BACKGROUNDSustained hypotension during hemodialysis (HD) is an important clinical issue. Plasma adrenomedullin (AM) is increased in HD patients with sustained hypotension, but little is known about whether removing AM can improve hypotension. The objective of this study was to investigate the beneficial effects of hemodialysis using a high-flux dialyzer on removal of increased plasma AM levels and improving low blood pressure in elderly HD patients with sustained hypotension.

METHODSForty-eight elderly patients (age 65 or older) who had undergone maintenance HD for more than one year were recruited and studied. We evaluated plasma levels of AM in sustained hypotension (SH; n = 28) and normotensive (NT; n = 20) patients. The patients with hypotension were further divided into two subgroups and treated with either high-flux dialyzer or low-flux dialyzer for 3 months. Plasma adrenomedullin levels and blood pressure were analyzed at days 0 and 181.

RESULTSPlasma levels of AM were significantly higher in SH than in NT patients ((24.92 ± 3.7) ng/L vs. (15.52 ± 6.01) ng/L, P < 0.05), and were inversely correlated with mean arterial blood pressure (MAP) at pre-HD. After 3 months, the level of plasma AM in high-flux group was decreased ((24.58 ± 4.36) ng/L vs. (16.18 ± 5.08) ng/L, P < 0.05), but MAP was increased ((67.37 ± 4.31) mmHg vs. (74.79 ± 3.59) mmHg, P < 0.05). There was no obvious change in low-flux group.

CONCLUSIONSPlasma AM levels were significantly elevated in elderly HD patients with SH. High-flux dialyzer therapy can decrease plasma AM level and improve hypotension.

Adrenomedullin ; blood ; Aged ; Female ; Humans ; Hypotension ; blood ; Male ; Renal Dialysis

OBJECTIVES: To study the role of adrenomedullin (ADM) in hyperoxia-induced lung injury by examining the effect of ADM on the expression of calcitonin receptor-like receptor (CRLR), receptor activity-modifying protein 2 (RAMP2), extracellular signal-regulated kinase (ERK), and protein kinase B (PKB) in human pulmonary microvascular endothelial cells (HPMECs) under different experimental conditions. METHODS: HPMECs were randomly divided into an air group and a hyperoxia group ( RESULTS: Compared with the air group, the hyperoxia group had significant increases in the mRNA and protein expression levels of ADM, CRLR, RAMP2, ERK1/2, and PKB ( CONCLUSIONS ERK1/2 and PKB may be the downstream targets of the ADM signaling pathway. ADM mediates the ERK/PKB signaling pathway by regulating CRLR/RAMP2 and participates in the protection of hyperoxia-induced lung injury.
Adrenomedullin/genetics* ; Endothelial Cells ; Humans ; Hyperoxia/complications* ; Lung Injury ; Receptor Activity-Modifying Proteins

PURPOSE: The aims investigated how how human osteosarcoma cell proliferation and the MAP kinases cascade are regulated, in the MG63 and U2OS human osteosarcoma cell lines after stimulating them with adrenomedullin (AM) with particular focus on extracellular signal-regulated kinase 1/2 (ERK 1 and 2) activation. MATERIALS AND METHODS: A cell proliferation assay was used to examined the effects of AM on the osteosarcoma cell lines (MG63 and U2OS). The effects of AM on ERK1/2 were examed by Western blot analysis. The roles of ERK 1/2 in the AM-induced proliferative signaling pathways in the two cell types were examed using PD98059, a selective inhibitor of the mitogen activated protein-ERK kinase (MEK) pathway. RESULTS: The addition of AM to the medium containing the osteosarcoma MG63 and U2OS cells induced proliferation in a dose-dependent manner. AM strongly activated ERK 1/2 mediated cell proliferation signaling, which was prevented using PD98059. CONCLUSION: These results suggest that AM plays an important role in the proliferation of human osteosarcoma MG63 and U2OS cells, and ERK kinase pathway plays a signal transduction role in AM treated human osteosarcoma MG63 and U2OS cell lines.
Adrenomedullin ; Blotting, Western ; Cell Line ; Cell Proliferation ; Flavonoids ; Humans ; Osteosarcoma ; Phosphotransferases ; Protein Kinases ; Signal Transduction

OBJECTIVETo investigate the expression and role of adrenomedullin (ADM) and adrenomedullin receptor (ADMR) in patients with chronic obstructive pulmonary disease (COPD).

