Rate, Factors, and Outcome of Delayed Graft Function After Kidney Transplantation of Deceased Donors.

BACKGROUND: Delayed graft function (DGF) is a frequent complication after kidney transplantation affecting long-term outcome. PATIENTS AND METHODS: A total of 525 consecutive recipients (age 54.2 ± 13.4 years, 33% female) of kidneys from deceased donors transplanted between 2005 and 2012 were retrospectively examined. DGF was defined as the need of dialysis within the first week after transplantation. RESULTS: DGF developed in 21.1% (n = 111). Factors associated with DGF (P ≤ .035, respectively) were recipient body mass index, C-reactive protein of the recipient, residual diuresis, cold ischemia time, donor age, and diuresis in the first hour after transplantation. Median duration of DGF was 16 (2-66) days. Patients after DGF had a significantly lower GFR compared with recipients without DGF either after 3 (32.9 ± 16.5 vs 46.3 ± 18.4 mL/min/1.73 m2) or after 12 months (38.9 ± 19.3 vs 48.6 ± 20.4 mL/min/1.73 m2, P < .001, resp.). During DGF, 12.4% developed BANFF II and 18.0% BANFF I rejection, 20.2% had signs of transplant glomerulitis (first biopsy), and 16.2% (n = 18) remained on dialysis. CONCLUSION: DGF affects 1 out of 5 kidney transplants from deceased donors. Minimizing modifiable risk factors, in particular immunologic risk, may ameliorate the incidence and outcome of DGF. The outcome of DGF depends mainly on the diagnosis of any rejection and worsens upon detection of transplant glomerulitis and pronounced interstitial fibrosis and tubular atrophy (IFTA).

Vitamin D3 Partly Antagonizes Advanced-Glycation Endproducts-Induced NFκB Activation in Mouse Podocytes.

BACKGROUND/AIMS: We have previously shown that advanced glycation-endproducts (AGEs) induced NFκB activation in differentiated mouse podocytes. This NFκB activation may contribute to the progression of renal disease and mediation of fibrosis by various mechanisms. This study was undertaken to test whether this detrimental response may be reversed by vitamin D3 or its analogue paricalcitol. METHODS: Differentiated mouse podocytes were challenged with glycated bovine serum albumin (AGE-BSA), or non-glycated control BSA (in the presence or absence of various concentrations of vitamin D3 (decostriol, 1α,25-dihydroxyvitamin D3)) or its active analog paricalcitol. Quantitative mRNA expressions were measured by real-time PCR, whereas protein expressions were determined by Western blotting followed by densitometry. Cytoplasmic and nuclear protein expression of the NFκB subunit p65 (Rel A) were determined by Western blotting. Furthermore, the ratio of phosphorylated to non-phosphorylated IκB-α was measured using specific antibodies. Electrophoretic mobility shift assays and a capture ELISA assay were used to assess NFκB transactivation in vitro. In addition, NFκB transactivation was also monitored in HEK-NFκBIA reporter cells using live cell luminometry. RESULTS: Podocytes expressed the receptor for vitamin D. The vitamins did not suppress receptor for AGEs (RAGE) expression; instead, they rather upregulated RAGE. Although vitamin D3 and paricalcitol partly and differentially modified some of the studied parameters, both hormones inhibited AGE-BSA-induced NFκB transactivation, presumably by various mechanisms including the upregulation of IκB-α protein, keeping NFκB sequestered in an inactive state in the cytoplasm. CONCLUSION: Vitamin D3 or its analog paricalcitol partly prevented AGE-mediated NFκB activation, an important feature of diabetic nephropathy (DN). Whether this in vitro finding is of clinical relevance to prevent/treat DN requires further studies.

Adipokines promote chronic kidney disease.

