous urine and blood creatinine and phosphate concentrations, and is applicable in both the fasting and non-fasting child. These studies also demonstrated that the use of Walton and Bijvoet nomogram in children may result in overestimation of TmP/GFR compared with TP/GFR calculated from the above formula. When using the formula, one should bear in mind that creatinine is used to express GFR and as a result a significant deviation from true GFR may occur in patients with renal failure. Therefore when employing TP/GFR for the investigation of the renal handling of phosphate in children, three factors should be taken into consideration: (1) the formula in reality expresses TP/C _Cr; (2) only data obtained by exactly the same methodology can be used as reference values; data obtained from studies in which the nomogram was utilized or in which methods other thanC _Cr were used to measure GFR should not be used for reference; (3) in patients with renal failure, TP/C _Cr will significantly overestimate TP/C _inulin.     

Prostacyclin in diarrhoea-associated haemolytic uraemic syndrome

The role of prostacyclin (PGI₂) in the pathogenesis of haemolytic uraemic syndrome (HUS) is controversial. In part, confusion has been caused by failure to distinguish between two main sub-types of the syndrome: extrinsic, diarrhoea-associated HUS (D+ HUS), usually caused by infection with verocytotoxin-producingEscherichia coli orShigella dysenteriae, and the heterogeneous group of non-prodromal forms where intrinsic factors predominate (D– HUS). This paper critically reviews data confined to D+ HUS. Two methods have been used to assess PGI₂ synthesis; the generation of PGI₂ from endothelium in the presence of HUS plasma in vitro and the measurement of stable metabolites in body fluids. No concensus could be reached with regard to the former. The reported increase of PGI₂ stable metabolites in plasma may represent reduced clearance or increased carriage by plasma lipids. Apparent differences between studies of urinary excretion of PGI₂ metabolites may reflect the way excretion was expressed. If the metabolite concentration is factored for urinary creatinine, it appears that renal excretion and thus renal synthesis of PGI₂ is reduced. However, these are insufficient data on which to attribute the pathogenesis of D+ HUS to disordered PGI₂ metabolism.Presented at the Festschrift for Professor R. H. R. White on March 6, 1992, Birmingham, UK     

Investigation of the long-term patency of a transmural heparinized polycaprolactone and poly(D,L-lactic/glycolic acid) scaffold

Background

The transmural biodegradable polycaprolactone/poly(D,L-lactic/glycolic acid) (PCL/PLGA) scaffold is a promising modality for diffuse coronary atherosclerosis cases that are not suitable for bypass grafting. The purpose of this study was to evaluate the long-term performance of the PCL/PLGA scaffold in vivo in the setting of polymer and heparin degradation.

Materials and methods

After mechanical drilling through the ventricular wall was performed in the whole ventricular wall, two scaffolds were implanted into the ventricular wall. Animals were grouped into the single drilling group (SD group), the blank scaffold group (BS group), and the heparinized scaffold group (HS group) and were allowed to survived for 6 mo. Next, the patency and integrity of the scaffolds were evaluated by echocardiography and 3D-DOCTOR software. Endothelium coverage of the lumen was evaluated by scanning electron microscopy. Neovessels and collagen fiber within the scaffolds were identified by histologic staining. Metabolite production of prostacyclin (PGI₂) and thromboxane A₂ (TXA₂) in the plasma was measured by an enzyme-linked immunosorbent assay. The expression levels of PGI₂ synthase and cyclooxygenase 2 (COX-2) involved in PGI₂ production and COX-1 involved in TXA₂ production were measured by Western blot analysis.

Results

The heparinized scaffolds were patent for up to 6 mo and the lumen was covered with confluent endothelial cells. Histologic staining revealed collagen fiber remodeling and reconstruction of the neovascular network immediately surrounding the lumen. The expression of PGI₂ synthase and COX-2 in the HS group was significantly higher compared with the SD and BS groups (P < 0.01). The expression of COX-1 was similar in the three groups (P > 0.05). Consistent with synthetase expression, a PGI₂ metabolite (6-keto-PGF1a) also showed a significant increase in the HS group relative to the SD and BS groups (P = 0.021 and P = 0.015, respectively). Concomitantly, as a PGI₂ antagonist, the TXA₂ metabolite (TXB₂) did not exhibit a significant difference among the three groups (P = 0.17).