METHODSSmall pulmonary artery remodeling was observed using morphometric analysis. The expression of ADM and ADMR mRNA in lung tissue was calculated by in situ hybridization in 9 COPD cases. Cardiac catheterization was performed in 22 COPD cases to monitor changes of hemodynamic parameters and patients were divided into two groups based on mean pulmonary artery pressure (mPAP). The cases without pulmonary hypertension (PH) were placed in Group A (n = 12) and those with PH were placed in Group B (n = 10). The levels of pulmonary arterial plasma ADM were measured by radioimmunoassay. Blood gas analysis was also conducted.

RESULTSThe ratio of vascular wall thickness to external diameter (MT%) and the ratio of vascular wall area to total area (MA%) were higher in patients with COPD (P < 0.01). In situ hybridization showed that ADM mRNA and ADMR mRNA were expressed in the pulmonary artery walls of control subjects. The expression levels were significantly higher in those of COPD sufferers (P < 0.01). Statistically positive relationships were visible between ADM and ADMR, and the plasma ADM level of Group B was significantly higher than that of Group A (P < 0.05). The plasma ADM level had a significantly positive correlation to mPAP and pulmonary vascular resistance (PVR), while being negatively correlated to levels of PaO(2).

CONCLUSIONADM may play an extremely protective role as a local autocrine/paracrine factor in COPD.

Adrenomedullin ; Adult ; Aged ; Aged, 80 and over ; Female ; Hemodynamics ; Humans ; Male ; Middle Aged ; Oxygen ; blood ; Peptides ; blood ; genetics ; physiology ; Pulmonary Disease, Chronic Obstructive ; prevention & control ; RNA, Messenger ; analysis ; Receptors, Adrenomedullin ; Receptors, Peptide ; genetics ; physiology

In this study, reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the changes in mRNAs levels of preproadrenomedullin (ppADM) gene encoding adrenomedullin (ADM) and the essential receptor components of ADM, calcitonin receptor-like receptor (CRLR), and the receptor activity modifying protein 2 and 3 (RAMP2 and RAMP3) in the medulla oblongata, hypothalamus, midbrain, pituitary gland and adrenal gland of the stress-induced hypertensive rats. It was shown that chronic foot-shock and noise stress for 15 consecutive days induced a significant increase in systolic blood pressure (SBP) and unique changes in ppADM and its receptor components mRNAs in all areas studied. As compared with the control group, the level of ppADM mRNA, normalized against a glyceraldehydes-3-phosphate dehydrogenase (GAPDH) control, was up-regulated in the hypothalamus-pituitary-adrenal (HPA) axis, but down-regulated in the medulla oblongata and midbrain (P<0.01 and P<0.05, respectively). The relative amount of CRLR mRNA was higher in the hypothalamus than that in other areas. The level of CRLR mRNA expression was significantly increased in the medulla oblongata of the stress group (P<0.01), but decreased in the midbrain (P<0.01) as well as hypothalamus(P<0.05), as compared with that of the control group. Chronic stress for 15 consecutive days produced an increase in the level of RAMP2 mRNA expression in the medulla oblongata (P<0.01) and a decrease in the adrenal gland (P<0.01), as compared with the control. No significant stress-related changes in RAMP2 mRNA were observed in the midbrain, hypothalamus and pituitary gland. The amount of RAMP3 mRNA was relatively higher in the midbrain and hypothalamus than that in the medulla oblongata, adrenal gland and adrenal gland. Stress-induced hypertensive rats exhibited an increased RAMP3 mRNA expression in the hypothalamus and pituitary gland (P<0.01 and P<0.05, respectively) and a decrease in the adrenal gland and midbrain (P<0.05). No significant stress-related change in RAMP3 mRAN was observed in the medulla oblongata. Taken together, our results indicate that the significant changes in ppADM and its receptor components mRNAs expression in the HPA axis and autonomic centers may be related to the development of the stress-induced hypertension. Nevertheless, the pathophysiological significance of brain-derived ADM and its receptors in stress and blood pressure regulation and their roles in stress-induced hypertension still await further investigation.
Adrenomedullin ; Animals ; Brain Stem ; metabolism ; Hypertension ; etiology ; metabolism ; Hypothalamo-Hypophyseal System ; metabolism ; Male ; Peptides ; genetics ; metabolism ; Pituitary-Adrenal System ; metabolism ; RNA, Messenger ; biosynthesis ; genetics ; Rats ; Rats, Sprague-Dawley ; Receptors, Adrenomedullin ; Receptors, Peptide ; biosynthesis ; genetics ; Stress, Physiological

