adrenomedullin and 9-(tetrahydro-2-furyl)-adenine

Direct administration of intermedin (IMD) into the brain elicits cardiovascular effects different from the systemic administration. Nucleus tractus solitarii (NTS) is an important region for the cardiovascular regulation. The present study was designed to determine the effect of IMD on modulating the sympathetic outflow and its related molecular mechanism in the NTS. Renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) were recorded in anesthetized rats. Site-specific microinjection of IMD (20pmol) bilaterally into the NTS significantly increased RSNA and MAP. IMD-evoked increases of RSNA and MAP were almost abolished by pretreatment with receptor antagonist ADM22-52, an adenylyl cyclase (AC) inhibitor SQ22536, or a protein kinase A (PKA) inhibitor Rp-cAMP. However, pretreatment with another receptor antagonist calcitonin gene-related peptide (CGRP)8-37 did not suppress the increases of RSNA and MAP induced by IMD. Furthermore, IMD increased the cyclic adenosine monophosphate (cAMP) level, which was inhibited by ADM22-52 pretreatment in the NTS. These results suggest that IMD participates in the sympathetic nerve activity and central regulation of the cardiovascular system and a receptor-mediated cAMP/PKA signaling pathway is involved in IMD-induced effects in the NTS.

Topics: Adenine; Adenylyl Cyclase Inhibitors; Adenylyl Cyclases; Adrenomedullin; Animals; Arterial Pressure; Calcitonin Gene-Related Peptide; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Ganglia, Sympathetic; Heart Rate; Injections, Intraventricular; Kidney; Male; Neuropeptides; Peptide Fragments; Rats; Rats, Sprague-Dawley; Signal Transduction; Solitary Nucleus; Thionucleotides

Adrenomedullin (ADM), a 52-amino acid peptide, elicits differential cardiovascular responses when it is administered systemically or directly to the brain. We evaluated in the present study the hypothesis that ADM may modulate baroreceptor reflex (BRR) response through an ADM receptor-mediated cAMP/ protein kinase A (PKA)-dependent mechanism in the nucleus tractus solitarii (NTS), the terminal site for primary baroreceptor afferents, using Sprague-Dawley rats. Our immunoblot and immunohistochemical results showed that the two component proteins of the ADM(1) receptor complex, calcitonin receptor-like receptor (CRLR) and receptor activity modifying protein (RAMP)-2, were uniformly distributed and highly co-localized in the NTS. Site-specific microinjection of ADM (0.02-0.2pmol) unilaterally into the NTS significantly increased BRR response and sensitivity in a time- and dose-related manner, without affecting arterial pressure and heart rate. The BRR enhancing effect of ADM was also temporally correlated with an up-regulation of PKA(beta), the active form of PKA and an increase in PKA activity. In addition, the ADM-evoked BRR enhancement or PKA activation was abolished by co-microinjection with a selective ADM(1) receptor antagonist, ADM(22-52), an adenylyl cyclase inhibitor, SQ22536, or a PKA inhibitor, Rp-8-bromo-cAMP. These results suggest that ADM enhances BRR via activation of a cAMP/PKA-dependent mechanism by acting site-specifically on ADM(1) receptors in NTS.

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Adenine; Adrenomedullin; Analysis of Variance; Animals; Baroreflex; Blood Pressure; Bronchodilator Agents; Calcitonin Receptor-Like Protein; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Dose-Response Relationship, Drug; Drug Interactions; Enzyme Inhibitors; Heart Rate; Intracellular Signaling Peptides and Proteins; Male; Membrane Proteins; Peptide Fragments; Rats; Rats, Sprague-Dawley; Receptor Activity-Modifying Proteins; Receptors, Calcitonin; Signal Transduction; Solitary Nucleus; Thionucleotides; Time Factors

