Activation of innate immune defense mechanisms contributes to polyomavirus BK-associated nephropathy.

Polyomavirus-associated nephropathy (PVAN) is a significant complication after kidney transplantation, often leading to premature graft loss. In order to identify antiviral responses of the renal tubular epithelium, we studied activation of the viral DNA and the double-stranded RNA (dsRNA) sensors Toll-like receptor 3 (TLR3) and retinoic acid inducible gene-I (RIG-I) in allograft biopsy samples of patients with PVAN, and in human collecting duct cells in culture after stimulation by the dsRNA mimic polyriboinosinic:polyribocytidylic acid (poly(I:C)), cytokines, or infection with BK virus. Double staining using immunofluorescence for BK virus and TLR3 showed strong signals in epithelial cells of distal cortical tubules and the collecting duct. In biopsies microdissected to isolate tubulointerstitial lesions, TLR3 but not RIG-I mRNA expression was found to be increased in PVAN. Collecting duct cells in culture expressed TLR3 intracellularly, and activation of TLR3 and RIG-I by poly(I:C) enhanced expression of cytokine, chemokine, and IFN-ß mRNA. This inflammatory response could be specifically blocked by siRNA to TLR3. Finally, infection of the collecting duct cells with BK virus enhanced the expression of cytokines and chemokines. This led to an efficient antiviral immune response with TLR3 and RIG-I upregulation without activation of IL-1ß or components of the inflammasome pathway. Thus, PVAN activation of innate immune defense mechanisms through TLR3 is involved in the antiviral and anti-inflammatory response leading to the expression of proinflammatory cytokines and chemokines.

Sphingosine-1-phosphate analogue FTY720 causes lymphocyte redistribution and hypercholesterolemia in ApoE-deficient mice.

OBJECTIVE: Resident immune cells are a hallmark of atherosclerotic lesions. The sphingolipid analogue drug FTY720 mediates retrafficking of immune cells and inhibits their homing to inflammatory sites. We have evaluated the effect of FTY720 on atherogenesis and lipid metabolism. METHODS AND RESULTS: ApoE-/- mice on a normal laboratory diet received oral FTY720 for 12 weeks, which led to a 2.4-fold increase in serum cholesterol (largely VLDL fraction) and a 1.8-fold increase in hepatic HMGCoA reductase mRNA. FTY720 increased plasma sphingosine-1-phosphate and induced marked peripheral blood lymphopenia. A discoordinate modulation of B, T and monocyte cell numbers was found in peripheral lymphoid organs. Overall depletion of T cells was accompanied by a relative (2-fold) increase in regulatory T cell content paralleled by a similar increase in effector memory T cells (CD4+ CD44hi CD62lo) as absolute numbers of both subpopulations remained essentially unchanged. Lymphocyte function was unaltered as indicated by anti-OxLDL antibodies and T cell proliferation. There were no changes in atherosclerotic lesions in early and established atherosclerosis. CONCLUSIONS: FTY720 mediated peripheral lymphocyte depletion and retrafficking without altering function and overall balance of pro- and antiatherogenic lymphocyte populations. A net decrease in lymphocyte numbers occurred concomitantly with a more proatherogenic hypercholesterolemia resulting in unaltered atherogenesis.

Intracapillary immune complexes recruit and activate slan-expressing CD16+ monocytes in human lupus nephritis.

Lupus nephritis is a major cause of morbidity in patients with systemic lupus erythematosus. Among the different types of lupus nephritis, intracapillary immune complex (IC) deposition and accumulation of monocytes are hallmarks of lupus nephritis class III and IV. The relevance of intracapillary ICs in terms of monocyte recruitment and activation, as well as the nature and function of these monocytes are not well understood. For the early focal form of lupus nephritis (class III) we demonstrate a selective accumulation of the proinflammatory population of 6-sulfo LacNAc+ (slan) monocytes (slanMo), which locally expressed TNF-α. Immobilized ICs induced a direct recruitment of slanMo from the microcirculation via interaction with Fc γ receptor IIIA (CD16). Interestingly, intravenous immunoglobulins blocked CD16 and prevented cell recruitment. Engagement of immobilized ICs by slanMo induced the production of neutrophil-attracting chemokine CXCL2 as well as TNF-α, which in a forward feedback loop stimulated endothelial cells to produce the slanMo-recruiting chemokine CX3CL1 (fractalkine). In conclusion, we observed that expression of CD16 equips slanMo with a unique capacity to orchestrate early IC-induced inflammatory responses in glomeruli and identified slanMo as a pathogenic proinflammatory cell type in lupus nephritis.