The increase of pronociceptive mediators in the dorsal root ganglia (DRG) and spinal dorsal horn is an important mechanism in the pathogenesis of inflammatory pain and opioid tolerance. Adrenomedullin (AM) belongs to calcitonin gene-related peptide (CGRP) family and has been recently demonstrated to be a pain-related peptide. It has also been shown that the expression and release of AM are increased in the DRG and spinal dorsal horn during inflammation and repeated use of morphine. Intrathecal administration of the selective AM receptor antagonist AM22-52 abolishes inflammatory pain and morphine tolerance, suggesting that enhanced AM receptor signaling in the DRG and spinal dorsal horn contributes to the induction of inflammatory pain and morphine tolerance. The present review highlights the recent developments regarding the involvement of AM in these two disorders. The neurological mechanisms of AM's actions are also discussed.
Adrenomedullin ; pharmacology ; Animals ; Calcitonin Gene-Related Peptide ; Drug Tolerance ; Ganglia, Spinal ; drug effects ; Inflammation ; drug therapy ; metabolism ; Morphine ; pharmacology ; Pain ; drug therapy ; metabolism ; Peptide Fragments ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Receptors, Adrenomedullin ; metabolism

OBJECTIVETo investigate the role of adrenomedullin (AM) in the development of hypoxic pulmonary hypertension (HPH), and to assess the expression of AM and adrenomedullin receptor (AMR) in the lungs of rats with HPH.

METHODSWe exposed 10 rats to normobaric hypoxic conditions for 3 weeks to establish rat model of pulmonary hypertension; and 10 other rats were used as normoxic controls. Mean pulmonary arterial pressure (mPAP) was measured by a right cardiac catheterization. The thickness of pulmonary arterioles was measured by a computerized image analyzer. We used the reverse transcription-polymerase chain reaction (RT-PCR) to assess the change of expression of AM and AMR in lung of HPH rat model.

RESULTSCompared with the control group, hypoxic rats developed remarkable pulmonary hypertension, increment in the thickness of pulmonary arterioles and right ventricular hypertrophy (P < 0.01). Chronic hypoxia elicited a considerable increment in expression of AM and AMR in the lungs of rats, and the ratio of AM/beta-actin and AMR/beta-actin in lungs of rats treated with hypoxia were significantly higher (P < 0.01).

CONCLUSIONSThe AM plays an important role in regulating pulmonary vascular tone and can ameliorate the development of hypoxic pulmonary hypertension in rats.

Adrenomedullin ; Animals ; Arterioles ; pathology ; Gene Expression ; Hypertension, Pulmonary ; metabolism ; pathology ; Hypertrophy, Right Ventricular ; etiology ; Hypoxia ; metabolism ; pathology ; Lung ; metabolism ; Male ; Peptides ; genetics ; Rats ; Rats, Wistar ; Receptors, Adrenomedullin ; Receptors, Peptide ; genetics ; Reverse Transcriptase Polymerase Chain Reaction

Intermedin/adrenomedullin-2 (IMD/AM2), a member of the calcitonin gene-related peptide/AM family, plays an important role in protecting the cardiovascular system. However, its role in the enhanced sympathoexcitation in obesity-related hypertension is unknown. In this study, we investigated the effects of IMD in the paraventricular nucleus (PVN) of the hypothalamus on sympathetic nerve activity (SNA), and lipopolysaccharide (LPS)-induced sympathetic activation in obesity-related hypertensive (OH) rats induced by a high-fat diet for 12 weeks. Acute experiments were performed under anesthesia. The dynamic alterations of sympathetic outflow were evaluated as changes in renal SNA and mean arterial pressure (MAP) in response to specific drugs. Male rats were fed a control diet (12% kcal as fat) or a high-fat diet (42% kcal as fat) for 12 weeks to induce OH. The results showed that IMD protein in the PVN was downregulated, but Toll-like receptor 4 (TLR4) and plasma norepinephrine (NE, indicating sympathetic hyperactivity) levels, and systolic blood pressure were increased in OH rats. LPS (0.5 µg/50 nL)-induced enhancement of renal SNA and MAP was greater in OH rats than in obese or control rats. Bilateral PVN microinjection of IMD (50 pmol) caused greater decreases in renal SNA and MAP in OH rats than in control rats, and inhibited LPS-induced sympathetic activation, and these were effectively prevented in OH rats by pretreatment with the AM receptor antagonist AM22-52. The mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) inhibitor U0126 in the PVN partially reversed the LPS-induced enhancement of SNA. However, IMD in the PVN decreased the LPS-induced ERK activation, which was also effectively prevented by AM22-52. Chronic IMD administration resulted in significant reductions in the plasma NE level and blood pressure in OH rats. Moreover, IMD lowered the TLR4 protein expression and ERK activation in the PVN, and decreased the LPS-induced sympathetic overactivity. These results indicate that IMD in the PVN attenuates SNA and hypertension, and decreases the ERK activation implicated in the LPS-induced enhancement of SNA in OH rats, and this is mediated by AM receptors.
Adrenomedullin ; metabolism ; Animals ; Blood Pressure ; drug effects ; physiology ; Hypertension ; etiology ; Lipopolysaccharides ; pharmacology ; Male ; Neuropeptides ; metabolism ; Obesity ; complications ; Rats, Sprague-Dawley ; Receptors, Adrenomedullin ; drug effects ; metabolism ; Sympathetic Nervous System ; drug effects ; metabolism ; Toll-Like Receptor 4 ; metabolism

