Gadolinium contrast agent-induced CD163+ ferroportin+ osteogenic cells in nephrogenic systemic fibrosis

Gadolinium-based contrast agents are linked to nephrogenic systemic fibrosis in patients with renal insufficiency. The pathology of nephrogenic systemic fibrosis is characterized by abnormal tissue repair: fibrosis and ectopic ossification. The mechanisms by which gadolinium could induce fibrosis and ossification are not known. We examined in vitro the effect of a gadolinium-based contrast agent on human peripheral blood mononuclear cells for phenotype and function relevant to the pathology of nephrogenic systemic fibrosis using immunofluorescence, flow cytometry, real-time PCR, and osteogenic assays. We also examined tissues from patients with nephrogenic systemic fibrosis, using IHC to identify the presence of cells with phenotype induced by gadolinium. Gadolinium contrast induced differentiation of human peripheral blood mononuclear cells into a unique cellular phenotype--CD163(+) cells expressing proteins involved in fibrosis and bone formation. These cells express fibroblast growth factor (FGF)23, osteoblast transcription factors Runt-related transcription factor 2, and osterix, and show an osteogenic phenotype in in vitro assays. We show in vivo the presence of CD163(+)/procollagen-1(+)/osteocalcin(+) cells in the fibrotic and calcified tissues of nephrogenic systemic fibrosis patients. Gadolinium contrast-induced CD163(+)/ferroportin(+)/FGF23(+) cells with osteogenic potential may play a role in systemic fibrosis and ectopic ossification in nephrogenic systemic fibrosis.

Ehrlichiosis presenting with toxic shock-like syndrome and secondary hemophagocytic lymphohistiocytosis

Human monocytotropic ehrlichios is a tick borne illness caused by Ehrlichia chaffeensis. Ehrlichiosis presenting with septic shock and severe azotemia is rare, and may be seen in immunocompromised individuals. We present a case of ehrlichia induced toxic shock like syndrome in a patient with rheumatoid arthritis on disease modifying agents. He also had oliguric renal failure requiring dialysis on presentation and later found to have Hemophagocytic Lymphohistiocytosis secondary to severe ehrlichia sepsis.

Meprin A metalloproteinase and its role in acute kidney injury

Meprin A, composed of α- and β-subunits, is a membrane-associated neutral metalloendoprotease that belongs to the astacin family of zinc endopeptidases. It was first discovered as an azocasein and benzoyl-l-tyrosyl-p-aminobenzoic acid hydrolase in the brush-border membranes of proximal tubules and intestines. Meprin isoforms are now found to be widely distributed in various organs (kidney, intestines, leukocytes, skin, bladder, and a variety of cancer cells) and are capable of hydrolyzing and processing a large number of substrates, including extracellular matrix proteins, cytokines, adherens junction proteins, hormones, bioactive peptides, and cell surface proteins. The ability of meprin A to cleave various substrates sheds new light on the functional properties of this enzyme, including matrix remodeling, inflammation, and cell-cell and cell-matrix processes. Following ischemia-reperfusion (IR)- and cisplatin-induced acute kidney injury (AKI), meprin A is redistributed toward the basolateral plasma membrane, and the cleaved form of meprin A is excreted in the urine. These studies suggest that altered localization and shedding of meprin A in places other than the apical membranes may be deleterious in vivo in acute tubular injury. These studies also provide new insight into the importance of a sheddase involved in the release of membrane-associated meprin A under pathological conditions. Meprin A is injurious to the kidney during AKI, as meprin A-knockout mice and meprin inhibition provide protective roles and improve renal function. Meprin A, therefore, plays an important role in AKI and potentially is a unique target for therapeutic intervention during AKI.

Effect of deferiprone, an oral iron chelator, in diabetic and non-diabetic glomerular disease

Compelling experimental evidence exists for the role of oxidants and iron in glomerular disease. In preliminary studies, we confirmed increased urinary catalytic iron in patients with glomerulonephritis and diabetic nephropathy. We conducted two separate single-center, prospective, single-armed, open-labeled, proof-of-concept studies to evaluate the safety and efficacy of an oral iron chelator in patients with glomerulonephritis and diabetic nephropathy. Study 1 comprised 15 patients with biopsy-proven glomerulonephritis who had persistent proteinuria despite treatment with steroids and/or cyclophosphamides. Study 2 comprised 38 adult patients with diabetic nephropathy. Patients in Study 1 were treated with deferiprone (50 mg/kg/day) in three divided doses for 6 months and Study 2 patients were treated for 9 months. In Study 1, two patients had severe gastrointestinal intolerance and withdrew from the study after one dose and are not included in the results. There was a significant reduction (47 ± 9% mean) in 24-h urinary protein (4.01 ± 1.61 to 2.21 ± 1.62 [p = 0.009]), with no significant changes in serum creatinine. In Study 2, treatment with deferiprone resulted in a marked, persistent drop in the mean albumin/creatinine ratio (187 ± 47 at baseline to 25 ± 7 mg/g, [p = 0.01]) and stable renal function over a 9-month period. No clinically significant adverse events were observed in either study. Although these are small, open-labeled, and non-randomized studies, our results suggest that future randomized, double-blind trials examining the utility of deferiprone to treat glomerular diseases appear warranted.

