Mazzocchi Giuseppina, Malendowicz Ludwik K, Ziolkowska Agnieszka, Spinazzi Raffaella, Rebuffat Piera, Aragona Francesco, Ferrazzi Eros, Parnigotto Pier Paolo, Nussdorfer Gastone G
Department of Human Anatomy and Physiology, Section of Anatomy, School of Medicine, University of Padua, I-35121 Padua, Italy.
Int J Oncol. 2004 Dec;25(6):1781-7.
Adrenomedullin (AM) is a hypotensive peptide, that acts via the calcitonin receptor-like receptor (CRLR), whose interaction with the subtypes 2 and 3 of a family of receptor activity-modifying proteins (RAMP) gives rise to two distinct AM receptors, named AM1 and AM2 receptors. AM derives from the post-translational proteolytic cleavage of pro(p)AM, the last step of which involves the conversion of the inactive AM to active AM by the peptidyl-glycine alpha-amidating monooxigenase (PAM). Compelling evidence suggests that AM, in addition to exerting its well-known regulatory action on blood pressure and water and electrolyte balance, also possesses a growth promoting effect in several normal and neoplastic tissues, including human prostate. Conventional reverse transcription (RT)-polymerase chain reaction (PCR) demonstrated the expression of pAM, PAM, CRLR and RAMP(1-3) mRNAs in both prostate hyperplasias (PH) and carcinomas (PC), and semiquantitative PCR showed that pAM, PAM and RAMP3 mRNA expression was higher in PCs than PHs. Radioimmunoassay measured higher concentrations of immunoreactive AM in PCs than PHs. The expression of pAM, CRLR and RAMP1,2 mRNAs was also detected in the PC-derived cell lines PC-3 and DU-145, RAMP3 expression being restricted to the latter line. AM did not affect the growth rate (duplication time) of PC-3 cells, but it did significantly increase that of DU-145 cells. The growth promoting effect of AM was found to ensue from both the rise in the proliferation rate and the lowering in the apoptosis rate of DU-145 cells. These effects of AM were counteracted by the AM receptor antagonists CGRP(8-37) and AM(22-52), the former antagonist, which is more selective for AM2 than AM1 receptors, being more effective than the latter one. Both antagonists were per se able to induce a slow, but significant decrease in the basal growth rate of DU-145 cells by inhibiting proliferation and enhancing apoptosis, again CGRP(8-37) being more effective than AM(22-52). Taken together, our findings allow us to suggest that: i) endogenous AM system plays an important autocrine-paracrine growth promoting action in the human prostate, being possibly involved in the development of the malignant phenotype of epithelial cells; and ii) the tumor promoting effect of AM in the human prostate is mainly mediated by the AM2 receptor (CRLR/RAMP3) subtype.
肾上腺髓质素（AM）是一种降压肽，它通过降钙素受体样受体（CRLR）发挥作用，CRLR与受体活性修饰蛋白（RAMP）家族的2型和3型亚型相互作用产生两种不同的AM受体，即AM1和AM2受体。AM来源于前体（p）AM的翻译后蛋白水解切割，其最后一步涉及肽基甘氨酸α-酰胺化单加氧酶（PAM）将无活性的AM转化为活性AM。有力证据表明，AM除了对血压以及水和电解质平衡发挥其众所周知的调节作用外，在包括人前列腺在内的几种正常和肿瘤组织中也具有促生长作用。传统的逆转录（RT）-聚合酶链反应（PCR）证明了pAM、PAM、CRLR和RAMP（1-3）mRNA在前列腺增生（PH）和癌（PC）中的表达，半定量PCR显示PC中pAM、PAM和RAMP3 mRNA表达高于PH。放射免疫分析测得PC中的免疫反应性AM浓度高于PH。在源自PC的细胞系PC-3和DU-145中也检测到了pAM、CRLR和RAMP1、2 mRNA的表达，RAMP3表达仅限于后者。AM不影响PC-3细胞的生长速率（倍增时间），但它确实显著增加了DU-145细胞的生长速率。发现AM的促生长作用源于DU-145细胞增殖速率的提高和凋亡率的降低。AM的这些作用被AM受体拮抗剂CGRP（8-37）和AM（22-52）抵消，前者对AM2受体的选择性高于AM1受体，比后者更有效。两种拮抗剂本身都能够通过抑制增殖和增强凋亡来诱导DU-145细胞的基础生长速率缓慢但显著下降，同样CGRP（8-37）比AM（22-52）更有效。综上所述，我们的研究结果表明：i）内源性AM系统在人前列腺中发挥重要的自分泌-旁分泌促生长作用，可能参与上皮细胞恶性表型的发展；ii）AM在人前列腺中的促肿瘤作用主要由AM2受体（CRLR/RAMP3）亚型介导。
