Tubulointerstitial Compartment Research Articles

Tubulointerstitial Injury and Drugs of Abuse

Drug abuse is widespread in many populations, and patients abusing illicit substances are at a significantly increased risk of kidney injury. The tubulointerstitial compartment is a common target of these nephrotoxic agents. This review will cover some of the common illicit drugs and will focus on the tubulointerstitial injuries seen in the setting of drug abuse. Agents addressed in this review are synthetic cannabinoids, "bath salts," ecstasy, anabolic steroids, inhaled solvents, heroin, and cocaine. The most frequent biopsy findings are those of acute tubular necrosis and acute interstitial nephritis. Unfortunately, histology is often unable to sufficiently narrow the differential diagnosis and point to a single likely cause. A high suspicion for drug abuse as a potential cause of kidney injury is needed to identify the patients for whom this is the cause of their kidney failure. Toxicology screens are often of little use in identifying patients using emerging drugs of abuse.

MDM2 mediates fibroblast activation and renal tubulointerstitial fibrosis via a p53-independent pathway.

It is well recognized that murine double minute gene 2 (MDM2) plays a critical role in cell proliferation and inflammatory processes during tumorigenesis. It is also reported that MDM2 is expressed in glomeruli and involved in podocyte injury. However, whether MDM2 is implicated in renal fibrosis remains unclear. Here we investigated the role of MDM2 in tubulointerstitial fibrosis (TIF). By immunohistochemical staining and Western blotting we confirmed that MDM2 is upregulated in the tubulointerstitial compartment in patients with TIF and unilateral urethral obstruction (UUO) mice, which mainly originates from myofibroblasts. Consistently, in vitro MDM2 is increased in TGF-β1-treated fibroblasts, one of the major sources of collagen-producing myofibroblasts during TIF, along with fibroblast activation. Importantly, genetic deletion of MDM2 significantly attenuates fibroblast activation. We then analyzed the possible downstream signaling of MDM2 during fibroblast activation. p53-dependent pathway is the classic downstream signaling of MDM2, and Nutlin-3 is a small molecular inhibitor of MDM2-p53 interaction. To our surprise, Nutlin-3 could not ameliorate fibroblast activation in vitro and TIF in UUO mice. However, we found that Notch1 signaling is attenuated during fibroblast activation, which could be markedly rescued by MDM2 knockdown. Overexpression of intracellular domain of Notch1 (NICD) by plasmid could obviously minimize fibroblast activation induced by TGF-β1. In addition, the degradation of NICD is strikingly suppressed by PYR-41, an inhibitor of ubiquitin-activating enzyme E1, and proteasome inhibitor MG132. Taken together, our findings provide the first evidence that MDM2 is involved in fibroblast activation and TIF, which associates with Notch1 ubiquitination and proteasome degradation.

Drug-induced nephropathies.

Drugs are associated frequently with the development of various types of acute and chronic kidney diseases. Nephrotoxicity is associated most commonly with injury in the tubulointerstitial compartment manifested as either acute tubular injury or acute interstitial nephritis. A growing number of reports has alsohighlighted the potential for drug-induced glomerular disease, including direct cellular injury and immune-mediated injury. Recognition of drug-induced nephropathies and rapid discontinuation of the offending agents are critical to maximizing the likelihood of renal function recovery. This review will focus on the pathology and pathogenesis of drug-induced acute interstitial nephritis and drug-induced glomerular diseases.

Systems biology analysis reveals role of MDM2 in diabetic nephropathy.

To derive new insights in diabetic complications, we integrated publicly available human protein-protein interaction (PPI) networks with global metabolic networks using metabolomic data from patients with diabetic nephropathy. We focused on the participating proteins in the network that were computationally predicted to connect the urine metabolites. MDM2 had the highest significant number of PPI connections. As validation, significant downregulation of MDM2 gene expression was found in both glomerular and tubulointerstitial compartments of kidney biopsy tissue from 2 independent cohorts of patients with diabetic nephropathy. In diabetic mice, chemical inhibition of MDM2 with Nutlin-3a led to reduction in the number of podocytes, increased blood urea nitrogen, and increased mortality. Addition of Nutlin-3a decreased WT1+ cells in embryonic kidneys. Both podocyte- and tubule-specific MDM2-knockout mice exhibited severe glomerular and tubular dysfunction, respectively. Interestingly, the only 2 metabolites that were reduced in both podocyte and tubule-specific MDM2-knockout mice were 3-methylcrotonylglycine and uracil, both of which were also reduced in human diabetic kidney disease. Thus, our bioinformatics tool combined with multi-omics studies identified an important functional role for MDM2 in glomeruli and tubules of the diabetic nephropathic kidney and links MDM2 to a reduction in 2 key metabolite biomarkers.