The present study was designed to investigate the effect of administration of adrenomedullin (ADM) into subfornical organ (SFO) on renal tubular Na(+),K(+)-ATPase activity in rats. Rats under anesthesia were injected with ADM 0.1 mL (20 ng/mL) via an implanted cannula into SFO (n=6). Plasma ADM and serum endogenous digitalis-like factor (EDLF) levels were assayed with radioimmunoassay, and urine samples were collected via a canoula intubated in bladder. Urinary sodium concentration was assayed with flame spectrophotometry. Single proximal renal tubule segments were obtained by hand under stereomicroscope and its Na(+),K(+)-ATPase activity was measured by liquid scintillation counting. In addition, single proximal renal tubule segments from normal rats (n=6) were incubated with serum from animals administered with ADM into SFO, and then the Na(+),K(+)-ATPase activity was determined. The results showed that both urinary volume and sodium excretion amounted to the peak value at 30 min after ADM administration, and sustained a significant high level at 60 min (P<0.01). At 30 min after ADM administration, there was a significant increase in serum EDLF and a decrease in Na(+),K(+)-ATPase activity of proximal tubule (P<0.01, respectively), but not in plasma ADM level. Na(+),K(+)-ATPase activity was decreased significantly in single proximal renal tubule segments from normal rats incubated with serum from rats administered with ADM into SFO (P<0.01). These results suggest that the diuretic and natriuretic responses following administration of ADM into SFO are associated with the inhibition of renal tubule Na(+),K(+)-ATPase activity. The inhibition of renal tubule Na(+),K(+)-ATPase activity is related to the increase in the serum level of EDLF.
Adrenomedullin ; pharmacology ; Animals ; Kidney Tubules, Proximal ; drug effects ; enzymology ; Rats ; Sodium-Potassium-Exchanging ATPase ; metabolism ; Subfornical Organ

AIMTo investigate the changes and probable roles of adrenomedullin2/intermedin (AIDM2/IMD), a novel micromolecular bioactive peptide, in the lungs of rats with chronic hypoxic pulmonary hypertension.

METHODSTwenty male SD rats were randomly divided into normal control group (NC) and normobaric hypoxia group (4H). The protein levels of ADM and ADM2/IMD) in the plasma and lung were measured by radioimmunoassay and immunohistochemistry. The mRNA expressions of ADM, ADM2/IMD and their receptors C (RLR, RAMP1, RAMP2 and RAMP3 in the lung tissue were determined by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS(1) The rat model of chronic pulmonary hypertension was confirmed by the increased mean pulmonary arterial pressure (mPAP) and weight ratio of right ventricle to left ventricle plus septum [RV/(LV + S)] in 4H group compared to NC group. (2) The concentrations of ADM in the plasma and lung homogenate of 4H group were 2.3 and 3.2 folds of NC group, respectively (all P < 0.01). The levels of ADM2/IMD were higher 89.6% and 45.0% in the plasma and lung homogenate of 4H group than those of NC group (respectively, P < 0.01, P < 0.05). (3) The mRNA expressions of ADM2/IMD and ADM in the lung of 4H group were up-regulated (respectively, P < 0.01, P < 0.05 vs. NC group). The expressions of CRLR and RAMP1 mRNAs were down-regulated (all P < 0.01 vs. NC group), while the levels of RAMP2 and RAMP3 mRNAs were no significant difference between the two groups. (4) The strong ADM2/IMD immunostaining was detected in the endothelial and adventitial cells of the rat pulmonary arteriole.

CONCLUSIONADM2/IMD, like its paralog ADM, might be closely related to the chronic hypoxic pulmonary hypertension in rats. The disorders of the gene expression and/or the synthesis and metabolism of ADM2/IMD and its receptor CRLR/RAMP1 possibly take part in the pathogenesis of chronic hypoxic pulmonary hypertension in rats.

Adrenomedullin ; metabolism ; Animals ; Hypertension, Pulmonary ; etiology ; metabolism ; Hypoxia ; complications ; metabolism ; Lung ; metabolism ; Male ; Neuropeptides ; metabolism ; Rats ; Rats, Sprague-Dawley