[Immunopathogenetic hypotheses in inflammatory rheumatic diseases].
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Anti-Inflammatory Agents↗
Biomedical subjects
H Burkhardt
Publications and source records attributed to H Burkhardt.
Chicken and egg in autoimmunity and joint inflammation.
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Arthritis↗
Computerized analysing system using the active contour in ultrasound measurement of carotid artery intima-media thickness.
BACKGROUND AND PURPOSE: B-mode measurement of the carotid intima-media (IM) thickness (T) based on manual tracing (MT) procedures are dependent on the subjectivity of the reader and the existing automatic tracing procedures often fail to detect the IM boundaries accurately. The purpose of this study was to compare the tracing results of the IM boundaries of the carotid wall with a new automatic identification (AI) procedure, based on an active contour model, and computer-assisted manual tracing (MT). METHODS: The detection of the IM boundaries was performed with both procedures in 126 ultrasound images [63 each of the common carotid artery (CCA) and carotid bulb] along the far wall of the distal CCA and the carotid bulb. Intra- and inter-reader variability for mean and maximum IMT with AI and MT and accuracy of identification of both IM boundaries were evaluated. RESULTS: Using MT the intra- and inter-reader variability amounted to 0.01-0.03 and 0.03-0.07 mm, respectively. The variability was slightly higher in the carotid bulb than in the CCA. Using AI the variability was almost eliminated. Mean and maximum IMT were measured systematically lower by AI compared with MT in all regions by 0.01 mm. The accuracy of identification was similar for both IM boundaries, but lower in the carotid bulb region than in the CCA. CONCLUSIONS: The new AI procedure identifies both IM boundaries in the region of the far wall of the CCA and carotid bulb with high precision, and eliminates most of the intra- and inter-reader variability of the IMT measurement using MT.
Adult↗
Identification of conformation-dependent epitopes and V gene selection in the B cell response to type II collagen in the DA rat.
Collagen-induced arthritis (CIA) is a widely used model for rheumatoid arthritis. Induction of CIA in rats using rat type II collagen (CII) results in a chronic arthritis in which anti-CII antibodies are believed to play a pathogenic role. In this study, we analyzed the epitope selection and V gene usage in the anti-CII response in the DA rat. A panel of CII-reactive B cell hybridomas was established from the draining lymph nodes 11 days after immunization. All of the CII-specific antibodies bound cartilage in vivo, showing that these are true autoantibodies. These antibodies were all IgG and specific for several distinct triple helical epitopes on CII. Interestingly, the major epitope, recognized by four different antibodies, was identical with the major B cell epitope in the mouse CII located at position 359--369 (denoted as C1(III)). The Q52 and PC7183 V(H) gene families encoded 12 out of 14 sequenced heavy chains. There was a relatively more heterogeneous usage of V(L) genes as the antibodies were encoded by four different V(kappa) families (V(kappa)1, V(kappa)2, V(kappa)12/13 and V(kappa)RF). As in the mouse, some of the V genes used showed germline characteristics. We conclude that the immune response in the rat shares epitope specificity and a constrained V gene repertoire with the mouse. However, the V genes used for recognition of the closely related collagen structures differed considerably between mouse and rat, indicating an influence of the species-specific variation in the V gene repertoire.
Amino Acid Sequence↗
Effect of different doses of prostaglandin E2 on intrauterine pressure and uterine motility during diestrus in experimental cows.
Studies in human medicine proved the important role of prostaglandin E2, which stimulates uterine contractions in vivo and in vitro and has been extensively used to ripen the cervix around labor. We wanted to demonstrate that increasing the dosage of prostaglandin E2 (1.25 mg, 2.5 mg, 5 mg and 10 mg) provokes an increase in intrauterine pressure and uterine motility in cattle. Five healthy, lactating dairy cows were used as experimental animals for this study. Intrauterine pressure was recorded during the diestrus phase (1 recording per cow and diestrus phase) by means of a transcervically placed intraluminal pressure microtransducer. Physiologic uterine motility was recorded for 30 min, then placebo or one of the prostaglandin E2- dosages was administered through an indwelling catheter in the jugular vein, followed by a 2-h recording period (eight 15-min periods). Area under the curve (AUC), mean amplitude, frequency of pressure waves and intrauterine pressure were analyzed. Furthermore, we recorded protocols for monitoring heart and respiratory rates and side effects at 9 given examination times. Significant differences were found for the AUC, the mean amplitude and the intrauterine pressure (P < or = 0.05), whereas the number of pressure waves per 15 min did not differ significantly among treatments. Peak values for AUC, mean amplitude and intrauterine pressure were found during the first 15 min after administration of 10 mg of prostaglandin E2. Dose-effect curves showed that the 2.5 mg dosage provided the optimal ratio between myometrial stimulation and undesirable side-effects.
