Kidney-limited thrombotic microangiopathy in patients with SLE treated with romiplostim.

We present the case of a 19 year-old Caucasian female with history of systemic lupus erythematosus (SLE) and normal baseline kidney function who developed severe acute renal failure following treatment of thrombocytopenia with the thrombopoietic agent romiplostim. Percutaneous kidney biopsy revealed thrombotic microangiopathy (TMA) without immune complex lupus glomerulonephritis. We discuss pathogenesis and differential diagnosis of TMA in patients with SLE and raise concerns regarding the use of thrombopoietic agents in such patients. Based on favorable long-term outcome in our case aggressive treatment and in particular prolonged use of plasma exchange in these patients are advocated.

Antagonist effect of a receptor-mimicking peptide encoded by human angiotensin II complementary RNA.

This article reports on the binding and the angiotensin II (Ang II) antagonistic properties of a peptide, referred to as hIIA, encoded by an RNA strand complementary to the human Ang II messenger RNA. Although Ang II and hIIA (H2N-Glu-Gly-Val-Tyr-Val-His-Pro-Val-COOH) share four amino acids, the iodinated and tritiated forms of hIIA were unreactive with seven monoclonal antibodies defining four distinct epitopes on the Ang II molecule and failed to bind to Ang II hepatic and mesangial receptors. However, hIIA did inhibit binding of 125I-Ang II to rat hepatocyte membranes (IC50, 2 x 10(-7) M) and to the various monoclonal antibodies. The lowest IC50 (5 x 10(-7) M) was measured with the monoclonal antibody specific for the Ang II sequence generally considered as implicated in receptor recognition. As predicted from the binding studies, hIIA was further shown to antagonize some biological properties of Ang II. On mesangial cells, hIIA alone had no effect on intracellular calcium concentration ([Ca2+]i) and prostaglandin E2 synthesis but did abolish the transient increase in [Ca2+]i in response to 100 nM Ang II and did induce a specific dose-dependent inhibition of the Ang II-stimulated prostaglandin E2 release. Furthermore, intravenous infusion of hIIA (200 micrograms.kg-1.min-1) inhibited by 66 +/- 3% the rat hypertensive response to 100 ng.kg-1 Ang II but had no effect on the pressor activity of agents such as alpha 1-adrenergic and HT2 serotonin agonists. Our data suggest that the "complementary" peptide hIIA interacts directly with Ang II by mimicking the Ang II complementary site on the receptor and can inhibit the physiological effects of Ang II. This type of Ang II complementary peptide may serve as a model for a new class of antihypertensive drugs.

Acute renal artery and vein thrombosis after renal transplant, associated with a short partial thromboplastin time and factor V Leiden mutation.

Renal graft thrombosis is a rare but devastating complication of renal transplantation. It accounts for one-third to one-half of early graft losses. We report a patient with acute renal artery and vein thrombosis associated with abnormally short activated partial thromboplastin time (aPTT) and factor V Leiden mutation. Vascular thrombosis developed on the ninth post-transplant day and led to a graft loss. Before transplantation, the patient had three episodes of thrombosis of arteriovenous access for hemodialysis. Our case illustrates the importance of investigating pretransplant patients for hypercoagulable states, particularly those with short aPTT.

Calciphylaxis in chronic renal failure.

Calciphylaxis is a rare and life-threatening complication that is estimated to occur in 1% of patients with ESRD each year. Typically, extensive microvascular calcification and occlusion/thrombosis leads to violaceous skin lesions, which progress to nonhealing ulcers and sepsis. Secondary infection of skin lesions is common, often leading to sepsis and death. The lower extremities are predominantly involved (roughly 90% of patients). Patients with skin involvement over the trunk or proximal extremities have a poorer prognosis. Although most calciphylaxis patients have abnormalities of the calcium:phosphate axis or elevated levels of parathyroid hormone, these abnormalities do not appear to be fundamental to the pathophysiology of the disorder, and the etiology of calciphylaxis remains unclear. Recently, functional protein C deficiency has been hypothesized to cause a hypercoagulable state that could induce thrombosis in small vessels, with resulting skin ischemia, necrosis, and gangrene. The lack of understanding of the pathophysiology of the disease results in treatments that are equally unsatisfactory. Patients who undergo parathyroidectomy have a tendency to improve, but the prognosis for the disease is poor and mortality remains high.