We tested the hypothesis that adrenomedullin reduces calcium influx independent of potassium channels in depolarized endothelium-denuded mesenteric artery from pregnant rats.. Adrenomedullin reduced the CaCl(2)-induced contraction, while the receptor antagonist calcitonin gene-related peptide (CGRP)(8-37), but not adrenomedullin(22-52), reversed these effects. Adenylate cyclase inhibition by SQ22536 did not prevent adrenomedullin effects on CaCl(2)-induced contraction. Adrenomedullin did not inhibit depolarization-induced calcium entry to isolated vascular smooth muscle. Inhibition of myosin light-chain (MLC) phosphatase by calyculin A reversed the effects of adrenomedullin on contraction caused by submillimolar concentrations of CaCl(2), while adrenomedullin still inhibited contraction caused by higher concentrations of CaCl(2). However, the ratio of phosphorylated to total myosin phosphatase target 1, the regulatory subunit of MLC phosphatase, did not change with adrenomedullin, indicating a lack of MLC phosphatase activation. Interestingly, sodium fluoride, a nonspecific protein phosphatase inhibitor, completely blocked the effect of adrenomedullin on CaCl(2)-induced contraction. Adrenomedullin inhibited calcium mobilization from intracellular stores induced by thapsigargin.. Adrenomedullin inhibits CaCl(2)-induced contraction, without affecting calcium influx, through a CGRP(8-37)-sensitive receptor, but not using the cyclic adenosine monophosphate pathway, probably through activation of protein phosphatases. Inhibition of intracellular calcium release is an additional role played by adrenomedullin in calcium homeostasis in vascular smooth muscle.

Topics: Adenine; Adenylyl Cyclase Inhibitors; Adenylyl Cyclases; Adrenomedullin; Animals; Calcitonin Gene-Related Peptide; Calcium Chloride; Calcium Signaling; Calcium-Transporting ATPases; Cells, Cultured; Cyclic AMP; Dose-Response Relationship, Drug; Enzyme Inhibitors; Female; Marine Toxins; Membrane Potentials; Mesenteric Arteries; Muscle, Smooth, Vascular; Myosin-Light-Chain Phosphatase; Oxazoles; Peptide Fragments; Phosphorylation; Potassium; Pregnancy; Protein Phosphatase 1; Rats; Receptors, Adrenomedullin; Receptors, G-Protein-Coupled; Sodium Fluoride; Thapsigargin; Time Factors; Vasoconstriction; Vasoconstrictor Agents

Adrenomedullin (AM) and corticotrophin (ACTH) are both vasoactive peptides produced by a variety of cell types, including endothelial cells. Although AM and ACTH are considered to be important in the control of blood pressure and the response to stress, respectively, their role in inflammation and the immune response has not been clarified. This study shows, with the use of a cell-based ELISA, that AM and ACTH induce cell surface expression of the adhesion molecules E-selectin, VCAM-1, and ICAM-1 on human umbilical vein endothelial cells (HUVEC). Furthermore, this effect appears to be mediated in part via elevation of cAMP, given that both peptides elevate cAMP, the cell-permeable cAMP analog dibutyryl cAMP is able to mimic induction of all three cell adhesion molecules and the effect of AM and ACTH is inhibited by the adenylyl cyclase inhibitor SQ-22536. These findings demonstrate a role for AM and ACTH in the regulation of the immune and inflammatory response.

Topics: Adenine; Adenylyl Cyclase Inhibitors; Adrenocorticotropic Hormone; Adrenomedullin; Biological Transport; Cell Membrane; Cell Nucleus; Cells, Cultured; Cyclic AMP; Dose-Response Relationship, Drug; E-Selectin; Endothelium, Vascular; Humans; Intercellular Adhesion Molecule-1; Intracellular Membranes; NF-kappa B; Osmolar Concentration; Peptides; Time Factors; Umbilical Veins; Vascular Cell Adhesion Molecule-1

Responses to human CGRP, adrenomedullin (ADM), and proadrenomedullin NH2-terminal 20 peptide (PAMP) were studied in small human thymic arteries. CGRP, ADM, and PAMP produced concentration-dependent vasodilator responses in arteries preconstricted with the thromboxane mimic U-46619. Responses to ADM and PAMP were attenuated, whereas responses to CGRP were not altered by endothelial denudation. Inhibitors of nitric oxide synthase and guanylyl cyclase attenuated responses to ADM and PAMP but not to CGRP. The CGRP1 receptor antagonist CGRP(8-37) attenuated responses to CGRP and ADM but not to PAMP. Responses to CGRP were reduced by SQ-22536 and Rp-cAMPS, inhibitors of adenylyl cyclase and PKA. These data suggest that responses to CGRP and ADM are mediated by CGRP(8-37)-sensitive receptors and that the endothelial ADM receptor induces vasodilation by a nitric oxide-guanylyl cyclase mechanism, whereas a smooth muscle CGRP receptor signals by a cAMP-dependent mechanism. A different endothelial receptor recognizes PAMP and signals by a nitric oxide-dependent mechanism.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adenine; Adenylyl Cyclase Inhibitors; Adrenomedullin; Arteries; Calcitonin Gene-Related Peptide; Cyclic AMP; Dose-Response Relationship, Drug; Endothelium, Vascular; Guanylate Cyclase; Humans; Nitric Oxide; Nitric Oxide Synthase; Peptide Fragments; Peptides; Proteins; Receptors, Calcitonin Gene-Related Peptide; Thionucleotides; Thymus Gland; Vasodilation

