Yuki Hamano

Resistance of Fc receptor- deficient mice to fatal glomerulonephritis.

Immune complex-mediated inflammation is a common mechanism of various autoimmune diseases. Glomerulonephritis (GN) is one of these diseases, and the main mechanism of the induction of GN has been unclear. We examined the contribution of Fc receptors in the induction of nephrotoxic GN by establishing and analyzing mice deficient in the Fc receptor gamma chain (FcRgamma). Whereas all wild-type mice died from severe glomerulonephritis with hypernitremia by administration of anti-glomerular basement membrane (GBM) antibodies, all FcRgamma-deficient mice survived. Histologically, wild-type mice showed glomerular hypercellularity and thrombotic changes, whereas the renal tissue in FcRgamma-deficient mice was almost intact. Deposition of anti-GBM antibody as well as complement components in the GBM were equally observed in both wild-type and knockout mice. These results demonstrate that the triggering of this type of glomerulonephritis is completely dependent on FcR+ cells.

Immune Complex and Fc Receptor-Mediated Augmentation of Antigen Presentation for in Vivo Th Cell Responses

It has recently been established that FcRs are involved in the triggering of type II and III inflammatory responses. Although FcR is not believed to be involved in the regulation of T cell function, the in vivo contribution of FcRs to T cell function still remains unclear. We analyzed in vivo responses of delayed-type hypersensitivity and proliferation of CD4+ T cells to Ags in FcRγ−/− mice lacking the expression and function of FcγRI, FcγRIII, and FcεRI. We found that the delayed-type hypersensitivity response in FcRγ−/− mice is significantly decreased compared with that in wild-type mice. Moreover, the secondary responses of proliferation and cytokine production as well as the Ab formation by CD4+ T cells from FcRγ−/− mice to Ag and normal APCs were also reduced. In contrast, in vitro primary T cell proliferative responses upon stimulation with anti-TCR Ab or MLR as well as in vivo primary response against staphylococcus enterotoxin B administration were not different between T cells from FcRγ−/− and wild-type mice. In addition, the Ag presentation function of APCs from unimmunized FcRγ−/− mice was normal. On the other hand, Ab-deficient mice also revealed impaired T cell responses. These results demonstrate that the defective T cell responses in FcRγ−/− mice were due to impaired Ag presentation during in vivo priming not to a defect in T cells. Therefore, they suggest that the FcRs on APCs mediate efficient priming of Th cell responses in vivo in an immune complex-dependent manner.

CAST, a Novel CD3ε-binding Protein Transducing Activation Signal for Interleukin-2 Production in T Cells

Antigen recognition through T cell receptor (TCR)-CD3 complex transduces signals into T cells, which regulate activation, function, and differentiation of T cells. The TCR-CD3 complex is composed of two signaling modules represented by CD3ζ and CD3ε. Signaling through CD3ζ has been extensively analyzed, but that via CD3ε, which is also crucial in immature thymocyte development, is still not clearly understood. We isolated cDNA encoding a novel CD3ε-binding protein CAST. CAST specifically interacts in vivo and in vitro with CD3ε but not with CD3ζ or FcRγ via a unique membrane-proximal region of CD3ε. CAST is composed of 512 amino acids including a single tyrosine and undergoes tyrosine phosphorylation upon TCR stimulation. Overexpression of two dominant-negative types of CAST, a minimum CD3ε-binding domain and a tyrosine-mutant, strongly suppressed NFAT activation and interleukin-2 production. These results demonstrate that CAST serves as a component of preformed TCR complex and transduces activation signals upon TCR stimulation and represents a new signaling pathway via the CD3ε-containing TCR signaling module.

