Temporal IgG Subtype Changes in Recurrent Idiopathic Membranous Nephropathy.

Determination of the IgG subtypes within the immune deposits in membranous nephropathy (MN) may be helpful in the differential diagnosis. IgG4 is the predominant subtype in idiopathic MN and recurrent MN, while IgG1, IgG2, and IgG3 subtypes are more common in secondary MN and de novo disease in the allograft. The temporal change of IgG subclasses in individual patients and its correlation with clinical variables have not been studied. We reviewed all posttransplantation protocol and indication biopsies (49) in 18 patients with recurrent MN who underwent transplantation at our center between 1998 and 2013 and performed IgG subtyping (IgG1-4). We tested serum for M-type phospholipase A2 receptor (PLA2 R) autoantibodies or performed PLA2 R antigen staining on the kidney biopsy. IgG4 was the (co)dominant IgG subtype in 10 of 14 biopsies at the diagnosis of recurrence regardless of PLA2 R association. In 8 of 12 transplantations with serial biopsies, the (co)dominant subtype did not change over time. There was a trend toward IgG1 and IgG3 (co)dominance in biopsies >1 year from recurrence and more IgG1 (co)dominant subtyping in the setting of more-advanced EM deposits. Treatment with rituximab did not affect the IgG subtype. In conclusion, the dominant IgG subtype did not change over time in recurrent MN.

The pharmacokinetics and pharmacodynamics of vancomycin in clinical practice: evidence and uncertainties.

Vancomycin has been used extensively since the late 1950s. Despite the introduction of several new valuable anti-Gram-positive antibiotics during recent years and the waning susceptibility of staphylococci to vancomycin, it remains the gold standard for the treatment of bacteraemia caused by methicillin-resistant staphylococci. Vancomycin has clear dose-response and dose-toxicity correlations. It is widely accepted that these correlations are best predicted by the AUC/MIC model, with target levels of >400 being the clinical cut-off. The experimental base of this model is less robust than frequently believed, and several important issues in vancomycin resistance, such as biofilm resistance and the inoculum effect, are not included. Based on this model, current dosing guidelines propose intermittent dosing of vancomycin with target trough levels of 15-20 mg/L. Dose adaptations according to renal function have been proposed but are not yet validated. Clinical data also support the use of continuous infusion with target plateau levels of 20-25 mg/L, with similar efficacy at the cost of lower nephrotoxicity. Despite decades of intense clinical use and numerous studies and publications, the optimal dosing strategy for vancomycin reconciling the high needs of the dose-response relationship with the serious drawbacks of the dose-toxicity relationship remains to be established.

Successful treatment of renal AA amyloidosis in familial Mediterranean fever with pegylated alpha-2a interferon.

Renal AA amyloidosis is a severe consequence of chronic inflammatory diseases such as familial Mediterranean fever (FMF). FMF is caused by mutations in the MEFV gene, resulting in defective control of granulocyte-mediated inflammation. Interferon-alpha is known to induce MEFV expression in monocytes and granulocytes in vitro. We present the first case of colchicine-resistant FMF in which a durable disease remission and regression of renal amyloidosis was induced by chronic treatment with pegylated interferon-alpha.

Autologous transplantation of bone marrow mononuclear cells for limb ischemia in a caucasian population with atherosclerosis obliterans.