Expression of A20 in the vessel wall of rat-kidney allografts correlates with protection from transplant arteriosclerosis.

BACKGROUND: Chronic rejection with development of transplant arteriosclerosis is the major culprit involved in loss of kidney allografts. The allografts' fate was thought to depend on the intensity of the host immune responses and the potency of immunosuppressive regimens. Recent data suggests that grafts contribute to their own survival by way of up-regulation of "cytoprotective" genes. METHODS: We analyzed the expression of four cytoprotective genes, A20, Bcl-2, Bcl-x(L) and heme oxygenase (HO)-1, in three rat renal allograft models of chronic rejection: Fisher 344-Lewis (F344/Lew), Dark Agouti-Brown Norway (DA/BN), and DA-Wistar-Furth (WF). We chose these genes for their known anti-inflammatory and anti-apoptotic function in endothelial cells (EC) and the atheroprotective function of A20 in smooth muscle cells (SMC). RESULTS: Twenty-eight and 9 weeks following transplantation, F344/Lew and DA/BN transplants had stable graft function. Histopathologic analysis showed moderate tissue damage, minimal cellular infiltrates, and preserved vascular integrity correlating with high expression of A20 in SMC. Conversely, impaired allograft function in the DA/WF combination with substantial transplant arteriosclerosis was noted in 60% of the grafts correlating with absent or decreased A20 expression in EC and SMC. In all combinations, expression of HO-1, Bcl-2, and Bcl-x(L) colocalized with infiltrating cells and was not informative on the graft status. CONCLUSIONS: We demonstrate for the first time a strict correlation between A20 expression in the vessel and the absence of transplant arteriosclerosis in rat kidney-allograft models. This data is similar to data obtained in human kidney allografts and suggests that A20 may represent a novel therapeutic target for the prevention of chronic allograft rejection.

A case of late-onset primary hyperoxaluria type 1.

Primary hyperoxaluria type 1 (PH1) is an inherited metabolic disorder characterized by recurrent urolithiasis and nephrocalcinosis frequently leading to progressive renal insufficiency during the second decade of life. Systemic organ involvement as a result of the accumulation of calcium oxalate crystal deposits in vessel walls often is observed. We report a case of a 56-year-old woman with late-onset of PH1 who developed rapidly progressive renal failure and severe systemic oxalosis with skin and eye involvement despite intensified hemodialytic therapy during the waiting period for combined liver and kidney transplantation. This case illustrates the difficulties in treatment of PH1-induced end-stage renal disease. Combined liver and kidney transplantation should be offered to these patients as soon as possible to reverse the underlying metabolic defect and to restore renal function.

The liver-specific microRNA miR-122 controls systemic iron homeostasis in mice.

Systemic iron homeostasis is mainly controlled by the liver through synthesis of the peptide hormone hepcidin (encoded by Hamp), the key regulator of duodenal iron absorption and macrophage iron release. Here we show that the liver-specific microRNA miR-122 is important for regulating Hamp mRNA expression and tissue iron levels. Efficient and specific depletion of miR-122 by injection of a locked-nucleic-acid-modified (LNA-modified) anti-miR into WT mice caused systemic iron deficiency, characterized by reduced plasma and liver iron levels, mildly impaired hematopoiesis, and increased extramedullary erythropoiesis in the spleen. Moreover, miR-122 inhibition increased the amount of mRNA transcribed by genes that control systemic iron levels, such as hemochromatosis (Hfe), hemojuvelin (Hjv), bone morphogenetic protein receptor type 1A (Bmpr1a), and Hamp. Importantly, miR-122 directly targeted the 3' untranslated region of 2 mRNAs that encode activators of hepcidin expression, Hfe and Hjv. These data help to explain the increased Hamp mRNA levels and subsequent iron deficiency in mice with reduced miR-122 levels and establish a direct mechanistic link between miR-122 and the regulation of systemic iron metabolism.

Membranous nephropathy associated with familial chronic ulcerative colitis in a 12-year-old girl.