Epithelial-mesenchymal transition in pediatric nephropathies

IntroductionEpithelial-mesenchymal transition (EMT) is a process in which epithelial cells may express mesenchymal cell markers with subsequent change in their functions, and it may be part of the etiopathogenesis of kidney disease. ObjectiveThe aim of this study was to evaluate the immunexpression of some EMT inducers and markers in frequent nephropathies in pediatric patients. Methods59 patients aged 2–18 years old were selected and divided into 6 groups of frequent nephropathies in children and adolescents, as well as one control group. Urea and creatinine data of the patients were recorded. TGF-β3, fibronectin, α-SMA and vimentin were evaluated by immunohistochemistry. ResultsGlomerular TGF-β3 was higher in the Lupus Nephritis and Acute Diffuse Glomerulonephritis (ADGN) groups than in the control group. Glomerular fibronectin was higher in the Podocytopathy, Lupus Nephritis, ADGN and Membranous Glomerulopathy patients than in control subjects. The expression of α-SMA was higher in the tubulointerstitial compartment of ADGN and Membranous Glomerulopathy groups than in the control group. Glomerular α-SMA was higher in ADGN patients than in control and Berger’s Disease groups. Glomerular vimentin was higher in individuals with ADGN than in those with Podocytopathy, Lupus Nephritis, Berger’s Disease and Thin Basement Membrane Disease/Alport Syndrome. There was a positive correlation between fibronectin in the tubulointerstitial compartment and creatinine levels, between α-SMA and vimentin in both tubulointerstitial and glomerular compartments, and between urea and creatinine levels of patients, regardless of their nephropathy (p<0.05 for all results). ConclusionThese markers may possibly be used as indicators of renal functional impairment in various nephropathies in pediatric patients.

20 Defective placental bed vascular remodeling precedes manifestations of superimposed preeclampsia in stroke-prone spontaneously hypertensive rats

Introduction Pregnant women suffering from chronic hypertension are at increased risk of developing superimposed preeclampsia (SPE), often associated with poor fetal and maternal outcomes. Most animal models available to date reproduce ‘de novo' PE-like features through different experimental approaches, but the development of a SPE syndrome in pregnant animals with pre-existing arterial hypertension has been greatly overlooked in basic research pertaining hypertensive pregnancies. Objectives To characterize timed pregnancies in the Stroke Prone Spontaneously Hypertensive Rat (SHRSP) strain, a well-known model for essential hypertension, focusing on the development of clinical, fetal and placental manifestations of SPE. Methods SHRSP and Wistar Kyoto (WKY) females (10–12weeks old, N =5animals/day analyzed) were mated to congenic males and checked daily for vaginal plugs, denoted as gestation day (GD) 1. Blood pressure (BP) was determined by the tail-cuff method pre-mating and on the morning of GD1, 7, 9, 13, 17 and 19. On the selected dates, females were housed in metabolic cages for collection of 24h urine samples. Following collection of blood samples, animals were euthanized and implantation sites isolated for morphological analyzes. Fetal and placental weights were recorded on GD 18 and GD20. Results Compared to WKY, the SHRSP exhibited a significant elevation of baseline hypertension towards the last third of pregnancy (i.e, from GD13 to GD20) together with increased protein excretion, considered diagnostic hallmarks for SPE. Renal compromise was also evident as a progressive decrease of urinary output and histopathological changes in the glomerular and tubulointerstitial compartments of SHRSP kidneys. The SHRSP offspring were growth restricted and morphometrical analyzes showed underlying abnormal placentation, including signs of placental insufficiency such as decreased fetal to placental weight ratio and hypertrophy of the labyrinth layer linked to defective vascularization. Notably, our analysis also showed that the onset of the maternal syndrome was preceded by incomplete remodeling of the placental bed spiral arteries, which showed luminal narrowing and decreased densities of perivascular uterine NK cells at GD14 followed by defective infiltration of endovascular trophoblasts at GD18. Conclusion Our data confirms the characterization of pregnant SHRSP as a model reproducing clinical diagnostic traits and the underlying placental pathology observed in preeclampsia superimposed on chronic hypertension. This novel model provides an attractive system for interventional studies and dissection of the multifactorial origins of hypertensive disorders of pregnancy.