Lack of Collagen XVIII/Endostatin Exacerbates Immune-Mediated Glomerulonephritis

Collagen XVIII is a component of the highly specialized extracellular matrix associated with basement membranes of epithelia and endothelia. In the normal kidney, collagen XVIII is distributed throughout glomerular and tubular basement membranes, mesangial matrix, and Bowmans capsule. Proteolytic cleavage within its C-terminal domain releases the fragment endostatin, which has antiangiogenic properties. Because damage to the glomerular basement membrane (GBM) accompanies immune-mediated renal injury, we investigated the role of collagen XVIII/endostatin in this disorder. We induced anti-GBM glomerulonephritis in collagen XVIII alpha1-null and wild-type mice and compared the resulting matrix accumulation, inflammation, and capillary rarefaction. Anti-GBM disease upregulated collagen XVIII/endostatin expression within the GBM and Bowmans capsule of wild-type mice. Collagen XVIII/endostatin-deficient mice developed more severe glomerular and tubulointerstitial injury than wild-type mice. Collagen XVIII/endostatin deficiency altered matrix remodeling, enhanced the inflammatory response, and promoted capillary rarefaction and vascular endothelial cell damage, but did not affect endothelial proliferation. Supplementing collagen XVIII-deficient mice with exogenous endostatin did not affect the progression of anti-GBM disease. Taken together, these results suggest that collagen XVIII/endostatin preserves the integrity of the extracellular matrix and capillaries in the kidney, protecting against progressive glomerulonephritis.

Low-Dose Darbepoetin α Attenuates Progression of a Mouse Model of Aristolochic Acid Nephropathy through Early Tubular Protection

Background/Aim: Aristolochic acid (AA) nephropathy, first reported as Chinese herbs nephropathy, is a rapidly progressive tubulointerstitial nephropathy that results in severe anemia, interstitial fibrosis and end-stage renal disease. Tubulointerstitial injury was studied in a mouse model of AA nephropathy to determine whether low-dose darbepoetin α (DPO) treatment prevents acute tubular necrosis and interstitial fibrosis. Methods: AA was administered to C3H/He mice intraperitoneally and some mice were also treated with 0.1 µg/kg of DPO weekly starting on the day of AA administration or on day 28. At 28, 56 or 84 days, blood and urine samples were collected and mice were sacrificed for histological assessment of the kidneys. Results: AA-treated mice developed anemia, elevation of serum creatinine, severe tubular injury similar to acute tubular necrosis and progressive interstitial fibrosis. Although early treatment with low-dose DPO had minimal effects on the hematocrit, it significantly ameliorated acute tubular injury and interstitial inflammation through increasing the survival of tubular cells. As a result, it contributed to preservation of peritubular capillaries and reduction of interstitial fibrosis. Conclusion: Low-dose DPO treatment conferred protection against acute tubular damage and attenuated interstitial fibrosis in a mouse model of AA nephropathy. Early administration of low-dose DPO may prevent the progression of acute tubular necrosis and the subsequent renal fibrosis in human AA nephropathy.

Attenuation of Immune-Mediated Renal Injury by Telmisartan, an Angiotensin Receptor Blocker and a Selective PPAR-γ Activator.

Background/Aims: Anti-glomerular basement membrane (GBM) nephritis is characterized by activation of the renin-angiotensin system. This study aimed to determine the question of whether a temporary angiotensin II blockade at the initial stage of anti-GBM nephritis is able to attenuate the disease as well as differences in renoprotection among angiotensin II receptor blockers (ARBs) with distinct peroxisome proliferator-activated receptor (PPAR)-γ-modulating activities. Methods: C57BL/6J mice were immunized with rabbit IgG, followed by intravenous injection of rabbit anti-mouse antibodies. Mice were then treated with telmisartan, losartan, and telmisartan + GW9662 (a PPAR-γ antagonist) for 5 days, or hydralazine for 9 days. On days 8 and 13, mice were sacrificed to obtain tissues for histological analysis. Results: The temporary administration of telmisartan significantly suppressed glomerular damage compared to hydralazine. Losartan showed a similar effect but was less effective. Co-administration of GW9662 attenuated the renoprotective effect of telmisartan, almost to levels observed with losartan. In particular, it limited the decreased infiltration of inflammatory cells and preservation of capillaries in the glomeruli induced by telmisartan. Conclusion: Temporary angiotensin II blockade at the initial stage of anti-GBM disease dramatically inhibited its progression. In addition to a class effect of ARBs, telmisartan modified inflammation and endothelial damage in the kidney through its PPAR-γ-agonistic action.