Animals↗
Synergistic activation of the mkp-1 gene by protein kinase A signaling and USF, but not c-Myc.
Mitogen-activated protein kinase phosphatase 1 (MKP-1) is negatively regulating mitogen-activated protein kinases and is therefore involved in early signaling processes. The expression of the mkp-1 gene is induced by growth factors and stress. The promoters of the human and murine mkp-1 genes contain several conserved DNA binding elements, including two cAMP response elements and an E box. We observed that the upstream stimulatory factor (USF), but not c-Myc, activated mkp-1. USF synergized with protein kinase A, thus providing evidence for a role of the E box, during signal-regulated stimulation of mkp-1.
Animals↗
123I-antileukoproteinase scintigraphy reveals microscopic cartilage alterations in the contralateral knee joint of rats with "monarticular" antigen-induced arthritis.
OBJECTIVE: To assess the involvement of the contralateral knee joint in monarticular antigen-induced arthritis (AIA) by scintigraphy with the cationic (pI >10), 123I-labeled, serine proteinase inhibitor antileukoproteinase (123I-ALP) and to compare the scintigraphic findings with those of radiography and high-resolution ex vivo magnetic resonance imaging (MRI). METHODS: Lewis rats with chronic AIA were examined 2.5 months following arthritis induction (injection of 500 microg of methylated bovine serum albumin/saline into the ipsilateral [arthritic] knee joint and injection of phosphate buffered saline into the contralateral knee joint following systemic immunization). 123I-ALP was injected intravenously into normal rats (n = 4) or rats with AIA (n = 6). The ipsilateral and contralateral knee joints and both ankles were examined by scintigraphy and radiography. Joint cartilage was examined by high-resolution ex vivo MRI, histopathology, and measurement of tissue radioactivity. RESULTS: ALP accumulation (typically observed in normal articular cartilage) was lost in both the ipsilateral and the contralateral knee joints, but not in the clinically unaffected ankles of rats with AIA. In both knee joints, 123I-ALP target:background ratios and cartilage radioactivity correlated negatively with the loss of toluidine blue staining in cartilage, which documents the depletion of charged matrix molecules. Findings of histopathology confirmed mild alterations in the ipsilateral knee joint and even milder alterations in the contralateral knee joint, while the ankles were normal. Radiography and high-resolution ex vivo MRI failed to detect abnormalities in the contralateral knee joint. CONCLUSION: Loss of ALP accumulation appears to document proteoglycan depletion, even in the microscopically altered cartilage of the contralateral knee joint in AIA. These findings underscore the high sensitivity of 123I-ALP for in vivo detection of biochemical cartilage alterations in arthritis, and furthermore, question the use of the contralateral knee joint as a normal control in AIA.
Animals↗
[Prospective multicenter observational study of early rheumatoid arthritis--prognostic factors and predictors of disease course].
The aim of a new prospective, multicenter trial on early rheumatoid arthritis is to evaluate parameters of potential relevance for the prediction of an erosive disease course. The integration of general practitioners, rheumatologists, arthritis care units and experimental research groups in a network structure is intended to improve the cooperation between basic and clinical research as well as the treatment of the patients. The final goal is to identify new parameters that may improve an early stratification of patients into the appropriate treatment areas.
Adult↗
Interaction of the fork head domain transcription factor MPP2 with the human papilloma virus 16 E7 protein: enhancement of transformation and transactivation.
The high risk human papillomavirus (HPV) type 16 E7 protein affects cell growth control and promotes transformation by interfering with functions of cellular proteins. A key target of E7 is the tumor suppressor protein p105RB. Although this interaction is required for E7-dependent transformation, other cellular molecules must also be involved, because some E7 mutants that have reduced transforming abilities still bind to p105RB. In order to identify additional proteins that interact with E7 and that may be responsible to mediate its transforming function, we have used the C-terminal half of E7 in a yeast two-hybrid screen. We identified the fork head domain transcription factor M phase phosphoprotein 2 (MPP2) as an interaction partner of E7. Specific interaction of the two proteins both in vitro and in vivo in mammalian cells was detected. The interaction of MPP2 with E7 is functionally relevant since MPP2 enhances the E7/Ha-Ras co-transformation of rat embryo fibroblasts. In addition HPV16 E7, but neither non-transforming mutants of HPV16 E7 nor low risk HPV6 E7, was able to stimulate MPP2-specific transcriptional activity. Thus, MPP2 is a potentially important target for E7-mediated transformation.
Animals↗
Goodpasture disease. Characterization of a single conformational epitope as the target of pathogenic autoantibodies.