MAD2B-mediated SnoN downregulation is implicated in fibroblast activation and tubulointerstitial fibrosis

MAD2B, an anaphase-promoting complex/cyclosome (APC/C) inhibitor and a small subunit of DNA polymerase ζ, is indispensible for mitotic checkpoint control and DNA repair. Previously, we established that MAD2B is expressed in glomerular and tubulointerstitial compartments and participates in high glucose-induced podocyte injury. However, its role in other renal diseases remains elusive. In the present study, we aim to illustrate the potential role of MAD2B in the pathogenesis of renal fibrosis. By immunofluorescence and Western blotting, we found MAD2B expression is obviously increased in tubulointerstitial fibrosis (TIF) patients and unilateral ureteral obstruction (UUO) mice. It is widely accepted that resident fibroblasts are the major source of collagen-producing myofibroblasts during TIF. Therefore, we evaluated the level of MAD2B in fibroblasts (NRK-49F) exposed to transforming growth factor (TGF)-β1 by immunoblotting and revealed that MAD2B is upregulated in a time-dependent manner. Intriguingly, SnoN, a transcriptional repressor of the TGF-β1/Smad signaling pathway, is decreased in TGF-β1-treated fibroblasts as well as the kidney cortex from TIF patients and UUO mice. Either in vitro or in vivo, local genetic depletion of MAD2B by lentiviral transfection could preserve SnoN abundance and suppress Smad3 phosphorylation, which finally dampens fibroblast activation, ECM accumulation, and alleviates the severity of TIF. However, the ubiquitin ligase APC/C is not involved in the MAD2B-mediated SnoN decline, although this process is ubiquitination dependent. In conclusion, our observation proposes that besides cell cycle management, MAD2B has a profibrotic role during fibroblast activation and TIF by suppressing SnoN expression. Targeting the MAD2B-SnoN pathway is a promising intervention for TIF.

The lymphotoxin β receptor is a potential therapeutic target in renal inflammation.

Accumulation of inflammatory cells in different renal compartments is a hallmark of progressive kidney diseases including glomerulonephritis (GN). Lymphotoxin β receptor (LTβR) signaling is crucial for the formation of lymphoid tissue, and inhibition of LTβR signaling has ameliorated several non-renal inflammatory models. Therefore, we tested whether LTβR signaling could also have a role in renal injury. Renal biopsies from patients with GN were found to express both LTα and LTβ ligands, as well as LTβR. The LTβR protein and mRNA were localized to tubular epithelial cells, parietal epithelial cells, crescents, and cells of the glomerular tuft, whereas LTβ was found on lymphocytes and tubular epithelial cells. Human tubular epithelial cells, mesangial cells, and mouse parietal epithelial cells expressed both LTα and LTβ mRNA upon stimulation with TNF in vitro. Several chemokine mRNAs and proteins were expressed in response to LTβR signaling. Importantly, in a murine lupus model, LTβR blockade improved renal function without the reduction of serum autoantibody titers or glomerular immune complex deposition. Thus, a preclinical mouse model and human studies strongly suggest that LTβR signaling is involved in renal injury and may be a suitable therapeutic target in renal diseases.

Transcriptional and Translational Modulation of myo-Inositol Oxygenase (Miox) by Fatty Acids: IMPLICATIONS IN RENAL TUBULAR INJURY INDUCED IN OBESITY AND DIABETES

The kidney is one of the target organs for various metabolic diseases, including diabetes, metabolic syndrome, and obesity. Most of the metabolic studies underscore glomerular pathobiology, although the tubulo-interstitial compartment has been underemphasized. This study highlights mechanisms concerning the pathobiology of tubular injury in the context of myo-inositol oxygenase (Miox), a tubular enzyme. The kidneys of mice fed a high fat diet (HFD) had increased Miox expression and activity, and the latter was related to phosphorylation of serine/threonine residues. Also, expression of sterol regulatory element-binding protein1 (Srebp1) and markers of cellular/nuclear damage was increased along with accentuated apoptosis and loss of tubular brush border. Similar results were observed in cells treated with palmitate/BSA. Multiple sterol-response elements and E-box motifs were found in the miox promoter, and its activity was modulated by palmitate/BSA. Electrophoretic mobility and ChIP assays confirmed binding of Srebp to consensus sequences of the miox promoter. Exposure of palmitate/BSA-treated cells to rapamycin normalized Miox expression and prevented Srebp1 nuclear translocation. In addition, rapamycin treatment reduced p53 expression and apoptosis. Like rapamycin, srebp siRNA reduced Miox expression. Increased expression of Miox was associated with the generation of reactive oxygen species (ROS) in kidney tubules of mice fed an HFD and cell exposed to palmitate/BSA. Both miox and srebp1 siRNAs reduced generation of ROS. Collectively, these findings suggest that HFD or fatty acids modulate transcriptional, translational, and post-translational regulation of Miox expression/activity and underscore Miox being a novel target of the transcription factor Srebp1. Conceivably, activation of the mTORC1/Srebp1/Miox pathway leads to the generation of ROS culminating into tubulo-interstitial injury in states of obesity.

