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J P Buyon

Publications and source records attributed to J P Buyon.

At least 19 recordsLinked to original sources
PubMed2004

Neonatal lupus syndromes.

The neonatal lupus syndromes (NLS), while quite rare, carry significant mortality and morbidity in cases of cardiac manifestations. Although anti-SSA/Ro-SSB/La antibodies are detected in > 85% of mothers whose fetuses are identified with congenital heart block (CHB) in a structurally normal heart, when clinicians applied this testing to their pregnant patients, the risk for a woman with the candidate antibodies to have a child with CHB was at or below 1 in 50. While the precise pathogenic mechanism of antibody-mediated injury remains unknown, it is clear that the antibodies alone are insufficient to cause disease and fetal factors are likely contributory. In vivo and in vitro evidence supports a pathologic cascade involving apoptosis of cardiocytes, surface translocation of Ro and La antigens, binding of maternal autoantibodies, secretion of profibrosing factors (e.g., TGFbeta) from the scavenging macrophages and modulation of cardiac fibroblasts to a myofibroflast scarring phenotype. The spectrum of cardiac abnormalities continues to expand, with varying degrees of block identified in utero and reports of late onset cardiomyopathy (some of which display endocardial fibroelastosis). Moreover, there is now clear documentation that incomplete blocks (including those improving in utero with dexamethasone) can progress postnatally, despite the clearance of the maternal antibodies from the neonatal circulation. Better echocardiographic measurements which identify first degree block in utero may be the optimal means of approaching pregnant women at risk. Prophylactic therapies, including treatment with intravenous immunoglobulin, await larger trials. In order to achieve advances at both the bench and bedside, national research registries established in the US and Canada are critical.

Autoantibodies↗
PubMed2002

Spectrum and progression of conduction abnormalities in infants born to mothers with anti-SSA/Ro-SSB/La antibodies.

The classic cardiac manifestation of neonatal lupus is congenital heart block, attributed to antibody-mediated inflammation and subsequent fibrosis of the atrioventricular (AV) node. In considering the pathologic process of injury it may be that tissue damage results in a range of conduction abnormalities. Identification of less-advanced degrees of block or of fibrosis around the AV node without any conduction abnormality on EKG would support this pathologic model, and serve as a potential marker for treatment if the conduction defect could be shown to progress. To ascertain the spectrum of arrhythmias associated with maternal anti-SSA/Ro-SSB/La antibodies, records of all children enrolled in the Research Registry for Neonatal Lupus were reviewed. Of 187 children with congenital heart block whose mothers have anti-SSA/Ro-SSB/La antibodies, nine had a prolonged PR interval on EKG at birth, four of whom progressed to more advanced AV block. A child whose younger sibling had third degree block was diagnosed with first degree block at age 10 years at the time of surgery for a broken wrist. Two children diagnosed in utero with second degree block were treated with dexamethasone and reverted to normal sinus rhythm by birth, but ultimately progressed to third degree block. Four children had second degree block at birth: of these, two progressed to third degree block. Sinus bradycardia (< 100 bpm) was present in three (3.8%) of 78 fetuses for whom atrial rates were recorded by echocardiogram. Of 40 neonates for whom EKGs were available, the mean atrial rate was 137+/-20 bpm (range 75-200). These data have important research and clinical implications. In contrast to the AV node, permanent sinoatrial nodal involvement is not clinically apparent. Perhaps many fetuses sustain mild inflammation, but resolution is variable, as suggested by the presence of incomplete AV block. Since subsequent progression of less-advanced degrees of block can occur, an EKG should be performed on all infants born to mothers with anti-SSA/Ro-SSB/La antibodies.

Antibodies, Antinuclear↗
PubMed2001

Leucine zipper domain of 52 kDa SS-A/Ro promotes protein dimer formation and inhibits in vitro transcription activity.