In this study we investigated the effect of adrenomedullin (AM) on fMLP-mediated activation of human neutrophils. AM partially, but significantly, suppressed fMLP-induced upregulation of CD11b expression. The inhibitory effects of AM upon fMLP-induced upregulation of CD11b expression were completely blocked by CGRP [8-37], a CGRP receptor antagonist. AM significantly increased cAMP content in neutrophils and SQ-22,536, an adenylate cyclase inhibitor, and KT-5720, a PKA inhibitor, significantly blocked the inhibitory effects of AM upon fMLP-induced upregulation of CD11b expression. This study indicates that binding of AM to the CGRP receptor suppresses fMLP-induced upregulation of CD11b expression of human neutrophils by increasing intracellular cAMP levels. AM may play an important role in the regulation of inflammatory processes, especially in the binding of neutrophils to vascular endothelial cells and subsequent neutrophil emigration evident in acute pulmonary inflammation.

Topics: Adenine; Adenylyl Cyclase Inhibitors; Adrenomedullin; Calcitonin Gene-Related Peptide; Calcitonin Gene-Related Peptide Receptor Antagonists; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Drug Interactions; Enzyme Inhibitors; Humans; In Vitro Techniques; Inflammation; Macrophage-1 Antigen; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Peptide Fragments; Peptides; Up-Regulation

Adrenomedullin (ADM) is a vasodilator produced by vascular endothelium and smooth muscle cells. Although plasma ADM levels are increased in patients with hypertension, heart failure, and myocardial infarction, little information exists regarding the microvascular response to ADM in the human heart. In the present study we tested the hypothesis that ADM produces coronary arteriolar dilation in humans and examined the mechanism of this dilation. Human coronary arterioles were dissected and cannulated with micropipettes. Internal diameter was measured by video microscopy. In vessels constricted with ACh, the diameter response to cumulative doses of ADM (10(-12)-10(-7) M) was measured in the presence and absence of human ADM-(22-52), calcitonin gene-related peptide-(8-37), N(omega)-nitro-L-arginine methyl ester (L-NAME), indomethacin (Indo), (1)H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one, SQ-22536, or KCl (60 mM). ADM dilated human coronary arterioles through specific ADM receptors (maximum dilation = 69 +/- 11%). L-NAME or N-monomethyl-L-arginine attenuated dilation to ADM (for L-NAME, maximum dilation = 66 +/- 7 vs. 41 +/- 13%, P < 0.05). Thus the mechanism of ADM-induced dilation involves generation of nitric oxide. However, neither (1)H-[1,2,4]oxadiazolo-[4, 3-a]quinoxalin-1-one, SQ-22536, nor Indo alone altered dilation to ADM. High concentrations of KCl blocked dilation to ADM. The magnitude of ADM dilation was reduced in subjects with hypertension. We propose that, in human coronary arterioles, ADM elicits vasodilation in part through production of nitric oxide and in part through activation of K(+) channels, with little contribution from adenylyl cyclase. The former dilator mechanism is independent of the more traditional pathway involving activation of soluble guanylate cyclase.

Topics: Adenine; Adrenomedullin; Aged; Arterioles; Calcitonin Gene-Related Peptide; Coronary Circulation; Coronary Disease; Coronary Vessels; Enzyme Inhibitors; Female; Heart Failure; Humans; Hypertension; In Vitro Techniques; Male; Microcirculation; Middle Aged; Miotics; NG-Nitroarginine Methyl Ester; Nitric Oxide; omega-N-Methylarginine; Peptide Fragments; Potassium Channels; Vasodilation; Vasodilator Agents