BACKGROUND: Autologous transplantation of bone marrow mononuclear cells (ATBMMNC) has been used successfully in critical limb ischemia. All reported patients were of Asian descent, however, and several studies included only young patients with thromboangiitis obliterans. Whether the beneficial results can be extrapolated to older Caucasian patients with atherosclerosis obliterans and a heavy burden of cardiovascular risk factors remains unclear. METHODS: We enrolled 16 patients (age 78 +/- 2 year) with critical limb ischemia and a high prevalence of hypertension, smoking, diabetes, hypercholesterolemia and uremia. Mononuclear cells were isolated from the bone marrow and injected in the gastrocnemius muscle of the affected limb. RESULTS: Four patients died because of progressive gangrene (two) or unrelated causes (two). Three patients required an amputation and one patient a femorocrural bypass within 12 weeks. The remaining eight patients had a modest improvement of resting pain and/or trophic lesions. Transcutaneous oxygen pressure (ratio lesion/reference) improved from 0.51 +/- 0.11 before to 0.86 +/- 0.03 (P < 0.001) after 12 weeks, whereas ankle-brachial index did not change significantly (0.42 +/- 0.15 vs. 0.59 +/- 0.1; P = 0.23). The number of visible collateral vessels on digital subtraction angiography changed with 0.89 +/- 0.86 on a scale of 1-4 (P = 0.33). Capillary surface area in a biopsy of gastrocnemius, evaluated by immunostaining for endothelial nitric oxide synthase, increased from 0.61 +/- 0.07% to 2.38 +/- 0.73% (P < 0.05). CONCLUSIONS: Although ATBMMNC was associated with objective signs of neovascularization, symptomatic improvement was only modest and restricted to the least affected patients. The discrepancy with previous findings may be related to the high prevalence of cardiovascular risk factors which causes endothelial progenitor cell dysfunction.

Novel insights in the treatment of diabetic nephropathy.

Diabetes is currently one of the leading causes of end-stage renal failure requiring renal replacement therapy in the Western World. About 15% to 20% of type 1 diabetic patients and 30% to 40% of type 2 diabetic patients will eventually develop end-stage renal failure. To prevent the development or progression of diabetic kidney disease, good glycaemic control remains the cornerstone in the management of diabetic patients. Beyond glycaemic control, other metabolic factors have been shown to be involved in the development of diabetic kidney disease, i.e. advanced glycation endproducts (AGEs) and the aldose reductase pathway. Furthermore, an adequate control of high blood pressure and treatment of microalbuminuria are major therapeutic targes. To achieve adequate blood pressure control, a combination therapy with different classes of antihypertensive agents is often necessary, especially including angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. Other vasoactive factors involved in diabetic nephropathy such as endothelin and nitric oxide will be covered briefly. Besides hyperglycaemia and high blood pressure, other risk factors have been identified in the development or progression of diabetic kidney disease: smoking, hyperlipidaemia, obesity and high protein intake. Their impact on renal function will be highlighted. Finally, recent research has also identified intracellular pathways such as the diacylglycerol-protein kinase C pathway and several growth factors, such as growth hormone, insulin-like growth factor, transforming growth factor-beta, vascular endothelial growth factor, and platelet derived growth factor as players in diabetic kidney disease.

Inhibition of vascular endothelial growth factor (VEGF) does not affect early renal changes in a rat model of lean type 2 diabetes.

Type 2 diabetes is the most frequent cause of end-stage renal failure in many Western countries. Approximately 10-15 % of all type 2 diabetics are lean. Various growth factors and cytokines have been implicated in the pathophysiology of diabetic kidney disease, including vascular endothelial growth factor (VEGF). To elucidate a role for VEGF in the renal changes associated with type 2 diabetes, we examined the effect of a VEGF-antibody (ab) on early renal changes in the Goto-Kakizaki (GK) rat, a lean type 2 diabetes model. GK-rats were treated for 6 weeks with the VEGF-ab or with an isotype-matched irrelevant IgG. Wistar rats were used as non-diabetic controls. Placebo-treated GK-rats showed a pronounced increase in glomerular volume and urinary albumin excretion (UAE) and no change in the renal expression of endothelial nitric oxide synthase (eNOS) compared to placebo-treated non-diabetic controls. Kidney weight and creatinine clearance were no different between the groups. VEGF-ab treatment had no effect on glomerular volume, UAE, eNOS expression, body weight, blood glucose levels or food intake, but lowered serum insulin levels in non-diabetic and diabetic animals. We conclude that VEGF inhibition has minimal effects on early renal changes in GK-rats.

