Hutchinson H G, Trindade P T, Cunanan D B, Wu C F, Pratt R E
Falk Cardiovascular Research Center, Stanford University School of Medicine, CA 94305, USA.
Cardiovasc Res. 1997 Jul;35(1):158-67. doi: 10.1016/s0008-6363(97)00086-2.
While natriuretic peptides can inhibit growth of vascular muscle cells (VSMC), controversy exists as to whether this effect is mediated via the guanylate cyclase-coupled receptors, NPR-A and NPR-B, or the clearance receptor, NPR-C. The original aim of this study was to examine the mechanism by which the NPR-C receptor regulates growth.
Rat VSMC were characterized with regard to natriuretic peptide receptor expression by RT/PCR and radioligand binding studies. The effect on growth following addition of the peptides and the ligands for NPR-C was measured by [3H]thymidine incorporation. Cyclic guanosine monophosphate (cGMP) levels were determined by radioimmunoassay and mitogen activating protein kinase activity was based on the phosphorylation of myelin basic protein.
In rat VSMC, passages 4-12, both atrial natriuretic peptide (ANP) and C-type natriuretic peptide (CNP) dose-dependently inhibited serum and PDGF-induced VSMC growth. In contrast, NPR-C specific ligands alone had no effect on cell growth but enhanced growth inhibition when co-administered with ANP and CNP. ANP and CNP also decreased PDGF-BB-stimulated MAP kinase activity. Once again, NPR-C specific ligands alone had no effect but enhanced the effects of ANP. Furthermore, a cGMP specific phosphodiesterase inhibitor dose-dependently inhibited VSMC growth and markedly enhanced natriuretic-peptide-induced inhibition at low peptide concentrations. To examine a potential mechanism for the controversy concerning the NPR-C, we investigated the autocrine expression of ANP and CNP by VSMC and found that mRNA encoding both peptides could be detected by RT/PCR.
Our findings indicate that the guanyl-cyclase-linked receptors mediate the antiproliferative actions of the natriuretic peptides on vascular smooth muscle cell growth. Moreover, we hypothesize that the apparent inhibition of growth by NPR-C specific ligands reported by others may be due to stabilization of natriuretic peptides produced by the cultured VSMC and subsequent action of these peptides at guanyl-cyclase-linked receptors.
虽然利钠肽可抑制血管平滑肌细胞（VSMC）的生长，但对于这种效应是通过鸟苷酸环化酶偶联受体NPR - A和NPR - B，还是清除受体NPR - C介导存在争议。本研究的最初目的是研究NPR - C受体调节生长的机制。
通过RT/PCR和放射性配体结合研究对大鼠VSMC的利钠肽受体表达进行表征。通过[3H]胸苷掺入法测定添加肽和NPR - C配体后对生长的影响。通过放射免疫测定法测定环磷酸鸟苷（cGMP）水平，丝裂原活化蛋白激酶活性基于髓鞘碱性蛋白的磷酸化。
在第4 - 12代大鼠VSMC中，心房利钠肽（ANP）和C型利钠肽（CNP）均剂量依赖性地抑制血清和血小板衍生生长因子（PDGF）诱导的VSMC生长。相比之下，单独的NPR - C特异性配体对细胞生长没有影响，但与ANP和CNP共同给药时可增强生长抑制作用。ANP和CNP还降低了PDGF - BB刺激的丝裂原活化蛋白激酶活性。同样，单独的NPR - C特异性配体没有作用，但增强了ANP的作用。此外，一种cGMP特异性磷酸二酯酶抑制剂剂量依赖性地抑制VSMC生长，并在低肽浓度下显著增强利钠肽诱导的抑制作用。为了研究关于NPR - C争议的潜在机制，我们研究了VSMC中ANP和CNP的自分泌表达，发现通过RT/PCR可以检测到编码这两种肽的mRNA。
我们的研究结果表明，鸟苷酸环化酶连接的受体介导利钠肽对血管平滑肌细胞生长的抗增殖作用。此外，我们推测其他人报道的NPR - C特异性配体对生长的明显抑制可能是由于培养的VSMC产生的利钠肽的稳定化以及这些肽随后在鸟苷酸环化酶连接的受体上的作用。