The rapid growth in obesity worldwide contributes to an increase in metabolic syndrome and obesity-related kidney disease with an enhanced increased risk for chronic kidney disease, finally progressing to end-stage renal disease. Adipose tissue is a highly active endocrine organ secreting numerous factors that contribute to renal and cardiovascular complications. In renal damage, various adipokines are involved through mediating endothelial dysfunction, inducing oxidative stress and inflammation as well as stimulating renal sympathetic nervous activity, and it reduces cancellous bone but conversely increases cortical bone. Adipokines may also be involved in the development of renal anaemia. A balance exists between more protective adipokines (adiponectin) and factors mediating pathophysiological effects (angiotensin II, TNFα). Obesity may cause a disruption of this delicate balance, thereby inducing renal disease. Consequently, weight reduction and lifestyle changes affecting all components of the metabolic syndrome are essential to disrupt this vicious cycle.

Novel approach for bacteremia detection in patients with end-stage renal failure undergoing hemodialysis.

Severe systemic infections are one of the leading causes of death in patients with end-stage renal disease and are often associated with hospitalization. Since bacteria can be identified in used hemofilters in an ICU setting, it was investigated whether this method might be useful in patients undergoing regular intermittent hemodialysis. By analyzing used hemodialyzers in (n = 13) patients, we identified systemic bacteremia in two patients (15.4%) while corresponding blood cultures were negative. In two further patients, positive microbiological findings from hemodialyzers appeared to be of unclear clinical relevance. Cultures from hemodialyzers might be an add-on approach for the identification of bacteria in the blood stream of patients undergoing regular intermittent hemodialysis.

Erythropoietin ameliorates podocyte injury in advanced diabetic nephropathy in the db/db mouse.

Podocyte damage and accumulation of advanced glycation end products (AGEs) are characteristics of diabetic nephropathy (DN). The pathophysiology of AGE-challenged podocytes, such as hypertrophy, apoptosis, and reduced cell migration, is closely related to the induction of the cell cycle inhibitor p27(Kip1) and to the inhibition of neuropilin 1 (NRP1). We have previously demonstrated that treatment with erythropoietin is associated with protective effects for podocytes in vitro. db/db mice with overt DN aged 15-16 wk were treated with either placebo, epoetin-ß, or continuous erythropoietin receptor activator (CERA) for 2 wk. db/db mice compared with nondiabetic db/m control mice revealed the expected increases in body weight, blood glucose, albumin-to-creatinine ratio, and AGE accumulation. Whereas there were no differences in body weight, hyperglycemia and AGEs were observed among diabetic mice that received epoetin-ß compared with CERA and placebo treatment, indicating that epoetin-ß/CERA treatment does not interfere with the development of diabetes in this model. However, the albumin-to-creatinine ratio was significantly lower in db/db mice treated with epoetin-ß or CERA. Furthermore, kidney weights in db/db mice were increased compared with db/m control mice, indicating renal hypertrophy, whereas the increase in renal weight in epoetin-ß- or CERA-treated db/db mice was significantly lower than in placebo-treated control mice. Induction of p27(Kip1) and suppression of NRP1 were significantly reduced in the epoetin-ß treatment group versus the CERA treatment group. Furthermore, erythropoietin treatment diminished the diabetes-induced podocyte loss. Together, independently from hematopoetic effects, epoetin-ß or CERA treatment was associated with protective changes in DN, especially that NRP1 and p27(Kip1) expressions as well as numbers of podocytes returned to normal levels. Our data show, for the first time, that medication of overt DN with erythropoietin for a short time can ameliorate albuminuria and podocyte loss.

Rituximab for the second- and third-line therapy of idiopathic membranous nephropathy: a prospective single center study using a new treatment strategy.

