Immunohistochemical and ultrastructural changes in the renal cortex of cadmium-treated rats

The aim of this study was to determine the cadmium-induced immunohistochemical and morphological changes in the renal cortex of adult male rats exposed to high doses of cadmium for 30 d. Animals used as controls received a standard diet and water ad libitum. The animals used for this study received 15 ppm CdCl₂ in their drinking water for 1 mo. The mean arterial pressure (MAP), the mean blood Cd level, and the mean tissue Cd content were significantly higher when compared to controls (p < 0.01). Immunohistochemical studies demonstrated a weak labeling to type IV collagen and laminin, but a strong labeling to fibronectin in the renal cortex of the Cd-treated animals when compared to controls. The ultrastructural alterations found in Cd-treated rats were a diminution in the amount of filtration slits, increased fusion of foot processes in epithelial cells of the glomeruli, increase of lysosomal structures and pinocytic vesicles as well as large mitochondria in proximal tubule cells, and degenerated cells in distal tubules. Additionally, the glomerular basement membrane was slightly thickened. In conclusion, cadmium toxicity results in alterations in the renal extracellular matrix and tubular or glomerular cells, which could play an important role in renal dysfunction.     

Loxosceles gaucho venom-induced acute kidney injury--in vivo and in vitro studies

Background

Accidents caused by Loxosceles spider may cause severe systemic reactions, including acute kidney injury (AKI). There are few experimental studies assessing Loxosceles venom effects on kidney function in vivo.

Methodology/Principal Findings

In order to test Loxosceles gaucho venom (LV) nephrotoxicity and to assess some of the possible mechanisms of renal injury, rats were studied up to 60 minutes after LV 0.24 mg/kg or saline IV injection (control). LV caused a sharp and significant drop in glomerular filtration rate, renal blood flow and urinary output and increased renal vascular resistance, without changing blood pressure. Venom infusion increased significantly serum creatine kinase and aspartate aminotransferase. In the LV group renal histology analysis found acute epithelial tubular cells degenerative changes, presence of cell debris and detached epithelial cells in tubular lumen without glomerular or vascular changes. Immunohistochemistry disclosed renal deposition of myoglobin and hemoglobin. LV did not cause injury to a suspension of fresh proximal tubules isolated from rats.

Conclusions/Significance

Loxosceles gaucho venom injection caused early AKI, which occurred without blood pressure variation. Changes in glomerular function occurred likely due to renal vasoconstriction and rhabdomyolysis. Direct nephrotoxicity could not be demonstrated in vitro. The development of a consistent model of Loxosceles venom-induced AKI and a better understanding of the mechanisms involved in the renal injury may allow more efficient ways to prevent or attenuate the systemic injury after Loxosceles bite.     

Ochratoxin A and citrinin nephrotoxicity in New Zealand White rabbits: an ultrastructural assessment

In the present investigation, ochratoxin A (OTA) (0.75 mg/kg feed) and citrinin (CIT) (15 mg/kg feed) were fed alone and in combination to young growing New Zealand White rabbits for 60 days to evaluate renal ultrastructural alterations. The severity and intensity of renal ultrastructural changes varied with the type of the treatment, and predominant and consistent lesions were recorded in the proximal convoluted tubule (PCT) lining cells. The significant changes in mitochondria, the most affected cell organelle in all the treatment groups, included mitochondrial disintegration and distortion, pleomorphism, cluster formation and misshapen appearance such as signet ring, dumbbell, cup and U shapes. Intra-cisternal sequestrations of involuting mitochondria, and thickening of basal layer of PCT epithelial cells with partial detachment, were the characteristic features observed in OTA and combination treatments. CIT treatment revealed crenated nucleus, loss of nucleolus, depletion of cytoplasmic organelles, mitochondrial pleomorphism, nuclear fragmentation, uniform folding of cell membrane and cytoplasmic vacuolations in the PCTs. Focal thickening of the glomerular basement membrane and degeneration of endothelial cells were the prominent alterations in the glomeruli in OTA and combination treatments. Distal convoluted tubules were unaffected in CIT treatment, however, mild to moderate lesions were observed in OTA and combination treated rabbits. It may be concluded that on simultaneous exposure, CIT potentiated the toxic effects of OTA on renal ultrastructure. Part of M.V.Sc thesis research work of first author, Deemed University, Indian Veterinary Research Institute, Izatnagar-243 122 (U. P.), India.     