An Inflammatory Nexus: Serum Amyloid A and inflammation in Diabetic Kidney Disease

Inflammation contributes a significant part to the advancement of diabetic kidney disease (DKD), yet relatively little is known about the root cause of these inflammatory events. Serum Amyloid A (SAA) triggers a potent inflammatory response in a variety of tissues and is up-regulated in glomerular and tubulointerstitial compartments of the diabetic kidney. Under inflammatory conditions, podocytes, along with other intrinsic cells, produce SAA locally in the kidney. Our recent work has shown that SAA induces NF-κB activation and subsequent inflammatory chemokines and cytokines in cultured podocytes. Recent evidence suggests that local production of SAA in diabetes may lead to monocyte and macrophage recruitment, neutrophil activation, and other related incidents resulting in sustained chronic inflammatory conditions in the kidney which may further exacerbate DKD.

Urinary enzymatic markers (N-acetyl-beta-D-glucosaminidase) in assessing the tubulointerstitial compartment in chronic glomerulonephritis related to odontogenic foci.

Chronic glomerulonephritis is related to focus infection. Odontogenic foci are frequently involved in glomerulonephritis. The relationship with the odontogenic focus infection can be demonstrated by the occurrence or aggravation of the symptoms of glomerulonephritis: proteinuria, haematuria, high blood pressure and oedema. Glomerular impairment in glomerulonephritis occurs together with inflammatory alterations of the tubulointerstitial compartment that can play an important part in the evolution of the disease. Tubular urinary markers can indicate the activation of this compartment during an infection of a focus, an odontogenic focus in our study.The paper aims at demonstrating the relationship between the odontogenic focus infection and tubulointerstitial lesions, assessed by a tubular urinary marker, N-acetyl beta-D glucosaminidase (NAG).We investigated the urinary N-acetyl beta-D glucosaminidase of 20 patients with chronic glomerulonephritis who presented odontogenic focus infections, comparing them with patients with chronic glomerulonephritis without odontogenic foci and of 20 controls, clinically healthy persons.Chronic glomerulonephritis patients with odontogenic focus infection presented clearly increased values as compared to clinically healthy control persons of urinary N-acetyl beta-D glucosaminidase.These patients underwent surgical intervention on the odontogenic focus under antibacterial prophylactic treatment. In 75% cases, the values of N-acetyl beta-D glucosaminidase diminished, indicating the favourable effect of the treatment of the odontogenic focus on the tubulointerstitial compartment in patients with chronic glomerulonephritis. In 25% cases this therapeutic treatment was associated with an increase of the values of urinary N-acetyl beta-D glucosaminidase, expressing its unfavourable effect on chronic glomerulonephritis.Urinary N-acetyl beta-D glucosaminidase indicated an etiopathogenetic relationship between the odontogenic focus and the tubulointerstitial compartment in chronic glomerulonephritis.

The role of interstitial changes in the progression of chronic kidney disease.