Destabilization of natriuretic peptide C-receptor mRNA by phorbol myristate acetate.

Natriuretic peptide C receptor (NPR-C) expression in rat mesangial cells is downregulated by platelet-derived growth factor (PDGF) and the protein kinase C agonist phorbol myristate acetate (PMA). This study shows that PDGF and PMA diminish NPR-C mRNA abundance and that PMA does so by accelerating the degradation of the transcript. Exposure to PMA (0.1 microM) decreased mesangial cell NPR-C mRNA levels by more than 50% within 3 h and 125I-atrial natriuretic peptide binding by approximately 50% within 6 h. Disappearance of NPR-C transcripts after PMA treatment was more than twice as rapid as that seen after inhibition of RNA transcription with actinomycin D. Treatment with PDGF A/B (10 ng/ml) also produced downregulation of NPR-C mRNA, but the rate of transcript disappearance was similar to that seen after actinomycin D. Coincubation with actinomycin D inhibited the rapid disappearance of NPR-C mRNA with PMA. NPR-C mRNA levels increased four- to eightfold within 6 h after treatment with the protein synthesis inhibitor cycloheximide, but simultaneous treatment with PMA or PDGF still decreased the level of NPR-C mRNA despite the presence of cycloheximide. These results indicate that NPR-C expression is rapidly regulated by changes in the rate of catabolism of its mRNA through a protein kinase C-activated mechanism that depends on transcription. Treatment with cycloheximide induces NPR-C mRNA, but downregulation of this mRNA by either PDGF or PMA does not depend on synthesis of new protein.

Angiotensin II (AII)-related idiotypic network. III. Comparative analysis of idiotopes and paratopes borne by monoclonal antibodies raised against AII (AB1) and its internal image (AB3).

We have previously produced mAb against angiotensin II (AII), a phylogenetically conserved vasopressive octapeptide, and shown that they identify four distinct epitopes on the AII molecule. In addition we used internal image bearing polyclonal antiidiotypic antibodies raised against rabbit anti AII to produce mAb3. In this study we analyze the segregation of the idiotypic and paratopic repertoires of the mAb1 and mAb3. Analysis of mAb1 carried out with polyclonal Ab2 raised against the four distinct paratopes permitted classification of the mAb1 into four categories: (p+, id+) comprises antibodies with shared paratopic and idiotypic specificities: (p+, id-) is made up of antibodies that fail to express the Id defined by Ab2 raised against other antibodies pertaining to the same paratopic group; (p-, id+) includes antibodies that express cross-reactive Id on distinct paratopes; (p-, id-) refers to antibodies unrelated by their paratopes and Id mAb2 confirmed these results and showed expression of identical or closely related Id on clearly distinct paratopes. At the Ab3 level, using polyclonal Ab4, there was a higher degree of Id cross-reactivity between the two paratopes available. These data suggest that the parallel set concept may apply to the immune response to a natural peptidic Ag and its internal image. Comparison of idiotypic repertoires of mAb1 and mAb3 (using Ab2 and Ab4 antibodies) confirmed the lack of public Id and showed the predominance on mAb3 of "new" idiotypes absent from mAb1 molecules, as expected for internal image-induced antibodies. Cross-reactive idiotypes defined on mAb1 and conserved on mAb3 were expressed on the two paratopes defined at the Ab3 level. They were located on the H chain of the homologous paratope and required the association of H and L chains on the heterologous paratope. Our analysis suggests that, in the AII system, the idiotypic and paratopic repertoires segregate at least in part independently. The paratopic repertoire is limited to a small number of phylogenetically conserved specificities and may be encoded by germline genes. In contrast, the idiotypic repertoire is broader with respect to specificities, species, and localization on H and L chains. This extended diversity may be generated by somatic mutations or use of various combinations of H and L chains and/or V, D, J segments.

Regulation of atrial natriuretic peptide clearance receptors in mesangial cells by growth factors.