HIV-associated nephropathy: role of AT2R

AT₁R has been reported to play an important role in the progression of HIV-associated nephropathy (HIVAN); however, the effect of AT₂R has not been studied. Age and sex matched control (FVB/N) and Tg26 mice aged 4, 8, and 16 weeks were studied for renal tissue expression of AT₁R and AT₂R (Protocol A). Renal tissue mRNA expression of AT₂R was lower in Tg26 mice when compared with control mice. In Protocol B, Tg26 mice were treated with either saline, telmisartan (TEL, AT₁ blocker), PD123319 (PD, AT₂R blocker), or TEL + PD for two weeks. TEL-receiving Tg26 (TRTg) displayed less advanced glomerular and tubular lesions when compared with saline-receiving Tg26 (SRTg). TRTgs displayed enhanced renal tissue AT₂R expression when compared to SRTgs. Diminution of renal tissue AT₂R expression was associated with advanced renal lesions in SRTgs; whereas, upregulation of AT₂R expression in TRTgs was associated with attenuated renal lesions. PD-receiving Tg26 mice (PDRTg) did not show any alteration in the course of HIVAN; whereas, PD + TEL-receiving Tg26 (PD-TRTg) showed worsening of renal lesions when compared to TRTgs. Interestingly, plasma as well as renal tissues of Tg26 mice displayed several fold higher concentration of Ang III, a ligand of AT₂R.     

Hereditary Nephropathy with Hematuria (Alport's Syndrome)

Among 82 members and four generations of a French-Canadian family, 14 cases of hereditary nephropathy (Alport''s syndrome) were documented. Five additional members of the family had died, probably because of this same illness. Deafness occurred in five family members with nephropathy and in one without renal disease. Ten of 12 affected males died in uremia before they had reached the age of 40 years. One of seven affected females died following a pregnancy. In two surviving patients, special investigations failed to elicit intrinsic tubular defects such as amino-aciduria, renal tubular acidosis, hyperphosphaturia or renal glucosuria. Systemic illness such as abnormal aminoacids in serum, primary hyperoxaluria, diabetes mellitus and infections were also excluded. Immunological defects were not demonstrable and the staining of renal biopsy tissue with fluorescein-labelled anti-β₁c, anti-IgG and antifibrinogen was negative. Renal tissue material of early, advanced and terminal hereditary nephropathy showed both tubular and interstitial, vascular and glomerular lesions. Electronmicroscopy showed marked thickening of tubular and glomerular basement membranes, increase of mesangial tissue and fusion of foot processes but failed to demonstrate “immune deposits.” It is postulated therefore that hereditary nephropathy results from an inborn error of metabolism where an as yet unidentified metabolite damages the renal tissue as well as the acoustic nerve, analogous perhaps to the action of certain drugs, e.g. nephro-ototoxic antibiotics.     

The Association of Serum Bilirubin on Kidney Clinicopathologic Features and Renal Outcome in Patients with Diabetic Nephropathy: A Biopsy-Based Study