Glomerulonephritis is a rare complication in patients with inflammatory bowel disease. We report a case of membranous nephropathy (MN) in a 12.6-year-old girl with chronic ulcerative colitis. The girl was referred to the hospital with bloody diarrhea and arthralgia. Routine urinalysis showed 1 g/m(2) protein excretion in 24 h. Serum ANCA titers were positive. The diagnoses were confirmed by coloscopy and kidney biopsy. The patient's mother had also suffered from ulcerative colitis in adolescence. Proteinuria normalized under treatment with prednisone (60 mg/m(2)/day) and azathioprine, which was initiated to treat the colitis. Chronic ulcerative colitis can be associated with glomerulonephritis.

Selective COX-2 inhibitors and renal injury in salt-sensitive hypertension.

In view of the ongoing controversy of cardiorenal safety of selective COX-2 inhibitors (coxibs), the present study was designed to examine the effects of 2 different coxibs, celecoxib and rofecoxib, compared with a traditional NSAID, diclofenac, and placebo on renal morphology and function in salt-sensitive hypertension. Salt-sensitive (DS) and salt-resistant (DR) Dahl rats were fed with NaCl-enriched diet (4% NaCl) for 8 weeks. Diclofenac (DS-diclofenac), rofecoxib (DS-rofecoxib), celecoxib (DS-celecoxib), or placebo was added to chow from weeks 6 to 8. Immunostaining for monocytes/macrophages (ED1) and cytotoxic T lymphocytes (CD8) was performed. In addition, renal morphology and proteinuria were assessed. Renal cortex mRNA was isolated for determination of COX-2, eNOS, and CRP mRNA by real-time reverse-transcriptase polymerase chain reaction. Untreated hypertensive animals showed glomerular injury including collapsing glomerulopathy, mesangial sclerosis, mesangiolysis, extracapillary proliferation, protein drops, and an especially high grade of glomerulosclerosis (P<0.05 versus DR-placebo) and CD8-positive and ED1-positive cells (P<0.01 versus DR-placebo), which was improved by celecoxib but not by diclofenac and rofecoxib. C-reactive protein mRNA in renal cortex was increased in DS-placebo animals (P<0.05 versus DR-placebo) and normalized by celecoxib (P<0.05 versus DS-placebo), whereas eNOS mRNA was decreased in the DS-rofecoxib group (P<0.05 versus DR-placebo, DS-celecoxib, and DS-diclofenac). Proteinuria was observed in hypertensive animals (P<0.0001 versus DR-placebo), increased by rofecoxib (P<0.05 versus DS-placebo), and normalized by celecoxib (P=0.0015 versus DS-placebo). This head-to-head comparison of selective and nonselective COX inhibitors demonstrates differential effects of coxibs on renal morphology and function in salt-dependent hypertension.

Induction of microsomal prostaglandin E2 synthase in the macula densa in children with hypokalemic salt-losing tubulopathies.

In hyperprostaglandin E syndrome (HPGES) and classic Bartter syndrome (cBS), tubular salt and water losses stimulate renin secretion, which is dependent on enhanced cyclooxygenase-2 (COX-2) enzymatic activity. In contrast to other renal COX metabolites, only prostaglandin E(2) (PGE(2)) is selectively up-regulated in these patients. To determine the intrarenal source of PGE(2) synthesis, we analyzed the expression of microsomal PGE(2) synthase (mPGES; EC: 5.3.99.3), whose product PGE(2) has been shown to stimulate renin secretion in vitro. Expression of mPGES was analyzed by immunohistochemistry in eight patients with HPGES, in two patients with cBS, and in six control subjects. Expression of mPGES immunoreactive protein was observed in cells of the macula densa in five of eight HPGES patients and in one of two cBS patients. Expression of mPGES immunoreactive protein was not observed in cells associated with the macula densa in kidneys from control subjects without a history consistent with activation of the renin angiotensin system. Co-induction of COX-2 and mPGES in cells of the macula densa suggests that PGE(2) activates renin secretion in humans.

A rare cause of pulmonary-renal syndrome.

Diseases affecting both the lung and the kidney have grave prognosis and serious diagnostic and therapeutic consequences. Here, 3 cases of pulmonary-renal syndrome caused by antiphospholipid syndrome are reported. The patients presented with dyspnea, renal insufficiency, pulmonary infiltrates on chest X-ray and areas of ground glass attenuation on computed tomography of the lungs. There were no signs of infectious disease, vasculitis or myocardial insufficiency. Clinical findings, antiphospholipid levels and histological findings in transbronchial and/or renal biopsy proved the diagnosis of antiphospholipid syndrome. Antiphospholipid syndrome is a comparatively rare disorder which is relevant in the differential diagnosis of diseases affecting both lung and kidney and requires specific therapeutic measures.