Goodpasture disease is a prototype autoimmune disease characterized by the formation of autoantibodies against the heterotrimeric basement membrane collagen type IV, which causes a rapidly progressive glomerulonephritis. The pathogenic antibody response is directed to the non-collagenous (NC1) domain of the alpha3 chain of type IV collagen (alpha3(IV)NC1), but not to the homologous region of the alpha1(IV)NC1. To identify the conformation-dependent immunodominant epitope on the alpha3(IV)NC1, a variety of recombinant NC1 domains were constructed by replacing single residues of alpha3(IV) with the corresponding amino acids from the nonreactive alpha1(IV) chain. Replacement mutations were identified that completely destroyed the Goodpasture epitope in the alpha3(IV) chain. Based on the identification of these critical positions, the epitope was finally reconstructed within the frame of the alpha1(IV) chain. The substitution of nine discontinuous positions in the alpha1(IV)NC1 with amino acid residues from the alpha3 chain resulted in a recombinant construct that was recognized by all patients' sera (n = 20) but by none of the sera from healthy controls (n = 10). This provides, for the first time, the molecular characterization of a single immunodominant conformational epitope recognized by pathogenic autoantibodies in a human autoimmune disease, representing the basis for the development of new epitope-specific strategies in the treatment of Goodpasture disease.
Anti-Glomerular Basement Membrane Disease↗
Up-regulation of MDC15 (metargidin) messenger RNA in human osteoarthritic cartilage.
OBJECTIVE: The aim of the study was to investigate the messenger RNA (mRNA) expression of the disintegrin metalloproteinase MDC15 (metargidin, or ADAM-15) in normal and osteoarthritic (OA) articular cartilage. METHODS: In situ hybridization experiments and reverse transcription-polymerase chain reaction (RT-PCR) were performed on tissue samples of adult normal and OA articular cartilage. RESULTS: MDC15 mRNA could be detected in normal articular cartilage by RT-PCR using tissue-extracted total RNA as a template. However, the mRNA level remained below the sensitivity of in situ hybridization. In contrast, in situ hybridizations of OA cartilage revealed an intense staining with the MDC15-specific riboprobes. The extension of the analysis to chondrosarcomas showed a strong up-regulation of MDC15 mRNA in these malignant transformed cells. CONCLUSION: Our results demonstrate a markedly strong up-regulation of MDC15 in adult OA and neoplastic cartilage compared with adult normal articular cartilage, indicating a potential role of the disintegrin metalloproteinase in cartilage remodeling.
ADAM Proteins↗
Effect of two dosages of d-cloprostenol on intrauterine pressure and uterine motility during dioestrus in experimental cows.
Prostaglandins are commonly used in herd management for their luteolytic properties; however, prostaglandins also have a direct contractile effect on the myometrium. We hypothesized that different dosages (0.15 and 0.3 mg) of d-cloprostenol, a synthetical prostaglandin F2 alpha preparation, would differ as to their contractile effects on the uterus. Intrauterine pressure was recorded during dioestrus of lactating dairy cows, using a transcervically placed intraluminal pressure microtransducer. After recording of physiological uterine motility for 30 min, a placebo or d-cloprostenol at one of the two different dosages was administered intramuscularly, followed by a 2-h recording period. Significant differences were found for the area under the curve (P < or = 0.05) and mean amplitude (P < or = 0.05), whereas the number of spikes per 15 min and the baseline pressure during the last 3 min of every 15-min period did not differ significantly among treatments. Peak values for area under the curve and mean amplitude were found between 15 and 30 min after administration of the lower dosage of d-cloprostenol, and between 75 and 90 min after administration of the higher dosage. Using the higher dosage of d-cloprostenol, a steady plateau from 15 to 30 min after administration until the end of the recording session was obtained. Thus, double the luteolytic dose of the d-cloprostenol preparation gives a significantly better reaction in terms of uterine contractility than the single dose.
Animals↗
Identification of a clinically relevant immunodominant region of collagen IV in Goodpasture disease.
BACKGROUND: The characteristic feature of Goodpasture disease is the occurrence of an autoantibody response to the noncollagenous domain of the alpha3 chain of type IV collagen [alpha3(IV)NC1] in the alveolar and glomerular basement membrane. These antibodies are associated with the development of a rapidly progressive glomerulonephritis, with or without lung hemorrhage, whereas autoantibodies specific for the other alpha chains of the heterotrimeric type IV collagen probably do not cause disease. In this study, we have investigated whether differences in fine specificity of autoimmune recognition of the alpha3(IV)NC1 correlate with clinical outcome. METHODS: For mapping of antibody binding to type IV collagen, chimeric collagen constructs were generated in which parts of the alpha3(IV)NC1 domain were replaced by the corresponding sequences of homologous nonreactive alpha1(IV). The different recombinant collagen chimeras allowed the analysis of antibody specificities in 77 sera from well-documented patients. RESULTS: One construct that harbors the aminoterminal third of the alpha3(IV)NC1 was recognized by all sera, indicating that it represents the dominant target of the B-cell response in Goodpasture disease. Seventy percent of the samples recognized other parts of the molecule as well. However, only reactivity to the N-terminus of the alpha3(IV)NC1 correlated with prognosis, that is, kidney survival after six months of follow-up. CONCLUSION: The results indicate the crucial importance of antibody recognition of this particular domain for the pathogenesis of Goodpasture disease, thereby opening new avenues for the development of better diagnostic and therapeutic procedures.