Conclusions

Despite polymer and heparin degradation, the scaffold could continuously maintain the structural integrity and lumen patency for up to 6 mo by reinforcement of host collagen fiber and the balance of PGI₂/TXA₂.     

8‐isoprostane F2α up‐regulates the expression of type 5 phosphodiesterase in cavernosal vascular smooth muscle cells: inhibition with sildenafil,iloprost, nitric oxide and picotamide

OBJECTIVES

To explore the possible role of of 8‐isoprostane F_2α (8‐IPF_2α) in the aetiology of erectile dysfunction (ED), as the over‐production of superoxide (O₂^‐) derived from nicotinamide adenine dinucleotide phosphate (NADPH) oxidase results in the formation of 8‐IPF_2α in vascular tissue, which has similar properties to thromboxane A₂ (TXA₂). TXA₂ is vasoconstrictor and up‐regulates the expression of NADPH oxidase and phosphodiesterase type 5 (PDE5).

MATERIALS AND METHODS

Cavernosal vascular smooth muscle cells (CVSMCs) were incubated with 8‐IPF_2α or the TXA₂ analogue, U46619, ±sildenafil, iloprost (a stable prostacyclin [PGI₂] analogue) or the nitric oxide (NO) donor NONOate for 16 h. The formation of O₂^‐ was then measured, PDE5 expression assessed using Western blotting and PGI₂ and 8‐IPF_2α formation measured using enzyme‐linked immunoassays.

RESULTS

8‐IPF_2α promoted the formation of O₂^‐, an effect inhibited by apocynin (an NADPH oxidase inhibitor) and up‐regulated the expression of PDE5. Under identical incubation conditions, 8‐IPF_2α induced an increase in the formation of 8‐IPF_2α but reduced the formation of PGI₂. All, these effects were reversed by sildenafil, iloprost, NONOate and picotamide.

CONCLUSIONS

These data show that O₂^‐ derived from NADPH oxidase influences the relative balance of PGI₂ and 8‐IPF_2α in CVSMCs, which in turn alters the degree of PDE5 expression. This is a novel pathogenic mechanism underlying ED and a novel mechanism of action of sildenafil.     

Maladaptive role of IL-6 in ischemic acute renal failure

The role of IL-6 was investigated in murine ischemic acute renal failure. The renal pedicles were clamped for 17 min, and the mice were studied at various times after reperfusion. We found that serum IL-6 increased after murine ischemic renal injury. This increase was associated with increased IL-6 mRNA in the ischemic kidney but not in the contralateral kidney or the liver. Maximal IL-6 production occurred at 4 to 8 h and decreased to baseline by 24 h. Reperfusion of the kidney was required for IL-6 production. In situ hybridization and immunohistochemistry showed that macrophages infiltrated areas adjacent to the vascular bundles in the outer medulla within hours of reperfusion and showed that these macrophages produced IL-6 mRNA. For understanding how macrophages were stimulated to produce IL-6, an in vitro model in which S3 proximal tubular cells were injured by reactive oxygen species was set up. These injured cells released molecules that activated macrophages to produce IL-6 in vitro. IL-6 that was produced in response to renal ischemia was maladaptive because transgenic knockout of IL-6 ameliorated renal injury as measured by serum creatinine and histology. IL-6 transgenic knockout mice were lethally irradiated, and their bone marrow was reconstituted with wild-type IL-6 cells. Such bone marrow transfers abolished the protective effects of transgenic IL-6 knockout. It is concluded that macrophages infiltrate the area of the vascular bundles of the outer medulla, these macrophages produce IL-6, and this IL-6 exacerbates ischemic murine acute renal failure.     