Two forms of the human 52 kDa SS-A/Ro protein autoantigen, 52alpha and 52beta, are products of alternative mRNA splicing. The 52alpha form is ubiquitously expressed whereas 52beta, lacking the central leucine zipper domain, has been detected at higher levels than 52alpha during certain stages of fetal development. Because 52alpha has sequence similarity with macromolecules associated with transcriptional regulation and the two forms differ only in that 52beta does not contain the leucine zipper, their roles in protein dimer formation and in transcriptional activity were examined. Employing the yeast two-hybrid system, 52alpha was shown to interact with itself but not 52beta. The homodimerization of 52alpha was independently confirmed in gel filtration chromatography using in vitro cDNA template derived translation products and in HL-60 cell extracts; two peaks were observed corresponding to dimer and monomer of 52alpha, while in vitro the translation product of 52beta exhibited only a single monomer peak. In addition, dimer formation was also demonstrated in a chemical cross-linking experiment using HeLa cells transfected with 52alpha. To evaluate effects on transcription, eukaryotic expression plasmids encoding 52alpha or 52beta fused with the GAL4 DNA binding (DB) domain were co-transfected into 293 cells together with a luciferase reporter vector. A 6-fold increase in transcription activity of the reporter was detected with the GAL4-DB-52beta fusion constructs compared to GAL4-DB-52alpha or the empty vector control. We speculate that the ratio of cellular 52alpha and 52beta may play an important role in regulating gene expression as potential repressor and activator respectively.

Autoantigens↗
PubMed2001

Congenital heart block: development of late-onset cardiomyopathy, a previously underappreciated sequela.

OBJECTIVE: We report 16 infants with complete congenital heart block (CHB) who developed late-onset dilated cardiomyopathy despite early institution of cardiac pacing. BACKGROUND: Isolated CHB has an excellent prognosis following pacemaker implantation. Most early deaths result from delayed initiation of pacing therapy or hemodynamic abnormalities associated with congenital heart defects. METHODS: A multi-institutional study was performed to identify common clinical features and possible risk factors associated with late-onset dilated cardiomyopathy in patients born with congenital CHB. RESULTS: Congenital heart block was diagnosed in utero in 12 patients and at birth in four patients. Ten of 16 patients had serologic findings consistent with neonatal lupus syndrome (NLS). A pericardial effusion was evident on fetal ultrasound in six patients. In utero determination of left ventricular (LV) function was normal in all. Following birth, one infant exhibited a rash consistent with NLS and two had elevated hepatic transaminases and transient thrombocytopenia. In the early postnatal period, LV function was normal in 15 patients (shortening fraction [SF] = 34 +/- 7%) and was decreased in one (SF = 20%). A cardiac pacemaker was implanted during the first two weeks of life in 15 patients and at seven months in one patient. Left ventricular function significantly decreased during follow-up (14 days to 9.3 years, SF = 9% +/- 5%). Twelve of 16 patients developed congestive heart failure before age 24 months. Myocardial biopsy revealed hypertrophy in 11 patients, interstitial fibrosis in 11 patients, and myocyte degeneration in two patients. Clinical status during follow-up was guarded: four patients died from congestive heart failure; seven required cardiac transplantation; one was awaiting cardiac transplantation; and four exhibited recovery of SF (31 +/- 2%). CONCLUSIONS: Despite early institution of cardiac pacing, some infants with CHB develop LV cardiomyopathy. Patients with CHB require close follow-up not only of their cardiac rate and rhythm, but also ventricular function.

Cardiomyopathy, Dilated↗
PubMed2001

Interaction between 52 kDa SSA/Ro and deubiquitinating enzyme UnpEL: a clue to function.

The detection of isolated heart block in utero strongly predicts the presence of maternal autoantibodies reactive with 52 kDa SSA/Ro. The mechanisms that underlie this observation may be elucidated by defining the function of the target antigen. The initial approach was to identify proteins interactive with 52Ro using transcriptional activity in the yeast 2-hybrid system. A cDNA library was constructed using RNA isolated from human fetal hearts (12-23 weeks) and cloned into the HybriZAP vector encoding the activation domain of GAL4(AD) as target. Approximately 7 x 10(6) cDNAs were cotransformed with the bait into YRG-2. Plasmids from five interactive colonies were sequenced and three identified as the specific human deubiquitinating enzyme, UnpEL. UnpEL did not interact with bait plasmid encoding 52 beta, an alternative leucine zipper-minus form of 52 kDa SSA/Ro which is maximally expressed in fetal life. The mammalian 2-hybrid assay confirmed the interaction between full-length 52Ro and UnpEL. Further support for a biologic interaction was the marked redistribution in cellular localization of UnpEL following cotransfection of the two proteins into cultured human cardiocytes, human renal carcinoma cells (293 cells), and monkey kidney fibroblasts (COS-1). In conclusion, the interaction of full-length 52Ro and UnpEL implies that the former may also be involved in the ubiquitin pathway, an observation of particular interest since 52Ro contains a RING finger domain, a motif common to several recently reported proteins involved in modulating ubiquitination. The absence of an interaction with 52 beta raises the consideration that regulation of protein ubiquitination might differ in fetal life.