Objective: To explore the relationship between serum bilirubin concentration and clinicopathologic features and renal outcome in biopsy-diagnosed diabetic nephropathy (DN) in patients with type 2 diabetes mellitus.Methods: In this retrospective study, 118 patients with DN were enrolled. Participants were divided into two groups according to their median baseline serum bilirubin concentration: Group 1 (serum bilirubin ≤7.5 μmol /L); Group 2 (serum bilirubin >7.5 μmol /L). Basic clinical parameters were measured at the time of renal biopsy, and the relationships between serum bilirubin and the clinicopathologic features and renal outcome were analyzed.Results: Patients in Group 1 often had inferior renal function. Compared with Group 2, the glomerular classification and interstitial inflammation were more severe in subjects of Group 1, while arteriolar hyalinosis and interstitial fibrosis and tubular atrophy (IFTA) were comparable between the groups. Serum bilirubin was negatively correlated with the severity of the glomerular classification, interstitial inflammation, and IFTA. In the prognostic analysis, higher serum bilirubin level was associated with a lower risk of progression to end-stage renal disease, which was independent of the effects of age, gender, duration of diabetes, anemia, serum glucose, and hypertension but not of estimated glomerular filtration rate (hazard ratio, 0.406; 95% confidence interval, 0.074 to 2.225; P = .299).Conclusion: Our study showed a negative correlation between serum bilirubin level and renal pathologic lesions in patients with DN; serum bilirubin showed an inverse association with DN progression, but this was not independent.Abbreviations: CI = confidence interval; CKD = chronic kidney disease; DM = diabetes mellitus; DN = diabetic nephropathy; DR = diabetic retinopathy; eGFR = estimated glomerular filtration rate; ESRD = end-stage renal disease; HbA1c = glycated hemoglobin; HO-1 = heme oxygenase 1; HR = hazard ratio; IFTA = interstitial fibrosis and tubular atrophy; log-BIL = log-transformed baseline serum bilirubin; T2DM = type 2 diabetes mellitus     

Changes in the NFκB and E-cadherin expression are associated to diabetic nephropathy in Psammomys obesus

Diabetes mellitus is a major leading cause of end-stage renal failure, characterized by kidney inflammation and glomerular dysfunction, in worldwide. Kidney inflammation is associated to modifications in the expression levels of pro-inflammatory molecules, such as nuclear factor-κB (NFκB) and adhesion molecules, such as E-cadherin, leading to glomerular dysfunction. However, the relationships between these two processes in human diabetic nephropathy remain an open question. Since Psammomys obesus is an ideal animal model to study diabetes mellitus temporal evolution, we have used this model to study the correlation between kidney structural changes and modification on the expression levels of NFκB and E-cadherin over time. We have demonstrated that, after induction of diabetes metillus with a high energy diet (HED), P. obesus develops the characteristic symptoms of human disease. In detail, at the third month nuclear factor NFκB is expressed in the kidney of diabetic P. obesus and structural renal changes, such as mesangial expansion or interstitial fibrosis, are detectable; at 6 months, thickening of glomerular basement membrane, glomerular sclerosis, and tubular atrophy occurs; at 9 months, symptoms of the final stages of the disease, such as down expression of E-cadherin, happens. As a result of these observations we proposed that NFκB activation and E-cadherin down-expression are interlinked on diabetic kidney disease (DKD).     

Knockout of receptor for advanced glycation end‐products attenuates age‐related renal lesions

Pro‐aging effects of endogenous advanced glycation end‐products (AGEs) have been reported, and there is increasing interest in the pro‐inflammatory and ‐fibrotic effects of their binding to RAGE (the main AGE receptor). The role of dietary AGEs in aging remains ill‐defined, but the predominantly renal accumulation of dietary carboxymethyllysine (CML) suggests the kidneys may be particularly affected. We studied the impact of RAGE invalidation and a CML‐enriched diet on renal aging. Two‐month‐old male, wild‐type (WT) and RAGE^?/? C57Bl/6 mice were fed a control or a CML‐enriched diet (200 μg CML/g_food) for 18 months. Compared to controls, we observed higher CML levels in the kidneys of both CML WT and CML RAGE^?/? mice, with a predominantly tubular localization. The CML‐rich diet had no significant impact on the studied renal parameters, whereby only a trend to worsening glomerular sclerosis was detected. Irrespective of diet, RAGE^?/? mice were significantly protected against nephrosclerosis lesions (hyalinosis, tubular atrophy, fibrosis and glomerular sclerosis) and renal senile apolipoprotein A‐II (ApoA‐II) amyloidosis (p < 0.001). A positive linear correlation between sclerosis score and ApoA‐II amyloidosis score (r = 0.92) was observed. Compared with old WT mice, old RAGE^?/? mice exhibited lower expression of inflammation markers and activation of AKT, and greater expression of Sod2 and SIRT1. Overall, nephrosclerosis lesions and senile amyloidosis were significantly reduced in RAGE^?/? mice, indicating a protective effect of RAGE deletion with respect to renal aging. This could be due to reduced inflammation and oxidative stress in RAGE^?/? mice, suggesting RAGE is an important receptor in so‐called inflamm‐aging.     