A case of secondary frosted branch angiitis in Behçet's disease.

We report a case of Behcet's disease in a pregnant woman associated with secondary Frosted Branch Angiitis (FBA). FBA is a rare entity characterized by a florid translucent retinal perivascular sheathing of both arterioles and venules, with variable uveitis, retinal oedema and visual loss. To our knowledge, this is the first published report of FBA secondary to Behcet's disease in pregnancy.

The role of hyperhomocysteinemia in nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF)-mediated vasodilatation.

Hyperhomocysteinemia (HHcy) is associated with impaired endothelial-dependent vasodilatation and increased risk of atherosclerosis and thrombosis. Here, we summarize some of our previous work on the effect of HHcy on pathways involved in endothelium-dependent vasodilatation, and present new data concerning the endothelium-derived hyperpolarizing factor (EDHF)-mediated vasodilatation. We showed that the 894 G>T single-nucleotide polymorphism in the human endothelial nitric oxide synthase gene (eNOS) increased the risk of recurrent venous thrombosis in individuals with elevated homocysteine levels, indicating that the pathophysiological mechanism in HHcy involves impaired NO-mediated vasodilatation. In addition, the EDHF-mediated vasodilatation of the renal artery was disturbed in diet-induced hyperhomocysteinemic rats. Interestingly, we demonstrated that pretreatment of rats with periodate-oxidized adenosine (Adox), which is an inhibitor of S-adenosylhomocysteine hydrolase, prevented the methionine-induced rise in plasma total Hcy (tHcy) levels but not the inhibition of the EDHF pathway. Furthermore, we demonstrated that S-adenosylhomocysteine (AdoHcy) and S-adenosylmethionine (AdoMet) levels were increased in the kidneys of diet-induced HHcy rats, resulting in a decreased AdoMet:AdoHcy ratio. In addition, we demonstrated that mRNA expression of Connexin 40, which is one of the structural subunits of gap-junctions, was down-regulated in endothelial cells of HHcy rats, and correlated with elevated AdoHcy levels in kidney of these rats. These finding suggest a key role for AdoHcy in relation to decreased Cx40 mRNA expression and impaired EDHF-mediated vasodilatation of HHcy rats.

Extensive acronecrosis as a manifestation of mixed cryoglobulinaemia: a case report.

Cryoglobulinaemia is a systemic disorder characterized by circulating antibodies that precipitate in the cold and resolve on rewarming. Three different types have been described, distinct in the class of immunoglobulins and their clonality. The clinical expression varies from purpura and arthralgia to progressive renal failure and even acronecrosis (1-3). Associated conditions are lymphoproliferative disorders, auto-immune diseases and chronic infections, but several cases occur in the absence of identifyable other disease states. The present communication reports on a case of mixed cryoglobulinaemia. Of particular interest are the rapidly progressive clinical evolution to acronecrosis of the four limbs, necessitating amputation, the presence of spurious leucocytosis and the absence of other systemic symptoms.

Early molecular events in the development of the diabetic cardiomyopathy.

UNLABELLED: Oxidative damage to DNA has been well documented in cardiac cells isolated from diabetic patients and rats with streptozotocin-induced diabetes mellitus (DM). This study evaluates possible molecular mechanisms for early events in the development of DM-induced cardiomyopathy. METHODS: To analyze the mechanism of overexpression of p21(WAF1/CIP1) and inhibition of cyclin D(1) expression in cardiomyocytes of diabetic rats we examined the methylation status of these genes by MS-PCR and assessed the possibility of epigenetic control of their expression. RESULTS: We found that the steady-state expression of both genes is influenced by their methylation status, as an epigenetic event, of their 5'-flanking regions upon development of diabetes. CONCLUSIONS: Oxidative damage contributes to the development of cardiomyopathy via p53-dependent activation of cardiac cell death. This pathway includes de novomethylation of the P53-inducible p21(WAF1/CIP1)-gene encoding a protein which binds to and inhibits a broad range of cyclin-cyclin-dependent kinase complexes.