Animals↗
PubMed2000

Anti-SSA/Ro and anti-SSB/La autoantibodies bind the surface of apoptotic fetal cardiocytes and promote secretion of TNF-alpha by macrophages.

Despite the near universal association of congenital heart block and maternal Abs to SSA/Ro and SSB/La, the intracellular location of these Ags has made it difficult to substantiate their involvement in pathogenicity. To define whether components of the SSA/Ro-SSB/La complex, which translocate during apoptosis, are indeed accessible to extracellular Abs, two approaches were taken: immunoprecipitation of surface biotinylated proteins and scanning electron microscopy. Human fetal cardiocytes from 16-24-wk abortuses were cultured and incubated with staurosporine to induce apoptosis. Surface biotinylated 48-kDa SSB/La was reproducibly immunoprecipitated from apoptotic, but not nonapoptotic cardiocytes. Surface expression of SSA/Ro and SSB/La was further substantiated by scanning electron microscopy. Gold particles (following incubation with gold-labeled sera containing various specificities of anti-SSA/Ro-SSB/La Abs and murine mAb to SSB/La and 60-kDa SSA/Ro) were consistently observed on early and late apoptotic cardiocytes. No particles were seen after incubation with control antisera. To evaluate whether opsonized apoptotic cardiocytes promote inflammation, cells were cocultured with macrophages. Compared with nonapoptotic cardiocytes or apoptotic cardiocytes incubated with normal sera, apoptotic cardiocytes preincubated with affinity-purified Abs to SSB/La, 52-kDa SSA/Ro, or 60-kDa SSA/Ro increased the secretion of TNF-alpha from cocultured macrophages. In summary, apoptosis results in surface accessibility of all SSA/Ro-SSB/La Ags for recognition by circulating maternal Abs. It is speculated that in vivo such opsonized apoptotic cardiocytes promote an inflammatory response by resident macrophages with damage to surrounding conducting tissue.

Antibodies, Antinuclear↗
PubMed2000

Expression of SS-A/Ro and SS-B/La antigens in skin biopsy specimens of patients with photosensitive forms of lupus erythematosus.

CONTEXT: The reason that only some patients with lupus erythematosus (LE) develop autoantibodies to SS-A/Ro and SS-B/La antigens and photosensitivity is unknown. One hypothesis is that both events are related to the level of expression of these antigens in the skin. OBJECTIVE AND DESIGN: To test this hypothesis, we measured the expression of the 52-kd SS-A/Ro, 60-kd SS-A/Ro, and 48-kd SS-B/La antigens in normal sun-protected and sun-exposed skin in 14 patients with LE with photosensitivity, 12 patients with LE without photosensitivity, and 4 normal individuals. The presence of circulating antibodies to these antigens was measured in all patients. SETTING: Outpatient clinic in an academic medical center. RESULTS: We found that the expression of the 52-kd SS-A/Ro, 60-kd SS-A/Ro, and 48-kd SS-B/La antigens in skin biopsy specimens obtained from the same site was 4- to 10-fold higher in patients with LE with photosensitivity than in those patients with LE without photosensitivity (P<.001). Antigen expression was highly correlated with the presence and titer of circulating anti-SS-A/Ro and anti-SS-B/La antibodies (P<.001). CONCLUSIONS: These findings indicate that photosensitivity and the presence and titer of circulating anti-SS-A/Ro and anti-SS-B/La antibodies are both directly correlated with the expression of accessible and immunoreactive SS-A/Ro and SS-B/La antigens in the skin specimens of patients with LE. Thus, the expression of these antigens in keratinocytes may be an important determinant of the development of both SS-A/Ro and SS-B/La autoantibodies and of photosensitive forms of LE.

Adult↗
PubMed2000

Cutaneous manifestations of neonatal lupus without heart block: characteristics of mothers and children enrolled in a national registry.