The renal type IIa Na/Pi cotransporter: structure-function relationships

The type IIa Na/P_i cotransporter mediates proximal tubular brush-border membrane secondary active phosphate (P_i) flux. It is rate limiting in tubular P_i reabsorption and, thus, a final target in many physiological and pathophysiological situations of altered renal P_i handling (1–4). In the present short review, we will briefly summarize our current knowledge about the transport mechanism (cycle) as well as particular regions of the transporter protein (“molecular domains”) that potentially determine transport characteristics.     

Blood chemical changes and renal histological alterations induced by gentamicin in rats

Gentamicin is an effective widely used antibiotic, but the risk of nephrotoxicity and oxidative damage limit its long-term use. Hence, the current study aims to elucidate such hazardous effects. To achieve the study aim male Wistar albino rats (Rattus norvegicus) were exposed to gentamicin to investigate the resultant blood chemical changes and renal histological alterations. In comparison with control rats, gentamicin produced outstanding tubular, glomerular and interstitial alterations that included degeneration, necrosis, cytolysis and cortical tubular desquamation together with mesangial hypercellularity, endothelial cell proliferation and blood capillary congestion. Compared with control animals significant blood chemical changes (P < 0.05) including free radicals, ALT, AST, ALP, serum creatinine and serum urea were recorded in gentamicin-injected animals. The findings revealed that exposure to gentamicin can induce significant histological alterations in the kidney as well as remarkable blood chemical changes that might indicate marked renal failure.     

Diabetic Retinopathy,Classified Using the Lesion-Aware Deep Learning System,Predicts Diabetic End-Stage Renal Disease in Chinese Patients

Objective: To characterize the relationship between diabetic retinopathy (DR) and diabetic nephropathy (DN) in Chinese patients and to determine whether the severity of DR predicts end-stage renal disease (ESRD).Methods: Bilateral fundic photographs of 91 Chinese type 2 diabetic patients with biopsy-confirmed DN, not in ESRD stage, were obtained at the time of renal biopsy in this longitudinal study. The baseline severity of DR was determined using the Lesion-aware Deep Learning System (RetinalNET) in an open framework for deep learning and was graded using the Early Treatment Diabetic Retinopathy Study severity scale. Cox proportional hazard models were used to estimate the hazard ratio (HR) for the effect of the severity of diabetic retinopathy on ESRD.Results: During a median follow-up of 15 months, 25 patients progressed to ESRD. The severity of retinopathy at the time of biopsy was a prognostic factor for progression to ESRD (HR 2.18, 95% confidence interval 1.05 to 4.53, P = .04). At baseline, more severe retinopathy was associated with poor renal function, and more severe glomerular lesions. However, 30% of patients with mild retinopathy and severe glomerular lesions had higher low-density lipo-protein-cholesterol and more severe proteinuria than those with mild glomerular lesions. Additionally, 3% of patients with severe retinopathy and mild glomerular changes were more likely to have had diabetes a long time than those with severe glomerular lesions.Conclusion: Although the severity of DR predicted diabetic ESRD in patients with type 2 diabetes mellitus and DN, the severities of DR and DN were not always consistent, especially in patients with mild retinopathy or microalbuminuria.Abbreviations: CI = confidence interval; DM = diabetic mellitus; DN = diabetic nephropathy; DR = diabetic retinopathy; eGFR = estimated glomerular filtration rate; ESRD = end-stage renal disease; HbA1c = hemoglobin A1c; HR = hazard ratio; NPDR = nonproliferative diabetic retinopathy; PDR = proliferative diabetic retinopathy; SBP = systolic blood pressure; T2DM = type 2 diabetes mellitus; VEGF = vascular endothelial growth factor     

