Ro 01-6128

Anti-La positive, anti-Ro negative subset of primary Sjogren's syndrome: anti-La is a reality but is the disease?[Pubmed:28229827]

Clin Exp Rheumatol. 2017 May-Jun;35(3):438-444. Epub 2017 Feb 20.

OBJECTIVES: To characterise the serological and clinical findings in primary Sjogren's syndrome in which anti-La was found without anti-Ro. We hypothesised that a significant portion of these are falsely negative for anti-Ro60. METHODS: Twenty-nine sera from primary Sjogren's syndrome patients were tested for antibodies directed against La and Ro. Anti-La was detected using bovine La treated with or without DNAase and RNAase to identify potential false positivity. Anti-Ro60 antibodies were detected using HEp-2000 substrate (in which cells are transfected with human Ro60) and HEp-2 substrate. Anti-Ro60 and Ro-52 were also tested by in vitro transcription/translation followed by immunoprecipitation assay. RESULTS: All 29 sera bound La, even after treatment with DNAase and RNAase. Of the 29 sera, 25 were unequivocally negative on HEp-2000 (1:40 dilution). Four samples were anti-Ro60 positive with a speckled pattern, three of the four at 1:320 dilution. Thus, false negative anti-Ro60 exists in a small fraction (14%) of the Ro-negative/La-positive primary Sjogren's patients. However, all the samples were negative for Ro60 and Ro52 by in vitro immunoprecipitation assay. Clinically these patients tended not to have salivary gland pathology characteristic of Sjogren's syndrome. CONCLUSIONS: We found only a small fraction of Ro negative/La positive sera to show positive HEp-2000 pattern. These subjects did not have characteristic findings on pathological examination of minor salivary glands, suggesting these subjects have a process distinct from Sjogren's syndrome.

Spontaneous Remission of Congenital Complete Atrioventricular Block in Anti-Ro/La Antibody-Negative Monozygotic Twins: Case Report.[Pubmed:28251027]

Balkan Med J. 2017 Jan;34(1):71-73.

BACKGROUND: Congenital complete atrioventricular block without any structural heart disease and anti-Ro/La negativity is very rare. Discordant complete atrioventricular block, which is more frequently defined in the literature as an autoimmune mechanism, is much more rare in monozygotic twins. CASE REPORT: The 26-year-old healthy mother had given birth in her first spontaneous, uneventful pregnancy to monozygotic twins at week 35. While the first twin's physical examination proved her to be normal with a pulse rate consistent with her age, the second twin had a pulse rate of approximately 40 beats/minute.The patient was confirmed to have congenital complete atrioventricular block. CONCLUSION: Despite this case appears to be an isolated one, a discordant complete atrioventricular block regression without any autoimmune evidence should be included in the differential diagnosis of bradycardia in infants.

Low titer, isolated anti Ro/SSA 60 kd antibodies is correlated with positive pregnancy outcomes in women at risk of congenital heart block.[Pubmed:28204891]

Clin Rheumatol. 2017 May;36(5):1155-1160.

Congenital heart block (CHB) is an autoantibody mediated disorder presumably caused by placental transmission of maternal autoantibodies to Ro/SSA 52 kd, p200, Ro/SSA 60 kd, La/SSB ribonucleoproteins. This study investigated the clinical significance of isolated anti-Ro/SSA 52 kd, anti-p200, anti-Ro/SSA 60 kd, and anti-La/SSB antibodies in positive pregnant patients. One hundred sixty-three pregnant women positive to anti-Ro/SSA 52 kd and/or anti-Ro/SSA 60 kd and/or anti-La/SSB antibodies were prospectively enrolled in the study. Anti-Ro52, anti-Ro60, anti-p200, and anti-La antibodies were assayed using home-made ELISA assays. Isolated antibody positivity was found in 25 women (15.3%), while multiple antibody positivity in 138 (84.7%). Twenty-four developed CHB, and the 139 had a favorable pregnancy outcome. The prevalence of isolated anti-Ro/SSA 60 kd antibodies was significantly higher (p < 0.046) as the prevalence of lower mean antibody titers (p < 0.0001) in the later group. Confirmation of these results by large-scale studies could lead clinicians to recommend less stringent fetal echocardiography monitoring in women with isolated anti-Ro/SSA 60 kd antibodies.

Neonatal lupus: Follow-up in infants with anti-SSA/Ro antibodies and review of the literature.[Pubmed:28212920]

Autoimmun Rev. 2017 Apr;16(4):427-432.

