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

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

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

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 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

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

OBJECTIVETo study the effect of human urotensin II (HU II) on secretion of adrenomedullin (ADM) from human vascular endothelial cells (HVEC) and its mechanism.

METHODSIn cultured HVEC, different concentrations of HUII were used to stimulate the ADM secretion from HVEC, and the inhibitors of different signal transduction pathway were used to investigate their effects on ADM secretion. The contents of ADM in medium were determined by radio immunoassay.

RESULTSHUII stimulated secretion of ADM from HVEC in a time-dependent and concentration-dependent manner. The contents of ADM in the experiment groups were changed compared with that in control group (P < 0.05). The increase of ADM could be inhibited by inhibitor of extracellular signal-regulated protein kinase (PD(98059)), inhibitor of P38 kinase (SB(202190)), inhibitor of calmodulin (W(7)) and inhibitor of Ca(2+) (nicardipine) (P < 0.05). The inhibition ratio in those groups was 68%, 78%, 24% and 25% respectively. But the inhibitor of Calcineurin (CaN) and inhibitor of protein kinase C (H(7)) had no influence on the secretion of ADM from HVEC (P > 0.05).

CONCLUSIONThe stimulated effect of HUII on the ADM secretion from HVEC may be mediated by Ca(2+), ERKs, CaM-PK and P38 signal transduction pathways.

Adrenomedullin ; metabolism ; Calcium ; metabolism ; Calcium Signaling ; Cells, Cultured ; Endothelial Cells ; secretion ; Humans ; Signal Transduction ; drug effects ; Urotensins ; pharmacology

OBJECTIVEEndogenous hydrogen sulfide (H2S), a novel gasotransmitter in cardiovascular regulation, plays an important protective role in the development and progression of atherosclerosis (AS). This study was designed to explore the effects of H2S donor on the production of adrenomedullin (ADM) and atrial natriuretic peptide (ANP) in AS rats.

METHODSMale Sprague-Dawley rats were randomly divided into control group (n=10), AS group (n=10), and AS+NaHS group (n=10). Rats in the AS and AS+NaHS groups were given 3-day intraperitoneal injections of vitamin D3 and 8-week high-fat diet to induce AS, and the rats in the AS+NaHS group were intraperitoneally injected with H2S donor NaHS. Oil red O staining was applied to detect changes in the areas of the atherosclerotic plaques in the aortic root and the coronary artery; sulfide-sensitive electrode method was used to measure the plasma concentration of H2S. ADM and ANP levels in plasma were determined by radioimmunoassay.

RESULTSCompared with the control group, marked atherosclerotic plaques were observed in the aortic root and the coronary artery in AS rats. Moreover, plasma H2S level decreased significantly, ADM level increased, and ANP level decreased significantly in AS rats (P<0.01). However, after the treatment with H2S donor NaHS for 8 weeks, the above changes in AS rats were reversed, demonstrated by significantly reduced areas of the atherosclerotic plaques in both the aortic root and the coronary artery, significantly increased plasma H2S level, significantly decreased plasma ADM level, and significantly increased plasma ANP level (P<0.01).

CONCLUSIONSH2S plays an important regulatory effect on vasoactive peptides ADM and ANP in AS rats.

Adrenomedullin ; biosynthesis ; Animals ; Atherosclerosis ; metabolism ; pathology ; Atrial Natriuretic Factor ; biosynthesis ; Hydrogen Sulfide ; pharmacology ; Male ; Rats ; Rats, Sprague-Dawley