Anti-Glomerular Basement Membrane Disease↗
Symptomatic bone lesion of the tibia head as onset manifestation of sarcoidosis.
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Adult↗
Arthritis-related B cell epitopes in collagen II are conformation-dependent and sterically privileged in accessible sites of cartilage collagen fibrils.
In collagen-induced arthritis, a murine autoimmune model for rheumatoid arthritis, immunization with native but not heat-denatured cartilage-specific collagen type II (CII) induces a B cell response that largely contributes to arthritogenicity. Previously, we have shown that monoclonal antibodies established from arthritis prone DBA/1 mice require the triple-helical conformation of their epitopes for antigen recognition. Here, we present a novel approach to characterize arthritis-related conformational epitopes by preparing a panel of 130 chimeric collagen X/CII molecules. The insertion of a series of CII cassettes into the triple-helical recombinant collagen X allowed for the first time the identification of five triple-helical immunodominant domains of 5-11 amino acid length, to which 75% of 36 monoclonal antibodies bound. A consensus motif, "R G hydrophobic," was found in all immunodominant epitopes. The antibodies were encoded by a certain combination of V-genes in germline configuration, indicating a role of the consensus motif in V-gene selection. The immunodominant domains are spread over the entire monomeric CII molecule with no apparent order; however, a highly organized arrangement became apparent when the CII molecules were displayed in the quarter-staggered assembly within a fibril. This discrete epitope organization most likely reflects structural constraints that restrict the exposure of CII epitopes on the surface of heterotypically assembled cartilage fibrils. Thus, our data suggest a preimmune B cell selection process that is biased by the accessibility of CII determinants in the intact cartilage tissue.
Animals↗
Immunological treatment of autoimmune diseases.
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Animals↗
Effect of different prostaglandins on intrauterine pressure and uterine motility during diestrus in experimental cows.
Prostaglandins are widely used in herd management due to their luteolytic properties. They have also a direct effect on the myometrium. We hypothesized, that dissimilar prostaglandin preparations would differ as to their contractile effect. Intrauterine pressure was recorded during the diestrus of lactating dairy cows using a transcervically placed intraluminal pressure microtransducer. After recording physiologic uterine motility for 30 min, prostaglandins (dinoprost, DL-cloprostenol, D-cloprostenol) or a placebo was administered intramuscularly, followed by a 2-h recording period. Significant differences were found for the area under the curve (P < or = 0.05) and mean amplitude (P < or = 0.05), whereas the number of spikes per 15 min and the baseline pressure during the last 3 min of every recording period did not differ significantly among treatments. Peak values for area under the curve and mean amplitude were found between 15 and 30 min after administration of DL-cloprostenol, while dinoprost yielded the steadiest plateau from this period until the end of the recording session. These results contrast with those of earlier studies comparing prostaglandins after intravenous administration.
Animals↗
Mapping of a carboxyl-terminal active site of parathyroid hormone by calcium-imaging.
We recently showed that the C-terminal fragment PTH (52-84) effectively increases intracellular free calcium ([Ca2+]i) in a subset of growth plate chondrocytes not activated by the N-terminal PTH fragment (1-34). Here we characterize the active site on C-terminal PTH (52-84) with respect to calcium (Ca2+)-signaling and the mechanism involved by using synthetic PTH-subfragments in digital CCD ratio-imaging experiments. Our results show amino acids 73-76 to be the core region for increasing [Ca2+]i. Ryanodine (1 microM), caffeine (10 mM), lithium (2 mM), or cyclopiazonic acid (2-5 microM), agents that interfere with intracellular Ca2+ release, all failed to block PTH (52-84) induced [Ca2+]i increases. Depletion of extracellular calcium ([Ca2+]o) blocked PTH (52-84) induced [Ca2+]i increases, indicating a transmembrane Ca2+ influx. In contrast to voltage-gated and Ca2+ release activated Ca2+ influx, PTH (52-84) evoked Ca2+ influx was not blocked by nickel (1 mM). We conclude that PTH amino acids 73-76 are essential for activation of a nickel-insensitive Ca2+ influx pathway in growth plate chondrocytes that is likely to be of relevance for matrix calcification, a key step in endochondral bone formation.
Binding Sites↗