Adult Patient with Novel H1N1 Infection Presented with Encephalitis, Rhabdomyolysis, Pneumonia and Polyneuropathy

Neurological complications of influenza are well known. Influenza A is commonly associated with neurological complications. Neurological complications especially encephalitis is described in the pediatric age group of patients with current pandemic novel H1N1 infection. We are describing a case of novel H1N1 infection presenting with multi-system involvement (encephalitis, bilateral pneumonia, severe rhabdomyolysis leading to renal failure and polyneuropathy) in adult patient.

Design of clinical trials in AKI: a report from an NIDDK workshop. Trials of patients with sepsis and in selected hospital settings

AKI remains an important clinical problem, with a high mortality rate, increasing incidence, and no Food and Drug Administration-approved therapeutics. Advances in addressing this clinical need require approaches for rapid diagnosis and stratification of injury, development of therapeutic agents based on precise understanding of key pathophysiological events, and implementation of well designed clinical trials. In the near future, AKI biomarkers may facilitate trial design. To address these issues, the National Institute of Diabetes and Digestive and Kidney Diseases sponsored a meeting, "Clinical Trials in Acute Kidney Injury: Current Opportunities and Barriers," in December of 2010 that brought together academic investigators, industry partners, and representatives from the National Institutes of Health and the Food and Drug Administration. Important issues in the design of clinical trials for interventions in AKI in patients with sepsis or AKI in the setting of critical illness after surgery or trauma were discussed. The sepsis working group discussed use of severity of illness scores and focus on patients with specific etiologies to enhance homogeneity of trial participants. The group also discussed endpoints congruent with those endpoints used in critical care studies. The second workgroup emphasized difficulties in obtaining consent before admission and collaboration among interdisciplinary healthcare groups. Despite the difficult trial design issues, these clinical situations represent a clinical opportunity because of the high event rates, severity of AKI, and poor outcomes. The groups considered trial design issues and discussed advantages and disadvantages of several short- and long-term primary endpoints in these patients.

Design of clinical trials in acute kidney injury: a report from an NIDDK workshop--prevention trials

AKI is an important clinical problem that has become increasingly more common. Mortality rates associated with AKI remain high despite advances in supportive care. Patients surviving AKI have increased long-term mortality and appear to be at increased risk of developing CKD and progressing to ESRD. No proven effective pharmacologic therapies are currently available for the prevention or treatment of AKI. Advances in addressing this unmet need will require the development of novel therapeutic agents based on precise understanding of key pathophysiological events and the implementation of well designed clinical trials. To address this need, the National Institute of Diabetes and Digestive and Kidney Diseases sponsored the "Clinical Trials in Acute Kidney Injury: Current Opportunities and Barriers" workshop in December 2010. The event brought together representatives from academia, industry, the National Institutes of Health, and the US Food and Drug Administration. We report the discussions of workgroups that developed outlines of clinical trials for the prevention of AKI in two patient populations: patients undergoing elective surgery who are at risk for or who develop AKI, and patients who are at risk for contrast-induced AKI. In both of these populations, primary prevention or secondary therapy can be delivered at an optimal time relative to kidney injury. The workgroups detailed primary and secondary endpoints for studies in these groups, and explored the use of adaptive clinical trial designs for trials of novel preventive strategies to improve outcomes of patients with AKI.