Transplantation of Bone Marrow Mononuclear Cells Reduces Mortality and Improves Renal Function on Mercury-Induced Kidney Injury in Mice

Objective: Recent studies have demonstrated the therapeutic effects of bone marrow–derived cells in tissue regeneration. The aim of this study was to investigate the effects of bone marrow mononuclear cell (BMMC) transplantation in a mouse model of acute renal failure (ARF) induced by mercuric chloride. Methods: BMMC was isolated from male BALB/c mice and injected into female mice treated with a lethal dose (LD90) of mercuric chloride. Survival rate, histopathological analysis, and assessment of urea, creatinine, sodium, potassium, and mercury levels were carried out. Results: Cellular therapy with BMMC significantly reduced the mortality induced by mercuric chloride (p < 0.05). This finding correlated with a decrease in serum levels of urea (p = 0.04) and potassium (p < 0.01). However, no differences in renal morphology were observed when BMMC-treated and control group were compared. Conclusion: Transplanted BMMC improve renal function and reduce mortality and, therefore, may represent a new therapeutic alternative to treat ARF.     

Pancreatic Injury in Rabbits with Acute Renal Failure

Background.?Acute renal failure (ARF) is a common critical disorder. To decrease the mortality, it is important to prevent ARF from invading other organs in clinical setting. It is not known whether there is a dysfunction in pancreas during the pathogenesis of ARF. This study aimed to investigate the changes of morphology and function on pancreas in ARF rabbits. Methods.?Sixty rabbits were randomly divided into four groups. The ARF model of groups 1 and 2 rabbits was established by hypodermic injection of 1% HgCl₂ (1.3 mL/kg) and intramuscular injection of 50% glyceritum (10 mL/kg), respectively. The control groups 1 and 2 were injected with same volume of normal saline. After 24 hours, urea and creatinine contents and pancreatic amylase (AMY) activities in serum were measured using an automatic biochemical analyzer; the insulin levels were measured with radioimmunoassay method. Moreover, morphological alterations were examined by light microscopy; free radicals, nitric oxide (NO), and nitric oxide synthase (NOS) in pancreas homogenate were determined.?Results.?Morphological study showed that there were vacuolar degeneration and necrosis in pancreas of ARF for both groups 1 and 2. Compared with corresponding control group, the AMY activity was significantly elevated, whereas the INS values were decreased significantly in ARF groups 1 and 2. Malonaldehyde, NO, and NOS in pancreas homogenate were significantly increased, and superoxide dismutase activity was decreased.?Conclusion.?These data suggested that there were morphological damage of pancreas and disturbance of pancreatic secretion function in rabbits with ARF. Free radicals-injury and NO excessive release may explain the observed dysfunction.     

Cardioprotection afforded by ischemic preconditioning interferes with chronic beta‐blocker treatment

Objectives—The efficacy of ischemic preconditioning of the heart has remained controversial. We investigated whether chronic treatment with beta‐blockers affects the ischemic preconditioning in the isolated rat heart model.

Design—Wistar rats were treated with propranolol (50?mg/kg/day, p.o.) (PRL), with nipradilol (10?mg/kg/day, p.o.) (NPL), or with vehicle, for 4 weeks. Isolated rat hearts were divided into global ischemia hearts (GI, PRL and NPL, each n=6) and ischemic preconditioned hearts (IP, PRL+IP and NPL+IP, each n=6).

Results—Significant differences in left ventricular pressure were observed between the PRL and PRL+IP, and between the NPL and NPL+IP groups. In the NPL group, significant amelioration and preservation of left ventricular peak pressure, coronary flow, reduction of infarct size, and NOx preservation were observed. Lipid peroxidation in the NPL group was significantly reduced before and after global ischemia compared to the GI group.

Conclusions—The effect of ischemic preconditioning was abolished in the hearts of rats following oral treatment of propranolol or nipradilol. However, the administration of nipradilol protected the ischemic and reperfused myocardium, partly due to the prevention of lipid peroxide formation.     