Neonatal Lupus Syndrome (NLS) is a distinct clinical entity caused by transplacental passage of maternal anti-SSA/Ro antibodies (Ab). Mothers may have systemic lupus erythematosus, Sjogren syndrome, or other connective tissue disease, or may be completely healthy at the time of giving birth. NLS includes several clinical manifestations: complete congenital heart block (CCHB) and cutaneous lupus are the most common, while hepatobiliary disease, hematological manifestations and central nervous system involvement may occur. Data from literature on the incidence of the different clinical manifestations of NLS are difficult to compare because they come mostly from retrospective studies or prospective studies, but up to date no systematic follow-up was carried out. We performed a large prospective single-center study with a systematic clinical and instrumental follow-up until 9months of life, in order to evaluate the incidence and the clinical impact of NLS features. From 2004 to 2014 all infants born in our center to mothers with anti-SSA/Ro Ab were enrolled in a specific diagnostic and follow-up (FU) program. At birth, 50 infants born to mothers with anti-SSA/Ro Ab were found positive for anti-SSA/Ro Ab. Infants were tested for anti SSA/Ro Ab at 3months of life, if positive they were re-tested at 6 and 9months. At 9months anti-SSA/Ro Ab were positive in 10% of children. In two cases (4%) a CCHB was identified during pregnancy and required pacemaker implantation at birth. In 10% of cases a transient ECG alterations was found during follow-up. Hematological NLS features (anemia, neutropenia, thrombocytopenia) were found at birth and during FU in several patients, in all cases without clinical manifestations and in most cases with complete normalization at 9months. Mild and transient elevation of aminotransferases between 3 and 6months of life were found in 56% and 40% of patient, respectively; non-specific ultrasound cerebral anomalies in absence of clinical neurological signs were found at birth in 9 patients (18%), subsequently normalized. Prenatal maternal screening is of primary importance in order to early detect CCHB, which requires maternal treatment and pacemaker implantation at birth. Infants born to mothers with anti-SSA/Ro Ab should be monitored for all NLS features at birth. However, during the first months of life, these infants seem to develop only mild, transient and self-limited clinical manifestations, which in most cases are completely solved at 9months of life. This consideration, together with the evidence that only 10% of infants had anti-SSA/Ro Ab persistent in blood at 9months, suggests that follow-up of these children can be performed until 6-9months of life with good clinical safety. Moreover, a clinical and laboratory monitoring at 3months of life, when the highest incidence of hematological features and liver tests alterations are observed, is strongly recommended. In the future, it would be clarified if a follow-up until adulthood would be indicated in cases with persistent anti SSA/Ro or in all infants born to mother with anti SSA/Ro.

Activation of a dimeric metabotropic glutamate receptor by intersubunit rearrangement.[Pubmed:17855348]

J Biol Chem. 2007 Nov 9;282(45):33000-8.

Although many G protein-coupled receptors (GPCRs) can form dimers, a possible role of this phenomenon in their activation remains elusive. A recent and exciting proposal is that a dynamic intersubunit interplay may contribute to GPCR activation. Here, we examined this possibility using dimeric metabotropic glutamate receptors (mGluRs). We first developed a system to perfectly control their subunit composition and show that mGluR dimers do not form larger oligomers. We then examined an mGluR dimer containing one subunit in which the extracellular agonist-binding domain was uncoupled from the G protein-activating transmembrane domain. Despite this uncoupling in one protomer, agonist stimulation resulted in symmetric activation of either transmembrane domain in the dimer with the same efficiency. This, plus other data, can only be explained by an intersubunit rearrangement as the activation mechanism. Although well established for other types of receptors such as tyrosine kinase and guanylate cyclase receptors, this is the first clear demonstration that such a mechanism may also apply to GPCRs.

A novel class of positive allosteric modulators of metabotropic glutamate receptor subtype 1 interact with a site distinct from that of negative allosteric modulators.[Pubmed:16645124]

Mol Pharmacol. 2006 Aug;70(2):616-26.

We recently reported a novel class of compounds, represented by 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamide (CD-PPB), that act as positive allosteric modulators (potentiators) of metabotropic glutamate receptor (mGluR) subtype 5. Studies of CDPPB analogs revealed that some compounds in this series serve also as positive allosteric modulators of mGluR1. Although CDPPB is selective for mGluR5 relative to other mGluR subtypes, several CDPPB analogs also showed 2.5-fold potentiation of glutamate-induced calcium transients in cells expressing mGluR1 at 10 muM, with 4-nitro-N-(1,4-diphenyl-1H-pyrazol-5-yl)benzamide (VU-71) being selective for mGluR1. In previous studies, we found that two structural classes of mGluR5-selective allosteric potentiators, including CDPPB, share a common binding site with the allosteric mGluR5 antagonist 2-methyl-6-(phenylethynyl)pyridine. Negative allosteric modulators of mGluR1, regardless of structural class, have been reported to bind to a common allosteric antagonist site on this receptor. However, neither the novel CDPPB analogs nor previously identified allosteric mGluR1 potentiators [e.g., (S)-2-(4-fluorophenyl)-1-(toluene-4-sulfonyl)pyrrolidine (Ro 67-7476), ethyl diphenylacetylcarbamate (Ro 01-6128), and butyl (9H-xanthene-9-carbonyl)carbamate (Ro 67-4853)] displaced the binding of [(3)H]1-(3,4-dihydro-2H-pyrano[2,3-b]quinolin-7-yl)-2-phenyl-1-ethanone (R214127), a high-affinity radioligand for the allosteric antagonist site on mGluR1 at concentrations several orders of magnitude higher than those required to induce allosteric potentiation of mGluR1 responses. These data suggest that allosteric potentiators of mGluR1 act at a site that is distinct from that of allosteric antagonists of mGluR1. Site-directed mutagenesis revealed that valine at position 757 in transmembrane V of mGluR1a is crucial for the activity of multiple classes of allosteric mGluR1 potentiators.

Positive allosteric modulators of metabotropic glutamate 1 receptor: characterization, mechanism of action, and binding site.[Pubmed:11606768]

Proc Natl Acad Sci U S A. 2001 Nov 6;98(23):13402-7.

We have identified two chemical series of compounds acting as selective positive allosteric modulators (enhancers) of native and recombinant metabotropic glutamate 1 (mGlu1) receptors. These compounds did not directly activate mGlu1 receptors but markedly potentiated agonist-stimulated responses, increasing potency and maximum efficacy. Binding of these compounds increased the affinity of a radiolabeled glutamate-site agonist at its extracellular N-terminal binding site. Chimeric and mutated receptors were used to localize amino acids in the receptor transmembrane region critical for these enhancing properties. Finally, the compounds potentiated synaptically evoked mGlu1 receptor responses in rat brain slices. The discovery of selective positive allosteric modulators of mGlu1 receptors opens up the possibility to develop a similar class of compounds for other family 3 G protein-coupled receptors.