BACKGROUND: Idiopathic membranous nephropathy (MN) is a major cause of nephrotic syndrome. Conventional treatment strategies induce remission but the relapse rates are high. Different doses of rituximab (RTX) appeared effective in reducing proteinuria in MN but long-term follow-up data are rare. METHODS: Since 2006, a total of 14 patients (median age 51 (26 - 69) years, 4 women, 10 men) with biopsy-proven MN (1 - 4 relapses, MN since 4 (1 - 13) years) were treated with RTX (4 doses of RTX 375 mg/m2 on Days 0, 30, 60, 90). All patients had prior immunosuppressive therapy with Cyclosporin A, 7 with alkylating agents. In 11 patients, an additional renal biopsy was performed 2 (1 - 10) months before RTX. RESULTS: Three months after the last RTX infusion, proteinuria decreased from a baseline of 5.5 (2.9 - 11.9) g/24 h to 1.8 (0.03 - 8.7) g/24 h (p = 0.012). Creatinine clearance remained stable (53 (29 - 160) ml/min at 3 months vs. 44 (29 - 159) at baseline). Until now, patients could be followed for a median of 3 (1 - 6) years. After 1 year, 21.4% (n = 3) had a complete response, 50.0% (n = 7) partial response. Two relapses occurred after 1 and 3.5 years. The presence of glomerulosclerosis before RTX was associated with a poorer outcome. CONCLUSIONS: The 4 × 4-weekly infusion of RTX is a reasonable option for the second- and third line therapy of MN providing a better safety profile compared to other immunosuppressive treatments of MN.

The role of the renin-angiotensin-aldosterone system in obesity-related renal diseases.

Obesity is an independent risk factor for the development and progression of chronic kidney disease and one of the emerging reasons for end-stage renal disease owing to its dramatic increase worldwide. Among the potential underlying pathophysiologic mechanisms, activation of the renin-angiotensin-aldosterone-system (RAAS) plays a central role. Increased angiotensin II (AngII) levels also are central in hypertension, dyslipidemia, and insulin resistance, which, taken together with obesity, represent the metabolic syndrome. Increased AngII levels contribute to hyperfiltration, glomerulomegaly, and subsequent focal glomerulosclerosis by altering renal hemodynamics via afferent arteriolar dilation, together with efferent renal arteriolar vasoconstriction as well as by its endocrine and paracrine properties linking the intrarenal and the systemic RAAS, adipose tissue dysfunction, as well as insulin resistance and hypertension. The imbalance between increased AngII levels and the angiotensin converting enzyme 2/Ang (1-7)/Mas receptor axis additionally contributes to renal injury in obesity and its concomitant metabolic disturbances. As shown in several large trials and experimental studies, treatment of obesity by weight loss is associated with an improvement of kidney disease because it also is beneficial in dyslipidemia, hypertension, and diabetes. The most promising data have been seen by RAAS blockade, pointing to the central position of RAAS within obesity, kidney disease, and the metabolic syndrome.

Podocytes of AT2 receptor knockout mice are protected from angiotensin II-mediated RAGE induction.

BACKGROUND/AIMS: The interaction of 'advanced glycation end products' (AGEs) and their receptor 'RAGE' plays an important role in diabetic nephropathy. We have previously found that in cultured differentiated podocytes, angiotensin II (ANG II) induces RAGE expression via an AT2 receptor-mediated pathway. METHODS: To further confirm our results in an in vivo study, AT2 receptor knockout mice (AT2(-/-)) and wild-type mice were infused with ANG II by osmotic minipumps for 14 days. RESULTS: As shown by immunohistochemistry, ANG II treatment of wild-type animals (C57BL6) allowed a significantly increased RAGE expression in renal podocytes in comparison to sham-operated C57BL6 mice. In contrast, RAGE expression in podocytes of ANG II-treated knockout mice (AT2(-/-)) was only moderately higher than in control animals, but significantly lower than in ANG II-treated wild-type mice. For the AGE species Nε-carboxymethyllysine, a similar immunohistochemical staining pattern was found. There was no significant change in glomerular AT1a receptor expression. However, no difference in RAGE mRNA expression could be found between ANG II-infused wild-type and AT2(-/-) animals by real-time PCR using whole kidney mRNA, presumably due to the low abundance of podocyte mRNA in these preparations. No effects were seen on glomerular apoptosis. CONCLUSION: These data support the fact that ANG II-mediated RAGE induction in podocytes occurs via AT2 receptors. The present findings may suggest that not all ANG II-mediated changes in diabetic nephropathy can be treated with AT1 receptor blockers.

Angiotensin II as a morphogenic cytokine stimulating renal fibrogenesis.

