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，我们利用实验性疾病模型研究了肾脏肾素-血管紧张素系统(RAS)、肾上腺髓质素(AM)系统和利钠肽系统(NPS)。血管紧张素II 2型(AT_2)受体在胎儿中大量表达，出生后显著下调，但在不同疾病状态下重新表达。在培养的大鼠肾小球系膜细胞(MC)中，AT_2受体在融合时被显著诱导，并发挥抗增殖和促凋亡作用，拮抗AT_1受体，并抑制MAP激动级联反应。AT2受体在自发性高血压大鼠早期肾小球及高增殖性肾小球MC中的低表达，提示其在肾小球损伤和高血压发病机制中的作用。目的：阐明AM作为Lo…的作用我们用抗AM的单抗检测了其在培养的系膜细胞和内皮细胞(EC)中的分泌和作用。我们发现，从培养的MC分泌的AM具有与EC一样丰富的抗生长特性，并且MAb中和内源性AM显著降低了基础cAMP水平，并刺激了EC的生长。这些结果表明，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。我们以前建立了低血压高表达脑钠素(BNP-TG)的转基因小鼠。为了评估肾脏RAS-NPS的相互作用，我们使用慢性RAS激活的小鼠肾脏疾病模型，即肾次全切除和抗GBM肾炎，研究了过量BNP的影响。我们发现BNP具有显著的肾脏保护作用，提示NPS在体内对RAS具有保护作用，可能是在细胞和分子水平上，包括MAP激酶和转化生长因子-β的表达。在另一种肾RAS激活的模型中，单侧输尿管梗阻时，随着间质纤维化的发展，肾组织AM的表达显著减少，提示AM可能具有正常的抗肾纤维化作用。较少

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