Interstitium - the renal tubulointerstitial compartment - is located between the renal tubule basement membrane and microcirculation vessels. Interstitial fibroblasts produce the extracellular matrix and constitute the structure's cellular skeleton, regulating spatial relationships between its components (microenvironment). The tubular epithelium and endothelium cooperate within an integrated microenvironment. Structural or functional impairment of the extracellular matrix, microcirculation vessels or tubular epithelium results in disturbances of tubulointerstitial compartment components. In the course of glomerular kidney diseases, the intrarenal RAA system becomes activated and inflammatory mediators are released. Interstitial inflammation and microcirculatory disorders develop, inducing adverse consequences, manifested mainly through the process of hypoxia and inflammation. Inflammation-induced increase in interleukin-1 (TNF-α) expression leads to increased concentrations of VEGF, ICAM-1, angiotensin II, IL-6 and IL-8. Cytokines activate fibroblasts, myofibroblasts and endothelial cells. Fibrosis is also triggered by HIF-1alpha pathway activation, resulting in vascular growth and fibroblast proliferation. This reaction likewise occurs through activation of NF-ĸβ, EPO, GLUT-1, IGF-1 and INOS. Interstitial fibrosis is one of the factors determining the clinical course of kidney diseases. Apart from inducing fibrosis, microcirculatory disorders lead to the progression of hypoxia. Angiogenesis is a part of the repair process accompanying fibrosis. Its determinant is the normal function and structure of endothelial cells manifested by their ability to migrate and proliferate in response to, inter alia, angiopoietins, VEGF and nitric oxide synthase. Administering a three-drug RAAS-inhibiting therapy to patients with chronic glomerulopathies improves tubular function, measured by the decrease in excretion of NAG and propeptide of type III procollagen fibres, and contributes to the improvement in microcirculation functioning.

Metformin prevents renal interstitial fibrosis in mice with unilateral ureteral obstruction

Unilateral ureteral obstruction causes important tubulo-interstitial fibrosis in the kidney. Metformin reduces fibrosis in mice with diabetic nephropathy. We examined the effects of metformin in a mouse model of unilateral ureteral obstruction (UUO). Expression of inflammation and fibrosis markers was studied by immunohistochemistry, immunoblot and quantitative real-time polymerase chain reaction. Seven days after UUO, kidneys presented dilated tubules, expansion of the tubulo-interstitial compartment, and significant infiltration of inflammatory cells. Macrophage infiltration and inflammation markers expression were increased in obstructed kidneys and reduced by metformin. Metformin reduced expression of extracellular matrix proteins and profibrotic factor TGFβ in obstructed kidneys, measured by immunohistochemistry. Interstitial fibroblast activation was evident in obstructed kidneys and ameliorated by metformin. UUO did not affect adenosine monophosphate-activated kinase (AMPK) activity, but metformin activated AMPK. Our results show that metformin prevents or slows down the onset of renal inflammation and fibrosis in mice with UUO, an effect that could be mediated by activation of AMPK.

Interstitial pericytes decrease in aged mouse kidneys.

With increasing age, the kidney undergoes characteristic changes in the glomerular and tubulo-interstitial compartments, which are ultimately accompanied by reduced kidney function. Studies have shown age-related loss of peritubular vessels. Normal peritubular vessel tone, function and survival depend on neighboring pericytes. Pericyte detachment leads to vascular damage, which can be accompanied by their differentiation to fibroblasts and myofibroblasts, a state that favors matrix production. To better understand the fate of pericytes in the aged kidney, 27 month-old mice were studied. Compared to 3 month-old young adult mice, aged kidneys showed a substantial decrease in capillaries, identified by CD31 staining, in both cortex and medulla. This was accompanied by a marked decrease in surrounding NG2+ / PDGFRβ+ pericytes. This decrease was more pronounced in the medulla. Capillaries devoid of pericytes were typically dilated in aged mice. Aged kidneys were also characterized by interstitial fibrosis due to increased collagen-I and -III staining. This was accompanied by an increase in the number of pericytes that acquired a pro-fibrotic phenotype, identified by increased PDGFRβ+ / αSMA+ staining. These findings are consistent with the decline in kidney interstitial pericytes as a critical step in the development of changes to the peritubular vasculature with aging, and accompanying fibrosis.

The molecular phenotypes of rejection in kidney transplant biopsies.

The recent emergence of a system for distinguishing T-cell-mediated rejection (TCMR) from antibody-mediated rejection (ABMR), including C4d-negative ABMR, allows us to map the molecular features of these conditions. The TCMR landscape is dominated by molecules expressed in effector T cells, antigen-presenting cells (macrophages, dendritic cells, B cells) and interferon-gamma (IFNG)-induced genes. A surprising finding is the association of transcripts for inhibitory molecules such as CTLA4 and PDL1 with TCMR, indicating that this tubulo-interstitial inflammatory compartment is actively controlled. ABMR is dominated by endothelial transcripts related to angiogenesis, reflecting endothelial injury; natural killer (NK)-cell transcripts; and selected IFNG-regulated transcripts. This suggests a cognate unit of NK cells engaging donor-specific antibody bound to donor human leukocyte antigen antigens through their CD16a (FCGR3A) Fc receptors, triggering IFNG release. TCMR and ABMR share many rejection-associated transcripts, mainly IFNG-induced genes and transcripts shared between NK cells and CD8 effector T cells (e.g., KLRD1). In addition, acute kidney injury transcripts, which reflect the parenchymal response to injury, are shared between different forms of rejection and are indicative of disease progression. Microarray assessment provides a new dimension in biopsy assessment for diagnosis that offers mechanistic insights and sometimes challenges histology assessments.

