Non-competitive antagonism of amylin on CGRP(1)-receptors in rat coronary small arteries

Resident macrophages mediate islet amyloid polypeptide-induced islet IL-1β production and β-cell dysfunction

Islet amyloid polypeptide (IAPP) aggregates to form amyloid fibrils in patients with type 2 diabetes and acts as a potent stimulus for interleukin (IL)-1β secretion by bone marrow-derived macrophages. We sought to determine the contribution of resident islet macrophages to IAPP-induced inflammation and β-cell dysfunction. In cultured islets, macrophages (F4/80(+)CD11b(+)CD11c(+) cells) were required for IAPP-induced mRNA expression of the proinflammatory cytokines IL-1β, tumor necrosis factor-α, and IL-6 and the anti-inflammatory cytokines IL-10 and IL-1 receptor antagonist. Moreover, IAPP-induced IL-1β synthesis and caspase-1 activation were detected in macrophages but not other islet cell types. Transgenic mice with β-cell human IAPP (hIAPP) expression had impaired glucose tolerance, elevated islet Il1b mRNA, and decreased Il10 and Il1rn expression following high-fat feeding. Islet macrophages were the major source of these transcripts and expressed increased cell surface Ly6C and CD11c in hIAPP transgenic mice. Clodronate liposome-mediated depletion of islet macrophages improved glucose tolerance and blocked proinflammatory gene expression in hIAPP-expressing mice, despite increasing the amount of islet amyloid. These data provide the first evidence that IAPP aggregates skew resident islet macrophages toward a proinflammatory phenotype and suggest a mechanism by which anti-inflammatory therapies may protect β-cells from IAPP-induced islet dysfunction.

CGRP receptors mediating CGRP-, adrenomedullin- and amylin-induced relaxation in porcine coronary arteries. Characterization with 'Compound 1' (WO98/11128), a non-peptide antagonist

1. Calcitonin gene-related peptide (CGRP), amylin and adrenomedullin (AM) belong to the same family of peptides. Accumulating evidence indicate that the calcitonin (CT) receptor, the CT receptor-like receptor (CRLR) and receptor-activity-modifying proteins (RAMPs) form the basis of all the receptors in this family of peptides. 2. Using reverse transcriptase - polymerase chain reaction the presence of mRNA sequences encoding the CRLR, RAMP1 and RAMP2 were demonstrated in porcine left anterior descending (LAD) coronary arteries, whereas porcine calcitonin (CT) receptor mRNA was not present. The partial porcine mRNA sequences shared 82 - 92% nucleotide identity with human sequences. 3. The human peptides alphaCGRP, betaCGRP, AM and amylin induced relaxation with pEC(50) values of 8.1, 8.1, 6.7 and 6.1 M respectively. 4. The antagonistic properties of a novel non-peptide CGRP antagonist 'Compound 1' (WO98/11128), betaCGRP(8 - 37) and the proposed AM receptor antagonist AM(22 - 52) were compared to the well-known CGRP(1) receptor antagonist alphaCGRP(8 - 37). 5. The alphaCGRP(8 - 37) and betaCGRP(8 - 37) induced concentration-dependent (10(-7) - 10(-5) M) rightward shift of both the alphaCGRP and betaCGRP concentration-response curves. betaCGRP(8 - 37) (10(-6) M) had the same effect as alphaCGRP(8 - 37) (10(-6) M), but with less potent rightward shift of the concentration-response curves for alphaCGRP, AM and amylin. 6. Preincubation with 'Compound 1' (10(-7) - 10(-5) M) and AM(22 - 52) (10(-6) M) had no significant antagonistic effect. 7. In conclusion, the building blocks forming CGRP and AM receptors were present in the porcine LAD, whereas those of the amylin receptor were not. alphaCGRP, betaCGRP, AM and amylin mediated vasorelaxation via the CGRP receptors. No functional response was detected to adrenomedullin via the adrenomedullin receptor.

Characterization of CGRP(1) receptors in the guinea pig basilar artery

The purpose of the present study was to characterise receptors mediating calcitonin gene-related peptide (CGRP)-induced relaxation of guinea pig basilar artery. This was done by investigating vasomotor responses in vitro and performing autoradiographic binding studies. We also intended to study the importance of an intact endothelium. Agonist studies showed that peptides of the CGRP family induced relaxation of the guinea pig basilar artery with the following order of potency: human beta-CGRP=human alpha-CGRP>>adrenomedullin=[acetamidomethyl-Cys(2,7)]alpha-human CGRP ([Cys(ACM)(2,7)]CGRP)=amylin. These data are in concord with those of the autoradiographic binding studies that showed displacement of [125I] human alpha-CGRP binding with the following order of potency: human alpha-CGRP=human beta-CGRP>>adrenomedullin=human alpha-CGRP-(8-37)>>Cys(ACM)(2,7)]CGRP. In blockade experiments, the relaxant responses to human alpha- and human beta-CGRP were competitively blocked by the CGRP(1) receptor antagonist human alpha-CGRP-(8-37), while those of adrenomedullin and amylin were blocked non-competitively. In order to examine whether amylin induced relaxation via amylin or CGRP receptors, we studied the antagonistic effect of amylin-(8-37) on the weak relaxant response to amylin and found that it was not blocked by amylin-(8-37). These findings, together with the finding that the CGRP(2) receptor agonist [Cys(ACM)(2,7)]CGRP only induced a weak relaxation in the highest concentrations examined, suggest that the CGRP family of peptides mediate relaxation by CGRP(1)-type receptors. Removal of the endothelium, the addition of N(G)-nitro-L-arginine methyl ester (L-NAME), methylene blue or indomethacin did not affect the concentration-response curves of the CGRP analogues, neither in the presence nor in the absence of human CGRP-(8-37). The study shows the presence of a relaxant CGRP(1) receptor on the smooth muscle cells of guinea pig basilar artery. Various endothelial factors did not influence relaxant responses.