Diabetes-induced microvascular dysfunction in the hydronephrotic kidney: role of nitric oxide.

BACKGROUND: Renal hemodynamics in early diabetes are characterized by preglomerular and postglomerular vasodilation and increased glomerular capillary pressure, leading to hyperfiltration. Despite intensive research, the etiology of the renal vasodilation in diabetes remains a matter of debate. The present study investigated the controversial role of nitric oxide (NO) in the renal vasodilation in streptozotocin-induced diabetic rats. METHODS: In the renal microcirculation, basal tone and response to NO synthase blockade were studied using the in vivo hydronephrotic kidney technique. L-arginine analog N-nitro-L-arginine methyl ester (L-NAME) was administered locally to avoid confounding by systemic blood pressure effects. The expression of endothelial NO synthase (eNOS) was investigated in total kidney by immunocytochemistry and in isolated renal vascular trees by Western blotting. Urinary excretion of nitrites/nitrates was measured. RESULTS: Diabetic rats demonstrated a significant basal vasodilation of all preglomerular and postglomerular vessels versus control rats. Vasoconstriction to L-NAME was significantly increased in diabetic vessels. After high-dose L-NAME, there was no difference in diameter between diabetic and control vessels, suggesting that the basal vasodilation is mediated by NO. Immunocytochemically, the expression of eNOS was mainly localized in the endothelium of preglomerular and postglomerular vessels and glomerular capillaries, and was increased in the diabetic kidneys. Immunoblots on isolated renal vascular trees revealed an up-regulation of eNOS protein expression in diabetic animals. The urinary excretion of nitrites/nitrates was elevated in diabetic rats. CONCLUSION: The present study suggests that an up-regulation of eNOS in the renal microvasculature, resulting in an increased basal generation of NO, is responsible for the intrarenal vasodilation characteristic of early diabetes.

Intravital microscopy: an integrated evaluation of peritoneal function and structure.

Peritoneal dialysis (PD) solutions may affect various aspects of peritoneal function and structure. The present communication describes the application of an intravital microscopy technique for the study of peritoneal pathophysiology. The technique allows the in vivo measurement of peritoneal blood flow rate, microvascular permeability to macromolecules, leukocyte-endothelial interactions, microvascular density and lymph vessel kinetics. The off-line coupling to a computer-assisted image analysis system permits the rapid quantitation and integrated evaluation of these different parameters. The model may be an attractive tool for the study of the pathophysiological consequences of acute or long-term dialysate exposure, as well as for the development and evaluation of novel PD solutions.

Non anticoagulant effects of heparin: implications for animal models of peritoneal dialysis.

Heparin is a glycosaminoglycan with well-known anticoagulant activity. That property is used in animal models of peritoneal dialysis to maintain catheter patency and to prevent the development of peritoneal adhesions. However, heparin has a host of biologic actions beyond its role as an anticoagulant. Heparin modulates the activity of various inflammatory cells, affects the synthesis of extracellular matrix, has antiproliferative effects on several cell types, and influences neoangiogenesis. By virtue of those actions, intraperitoneally administered heparin may interfere with peritoneal membrane homeostasis. The potential side effects of heparin use in animal models of peritoneal dialysis should be recognized to permit correct interpretation of experimental studies conducted in those models.

The impaired renal vasodilator response attributed to endothelium-derived hyperpolarizing factor in streptozotocin--induced diabetic rats is restored by 5-methyltetrahydrofolate.