Design of clinical trials in acute kidney injury: report from an NIDDK workshop on trial methodology

Acute kidney injury (AKI) remains a complex clinical problem associated with significant short-term morbidity and mortality and lacking effective pharmacologic interventions. Patients with AKI experience longer-term risks for progressive chronic ESRD, which diminish patients' health-related quality of life and create a larger burden on the healthcare system. Although experimental models have yielded numerous promising agents, translation into clinical practice has been unsuccessful, possibly because of issues in clinical trial design, such as delayed drug administration, masking of therapeutic benefit by adverse events, and inadequate sample size. To address issues of clinical trial design, the National Institute of Diabetes and Digestive and Kidney Diseases sponsored a workshop titled "Clinical Trials in Acute Kidney Injury: Current Opportunities and Barriers" in December 2010. Workshop participants included representatives from academia, industry, and government agencies whose areas of expertise spanned basic science, clinical nephrology, critical care medicine, biostatistics, pharmacology, and drug development. This document summarizes the discussions of collaborative workgroups that addressed issues related to patient selection, study endpoints, the role of novel biomarkers, sample size and power calculations, and adverse events and pilot/feasibility studies in prevention and treatment of AKI. Companion articles outline the discussions of workgroups for model trials related to prevention or treatment of established AKI in different clinical settings, such as in patients with sepsis.

Association of catalytic iron with cardiovascular disease

The ability of iron to cycle reversibly between its ferrous and ferric oxidation states is essential for the biological functions of iron but may contribute to vascular injury through the generation of powerful oxidant species. We examined the association between chemical forms of iron that can participate in redox cycling, often referred to as "catalytic" or "labile" iron, and cardiovascular disease (CVD). In our cross-sectional study of 496 participants, 85 had CVD. Serum catalytic iron was measured using the bleomycin-detectable iron assay that detects biologically active iron. The odds of existing CVD for subjects in the upper third of catalytic iron were 10 times that of subjects with lower catalytic iron in unadjusted analyses. The association was decreased by 1/2 by age adjustment, but little additional attenuation occurred after adjusting for age, Framingham Risk Score, estimated glomerular filtration rate, hypertension status, high-density lipoprotein cholesterol, and systolic blood pressure, with the association remaining strong and significant (odds ratio 3.8, 95% confidence interval 1.4 to 10.1). In conclusion, we provide preliminary evidence for a strong detrimental association between high serum catalytic iron and CVD even after adjusting for several co-morbid conditions; however, broader prospective studies are needed to confirm these findings, which would support therapeutic trials to assess the beneficial effects of iron chelators on CVD.

Endonuclease G mediates endothelial cell death induced by carbamylated LDL

End-stage kidney disease is a terminal stage of chronic kidney disease, which is associated with a high incidence of cardiovascular disease. Cardiovascular disease frequently results from endothelial injury caused by carbamylated LDL (cLDL), the product of LDL modification by urea-derived cyanate. Our previous data suggested that cLDL induces mitogen-activated protein kinase-dependent mitotic DNA fragmentation and cell death. However, the mechanism of this pathway is unknown. The current study demonstrated that cLDL-induced endothelial mitotic cell death is independent of caspase-3. The expression of endonuclease G (EndoG), the nuclease implicated in caspase-independent DNA fragmentation, was significantly increased in response to cLDL exposure to the cells. The inhibition of EndoG by RNAi protected cLDL-induced DNA fragmentation, whereas the overexpression of EndoG induced more DNA fragmentation in endothelial cells. Ex vivo experiments with primary endothelial cells isolated from wild-type (WT) and EndoG knockout (KO) mice demonstrated that EndoG KO cells are partially protected against cLDL toxicity compared with WT cells. To determine cLDL toxicity in vivo, we administered cLDL or native LDL (nLDL) intravenously to the WT and EndoG KO mice and then measured floating endothelial cells in blood using flow cytometry. The results showed an increased number of floating endothelial cells after cLDL versus nLDL injection in WT mice but not in EndoG KO mice. Finally, the inhibitors of MEK-ERK1/2 and JNK-c-jun pathways decreased cLDL-induced EndoG overexpression and DNA fragmentation. In summary, our data suggest that cLDL-induced endothelial toxicity is caspase independent and results from EndoG-dependent DNA fragmentation.

Progress toward novel treatments for chronic kidney disease

Chronic kidney failure remains a major health problem worldwide. Although current treatment is focused on the renin-angiotensin system, it is essential that new treatments targeted toward novel pathophysiological mechanisms are developed if we are to make significant progress in this area. In this review, we have outlined several promising new areas while emphasizing that large, randomized, well-controlled clinical trials are essential to reach a meaningful conclusion about the efficacy and safety of novel treatment.