Effects of cadmium and uranium on some in vitro renal targets

Metals are major pollutants not only in occupational settings but also in the general environment. Chronic exposure of workers has been related to severe damage, especially at the renal level. While toxic compounds such as metals are well known to severely impair tubular functions, it is clear that nephrotoxicants can act on various other renal targets, i.e., vascular and glomerular ones.In vitro models are available to assess these toxicities and can be used to better understand the different cell targets. This paper summarizes data obtained in our laboratory after exposure of isolated renal structures such as glomeruli, and cell cultures such as glomerular mesangial and tubular epithelial cells, to cadmium and uranium. Morphometric studies by image analysis of isolated glomeruli and mesangial cultured cells showed that cadmium and uranium induced a dose- and time-dependent glomerular contraction accompanied by disorganization of the cytoskeleton. Classical viability tests demonstrated various factors influencing the metal toxicity. The important roles of pH, extracellular protein concentrations and the nature of the anion accompanying the metal were demonstrated. These data obtained inin vitro models provide better understanding of the cytotoxicity after metal uptake and accumulation in glomerular and tubular cells. Moreover, the glomerular and tubular cytotoxicity they induce may be correlated with severe renal hemodynamic changes in vivo. Finally, we briefly present eventual improvements forin vitro renal models by the use of new cell models such as immortalized human cell lines or by the introduction of porous supports and perifusion devices. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Remedial Efficacy of Spirulina platensis versus Chromium-Induced Nephrotoxicity in Male Sprague-Dawley Rats

This study was conducted to investigate the possible protective effect of Spirulina platensis against chromium-induced nephrotoxicity. A total of 36 adult male Sprague-Dawley rats were divided into 4 equal groups (Gps). Gp1 served as control, rats of Gps 2, 3, and 4 were exposed to Spirulina platensis (300 mg/kg b.wt per os) and sodium dichromate dihydrate (SDD) via drinking water at concentration of 520 mg /l respectively. Chromium administration caused alterations in the renal function markers as evidenced by significant increase of blood urea and creatinine levels accompanied with significant increase in kidney’s chromium residues and MDA level as well as decreased catalase activity and glutathion content in kidney tissue. Histologically, Cr provoked deleterious changes including: vascular congestion, wide spread tubular epithelium necrobiotic changes, atrophy of glomerular tuft and proliferative hyperplasia. The latter was accompanied with positive PCNA expression in kidney tissues as well as DNA ploidy interpretation of major cellular population of degenerated cells, appearance of tetraploid cells, high proliferation index and high DNA index. Morphometrical measurements revealed marked glomerular and tubular lumen alterations. On contrary, spirulina co-treatment with Cr significantly restored the histopathological changes, antioxidants and renal function markers and all the previously mentioned changes as well.     

