natriuretic-peptide--brain and Glomerulosclerosis--Focal-Segmental

Adrenomedullin (AM) is a novel vasodilating peptide thought to have important effects on cardiovascular function. The aim of this study was to assess the activity of endogenous AM in the cardiovascular system using AM knockout mice.. Mice heterozygous for an AM-null mutation (AM+/-) and their wild-type littermates were subjected to aortic constriction or angiotensin II (Ang II) infusion. The resultant cardiovascular stress led to increases in heart weight/body weight ratios, left ventricular wall thickness, and perivascular fibrosis, as well as expression of genes encoding angiotensinogen, ACE, transforming growth factor-beta, collagen type I, brain natriuretic peptide, and c-fos. In addition, renal damage characterized by decreased creatinine clearance with glomerular sclerosis was noted. In all cases, the effects were significantly more pronounced in AM+/- mice. Hearts from adult mice subjected to aortic constriction showed enhanced extracellular signal-regulated kinase (ERK) activation, as did cardiac myocytes from neonates treated acutely with Ang II. Again the effect was more pronounced in AM+/- mice, which showed increases in cardiac myocyte size, protein synthesis, and fibroblast proliferation. ERK activation was suppressed by protein kinase C inhibition to a greater degree in AM+/- myocytes. In addition, treatment of cardiac myocytes with recombinant AM suppressed Ang II-induced ERK activation via a protein kinase A-dependent pathway.. Endogenous AM exerts a protective effect against stress-induced cardiac hypertrophy via protein kinase C- and protein kinase A-dependent regulation of ERK activation. AM may thus represent a useful new tool for the treatment of cardiovascular disease.

Topics: Adrenomedullin; Angiotensin II; Angiotensinogen; Animals; Aorta, Abdominal; Cardiomegaly; Collagen Type I; Constriction; Enzyme Activation; Enzyme Inhibitors; Fibroblasts; Fibrosis; Gene Expression Regulation; Genes, fos; Genes, Lethal; Glomerulosclerosis, Focal Segmental; Heterozygote; Male; MAP Kinase Signaling System; Mice; Mice, Knockout; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases; Myocytes, Cardiac; Natriuretic Peptide, Brain; Peptides; Peptidyl-Dipeptidase A; Protein Kinase C; Proto-Oncogene Proteins c-fos; Transforming Growth Factor beta; Ventricular Remodeling

Studied were the effects of myocardial infarction (MI) on mild renal function loss in unilateral nephrectomized (UnX) rats. UnX was performed, followed after 1 wk by a variable MI (UnX + MI; n = 24). Rats with only UnX (n = 15) or MI (n = 9) and double sham animals (CON, n = 15) served as controls. Renal outcome was measured by proteinuria and plasma creatinine. Focal glomerulosclerosis (FGS) incidence was evaluated by renal histology. Cardiac function and systolic BP were measured. A division into small and large infarcts after UnX was made a priori, resulting in two groups, one with a mild MI (<20%; n = 15) and one with a moderate MI (>20%; n = 9). Mild proteinuria up to 55.5 mg/d was observed in the UnX + mild MI group, whereas proteinuria rose significantly higher to 124.5 mg/d in the UnX + moderate MI group. Incidence of FGS was significantly increased in both UnX + MI groups compared with all other groups. The average MI size was 18%, 17%, and 25% in the MI, UnX + mild MI, and UnX + moderate MI group, respectively. LVP in both UnX + MI groups was correlated with proteinuria, indicative of a cardio-renal interaction. Clinically, these data imply that more patients are at risk for cardiovascular events and that after such an event, their chance of more renal function loss increases. Finding the underlying mechanism will enable improved protection for both kidneys and heart.

Topics: Animals; Creatinine; Disease Models, Animal; Glomerulosclerosis, Focal Segmental; Heart; Kidney; Male; Myocardial Infarction; Myocardium; Natriuretic Peptide, Brain; Nephrectomy; Organ Size; Proteinuria; Rats; Rats, Wistar; Risk Factors; Survival Rate