adrenomedullin and Hypertension--Renal

Topics: Adrenomedullin; Calcitonin Receptor-Like Protein; Cell Division; Cyclic AMP; Diuresis; Fibrosis; Genetic Therapy; Glomerular Mesangium; Humans; Hypertension, Renal; Intracellular Signaling Peptides and Proteins; Kidney; Kidney Diseases; Membrane Proteins; Natriuresis; Nitric Oxide; Peptides; Receptor Activity-Modifying Proteins; Receptors, Calcitonin; Renal Artery; Vasodilation

The studies concerning the structure and variations of the human adrenomedullin (AM) gene are reviewed, and their relations to the gene function and genetic predisposition to cardiovascular diseases are discussed. The genomic human AM gene is composed of four exons, and the whole nucleotide sequence corresponding to mature AM resides in the fourth exon. In chromosomal sublocalization, the AM gene is located in the distal portion of the short arm of chromosome 11 (11p15.1-3). Analysis of the promoter region of the AM gene has revealed that two transcription factors, nuclear factor for interleukin-6 expression (NF-IL6) and activator protein 2 (AP-2), participate in the regulation of AM gene expression. It is surmised that NF-IL6 mediates inflammatory stimuli and AP-2 mediates signals of phospholipase C and protein kinase C activation. In addition to these factors, hypoxia induces AM gene expression via the hypoxia inducible factor-1 (HIF-1) binding site. The 3'-end of the AM gene is flanked by a microsatellite marker of cytosine adenine (CA) repeats. In Japanese, there are four types of alleles with different CA-repeat numbers: 11, 13, 14 and 19. It is suggested that existence of the 19-repeat allele is associated with genetic predispositions to develop essential hypertension and diabetic nephropathy.

Topics: Adrenomedullin; Diabetic Nephropathies; Heart Failure; Humans; Hypertension, Renal; Peptides; Polymorphism, Genetic

Cirsium japonicum, a constituent of traditional Chinese medicine, has been shown to exert inflammatory effects as well as to improve the circulation and thus to counteract hematologic stasis. Studies have demonstrated that intermedin (IMD) has protective effects on hypertension in rats by regulating the Ang/NO metabolic pathway. In this study, we investigated whether by regulating the expression of IMD, Cirsium japonicum could improve cardiac function in rats with 2k1c-induced renal hypertension. Renal hypertension was induced in Sprague-Dawley rats by occluding the renal artery. The rats were maintained on a normal diet and randomly divided into four groups: sham, 2k1c, 2k1c with Cirsium japonicum (1.8 g/kg per day) and 2k1c with IMD (n = 10 in each group). Cardiac function, plasma angiotensin II (Ang II), IMD, serum nitric oxide (NO) and nitric oxide synthase (NOS), as well as the expression of IMD and adrenomedullin (ADM) in the aorta and left ventricle were analyzed. Administration of Cirsium japonicum or IMD significantly strengthened cardiac function in 2k1c-induced rats, increased serum NO and NOS levels, reduced plasma Ang II, and upregulated IMD expression in the aorta and left ventricle. These results demonstrate that Cirsium japonicum has cardioprotective effects on 2k1c-induced renal hypertension in rats via the IMD/NO pathway.

Topics: Adrenomedullin; Animals; Aorta; Cirsium; Hypertension, Renal; Male; Neuropeptides; Nitric Oxide; Plant Extracts; Random Allocation; Rats; Rats, Sprague-Dawley; Signal Transduction; Ventricular Function, Left

Adrenomedullin (AM) has various physiological actions on the cardiovascular system, including vasodilatation, diuresis, natriuresis, inhibition of aldosterone secretion, and increases of the cardiac output, all of which cause hypotension. Since AM plays a role in the pathophysiology of vascular diseases, genes controlling AM might be involved in the development and etiology of essential hypertension (EH). However, there have been few studies examining the relationship between the AM gene and hypertension. The aims of this study were to genotype some of the genetic markers for the human AM gene in Japanese subjects, and via a haplotype-based case-control study, assess the association between and the AM gene and EH or its risk factors, such as hyperlipidemia, renal damage, and proteinuria. We genotyped 205 EH patients and 210 age-matched normotensive (NT) individuals for two single nucleotide polymorphisms of rs4399321, rs7944706 and a microsatellite polymorphism located approximately 5,400 base pairs downstream of the 3' end of the human AM gene. The overall distribution in each variant and haplotype did not significantly differ between the two groups. However, after dividing the groups into those subjects with and without proteinuria, the haplotype analysis revealed a positive association. In conclusion, a possible mutation linked to the haplotype may indicate a genetic predisposition for proteinuria in EH.