Evidence for water channels in renal proximal tubule cell membranes

Summary Water transport mechanisms in rabbit proximal convoluted cell membranes were examined by measurement of: (1) osmotic (P _f ) and diffusional (P _d ) water permeabilities, (2) inhibition ofP _f by mercurials, and (3) activation energies (E _a ) forP _f .P _f was measured in PCT brush border (BBMV) and basolateral membrane (BLMV) vesicles, and in viable PCT cells by stopped-flow light scattering;P _d was measured in PCT cells by proton NMR T_i relaxation times using Mn as a paramagnetic quencher. In BLMV,P _f (0.019 cm/sec, 23°C) was inhibited 65% by 5mm pCMBS and 75% by 300 m HgCl₂ (K _l =42 m);E _a increased from 3.6 to 7.6 kcal/mole (15–40°C) with 300 m HgCl₂. In BBMV,P _f (0.073 cm/sec, 23°C,E _a =2.8 kcal/mole, <33°C and 13.7 kcal/mole, >33°C) was inhibited 65% with HgCl₂ withE _a =9.4 kcal/mole (15–45°C). Mercurial inhibition in BLMV and BBMV was reversed with 10 m mercaptoethanol. Viable PCT cells were isolated from renal cortex by Dounce homogenization and differential seiving. Impedence sizing studies show that PCT cells are perfect osmometers (100–1000 mOsm). Assuming a cell surface-to-volume ratio of 25,000 cm^–1,P _f was 0.010±0.002 cm/sec (37°C) andP _d was 0.0032 cm/sec.P _f was independent of osmotic gradient size (25–1000 mOsm) withE _a 2.5 kcal/mole (<27°C) and 12.7 kcal/mole (>27°C). CellP _f was inhibited 53% by 300 m HgCl₂ (23°C) withE _a 6.2 kcal/mole. These findings indicate that cellP _f is not restricted by extracellular or cytoplasmic unstirred layers and that cellP _f is not flow-dependent. The high BLMV and BBMVP _f , inhibition by HgCl₂, lowE _a which increases with inhibition, and the measuredP _f /P _d >1 in cells in the absence of unstirred layers provide strong evidence for the existence of water channels in proximal tubule brush border and basolateral membranes. These channels are similar to those found in erythrocytes and are likely required for rapid PCT transcellular water flow.     

myo-Inositol Oxygenase Overexpression Accentuates Generation of Reactive Oxygen Species and Exacerbates Cellular Injury following High Glucose Ambience: A NEW MECHANISM RELEVANT TO THE PATHOGENESIS OF DIABETIC NEPHROPATHY*

Diabetic nephropathy (DN) is characterized by perturbations in metabolic/cellular signaling pathways with generation of reactive oxygen species (ROS). The ROS are regarded as a common denominator of various pathways, and they inflict injury on renal glomerular cells. Recent studies indicate that tubular pathobiology also plays a role in the progression of DN. However, the mechanism(s) for how high (25 mm) glucose (HG) ambience induces tubular damage remains enigmatic. myo-Inositol oxygenase (MIOX) is a tubular enzyme that catabolizes myo-inositol to d-glucuronate via the glucuronate-xylulose (G-X) pathway. In this study, we demonstrated that G-X pathway enzymes are expressed in the kidney, and MIOX expression/bioactivity was up-regulated under HG ambience in LLC-PK1 cells, a tubular cell line. We further investigated whether MIOX overexpression leads to accentuation of tubulo-interstitial injury, as gauged by some of the parameters relevant to the progression of DN. Under HG ambience, MIOX overexpression accentuated redox imbalance, perturbed NAD⁺/NADH ratios, increased ROS generation, depleted reduced glutathione, reduced GSH/GSSG ratio, and enhanced adaptive changes in the profile of the antioxidant defense system. These changes were also accompanied by mitochondrial dysfunctions, DNA damage and induction of apoptosis, accentuated activity of profibrogenic cytokine, and expression of fibronectin, the latter two being the major hallmarks of DN. These perturbations were largely blocked by various ROS inhibitors (Mito Q, diphenyleneiodonium chloride, and N-acetylcysteine) and MIOX/NOX4 siRNA. In conclusion, this study highlights a novel mechanism where MIOX under HG ambience exacerbates renal injury during the progression of diabetic nephropathy following the generation of excessive ROS via an unexplored G-X pathway.     