Inhibitors of the renin-angiotensin-aldosterone system attenuate glomerulosclerosis and interstitial fibrosis. Although the mechanisms underlying their antifibrotic effects are complex, angiotensin II (Ang II) emerges as a major profibrogenic cytokine. Ang II modulates renal cell growth, extracellular matrix synthesis, and degradation by multiple fibrotic pathways. One of the main targets of Ang II in renal fibrosis is TGFß. Many, but not all, of the stimulatory effects of Ang II on fibrogenesis depend on the induction of TGFß and its downstream mediators of matrix accumulation, inflammation, and apoptosis. However because of the difficulty in targeting TGFß, connective tissue growth factor ß (CTGF), a downstream mediator of TGFß, has become a more promising antifibrotic target. Ang II can directly induce expression of renal CTGF and mediate epithelial-mesenchymal transition. Other profibrotic factors stimulated by Ang II include endothelin-1, plasminogen activator inhibitor-1, matrix metalloproteinase (MMP)-2, and a tissue inhibitor of metalloproteinase-2. Finally, connections among Ang II, hypoxia, and the induction of hypoxia-inducible factor-1α contribute to fibrogenesis. A better understanding of the multiple morphogenic effects of Ang II may be necessary to develop better strategies to halt the progression of renal disease.

Advanced glycation end-products and the kidney.

BACKGROUND: Advanced glycation end-products (AGEs) are increased in situations with hyperglycemia and oxidative stress such as diabetes mellitus. They are products of nonenzymatic glycation and oxidation of proteins and lipids. The kidney plays an important role in clearance and metabolism of AGEs. METHODS: Medline and other relevant databases were searched. In addition, key review articles were scanned for relevant original publication. Finally, original data from our research group were also included. RESULTS: Kidney podocytes and endothelial cells express specific receptors for AGEs. Their activation leads to multiple pathophysiological effects including hypertrophy with cell cycle arrest and apoptosis, altered migration, and generation of proinflammatory cytokines. AGEs have been primarily implicated in the pathophysiology of diabetic nephropathy and diabetic microvascular complications. AGEs are also involved in other primary renal diseases as well as in the development and progression of atherosclerosis. However, serum or plasma concentrations of AGEs do not correlate well with cardiovascular events in patients with chronic kidney disease (CKD). This is likely due to the fact that serum concentrations failed to correlate with AGEs deposited in target tissues. Several inhibitors of the AGE-RAGE axis are currently tested for various indications. CONCLUSION: AGEs and their receptors are involved in the pathogenesis of vascular and kidney disease. The role of circulating AGEs as biomarkers for cardiovascular risk estimation is questionable. Whether putative inhibitors of AGEs will get the maturity for its therapeutic use in the future remains open.

Advanced glycation end products induce cell cycle arrest and proinflammatory changes in osteoarthritic fibroblast-like synovial cells.

INTRODUCTION: Advanced glycation end products (AGEs) have been introduced to be involved in the pathogenesis of osteoarthritis (OA). The influence of AGEs on osteoarthritic fibroblast-like synovial cells (FLS) has been incompletely understood as yet. The present study investigates a potential influence of AGE-modified bovine serum albumin (AGE-BSA) on cell growth, and on the expression of proinflammatory and osteoclastogenic markers in cultured FLS. METHODS: FLS were established from OA joints and stimulated with AGE-BSA. The mRNA expression of p27Kip1, RAGE (receptor for AGEs), nuclear factor kappa B subunit p65 (NFkappaB p65), tumor necrosis factor alpha (TNF-alpha, interleukin-6 (IL-6), receptor activator of NFkappaB ligand (RANKL) and osteoprotegerin was measured by real-time PCR. The respective protein expression was evaluated by western blot analysis or ELISA. NFkappaB activation was investigated by luciferase assay and electrophoretic mobility shift assay (EMSA). Cell cycle analysis, cell proliferation and markers of necrosis and early apoptosis were assessed. The specificity of the response was tested in the presence of an anti-RAGE antibody. RESULTS: AGE-BSA was actively taken up into the cells as determined by immunohistochemistry and western blots. AGE-induced p27Kip1 mRNA and protein expression was associated with cell cycle arrest and an increase in necrotic, but not apoptotic cells. NFkappaB activation was confirmed by EMSAs including supershift experiments. Anti-RAGE antibodies attenuated all AGE-BSA induced responses. The increased expression of RAGE, IL-6 and TNF-alpha together with NFkappaB activation indicates AGE-mediated inflammation. The decreased expression of RANKL and osteoprotegerin may reflect a diminished osteoclastogenic potential. CONCLUSIONS: The present study demonstrates that AGEs modulate growth and expression of genes involved in the pathophysiological process of OA. This may lead to functional and structural impairment of the joints.