Topics: Adrenomedullin; Case-Control Studies; Haplotypes; Humans; Hypertension, Renal; Middle Aged; Peptides; Polymorphism, Single Nucleotide; Proteinuria; Risk Factors

To investigate regional aspects of hypoxic regulation of adrenomedullin (AM) in kidneys, we mapped the distribution of AM in the rat kidney after hypoxia (normobaric hypoxic hypoxia, carbon monoxide, and CoCl(2) for 6 h), anemia (hematocrit lowered by bleeding) and after global transient ischemia for 1 h (unilateral renal artery occlusion and reperfusion for 6 and 24 h) and segmental infarct (6 and 24 h). AM expression and localization was determined in normal human kidneys and in kidneys with arterial stenosis. Hypoxia stimulated AM mRNA expression significantly in rat inner medulla (CO 13 times, 8% O(2) 6 times, and CoCl(2) 8 times), followed by the outer medulla and cortex. AM mRNA level was significantly elevated in response to anemia and occlusion-reperfusion. Immunoreactive AM was associated with the thin limbs of Henle's loop, distal convoluted tubule, collecting ducts, papilla surface epithelium, and urothelium. AM labeling was prominent in the inner medulla after CO and in the outer medulla after occlusion-reperfusion. The infarct border zone was strongly labeled for AM. In cultured inner medullary collecting duct cells, AM mRNA was significantly increased by hypoxia. AM mRNA was equally distributed in human kidney and AM was localized as in the rat kidney. In human kidneys with artery stenosis, AM mRNA was not significantly enhanced compared with controls, but AM immunoreactivity was observed in tubules, vessels, and glomerular cells. In summary, AM expression was increased in the rat kidney in response to hypoxic and ischemic hypoxia in keeping with oxygen gradients. AM was widely distributed in the human kidney with arterial stenosis. AM may play a significant role to counteract hypoxia in the kidney.

Topics: Adrenomedullin; Anemia; Animals; Cells, Cultured; Gene Expression; Humans; Hypertension, Renal; Hypoxia; Immunohistochemistry; Ischemia; Kidney; Male; Peptides; Rats; Rats, Sprague-Dawley; Renal Artery Obstruction; RNA, Messenger

The 2-kidney 1-clip rat model was set up by clipping the left renal artery. At 5 weeks after clipping, there was an increase in preproadrenomedullin mRNA levels in both the left atria and the left ventricle. Adrenomedullin (AM) contents, however, increased in the left ventricle but decreased in the left atrium. These changes were not observed at 2 weeks after clipping. There were no changes in AM or preproadrenomedullin mRNA levels in the thoracic aorta and the mesenteric artery, and in plasma AM levels at 2 weeks or 5 weeks after clipping. We concluded that there was an increase in the secretion of AM in the left ventricle and the left atria in the 5 week renovascular hypertensive rat. The lack of change in plasma AM level suggests a paracrine function for the peptide in this setting.

Topics: Adrenomedullin; Animals; Gene Expression; Heart; Heart Atria; Heart Ventricles; Hypertension, Renal; Kidney; Male; Peptides; Radioimmunoassay; Rats; Rats, Sprague-Dawley; Renal Artery; RNA, Messenger; Surgical Instruments

To investigate a possible pathophysiological role of human adrenomedullin (AM), we measured the plasma concentration of immunoreactive-AM (ir-AM) in 38 patients with end-stage renal disease (ESRD) on hemodialysis (HD) and 38 healthy subjects (age and sex matched). In addition, plasma ir-AM was characterized by a reverse-phase high performance liquid chromatography. The mean value (+/- SEM) of plasma AM in the patients before HD (10.1 +/- 0.67 fmol/ml) was markedly higher than that in the control group (2.9 +/- 0.13 fmol/ml, p < 0.001), but plasma AM levels were not altered by HD. There was a significant correlation between plasma AM levels and mean blood pressure (MBP) in a group of subjects including both patients before HD and healthy subjects (p < 0.01). In chromatographic study, the major peak of ir-AM in the plasma from patients on HD, as well as healthy subjects, emerged at an elution time identical to that of synthetic AM, indicating that the active form of AM was present in the circulating blood. The secretion of AM seemed to be increased in response to the conditions elicited by ESRD such as hypervolemia and/or hypertension, and reduced renal excretion of the peptide may also contribute to its high plasma level.

Topics: Adrenomedullin; Blood Pressure; Chromatography, High Pressure Liquid; Creatinine; Female; Humans; Hypertension, Renal; Hypotension; Kidney Failure, Chronic; Male; Middle Aged; Peptides; Renal Dialysis