A study of nephron function in normal tropical residents using the creatinine and lithium clearances

 The kidney bears the brunt of the demands of a tropical climate for water and electrolyte homeostasis. We hypothesised that a tropical climate may cause adaptive changes in the entire organism leading to altered renal function in our subjects. Hence renal function data for residents of a temperate climate may not be applic- able to tropical residents. We therefore sought to elucidate renal function in subjects residing in a tropical climate. We used lithium clearance, C _Li, a non-invasive tool for assessing proximal tubular function in humans, and endogenous creatinine clearance, C _Cr, to estimate proximal tubular function and glomerular function, respectively, in our subjects. We did this in order to establish whether or not nephron function in our subjects differs from that for residents of a temperate climate. Nineteen male and 12 female Ghanaian subjects aged between 15 and 48 years were studied. The estimated G _Cr was 117.3±6.6 ml/min for male subjects and 97±6.4 ml/min for female subjects. C _Li was 20.3±1.6 ml/min for male and 19.1±0.4 ml/min for female subjects, respectively. The estimated absolute reabsorption rate of fluid of proximal tubules was 97.0±6.0 ml/min for males and 78.1±6.0 ml/min for females. The percentage proximal fluid reabsorption for male and female subjects was 81.2±1.4 and 79.5±1.6, respectively. The differences between male and female values (mean±SEM) were not statistically significant. The data suggest that the proximal tubule in residents of a tropical climate may reabsorb more fluid compared to that in residents of a temperate climate. Our values for proximal tubular reabsorption are higher than those reported for residents of a temperature climate. Our estimate of glomerular filtration, however, is similar to published data for Caucasians. The difference in proximal tubular function may reflect possible renal adaptation to a hot, humid climate. We conclude that renal function of tropical residents differs from that of residents of a temperate climate. This difference may be due to renal adaptation to the hot, tropical climate. Received: 1 July 1996 / Revised: 22 December 1996 / Accepted: 8 January 1997     

Environmentally induced nephrotoxicity and histopathological alternations in Wallago attu and Cirrhinus mrigla

Fish kidneys are sensitive to chemical changes in the freshwater ecosystem because they are directly and constantly exposed to chemicals dissolved in the water. This study evaluated nephrotoxicity in Wallago attu and Cirrhinus mrigala harvested from the Chenab River in an area of industrial and sewage waste disposal. Induced histological alternation data were correlated to the severity of environmental degradation in order to determine whether this biological system can be used as a tool for environmental monitoring programs. Kidneys from two fish species occupying different niches were collected and stored for 24 h in 10% formalin. Control fish were collected upstream of the polluted river area. Specimens were processed using topical histological methods. The major histological alterations observed in both species were renal tubule myxospora, hyperemia, glomerulonephritis, degeneration of renal tubule cells, dilation of glomerular capillaries, presence of pycnotic nuclei in the hematopoietic tissue, epithelial hypertrophy, vacuolization, reduced lumen of renal tubules, and shrinkage of glomeruli. Renal tubular atrophy, degeneration due to extensive degranulation, necrosis of glomeruli, glomerular expansion, absence of Bowman’s space, hypertrophied nucleus, necrosis and hyalinization of the interstitium, clogging of tubules, and regeneration of tubules was also observed. Wallago attu exhibited the maximum incidence of moderate to severe changes and was defined as having the highest “histopathologic alteration index”. These severe alterations were found to be related to environmental degradation, indicating the presence of stressors in freshwater. Control groups showed normal tissue morphology in the kidneys.     