OBJECTIVE: To extend the information base on cutaneous manifestations of neonatal lupus erythematosus (NLE) with regard to maternal disease, sex of child, onset, localization, influence of UV light, prognosis, and recurrence rates in subsequent pregnancies. METHODS: Review of records from the Research Registry for Neonatal Lupus. RESULTS: The cohort includes 47 mothers (83% white) whose sera contain anti-SSA/Ro, anti-SSB/La, and/or anti-U1-ribonucleoprotein antibodies and their 57 infants (20 boys and 37 girls) diagnosed with cutaneous NLE (absent heart disease) between 1981 and 1997. At detection of the child's rash, 13 mothers were asymptomatic, 11 had an undifferentiated autoimmune syndrome (UAS), 9 had systemic lupus erythematosus (SLE), 7 Sjögren's syndrome (SS), 6 SLE/SS, and 1 rheumatoid arthritis/SS; 20 reported photosensitivity. Within 5 years, 7 asymptomatic mothers experienced disease progression: 1 developed photosensitivity, 2 SLE, 3 SS, 1 SLE/SS; in 2 mothers UAS progressed to SLE; and 2 mothers with SS developed SLE. The infant's rash often followed UV light exposure; mean age at detection was 6 weeks, and mean duration was 17 weeks. All had facial involvement (periorbital region most common) followed by the scalp, trunk, extremities, neck, and intertriginous areas. In 37, the rash resolved without sequelae, 43% of which were untreated. A quarter had residual sequelae that included telangiectasia and dyspigmentation. One child developed Hashimoto's thyroiditis, and 2 developed systemic-onset juvenile rheumatoid arthritis. Of 20 subsequent births, 7 children were healthy, 2 had congenital heart block (CHB) only, 4 CHB and skin rash, and 7 skin rash only. CONCLUSIONS: Future pregnancies should be monitored by serial echocardiograms, given the substantial risk for heart block. Affected children should be observed for later development of a rheumatic disease.

Adult↗
PubMed1999

Comparison of treatment with fluorinated glucocorticoids to the natural history of autoantibody-associated congenital heart block: retrospective review of the research registry for neonatal lupus.

OBJECTIVE: To compare intervention with fluorinated glucocorticoids to the natural history of untreated congenital heart block (CHB) with respect to conduction abnormalities, associated effusions, ascites, and hydrops fetalis, and the requirement for a pacemaker. METHODS: Records of all mothers enrolled in the Research Registry for Neonatal Lupus were reviewed. The cohort includes 47 mothers whose sera contain anti-SSA/Ro or anti-SSB/La antibodies, and their 50 offspring with CHB, in whom at least 4 echocardiograms were performed after in utero diagnosis. In 28 pregnancies, mothers received dexamethasone 4-9 mg/day for 3-19 weeks or betamethasone 12-24 mg/week for >6 weeks (group A). In 22 pregnancies, fluorinated steroids were not used (group B). RESULTS: Third-degree block was present in 21 fetuses in group A and 18 fetuses in group B; none were reversible despite steroid treatment. Three fetuses in group A and 2 in group B progressed from second-degree block, alternating with third-degree block, to permanent third-degree block at birth and postnatally. Of 4 fetuses in group A with second-degree block at presentation, all reverted to first-degree block by birth; 2 remain so at age 4 years, 1 alternates between first-degree and second-degree block at 2 years, and the fourth is in second-degree block at age 4 years. Of 2 fetuses in group B with second-degree block at presentation, both progressed to permanent third-degree block postnatally. Initial echocardiographic evaluation revealed pericardial effusions in 13 group A versus 4 group B fetuses, pleural effusions in 2 group A versus 0 group B, ascites in 8 group A versus 0 group B (P < 0.007), hydrops fetalis in 8 group A versus 0 group B (P < 0.007), and intrauterine growth restriction in 1 group A versus 1 group B. Pericardial effusions resolved and reappeared in both groups. Steroid therapy was most effective in the resolution of pleural effusions (2 of 2), ascites (6 of 8), and hydrops fetalis (5 of 8). Oligohydramnios ensued in 9 group A and 2 group B fetuses. Although fetuses in group A had more complications at presentation than those in group B, there were no significant differences in the duration of pregnancy (35.7 weeks versus 37.0 weeks), the number of deaths (4 versus 1), final degree of heart block, or requirement for a pacemaker (14 versus 11). CONCLUSION: While prospective trials are needed, these data suggest that fluorinated steroids should be considered for fetuses with incomplete block or hydropic changes. Serial echocardiograms are recommended to monitor fetal progress. It remains to be determined whether third-degree block is reversible if therapy is initiated immediately upon detection.

Autoantibodies↗
PubMed1999

Defining a novel 75-kDa phosphoprotein associated with SS-A/Ro and identification of distinct human autoantibodies.