AIMS/HYPOTHESIS: Endothelial dysfunction contributes to the development of diabetic vascular complications. A better understanding of the pathophysiology of endothelial dysfunction in diabetes could lead to new approaches to prevent microvascular disease. METHODS: Endothelium-dependent and endothelium-independent vasodilator responses were investigated in the renal microcirculation of streptozotocin-induced diabetic rats. We measured renal blood flow changes with an electromagnetic flow probe. In addition, the responses of the different segments of the renal microcirculation were evaluated with videomicroscopy using the hydronephrotic kidney technique. Because endothelial cells release different relaxing factors (nitric oxide, prostacyclin and an unidentified endothelium-derived hyperpolarizing factor), responses to acetylcholine were measured before and after treatment with the nitric oxide synthase inhibitor L-NG-nitroarginine methylester HCI (L-NAME) and the cyclooxygenase inhibitor indomethacin. We evaluated with the effect of 5-methyltetrahydrofolate, the active form of folate, on the responses. RESULTS: The L-NAME- and indomethacin-resistant vasodilation to intra-renal acetylcholine was significantly reduced in the diabetic compared with control rats, suggesting impaired endothelium-derived hyperpolarizing factor-mediated vasodilation. The responses to the nitric oxide donor (Z)-1-[-2-(aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-i um-1,2-diolate (DETA-NONOate) and to the K+-channel opener pinacidil were similar in diabetics and controls, indicating intact endothelium-independent vasodilator mechanisms. The contribution of endothelium-derived hyperpolarizing factor to vasodilation induced by acetylcholine was greatest in the smallest arterioles. In diabetic rats, the response to acetylcholine was increasingly impared as vessel size decreased. Defective vasodilation in diabetic kidneys was rapidly normalized by 5-methyltetrahydrofolate. CONCLUSION-INTERPRETATION: Endothelium-derived hyperpolarizing factor-mediated vasodilation is impaired in the renal microcirculation of diabetic rats, in particular in the smallest arteries. Treatment with folate restores the impaired endothelial function in diabetes.

Endothelial dysfunction in diabetes.

Endothelial dysfunction plays a key role in the pathogenesis of diabetic vascular disease. The endothelium controls the tone of the underlying vascular smooth muscle through the production of vasodilator mediators. The endothelium-derived relaxing factors (EDRF) comprise nitric oxide (NO), prostacyclin, and a still elusive endothelium-derived hyperpolarizing factor (EDHF). Impaired endothelium-dependent vasodilation has been demonstrated in various vascular beds of different animal models of diabetes and in humans with type 1 and 2 diabetes. Several mechanisms of endothelial dysfunction have been reported, including impaired signal transduction or substrate availibility, impaired release of EDRF, increased destruction of EDRF, enhanced release of endothelium-derived constricting factors and decreased sensitivity of the vascular smooth muscle to EDRF. The principal mediators of hyperglycaemia-induced endothelial dysfunction may be activation of protein kinase C, increased activity of the polyol pathway, non-enzymatic glycation and oxidative stress. Correction of these pathways, as well as administration of ACE inhibitors and folate, has been shown to improve endothelium-dependent vasodilation in diabetes. Since the mechanisms of endothelial dysfunction appear to differ according to the diabetic model and the vascular bed under study, it is important to select clinically relevant models for future research of endothelial dysfunction.

Off-line analysis of red blood cell velocity in renal arterioles.

Videomicroscopic methods with off-line analysis of microcirculatory parameters by multifunctional computer-assisted image analysis systems have significant advantages for in vivo microvascular research. A limitation of these methods is, however, that red blood cell velocities (V(RBC)) exceeding 2 mm/s cannot be measured using standard video framing rates. In the present study, a high-speed video camera, recording up to 600 frames per second, was incorporated in the set-up, and V(RBC) was measured off-line with the line-shift-diagram method. The aim of this study was to test the reproducibility and validity of the method using a high-speed video camera and to evaluate its applicability in vivo. V(RBC) were measured in arterioles of the split hydronephrotic kidney. The intra- and interindividual variability was small for V(RBC) below 40 mm/s. The validity of the method was tested using the mass conservation principle and found to be at least as good as that of the dual-slit photometric technique. The present approach extends the application of videomicroscopy coupled to image analysis systems to the analysis of high V(RBC).