Diabetic nephropathy induces alterations in the glomerular and tubule lipid profiles

Diabetic nephropathy (DN) is a major life-threatening complication of diabetes. Renal lesions affect glomeruli and tubules, but the pathogenesis is not completely understood. Phospholipids and glycolipids are molecules that carry out multiple cell functions in health and disease, and their role in DN pathogenesis is unknown. We employed high spatial resolution MALDI imaging MS to determine lipid changes in kidneys of eNOS^−/− db/db mice, a robust model of DN. Phospholipid and glycolipid structures, localization patterns, and relative tissue levels were determined in individual renal glomeruli and tubules without disturbing tissue morphology. A significant increase in the levels of specific glomerular and tubular lipid species from four different classes, i.e., gangliosides, sulfoglycosphingolipids, lysophospholipids, and phosphatidylethanolamines, was detected in diabetic kidneys compared with nondiabetic controls. Inhibition of nonenzymatic oxidative and glycoxidative pathways attenuated the increase in lipid levels and ameliorated renal pathology, even though blood glucose levels remained unchanged. Our data demonstrate that the levels of specific phospho- and glycolipids in glomeruli and/or tubules are associated with diabetic renal pathology. We suggest that hyperglycemia-induced DN pathogenic mechanisms require intermediate oxidative steps that involve specific phospholipid and glycolipid species.     

Vascular transplant rejection of rat renal allografts across strong histocompatibility barriers

Sixty-one rat renal allografts were studied by light microscopy and in 18 cases also by immunohistology. Donor and recipient differ at a major histocompatibility locus in the one group (n=37), and by an additional weak histocompatibility antigen in the other (n=24). The mean survival time is 10.4 days and 8.3 days, respectively. A semiquantitative grading of the histologic findings shows that in both groups the rejection is predominantly manifested by lesions of extraglomerular and glomerular vessels, whereas mononuclear cell infiltration appears to be of less significance. The essential findings are necrosis of arteries and arterioles, necrosis of glomerular cells with mesangiolysis, and focal tubular necroses. This morphologic rejection type is interpreted as the result of a mixed humoral and cellular immune response, although the constant participation of circulating antibodies in the vascular damage could not be established. Since the tubular necroses correlate well with the degree of vascular alterations, but not with the mononuclear cell infiltration it would seem reasonable to conclude that these necroses are secondary to ischemia produced by vascular lesions. Finally, there is no significant difference in the degree of rejection between the two donor/recipient groups, and, therefore, there is no morphologic evidence for an increase of the rejection process by additional weak histoincompatibility in the examined strain combinations.     

Suppression of Rapidly Progressive Mouse Glomerulonephritis with the Non-Steroidal Mineralocorticoid Receptor Antagonist BR-4628

Background/Aim

Steroidal mineralocorticoid receptor antagonists (MRAs) are effective in the treatment of kidney disease; however, the side effect of hyperkalaemia, particularly in the context of renal impairment, is a major limitation to their clinical use. Recently developed non-steroidal MRAs have distinct characteristics suggesting that they may be superior to steroidal MRAs. Therefore, we explored the benefits of a non-steroidal MRA in a model of rapidly progressive glomerulonephritis.

Methods

Accelerated anti-glomerular basement membrane (GBM) glomerulonephritis was induced in groups of C57BL/6J mice which received no treatment, vehicle or a non-steroidal MRA (BR-4628, 5mg/kg/bid) from day 0 until being killed on day 15 of disease. Mice were examined for renal injury.

Results

Mice with anti-GBM glomerulonephritis which received no treatment or vehicle developed similar disease with severe albuminuria, impaired renal function, glomerular tuft damage and crescents in 40% of glomeruli. In comparison, mice which received BR-4628 displayed similar albuminuria, but had improved renal function, reduced severity of glomerular tuft lesions and a 50% reduction in crescents. The protection seen in BR-4628 treated mice was associated with a marked reduction in glomerular macrophages and T-cells and reduced kidney gene expression of proinflammatory (CCL2, TNF-α, IFN-γ) and profibrotic molecules (collagen I, fibronectin). In addition, treatment with BR-4626 did not cause hyperkalaemia or increase urine Na+/K+ excretion (a marker of tubular dysfunction).

Conclusions

The non-steroidal MRA (BR-4628) provided substantial suppression of mouse crescentic glomerulonephritis without causing tubular dysfunction. This finding warrants further investigation of non-steroidal MRAs as a therapy for inflammatory kidney diseases.