Membranous nephropathy associated with oxaprozin treatment.

Makoto Ogawa, MD, First Department of Internal Medicine, Chiba University School of Medicine, 1-8-1 Inohana, Chuouku 260, Chiba (Japan) change was minimal, and arteriolosclerosis was mild. Silver methenamine stain disclosed ‘spikes’ over the outer part of the basement membrane of some loops. Immu-nofluorescent studies showed granular deposits of IgG and C3 along the glomerular capillary wall. Electron microscopy examination showed effacement of foot processes with subepithelial dense deposits (fig. 1). Pulmonary or gastrointestinal diseases were not found by routine radiological examinations. Conservative treatment with diet and salt restriction was started instead of cortico-steroid. In addition, enalapril 5 mg daily was added to nifedipine. The urine protein gradDear Sir, Nephrotic syndrome (NS) sometimes develops during treatment with nonsteroi-dal antiinflammatory drugs (NSAIDs) [1, 2]. Minimal change nephrotic syndrome (MCNS) is most frequent [1-3], but membranous nephropathy (MN) has also been reported in association with NSAIDs [4-8]. Herewith we describe a case of MN developing after treatment with oxaprozin. A 36-year-old man with hypertension had been admitted to the Chiba University Hospital because of leg edema. The patient had no past history of renal disease, alcohol abuse, or recent infection. He had been given nifedipine for more than 2 years, but no side effect was noted. Two months before the admission, oxaprozin at a dose of 200 mg daily had been added because of persistent low back pain. Six weeks after oxaprozin was started, he noticed peripheral edema. He stopped taking oxaprozin, but the edema was progressive. On admission, he had massive edema of the legs and mild hypertension (165/92). Serum creatinine was 106 μmol/l, serum albumin concentration was 26 g/l, and urinary protein excretion was 4.5 g/day. Urinalysis showed a few red and white cells, but urine sugar was negative. Negative or normal values included complete blood count, fasting blood glucose, transaminases, HBs antigen, α-fetoprotein, carcinoem-bryonic antigen, rheumatoid factor, antinu-clear and anti-DNA antibodies, complement, and cryoglobulinemia. The renal biopsy

Loss of placental growth factor ameliorates maternal hypertension and preeclampsia in mice

Preeclampsia remains a clinical challenge due to its poorly understood pathogenesis. A prevailing notion is that increased placental production of soluble fms-like tyrosine kinase-1 (sFlt-1) causes the maternal syndrome by inhibiting proangiogenic placental growth factor (PlGF) and VEGF. However, the significance of PlGF suppression in preeclampsia is uncertain. To test whether preeclampsia results from the imbalance of angiogenic factors reflected by an abnormal sFlt-1/PlGF ratio, we studied PlGF KO (Pgf–/–) mice and noted that the mice did not develop signs or sequelae of preeclampsia despite a marked elevation in circulating sFLT-1. Notably, PlGF KO mice had morphologically distinct placentas, showing an accumulation of junctional zone glycogen. We next considered the role of placental PlGF in an established model of preeclampsia (pregnant catechol-O-methyltransferase–deficient [COMT-deficient] mice) by generating mice with deletions in both the Pgf and Comt genes. Deletion of placental PlGF in the context of COMT loss resulted in a reduction in maternal blood pressure and increased placental glycogen, indicating that loss of PlGF might be protective against the development of preeclampsia. These results identify a role for PlGF in placental development and support a complex model for the pathogenesis of preeclampsia beyond an angiogenic factor imbalance.