Prostaglandin response to intravenous nitroglycerin

Recent studies suggest that nitroglycerin (TNG)-induced vascular and myocardial effects may be mediated by arachidonic acid metabolites. We examined the correlation between prostacyclin (PGI₂) and thromboxane (TXA₂) release in the coronary sinus (CS) and intravenous administration of TNG. Concentrations of PGI₂ and TXA₂ were derived indirectly by measuring their stable metabolites, 6-ketoprostaglandin F_1α (6KF_1α) and thromboxane B₂ (TXB₂), respectively. Fifteen dogs were studied in three equal groups. Group I received 2 μg/kg/min TNG followed by 10 μg/kg/min. Group II received the same concentrations in reverse order. Group III received 10 μg/kg/min after pretreatment with 10 mg/kg ibuprofen. After 90 min stabilization blood samples drawn from the pulmonary artery (PA), left atrium (LA), inferior vena cava (IVC), and CS before and during TNG infusion were analyzed for TXB₂ and 6KF_1α. No 6KF_1α was generated in any groups. Groups I and II showed significant TXB₂ production exclusively in the CS during the first TNG infusion but not during the second. This response was prevented by pretreating with ibuprofen. We were unable to correlate the hemodynamic effects of TNG with the presence of increased TXA₂ in the coronary sinus blood. These data demonstrate that the action of TNG is not mediated by prostacyclin. TNG infusion does result in an initial significant thromboxane release in the myocardial circulation which can be blocked by ibuprofen.     

Induction of heat shock protein 70 inhibits ischemic renal injury

Heat shock protein 70 (Hsp70) is a potent antiapoptotic agent. Here, we tested whether it directly regulates renal cell survival and organ function in a model of transient renal ischemia using Hsp70 knockout, heterozygous, and wild-type mice. The kidney cortical Hsp70 content inversely correlated with tubular injury, apoptosis, and organ dysfunction after injury. In knockout mice, ischemia caused changes in the activity of Akt and glycogen synthase kinase 3-β (kinases that regulate the proapoptotic protein Bax), increased active Bax, and activated the proapoptotic protease caspase 3. As these changes were significantly reduced in the wild-type mice, we tested whether Hsp70 influences ischemia-induced apoptosis. An Hsp70 inducer, geranylgeranylacetone, increased Hsp70 expression in heterozygous and wild-type mice, and reduced both ischemic tubular injury and organ dysfunction. When administered after ischemia, this inducer also decreased tubular injury and organ failure in wild-type mice but did not protect the knockout mice. ATP depletion in vitro caused greater mitochondrial Bax accumulation and death in primary proximal tubule cells harvested from knockout compared with wild-type mice and altered serine phosphorylation of a Bax peptide at the Akt-specific target site. In contrast, lentiviral-mediated Hsp70 repletion decreased mitochondrial Bax accumulation and rescued Hsp70 knockout cells from death. Thus, increasing Hsp70 either before or after ischemic injury preserves renal function by attenuating acute kidney injury.     

Increased severity of glomerulonephritis in C-C chemokine receptor 2 knockout mice