Cytochrome P450 2B1 mediates complement-dependent sublytic injury in a model of membranous nephropathy

Membranous nephropathy is a disease that affects the filtering units of the kidney, the glomeruli, and results in proteinuria accompanied by loss of kidney function. Passive Heymann nephritis is an experimental model that mimics membranous nephropathy in humans, wherein the glomerular epithelial cell (GEC) injury induced by complement C5b-9 leads to proteinuria. We examined the role of cytochrome P450 2B1 (CYP2B1) in this complement-mediated sublytic injury. Overexpression of CYP2B1 in GECs significantly increased the formation of reactive oxygen species, cytotoxicity, and collapse of the actin cytoskeleton following treatment with anti-tubular brush-border antiserum (anti-Fx1A). In contrast, silencing of CYP2B1 markedly attenuated anti-Fx1A-induced reactive oxygen species generation and cytotoxicity with preservation of the actin cytoskeleton. Gelsolin, which maintains an organized actin cytoskeleton, was significantly decreased by complement C5b-9-mediated injury but was preserved in CYP2B1-silenced cells. In rats injected with anti-Fx1A, the cytochrome P450 inhibitor cimetidine blocked an increase in catalytic iron and ROS generation, reduced the formation of malondialdehyde adducts, maintained a normal distribution of nephrin in the glomeruli, and provided significant protection at the onset of proteinuria. Thus, GEC CYP2B1 contributes to complement C5b-9-mediated injury and plays an important role in the pathogenesis of passive Heymann nephritis.

Chronic uremia stimulates LDL carbamylation and atherosclerosis

Carbamylated LDL (cLDL) is a potential atherogenic factor in chronic kidney disease (CKD). However, whether elevated plasma cLDL associates with atherosclerosis in vivo is unknown. Here, we induced CKD surgically in apolipoprotein E-deficient (ApoE(-/-)) mice fed a high-fat diet to promote the development of atherosclerosis. These mice had two- to threefold higher plasma levels of both oxidized LDL (oxLDL) and cLDL compared with control mice. Oral administration of urea increased cLDL approximately eightfold in ApoE(-/-) mice subjected to unilateral nephrectomy and a high-fat diet, but oxLDL did not rise. Regardless of the model, the uremic mice with high plasma cLDL had more severe atherosclerosis as measured by intravital ultrasound echography and en face aortic staining of lipid deposits. Furthermore, cLDL accumulated in the aortic wall and colocalized with ICAM-1 and macrophage infiltration. In summary, these data demonstrate that elevated plasma cLDL may represent an independent risk factor for uremia-induced atherosclerosis.

Carbamylated LDL

Nonenzymatic modification of protein by cyanate, that is, carbamylation, has received new attention due to its apparent relevance in atherosclerosis. For example, carbamylation of low-density lipoprotein (LDL) is an important mechanism that potentially impacts high-risk atherosclerotic individuals with increased urea (renal insufficiency) or thiocyanate (tobacco smoking). Carbamylated LDL (cLDL) is increased in patients with end-stage kidney disease, especially those with atherosclerosis. In addition, cLDL exhibits distinct cytotoxic effects when tested in vitro on endothelial cells, induces the expression of adhesion molecules, and aggravates the monocyte adhesion to endothelial cells. It also facilitates the proliferation of vascular smooth-muscle cell (VSMC). Studies of potential pharmacological interruption of these processes in vivo may lead to discoveries of novel therapies for atherosclerosis.

Rhabdomyolysis with acute renal failure triggered by the seasonal flu vaccination in a patient taking simvastatin

A man in his 70s presented with bilateral, painful legs and feeling generally unwell following the seasonal flu vaccination. The patient had a background of B cell lymphoma in partial remission. His current medications included simvastatin. Initial investigations revealed rhabdomyolysis and acute renal failure. He was admitted to critical care for renal replacement treatment. Other causes of rhabdomyolysis were excluded and expert opinion agreed that the most likely cause was the influenza vaccination with the concurrent use of simvastatin. The patient's renal function gradually normalised and after several months the patient has regained full power in his legs.

Safety issues of iron chelation therapy in patients with normal range iron stores including thalassaemia, neurodegenerative, renal and infectious diseases

An increased number of thalassaemia patients treated with effective chelation therapy protocols are achieving body iron levels similar to those of normal individuals. Iron chelation therapy has also been recently used in a number of other categories of patients with no excess body iron load such as neurodegenerative, renal and infectious diseases. Chelation therapy in the absence of iron overload in the latter conditions raises many safety issues including chelator overdose toxicity and toxicity related to iron and other essential metal deficiencies. Preliminary preclinical and clinical toxicity evidence suggest that deferoxamine and deferasirox can only be safely used for these non-iron loaded conditions for short-term treatments of a few weeks, whereas deferiprone can be used for longer term treatments of many months. The selection of the chelating drug and appropriate dose protocols for targeting specific organs and conditions is critical for the safety of patients with normal iron stores. Chelation therapy is likely to play a major role as adjuvant, alternative or main therapy in many non-iron loading conditions in the forthcoming years.