Noritsugu Morino

Enhanced expression of platelet-derived growth factor-β receptor by high glucose. Involvement of platelet-derived growth factor in diabetic angiopathy

Coronary heart disease is a major complication of diabetic subjects, and platelet-derived growth factor (PDGF) has been implicated in the development of atherosclerosis. We investigated the effects of high glucose on expression of PDGF-β receptor. In a binding assay with 125I-labeled PDGF-BB homodimer, high concentrations of glucose increased high-affinity binding of PDGF-BB on human monocyte-derived macrophages and rabbit aortic medial smooth muscle cells. Northern blot analysis confirmed the enhanced effect of glucose on expression of PDGF-β receptor mRNA in human monocyte-derived macrophages. The protein kinase C inhibitor, staurosporin, completely suppressed an increase in PDGF-BB binding by high glucose, and high glucose significantly activated protein kinase C. These results indicated that PDGF-β receptor expression was enhanced by high glucose through the activation of protein kinase C. Furthermore, we observed similar effects of high glucose on both PDGF-β receptor expression and protein kinase C activation in rat mesangial cells and human capillary endothelial cells. Our results suggest that stimulation of the PDGF system is significantly involved in the development not only of diabetic atherosclerosis but also of microangiopathy.

Glomerular overexpression and increased tyrosine phosphorylation of focal adhesion kinase p125FAK in lupus-prone MRL/MP-lpr/lpr mice.

Much progress has been made in understanding how mammalian cells receive a diverse array of external stimuli and convert them into intracellular biochemical signals. Such efforts have identified a large number of signalling molecules. However, our knowledge is limited as to their pathophysiological role in particular diseases. We demonstrate herein that an integrin‐linked signalling molecule, focal adhesion kinase p125FAK (FAK), is overexpressed in glomeruli of lupus‐prone MRL/MP‐lpr/lpr (MRL‐lpr) mouse as compared to its congeneic MRL‐+/+ strain. Increased expression was specifically demonstrated in glomeruli but not in other tissues examined. The overexpression was observed in 16‐week‐old MRL‐lpr mice with active nephritis, as well as in younger animals at 4 weeks of age. Thus, the upregulation of FAK clearly preceded the clinical onset of nephritis. FAK in MRL‐lpr glomeruli is highly tyrosine phosphorylated and is associated with adapter protein Grb2. Previous in vitro studies have shown that the association of FAK/Grb2 links cell adhesion to the Ras pathway, which ultimately stimulates mitogen‐activated protein (MAP) kinase, an important regulator of cell proliferation. In accordance, we observed constitutive MAP kinase activation in MRL‐lpr glomeruli. Our findings suggest that signalling pathways involving FAK are activated in MRL‐lpr glomeruli, and are likely to play a role in the development and progression of autoimmune‐mediated murine nephritis.

Rabbit anti-chromatin antibodies recognize similar epitopes on a histone H1 molecule as lupus autoantibodies.

Autoantibodies in systemic lupus erythematosus (SLE) are believed to be produced through an antigen-driven mechanism, i.e., autosensitization with autoantigens. If this is the case, it is conceivable that antigenic determinants reactive with SLE autoantibodies and induced antibodies raised by immunization are quite similar. To examine this issue, rabbits were immunized with purified histone H1 or chromatin. Although immunization with purified histone H1 did not produce detectable amounts of anti-histone H1 antibodies, immunization with chromatin mounted relatively good antibody responses against not only all histone subunits but also ssDNA. Epitopes on a histone H1 molecule reactive with SLE autoantibodies and rabbit antisera were determined using deletion mutants of a histone H1 molecule. At least two epitopes reactive with induced antibodies were found on a histone H1 and these were closely related to or the same as major autoepitopes in SLE. These data might indicate that B cells producing anti-histone H1 autoantibodies are quite similar to those induced by immunization and provide additional evidence that autosensitization with an autoantigen might be operative and a particulate antigen chromatin could be one of the immunogens for the production of anti-nuclear antibodies of various kinds in SLE.

Nephrotic syndrome developed in a patient with acute promyelocytic leukemia treated with daunomycin.

Noritsugu Morino, MD, The Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113 (Japan) Dear Sir, Nephrotic syndrome (NS) is an unusual but well-recognized complication of malignant diseases [1,2]. Among the hematologi-cal neoplasms, lymphocytic leukemia and lymphoma have a known association with NS, while its occurrence in the acute myelog-enous leukemia (AML) appears to be exceedingly rare [2]. To the best of our knowledge, there have been only two reports in the literature [3, 4]. We report here a case of acute promyelocytic leukemia (APL) associated with NS. The development of NS was coincidental with the administration of chemotherapy in this case. A 32-year-old Japanese woman presented at our hospital with progressive fatigue and gingival bleeding which had developed 2 weeks earlier. Until then she had been in excellent health with no history of renal disease or drug exposure. The physical examination was normal except for anemic conjunctiva and purpuric lesions scattered on the upper chest. The hematocrit was 21.4%, WBC 34.1 × 109/1 with 12% blast cells and 70% promyelocytes, and the platelet count was 22 × 109/1. Coagulation studies demonstrated that the patient had disseminated intravascular coagulation (DIC). Urinalysis showed trace amounts of protein, and the sediment was normal. Serum albumin was 4.5 g/dl, urea nitrogen 16.3 mg/dl, and creat-inine 0.6 mg/dl. The bone marrow aspirate showed increased cellularity with 13.2% myeloblasts and 82.4% promyelocytes. The 1⁄8 · · β ‘ Fig. 1. a Ligh micrograph of a glomerulus showing minor abnormalities. HE. × 200. b Electron micrograph showing widespread detachment of epithelial cells from GBM. × 8,000. Serum albumin was 3.0 g/dl on the 15th hospital day. Thus, the patient developed NS during the course of chemotherapy for APL. Anticoagulant therapy had little effect on her severe DIC, and the patient died on the 16th day because of massive hemorrhage into both lungs.

Relationship Between Autoepitope and DNA-Binding Site on a Histone H1 Molecule

Autoepitope and DNA-binding domain on a histone H1 molecule were compared using truncated histone H1 peptides as antigens. At least two epitopes (epitope A, N-terminal side; epitope B, C-terminal side) were found both of which were composed of approximately 20 amino acids. IgM from all 17 anti-histone H1-positive SLE sera reacted with epitope A. IgG from 12 sera reacted with epitope A and IgG from 4 sera reacted with epitope B. In one case, no IgG anti-histone H1 reactivities were found while IgM from the same patient reacted with epitope A. Epitope A had the ability to bind DNA. The reactivities against histone H1 of affinity-purified antiepitope A autoantibodies were inhibited by DNA. These data suggest that some anti-histone H1 antibodies are directed against a histone H1 DNA-binding site, raising the possibility that an idiotype/anti-idiotype network, at least in part, is involved in the generation of anti-histone H1 autoantibodies.