Mothers of children with neonatal lupus erythematosus (NLE) and heart block, as well as patients with Sjögren's syndrome (SS) and systemic lupus erythematosus, have serum autoantibodies that recognize SS-A/Ro autoantigens including the 60-kDa ribonucleoprotein. By yeast 2-hybrid screening, we identified a novel 75-kDa protein (pp75) that interacts with the carboxyl 70% of 60-kDa SS-A/Ro. The specificity of interaction was confirmed using mammalian 2-hybrid and chemical crosslinking studies. Immunoprecipitation with radiolabeled HeLa cell extracts showed that pp75 was phosphorylated and associated with 2 other phosphoproteins of 64 kDa. In Northern blot analysis, pp75 was expressed in all tissues analyzed; the highest expression was in the human heart. Based on immunofluorescence of transfected HeLa cells, pp75 is localized predominantly in the cytoplasm, an observation confirmed by immunohistochemistry in untransfected cells. Based on Western blot and ELISA assays, sera from 14 of 84 mothers of children with NLE recognized pp75, including 1 mother in whom anti-SS-A/Ro antibodies were not detected. In addition, sera from 5 of 80 patients with SS were positive for anti-pp75 antibody. Identification of molecular partners is a first step toward elucidating the functions and possible involvement in pathogenesis of long-recognized autoantigens such as 60-kDa SS-A/Ro, which are at present poorly understood.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Equivalence trials in SLE research: issues to consider.

In contrast to the objective of most clinical trials, which is to demonstrate superiority of an experimental treatment over a standard or placebo, the aim of an equivalence trial is to show that two treatments are equivalent in outcome or only marginally different. This would be of interest when an experimental treatment offers advantages such as reduced toxicity, ease of administration, or cost relative to the standard. Demonstrating equivalence may also be a goal when evaluating the safety of certain drugs because similarity in the risks of an adverse event in subjects exposed and unexposed to the drug is an indication of its safety. The classical formulation of the null hypothesis of treatment equality that is used in superiority trials is not applicable to equivalence trials because absolute equivalence between treatment groups cannot be proven. The strategy in equivalence trials is to define a maximum difference between treatment groups that is clinically acceptable and then assess whether there is sufficient evidence from the trial to conclude that the true treatment difference is within this acceptable range. In this paper, we discuss issues surrounding the planning, conduct, and analysis of equivalence trials in the context of SLE, with examples from the SELENA study.

Biometry↗
PubMed1999

mRNA and protein expression of SSA/Ro and SSB/La in human fetal cardiac myocytes cultured using a novel application of the Langendorff procedure.

Irreversible congenital heart block (CHB) and the transient rash of neonatal lupus are strongly associated with maternal antibodies to SSA/Ro and SSB/La proteins; however, the precise mechanism by which these antibodies mediate organ-specific injury is not yet defined. Culturing of keratinocytes has provided critical insights. Accordingly, successful culturing of human fetal cardiac myocytes at high yield would constitute a powerful tool to directly examine conditions that promote expression of the target autoantigens. To accomplish this aim, fetal cardiac myocytes from 18- to 22-wk abortuses were established in culture using a novel technique in which cells were isolated after perfusion of the aorta with collagenase in a Langendorff apparatus. After preplating to decrease fibroblast contamination, cardiocytes were grown in flasks and slide chambers. Staining with monoclonal anti-sarcomeric alpha-actinin revealed the expected striations typical of cardiac myocytes in 70-90% of the cells after 4 d in culture. Furthermore, the cells were observed to beat at rates varying between 25-75 beats per minute (bpm) after the addition of 1.8 mM CaCl2. An average yield of 45-60 x 10(6) cells was obtained from a 3- to 5-g heart. Cellular localization of SSA/Ro and SSB/La by indirect immunofluorescence and demonstration of mRNA expression by reverse transcriptase polymerase chain reaction supports the feasibility of cultured cardiac myocytes for the study of congenital heart block. In contrast to the increased expression of SSA/Ro reported for keratinocytes, incubation of cultured human cardiac myocytes with either 17beta-estradiol or progesterone did not alter mRNA expression or cellular localization of 48 kD SSB/La, 52 kD SSA/Ro, or 60 kD SSA/Ro. In summary, we describe a novel method to successfully culture human fetal cardiac myocytes that should provide a valuable resource for investigation of the molecular mechanism(s) contributing to the development of congenital heart block. Differential constitutive and estradiol-induced expression of 52 and 60 kD SSA/Ro in human cardiac myocytes compared with keratinocytes may be a factor contributing to the marked discordance of clinically detectable injury in these two target tissues.

Abortion, Induced↗