Rat mesangial cells can express both 130-kDa guanylyl cyclase-coupled and 66-kDa non-coupled atrial natriuretic peptide (ANP) receptors (ANPR-A and ANPR-C, respectively). Exposure of mesangial cells, grown in 20% fetal calf serum, to 0.1% serum for 24 h increased total ANP receptor density more than 2-fold (Bmax = 87 versus 37 fmol/mg of cell protein) without changing binding affinity (Kd = 94 versus 88 pM). Radioligand binding and cross-linking studies demonstrated that up-regulation of ANP binding after serum deprivation was entirely due to an increase in ANPR-C, with little or no change in ANPR-A. Inhibition of protein synthesis with cycloheximide blocked up-regulation after serum deprivation. Steady-state ANPR-C mRNA level was increased 15-fold by serum deprivation, as judged by Northern blotting. There was no change in ANPR-A mRNA. Platelet-derived growth factor and phorbol myristate acetate, when added to low serum medium, blocked or reversed the effect of serum deprivation on ANPR-C. We conclude that synthesis and expression of ANPR-C but not ANPR-A is suppressed by serum, platelet-derived growth factor, and phorbol myristate acetate. Suppression of ANPR-C in vivo could contribute to mesangial cell proliferative responses to growth factors.

[Histiocytosis X--a comparative 2-country study of East Germany and Yugoslavia]. / Histiozytosis X--eine vergleichende Zweiländerstudie aus der DDR und SFR Jugoslawien.

In a retrospective study 25 patients with histologically confirmed histiocytosis X were investigated in the GDR and in Yugoslavia. No differences between the clinical course was observed in the two countries. The disease was found somewhat more frequent in men, and relative to age groups the age group 18-39 prevailed. Only one fourth of the patients were detected by radiophotography. Lung function was impaired in 2/3 of the patients. In the lung radiogramm reticular and micronodular changes predominated at the beginning of the disease while cystic lesions appeared in late stages of the disease. The diagnosis was established on the basis of biopsy (most often transthoracic lung biopsy) and pathohistologic examination. The course of the disease was unfavourable because of the 18 observed patients 3 died and in 6 progression of the disease was noted on average within several years.

Angiotensin II (AII)-related idiotypic network. II. Heterogeneity and fine specificity of AII internal images analyzed with monoclonal antibodies.

Although the structural basis of internal images borne by beta type monoclonal anti-idiotypic antibody (Ab2) begins to be elucidated, there is little information on the repertoire of epitopes which make up the internal images expressed by polyclonal Ab2. We addressed this question by using a two-way approach in the angiotensin II (AII)-related idiotypic network, a system characterized by common occurrence of internal images on rabbit Ab2. First, two sets of internal images were purified in parallel by affinity chromatography on Sepharose 4B covalently linked to either mAb 110 (S4B-110), a mAb specific for a phenylalanine requiring carboxy terminus epitope (Phe8) on AII, or mAb 133 (S4B-133), reactive with a more central epitope also expressed on Phe8 substituted peptide analogs. The respective eluates, EL1 110 and E11 133, exhibited only partially overlapping reactivity, as demonstrated by 1) a different pattern of inhibition by various AII peptide analogues of EL1 110 and E11 133 binding to the same anti-AII antibody (Ab1) (either the homologous polyclonal Ab1 102 or mAb 133), 2) and a distinct profile of EL1 110 and EL1 133 binding to 12 biotinylated monoclonal Ab1 identifying a variety of epitopes on AII. To analyze further the respective distribution of mAb 110 and mAb 133 defined epitopes on Ab2-beta molecules, Ab2 were submitted to sequential affinity chromatography on S4B-110 followed by S4B-133, and the fractionated internal images were characterized by the pattern of binding to the various monoclonal Ab1. It was thus possible to purify two Ab2-beta subpopulations that exclusively imaged the determinant identified by mAb 110 (ii 110) or that identified by mAb 133 (ii 133). A third subpopulation which was successively retained on S4B-110 and S4B-133 expressed both internal images (ii 110 + 133), and was additionally reactive with all the other monoclonal Ab1 tested. In any case, monoclonal Ab1 binding to the different sets of internal images was totally inhibited by an excess of AII. These results indicate that the repertoire of internal epitopes is similar to that of the nominal Ag, but is scattered over distinct subpopulations of Ab2-beta molecules that can be fractionated by affinity chromatography. Some of the latter seem to bear several epitopes and resemble the whole nominal Ag, whereas others appear to image only one determinant. Second, we raised 7 anti-anti-idiotypic mAb (monoclonal Ab3) against affinity-purified Ab2-beta and analyzed their fine specificity for AII.(ABSTRACT TRUNCATED AT 400 WORDS)