Increased severity of glomerulonephritis in C-C chemokine receptor 2 knockout mice. BACKGROUND: The C-C chemokine receptor 2 (CCR2) is expressed on monocytes and facilitates monocyte migration. CCR2 is a prominent receptor for monocyte chemoattractant protein-1 (MCP-1). This chemokine recruits monocytes to sites of inflammation. It has been suggested that CCR2 and its ligand, MCP-1, play a role in the pathogenesis of glomerulonephritis. The goal of this study was to determine the contribution of CCR2 in a murine model of accelerated nephrotoxic nephritis. We measured the extent of development of renal disease in CCR2 wild-type and knockout mice after the administration of antiglomerular basement membrane antibody. METHODS: Eight groups of animals were treated (N = 10 per group). Four days after IgG immunization, CCR2 wild-type and knockout mice received control serum or nephrotoxic serum. The urinary protein/creatinine ratio was measured on days 1 and 3; plasma and kidneys were collected on days 4 and 7. Kidneys were evaluated by light microscopy, immunohistochemistry, and immunofluorescence. The genotype of mice was confirmed by tissue analysis. RESULTS: Protective effects of CCR2 knockout on the urinary protein/creatinine ratio were observed on day 1, as values for this parameter were significantly lower (35 +/- 3.6) than in nephritic wild-type mice (50 +/- 6.8). There was a marked increase in proteinuria in nephritic wild-type mice on day 1 compared with vehicle-treated, wild-type animals (5 +/- 1.0). On day 3, the ameliorative effects of CCR2 knockout were not observed; the increase in the urinary protein/creatinine ratio was similar in nephritic CCR2 wild-type (92 +/- 11.2) and knockout mice (102 +/- 9. 2). Plasma markers of disease were evaluated on days 4 and 7. At these time points, there were no beneficial effects of CCR2 receptor knockout on plasma levels of urea nitrogen, creatinine, albumin, or cholesterol. On day 7, blood urea nitrogen (248 +/- 19.9 mg/dL) and plasma cholesterol were higher in nephritic CCR2 knockout mice than in wild-type mice (142 +/- 41.7 mg/dL) that received nephrotoxic serum. Histopathologic injury was more severe in nephritic CCR2 knockout mice than nephritic wild-type mice on day 4 (3.1 +/- 0.3 vs. 2.0 +/- 0.3) and day 7 (3.6 +/- 0.2 vs. 2.9 +/- 0.3). By immunohistochemical analysis at day 4, there were significantly fewer mac-2-positive cells, representative of macrophages in the glomeruli of nephritic CCR2 knockout (2.1 +/- 0.6) mice than nephritic wild-type (3.9 +/- 0.5) animals. By indirect immunofluorescence, there was a moderate, diffuse linear IgG deposition of equivalent severity present in glomeruli of both wild-type and CCR2 knockout nephritic mice. CONCLUSION: These results suggest that our strategy was successful in reducing macrophage infiltration, but this model of glomerulonephritis is not solely dependent on the presence of CCR2 for progression of disease. After a transient ameliorative effect on proteinuria, CCR2 knockout led to more severe injury in nephritic mice. This raises the intriguing possibility that a CCR2 gene product ameliorates glomerulonephritis in this murine model. Although effects that occur in chemokine knockout mice are not equivalent to those expected with prolonged use of a chemokine antagonist, this study may nevertheless have implications for consideration of long-term use of chemokine antagonists in renal disease.     

Arachidonic acid metabolites and haemodynamics of the neonate

The role of eicosanoids, arachidonic acid (AA) metabolites, in blood pressure regulation under physiological and pathological conditions during the perinatal period is still under investigation. This review focuses on the synthesis and catabolism of some vasoactive AA metabolites by fetal, neonatal and placental cells, and on the vascular responses of the fetus and neonate to prostanoids and to the inhibitors of their synthesis. Vasodilator prostaglandins, PGE₂ and prostacyclin (PGI₂), increase steadily during pregnancy, while thromboxane A₂ (TXA₂), a potent vasoconstrictor, remains low during pregnancy, increasing only shortly before delivery. TXA₂ participates in the closure of umbilical vessels and ductus arteriosus. In pregnancy-induced hypertension, increase in the synthesis of TXA₂ occurs early during pregnancy. Decrease in the catabolism of AA precedes the onset of hypertension in the developing spontaneously hypertensive rat. In newborn piglets, platelet-activating factor, vasoconstrictor prostaglandins and leukotriene D₄ have a marked constrictor effect on the pulmonary circulation and induce pulmonary hypertension, without affecting the systemic blood pressure. Although the role of AA metabolites in the regulation of haemodynamics during the perinatal period is not fully understood, it is apparent that several eicosanoids modulate the action of hormones and vasoactive agents.     

