Molecular and Clinical Study of Renal Angiotensin and Adrenomedullin Systems

心血管激素可能与各种肾脏和心血管疾病有关，如慢性肾功能衰竭、肾小球肾炎和高血压。为了探讨它们的作用，我们利用实验疾病模型研究了肾素-血管紧张素系统（RAS）、肾上腺髓质素系统（AM）和利钠肽系统（NPS）。血管紧张素II型2 （Angiotensin II type 2, AT_2）受体在胎儿体内大量表达，出生后显著下调，但在各种疾病状态下重新表达。在培养的大鼠系膜细胞（MC）中，AT_2受体在融合后被显著诱导，并发挥对抗AT_1受体的抗增殖和促凋亡作用，抑制MAP激酶级联反应。AT_2受体在自发性高血压大鼠（SHRSP）肾小球及具有高增殖性质的SHRSP的MC中较低表达，提示其与肾小球损伤和高血压的发病机制有关。为了阐明AM作为一种低钙调节因子的作用，我们使用制备的抗AM单克隆抗体（MAb）检测了其在培养的系膜和内皮细胞（EC）中的分泌和作用。我们发现，培养的MC和EC分泌的AM一样丰富，具有有效的抗生长特性，并且单克隆抗体中和内源性AM显着降低了基础cAMP水平，刺激了EC的生长。与WKY相比，SHRSP的MC分泌的AM较少。这些发现表明内源性AM在这些细胞中作为自分泌/旁分泌调节因子的作用。我们已经建立了过表达脑利钠肽（BNP-Tg）的转基因低血压小鼠。为了评估肾脏RAS- nps的相互作用，我们使用慢性RAS激活的肾脏疾病小鼠模型，即肾次全切除术和抗gbm肾炎，检测了BNP过量的影响。我们发现BNP具有显著的肾保护作用，这表明NPS在体内可能在细胞和分子水平上对RAS起作用，包括MAP激酶和tgf - β的表达。在另一种肾脏RAS激活模型——单侧输尿管梗阻中，AM在肾脏中的表达随着间质纤维化的发生而显著降低，提示AM可能在正常情况下起到抗肾纤维化的作用。少

Cardiovascular hormones may be implicated in various renal and cardiovascular disorders such as chronic renal failure, glomerulonephritis, and hypertension. To explore their roles, we studied the renal renin-angiotensin system (RAS), adrenomedullin (AM) system, and natriuretic peptide system (NPS) using experimental disease models.Angiotensin II type 2 (AT_2) receptor is abundantly expressed in the fetus and markedly down-regulated after birth, but reexpressed in various disease states. In cultured rat mesangial cells (MC), the AT_2 receptor was markedly induced upon confluence and exerted antiproliferative and proapoptotic effects counteracting the AT_1 receptor, and inhibited the MAP kinase cascade. Lower expression of the AT_2 receptor in glomeruli at the younger period from spontaneously hypertensive rats (SHRSP) as well as in MC of SHRSP with highly proliferative nature, suggested its implication in pathogenesis of glomerular injury and hypertension.To clarify a role of AM as a lo … More cal regulator, we examined its secretion and action in cultured mesangial and endothelial cells (EC) using a monoclonal antibody (MAb) prepared against AM.We found secretion of AM, with a potent antigrowth property, from cultured MC as abundantly as from EC, and neutralization of endogenous AM by MAb markedly reduced basal cAMP levels and stimulated growth of EC.MC from SHRSP secreted less AM compared to WKY.These findings suggested a role of endogenous AM as an autocrine/paracrine regulator in these cells.We have previously established the transgenic mice overexpressing brain natriuretic peptide (BNP-Tg) with low blood pressure. To assess the renal RAS-NPS interaction, we examined the effect of excess of BNP, using mouse models of renal diseases with chronic RAS activation, i.e. subtotal nephrectomy and anti-GBM nephritis. We found significant renoprotective effects of BNP, suggesting that NPS acts against RAS in vivo, perhaps at cellular and molecular levels including MAP kinase and TGF-beta expression. In another model of renal RAS activation, unilateral ureteral obstruction, renal expression of AM was significantly reduced along with development of interstitial fibrosis, suggesting that AM may normally act against renal fibrosis. Less