Deletion of the gene for adiponectin accelerates diabetic nephropathy in the Ins2 (+/C96Y) mouse.

Diabetic nephropathy is one of the most common forms of chronic kidney disease. The role of adiponectin in the development of diabetic nephropathy has not been elucidated, and the aim of the present study was to investigate the hypothesis that deletion of the gene for adiponectin would accelerate diabetic nephropathy in the Akita mouse. We followed four groups of mice from 4 weeks to 16 weeks of age (n ≥ 10 in each group): wild-type (WT) (Ins2 (+/+) Adipoq(+/+)) mice; APN(-/-) (Ins2(+/+) Adipoq(-/-)) mice; Akita (Ins2(+/C96Y) Adipoq(+/+)) mice and Akita/APN(-/-) (Ins2(+/C96Y) Adipoq(-/-)) mice. The mice were then killed and diabetic kidney injury was assessed. In vitro experiments were performed in primary mesangial cells. Mice from both diabetic groups exhibited increased glomerular adiponectin receptor 1 (adipoR1) expression, kidney hypertrophy, glomerular enlargement, increased albuminuria and tissue oxidative stress compared with the WT control. Deletion of the adiponectin gene had no effect on glycaemia. However, Akita/APN(-/-) mice exhibited a greater extent of renal hypertrophy. In vitro, adiponectin attenuated high-glucose-induced phosphorylation of mammalian target of rapamycin (mTOR) and ribosomal protein S6 kinase (S6K). A higher level of fibrosis was observed in the tubulointerstitial and glomerular compartments of the Akita/APN(-/-) mice and adiponectin was found to inhibit TGFβ-induced Smad2 and Smad3 phosphorylation in vitro. There was an exaggerated inflammatory response in the Akita/APN(-/-) mice. Adiponectin also inhibited high-glucose-induced activation of nuclear factor κB (NFκB) in mesangial cells. Our data suggest that adiponectin is an important determinant of the kidney response to high glucose in vivo and in vitro.

Hypothesis: Chronic Progressive Nephropathy in Rodents as a Disease Caused by an Expanding Somatic Mutant Clone.

Chronic progressive nephropathy is a common noninfectious disease in aging (mice, rats) and non-aging (naked mole rat) rodents, sometimes resulting in death. The etiology and pathogenesis of the disease remain mysterious. For instance, it remains unclear what is the immediate cause of the disease and where exactly in the kidneys, glomerular or tubulointerstitial compartment, do primary and secondary changes occur. Here, I propose a potential scenario for development of progressive nephropathy that is based on an assumption that the disease is caused by occurrence and spread of mutant cellular clones from tubular epithelium secreting proinflammatory and prosclerotic cytokines. The hypothesis considers some features of the disease that have never been discussed earlier. According to the proposed concept, a clone of mutant cells secretes cytokines inducing chronic inflammation, proliferation of fibroblasts, and active collagen production that eventually results in sclerosis and thickening of tubular basement membranes. Sclerosis of interstitium and thickening of tubular basement membranes cause narrowing of some parts of the nephron, especially collecting ducts, which hinders passage of the urine, elevates tubular hydrostatic pressure, and impairs filtration and reabsorption in the kidneys. High hydrostatic pressure and reabsorption-induced elevated concentration of macromolecular substances in the primary urine result in development of large cysts and glomerular hyalinosis followed by renal failure. Based on this, it might be concluded that chronic progressive nephropathy in rodents represents a special type of tubulointerstitial dysplasia (or "non-tumorous neoplasia") in kidneys with secondary glomerular disorder at late stage of the disease. The concept for development of the disease proposed here may be of special importance from the viewpoint of toxicological pathology and gerontology, particularly for analysis of pathological features resulting in death of non-aging animals (naked mole rats).

Drug-induced glomerular disease: direct cellular injury.