Angiotensin II upregulates RAGE expression on podocytes: role of AT2 receptors.

BACKGROUND: Advanced glycation end products (AGEs) play an important role in diabetic nephropathy. The receptor for AGEs, called RAGE, is present on podocytes. We investigated whether angiotensin II (ANG II) modulates RAGE expression on cultured differentiated podocytes. RESULTS: Cultured podocytes expressed AT1 and AT2 receptors. Surprisingly, ANG II induced RAGE mRNA and protein expression through AT2 receptors. ANG II had no influence on proliferation or protein content of podocytes. The increase in RAGE expression depended on stimulated transcriptional activity. Using various mutant reporter constructs of the RAGE promoter region, it was shown that a NF-kappaB binding site at -1519 was essential for ANG II-induced transcriptional activity. Preincubation with ANG II increased the expression of tumor necrosis factor-alpha mRNA and protein expression induced by AGE, indicating that the ANG II-mediated upregulation of RAGE has functional consequences. AGE-BSA was incorporated into cells as measured by Western blots for N epsilon-carboxymethyllysine, but ANG II did not influence this process. ANG II in the absence or presence of AGE-BSA did not induce apoptosis of podocytes. CONCLUSION: Our study revealed aninteraction between the renin-angiotensin system and the AGE/RAGE axis in podocytes. Since intraglomerular ANG II levels are increased in diabetic nephropathy, this interaction may have pathophysiological consequences for podocyte injury and inflammation associated with the development of diabetic nephropathy.

Advanced glycation end-products suppress neuropilin-1 expression in podocytes.

Advanced glycation end products (AGEs) have been linked to the pathogenesis of diabetic nephropathy. Here we tested the effect of AGE-modified bovine serum albumin (AGE-BSA) on differentiated mouse podocytes in culture. Differential display and real-time PCR analyses showed that in addition to neuropilin-1, the entire signaling receptor complex of neuropilin-2, semaphorin-3A, and plexin-A1, was significantly reduced by AGE-BSA as was neuropilin-1 protein. The effect was specific for podocytes compared to isolated mesangial and tubular epithelial cells. Further, AGE-BSA was not toxic to podocytes. Neuropilin-1 expression was decreased in glomeruli of diabetic db/db mice compared to their non-diabetic littermates. Transcripts of both neuropilins were found to be decreased in renal biopsies from patients with diabetic nephropathy compared to transplant donors. Podocyte migration was inhibited by AGE-BSA with similar results found in the absence of AGE-BSA when neuropilin-1 expression was down-regulated by siRNA. In contrast, podocyte migration was stimulated by overexpression of neuropilin-1 even in the presence of AGE-BSA. Our study shows that AGE-BSA inhibited podocyte migration by down-regulating neuropilin-1. The decreased migration could lead to adherence of uncovered areas of the glomerular basement membrane to Bowman's capsule contributing to focal glomerulosclerosis.

Advanced glycation end-products induce cell cycle arrest and hypertrophy in podocytes.