Differential gender differences in ischemic and nephrotoxic acute renal failure

BACKGROUND/AIMS: Recent work has shown that female animals are more resistant to ischemic acute renal failure (ARF) than male animals. The mechanism underlying the gender difference is unclear. Moreover, whether the gender difference holds true for ARF induced by other insults is unknown. This study sought to determine the gender differences in ischemic and nephrotoxic ARF. METHODS: Gender differences were tested in two experimental models of ARF. For ischemic ARF, bilateral clamping of renal pedicles was conducted in C57BL/6 and 129/Sv mice followed by reperfusion. For nephrotoxic ARF, cisplatin was administered to the animals. Renal function, tissue damage, animal survival, and renal cell apoptosis were examined. RESULTS: Ischemic ARF was significantly ameliorated in female mice, as shown by lower serum creatinine and blood urea nitrogen (BUN). Female mice also showed better renal histology, less apoptosis and caspase activation, and a much better survival rate than male mice following ischemic insult. On the contrary, female mice were more sensitive to cisplatin-induced ARF. In these animals, BUN increased at day 1 following cisplatin injection, while in males BUN increases were not shown until day 3. Higher levels of serum creatinine were also recorded in female mice. Renal histology showed severer necrotic tubular damage in females, although apoptosis and caspase activation appeared similar in both genders. Consistently, male mice survived better than females in the nephrotoxic model. CONCLUSION: While female mice were resistant to ischemic ARF, they appeared more sensitive to cisplatin-induced ARF. Investigation of the gender differences at the cellular and molecular levels might provide a new area for mechanistic study of ARF.     

NBCn1 Increases NH4+ Reabsorption Across Thick Ascending Limbs,the Capacity for Urinary NH4+ Excretion,and Early Recovery from Metabolic Acidosis

BackgroundThe electroneutral Na⁺/HCO₃⁻ cotransporter NBCn1 (Slc4a7) is expressed in basolateral membranes of renal medullary thick ascending limbs (mTALs). However, direct evidence that NBCn1 contributes to acid-base handling in mTALs, urinary net acid excretion, and systemic acid-base homeostasis has been lacking.MethodsMetabolic acidosis was induced in wild-type and NBCn1 knockout mice. Fluorescence-based intracellular pH recordings were performed and NH₄⁺ transport measured in isolated perfused mTALs. Quantitative RT-PCR and immunoblotting were used to evaluate NBCn1 expression. Tissue [NH₄⁺] was measured in renal biopsies, NH₄⁺ excretion and titratable acid quantified in spot urine, and arterial blood gasses evaluated in normoventilated mice.ResultsBasolateral Na⁺/HCO₃⁻ cotransport activity was similar in isolated perfused mTALs from wild-type and NBCn1 knockout mice under control conditions. During metabolic acidosis, basolateral Na⁺/HCO₃⁻ cotransport activity increased four-fold in mTALs from wild-type mice, but remained unchanged in mTALs from NBCn1 knockout mice. Correspondingly, NBCn1 protein expression in wild-type mice increased ten-fold in the inner stripe of renal outer medulla during metabolic acidosis. During systemic acid loading, knockout of NBCn1 inhibited the net NH₄⁺ reabsorption across mTALs by approximately 60%, abolished the renal corticomedullary NH₄⁺ gradient, reduced the capacity for urinary NH₄⁺ excretion by approximately 50%, and delayed recovery of arterial blood pH and standard [HCO₃⁻] from their initial decline.ConclusionsDuring metabolic acidosis, NBCn1 is required for the upregulated basolateral HCO₃⁻ uptake and transepithelial NH₄⁺ reabsorption in mTALs, renal medullary NH₄⁺ accumulation, urinary NH₄⁺ excretion, and early recovery of arterial blood pH and standard [HCO₃⁻]. These findings support that NBCn1 facilitates urinary net acid excretion by neutralizing intracellular H⁺ released during NH₄⁺ reabsorption across mTALs.