The potential of medications to cause kidney injury is well known. Although nephrotoxicity is most commonly associated with injury in the tubulointerstitial compartment as either acute tubular necrosis or acute interstitial nephritis, a growing body of literature has also highlighted the potential for drug-induced glomerular lesions. This review surveys the three primary patterns of drug-induced glomerular diseases stratified by the cell type at which the glomerular lesion is focused: visceral epithelial cell (or podoctye) injury, endothelial cell injury, and mesangial cell injury. A number of commonly prescribed medications, including IFNs, bisphosphonates, nonsteroidal anti-inflammatory drugs, antiplatelet agents, and antiangiogenesis drugs, that are both prescribed and available over the counter, have been implicated in these iatrogenic forms of glomerular disease. Recognition of these drug-induced etiologies of glomerular disease and rapid discontinuation of the offending agent are critical to maximizing the likelihood of renal function recovery.

The role of renin–angiotensin system in the chronic allograft nephropathy: an immunohistochemical study

Background: Evidences suggest a role of renin–angiotensin system (RAS) in the development of chronic allograft injury. Methods: We correlated intrarenal angiotensin-converting enzyme, angiotensin II (Angio II) and transforming growth factor β1 (TGFβ1) expression in 58 biopsies-proven chronic allograft nephropathy (CAN) with tissue injury and allograft survival. Results: The biopsies with CAN were graded according to Banff classification as I (22 cases), II (17) and III (19); 27 biopsies also showed a mononuclear inflammatory infiltrate in scarred areas. There were increased expression of angiotensin converting-enzyme (ACE), Angio II and TGFβ1 mainly in tubulointerstitial compartment in the group with CAN; there was no association of Angio II and TGFβ1 expression with interstitial fibrosis. There were no significant differences of ACE, Angio II and TGFβ1 expression between the patients treated and untreated with RAS blockade, and with the graft outcome. Interstitial inflammatory infiltrate had positive correlation with interstitial fibrosis and significant impact on graft survival at 8 years. Conclusions: Our study showed in a group of cases with CAN a high percentage of inflammatory infiltrate that correlated with interstitial fibrosis and graft outcome. The chronic inflammatory changes in these cases did not show significant association with local RAS expression.

Thioredoxin-Interacting Protein: A Potential Therapeutic Target for Treatment of Progressive Fibrosis in Diabetic Nephropathy

Thioredoxin-interacting protein (TXNIP) is an endogenous inhibitor of the antioxidant thioredoxin, and a critical agent in the in vivo regulation of glucose. The well-described induction of TXNIP by high glucose may represent an important pathogenic trigger of complications arising in the diabetic environment, with sustained overexpression of TXNIP triggering the increased production of reactive oxygen species and collagen, both major contributors to the development of diabetic nephropathy (DN). To examine a possible therapeutic role for targeted TXNIP inhibition in DN, transgenic (mRen-2)27 rats were rendered diabetic with streptozotocin and then treated with 20 μ<smlcap>M</smlcap> TXNIP deoxyribozyme (DNAzyme) delivered continuously over 12 weeks by an implanted osmotic mini-pump. Renal injury was measured using biochemical parameters of kidney function along with histological markers of damage. Catalytic activity of TXNIP DNAzyme was determined by TXNIP gene and peptide expression in the rat kidneys. TXNIP DNAzyme localization was demonstrated with a fluorescent-labelled TXNIP DNAzyme. A panel of markers was used to assess the extent of oxidative stress and renal fibrosis including superoxide level, nitrotyrosine staining, TGF-β1, NLRP3 and collagen IV expression. Fluorescent-labelled TXNIP DNAzyme was localized to tubulo-epithelial cells, but was not identified in glomeruli or endothelial cells. Elevated renal cortical TXNIP gene and protein expression seen in kidneys of DN animals were significantly attenuated by TXNIP DNAzyme (p < 0.05). Downstream markers of TXNIP activity, particularly oxidative stress, inflammasome signalling, tubulo-interstitial fibrosis and collagen deposition, were also attenuated in the tubulo-interstitium of DN rats treated with TXNIP DNAzyme. Consistent with the identified site of action of the DNAzyme, the effects of the TXNIP inhibition were limited to the tubulo-interstitial compartment. This study supports the role of TXNIP as an important mediator of progressive tubulo-interstitial fibrosis in DN, and also supports the notion of TXNIP inhibition as a potential new therapeutic target for DN.