BACKGROUND: Podocyte injury with loss of cells into the urine seems to be an early factor in diabetic nephropathy. Advanced glycation end-products (AGEs) are important mediators of structural and functional renal abnormalities in diabetic nephropathy. We and others have previously described that mice with a deletion in the gene for the cell cycle regulatory p27(Kip1) are protected from some features of diabetic nephropathy. METHODS: The present study investigates a potential influence of AGE-modified bovine serum albumin (AGE-BSA) on podocyte growth and p27(Kip1) expression in culture. The p27(Kip1) expression was measured by western blots and real-time PCR. Cell cycle analysis, cell hypertrophy, proliferation and various markers of apoptosis and necrosis were assessed. The p27(Kip) expression was inhibited by siRNA or was overexpressed in podocytes with an inducible expression system. RESULTS: AGE-BSA was actively taken up into the cell as determined by immunohistochemistry, western blots and HPLC. Incubation with AGE-BSA induced in differentiated podocytes, but not in tubular cells, p27(Kip1) mRNA and protein expression. This induction was associated with cell cycle arrest of podocytes, cell hypertrophy (as measured by increases in cell size and protein/cell number ratios) and an increase in necrotic, but not apoptotic cells. Inhibition of p27(Kip1) expression with siRNA halted the AGE-BSA-mediated cell cycle arrest and hypertrophy, but did not interfere with AGE uptake into podocytes. In contrast, overexpression of p27(Kip1) using an inducible expression system stimulated hypertrophy and cell cycle arrest of podocytes. CONCLUSION: Our data demonstrate that AGE-BSA-induced hypertrophy and damage of cultured podocytes occurs by a mechanism involving p27(Kip1). This effect can contribute to the loss of podocytes in diabetic nephropathy.

The role of chemokines and chemokine receptors in diabetic nephropathy.

Diabetic nephropathy is increasingly considered as an inflammatory disease characterized by leukocyte infiltration at every stage of renal involvement. Chemokines are important participators in the recruitment of specific subpopulations of inflammatory cells into renal compartments. MCP-1/CCL2 has been identified as having a key role in monocyte/macrophage recruitment in animal models of diabetic nephropathy, as well as in renal biopsies from patients with type 1 and 2 diabetes. Various factors of the diabetic milieu can induce renal expression of MCP-1/CCL2 and cell adhesion molecules, and thereby mediate the macrophage responses that ultimately cause renal injury. Possibly fractalkine/CX3CL1 functions as an arrest chemokine in monocyte/macrophage adhesion before migration into the kidney. T lymphocyte recruitment is influenced by up-regulation of RANTES/CCL5 throughout glomerular as well as tubulointerstitial structures as well as IP-10/CXCL10 mainly in the tubulointerstitium. Improved knowledge of gene polymorphisms of chemokines and their receptors could be useful to predict onset of diabetic nephropathy and define its progression. Blockade of the renin-angiotensin-aldosterone system is currently the only clinically used strategy to treat the inflammatory process in diabetic nephropathy. Newer strategies point to chemokine receptor antagonists and even to immunosuppressive therapy, but still remain in the experimental stage.

Renin-angiotensin-aldosterone system and progression of renal disease.

Inhibition of the renin-angiotensin-aldosterone system (RAAS) is one of the most powerful maneuvers to slow progression of renal disease. Angiotensin II (AngII) has emerged in the past decade as a multifunctional cytokine that exhibits many nonhemodynamic properties, such as acting as a growth factor and profibrogenic cytokine, and even having proinflammatory properties. Many of these deleterious functions are mediated by other factors, such as TGF-beta and chemoattractants that are induced in the kidney by AngII. Moreover, understanding of the RAAS has become much more complex in recent years with the identification of novel peptides (e.g., AngIV) that could bind to specific receptors, elucidating deleterious effects, and non-angiotensin-converting enzyme (ACE)-mediated generation of AngII. The ability of renal cells to produce AngII in a concentration that is much higher than what is found in the systemic circulation and the observation that aldosterone may be engaged directly in profibrogenic processes independent of hypertension have added to the complexity of the RAAS. Even renin has now been identified to have a "life on its own" and mediates profibrotic effects via binding to specific receptors. Finally, drugs that are used to block the RAAS, such as ACE inhibitors or certain AngII type 1 receptor antagonists, may have properties on cells independent of AngII (ACE inhibitor-mediated outside-inside signaling and peroxisome proliferator-activated receptor-gamma stimulatory effects of certain sartanes). Although blockade of the RAAS with ACE inhibitors, AngII type 1 receptor antagonists, or the combination of both should be part of every strategy to slow progression of renal disease, a better understanding of the novel aspects of the RAAS should contribute to the development of innovative strategies not only to completely halt progression but also to induce regression of human renal disease.