A b s t r a c tAntineutrophil cytoplasmic antibody (ANCA)

No abstract

There have been a number of recent advances in this field. First, the "International Consensus Statement on Testing and Reporting of Antineutrophil Cytoplasmic Antibodies (ANCA)" has been developed to optimize ANCA testing. It requires that all sera are tested by indirect immunofluorescent (IIF) examination of normal peripheral blood neutrophils and, where there is positive fluorescence, in enzyme-linked immunosorbent assays (ELISAs) for antibodies against both proteinase 3 (PR3) and myeloperoxidase (MPO). Testing will be further improved when international standards and common ELISA units are available. Second, new diagnostic criteria for the small vessel vasculitides that take into account ANCA-positivity and target antigen specificity as well as histologic features are currently being produced. Third, we understand that the complications associated with treatment of the ANCA-associated vasculitides are often more hazardous than the underlying disease, and regimens that use effective but less toxic agents are being evaluated. The factors associated with increased risk of relapse, however, remain incompletely understood. Finally, ANCA with specificities other than PR3 and MPO are present in many nonvasculitic autoimmune diseases. Their clinical significance is still largely unclear, and some of the target antigens are present in other cells as well as neutrophils and thus are not strictly "ANCA."

1 In this study we compared the vasoconstrictor activity of melatonin in rat isolated tail artery using two dierent recording systems, the Halpern pressure myograph and the Halpern-Mulvany wire myograph, with the view to determining a reliable method for obtaining pharmacological data on vascular melatonin receptors. In addition, we characterized the melatonin receptor in this preparation, using analogues of melatonin, and examined the activity of various naphthalenic derivatives with biological activity in non-vascular models of melatonin receptors. 2 Using the Halpern pressure myograph, cumulative addition of melatonin (0.1 nM to 1 mM) produced direct vasoconstriction (19.3+6.4% reduction in lumen diameter, n=5) in ®ve of 11 pressurized segments, with pEC 50 of 9.14+0.17. Similarly, non-cumulative application of melatonin caused vasoconstriction (19.7+4.6% reduction in lumen diameter, n=7) in seven of 20 preparations examined with pEC 50 of 8.74+0.26. The selective alpha 2 -adrenoceptor agonist, UK-14304 (5-bromo-6-[2-imidazolin-2-ylamino]-quinoxaline bitartrate), produced vasoconstriction in all`melatonin-insensitive' preparations.3 Melatonin (0.1 nM to 1 mM) failed to elicit isometric contractions of tail artery segments in the Halpern wire myograph, but produced concentration-dependent potentiation of electrically-evoked, isometric contractions (maximum eect of 150 ± 200% enhancement) when applied either noncumulatively (seven of seven preparations) or cumulatively (four of seven preparations). The pEC 50 value of melatonin (non-cumulative) was 8.50+0.10 (n=7) which was not dierent from that obtained in the pressure myograph. All further experiments were conducted using a non-cumulative protocol against electrically-evoked, isometric contractions. 4 Based on the pEC 50 values for the melatonin analogues examined, the pharmacological pro®le for the enhancement of electrically-evoked contractions was 2-iodomelatonin46-chloromelatonin5(7)-AMMTC 5 S216345melatonin5S200984S202425S2030446-hydroxymelatonin4S209324 (+) -AM-MTC4N-acetyl-5-HT. Our data suggests the vascular receptor belongs to the MEL 1 -like subtype. All the indole-based analogues of melatonin, 2-iodomelatonin, (7)-AMMTC, (+)-AMMTC, S20932, 6-chloromelatonin, 6-hydroxymelatonin and N-acetyl-5-HT, behaved as full agonists. All the naphthalenic derivatives examined, S21634, S20098, S20242 and S20304 behaved as partial agonists relative to melatonin. 5 The naphthalenic-based antagonists, S20928 and S20929, did not modify electrically-evoked, isometric contractions of the tail artery, but produced a parallel, rightward displacement of the melatonin concentration-response curve. Based upon the eect of 1 mM S20928 and S20929, the estimated pK B values for these antagonists were 7.18+0.25 (n=4) and 7.17+0.25 (n=5), respectively. 6 We demonstrated that enhancement of electrically-evoked, isometric contractions of the rat isolated tail artery (using the Halpern-Mulvany wire myograph) is a simple and reproducible model for assessing the activity of putative a...

Tetrahydrocyclopent[b]indoles, tetrahydrocarbazoles, and hexahydrocyclohept[b]indoles have been prepared as melatonin analogues to investigate the nature of the binding site of the melatonin receptor. The affinity of analogues was compared in a radioligand binding assay using chicken brain membranes and agonist and antagonist potency measured in clonal Xenopus laevis melanophore cells. Comparison of the N-acyl-3-amino-6-methoxytetrahydrocarbazoles (2) with N-acyl-4-(aminomethyl)-6-methoxy-9-methyltetrahydrocarbazoles (9) showed that the latter have much higher binding affinities for the chicken brain receptor. Comparison of N-acyl-1-(aminomethyl)-7-methoxy-4-methyltetrahydrocyclopent[b]ind oles (10), 6-methoxytetrahydrocarbazoles (9), and N-acyl-10-(aminomethyl)-2-methoxy-5-methylhexahydrocyclohept[b]ind oles (11) showed that the tetrahydrocarbazoles had the highest binding affinity with the cyclohept[b]indoles and the cyclopent[b]indoles having rather lower affinities. All of these observations are in agreement with our postulated model of melatonin orientation at the binding pocket in which the 3-amidoethane side chain is in a conformation close to the 5-methoxyl group, as is shown in the X-ray crystallographic structure of 9m and in the energy-minimized computed structures. Separation of the enantiomers of members from each of these three systems was accomplished by chiral HPLC. It was found that in all cases the (-)-enantiomer had a higher binding affinity than the (+)-enantiomer. An X-ray crystallographic analysis of the two enantiomers of 9a showed that the (+)-enantiomer had the (R) absolute stereochemistry. Since the sign of the Cotton curves, determined from circular dichroism studies, was the same for all (+)-enantiomers, it is assumed that the absolute stereochemistry at these centers is identical. In the Xenopus melanophore assay, the tetrahydrocarbazoles 2 (R = H) were mainly weak antagonists, while those with R = OMe were agonists. The biological behavior of the tetrahydrocarbazoles 9 (R = H) depended on R1, some being agonists and some antagonists, whereas those with R = OMe were generally agonists. Variation of the R and R1 groups in compounds of type 9 produced both agonists and antagonists. The tetrahydrocylopentaindoles 10 had similar biological properties to the corresponding analogues of 9, but the hexahydrocycloheptaindoles 11 showed a much greater propensity to be antagonists. In all cases the (S)-enantiomers were found to be more potent agonists than the (R)-enantiomers.