Differential effects of rat pregnancy on uterine and lung atrial natriuretic factor receptors

Role of corin and atrial natriuretic peptide in preeclampsia

In pregnancy, uterine spiral artery remodeling is an adaptive morphological change at the maternal and fetal interface, which is critical for dilating the artery and promoting blood flow to the fetus. Incompletely remodeled spiral arteries have been recognized as a common pathological feature in preeclamptic patients. To date, the molecular mechanism that controls spiral artery remodeling is not well defined. Corin is a transmembrane serine protease discovered in the heart, where it converts pro-atrial natriuretic peptide (pro-ANP) to active ANP, a cardiac hormone that regulates salt-water balance and blood pressure. Recent studies show that corin is up-regulated in the decidua of the pregnant uterus, suggesting a potential role of corin in pregnancy. In mice lacking corin or ANP, high blood pressure and proteinuria were found at late gestational stages. Histological analysis indicated delayed trophoblast invasion and impaired spiral artery remodeling in the uterus. In humans, CORIN gene mutations were identified in patients with preeclampsia. In this review, we discuss the function of corin and ANP in regulating blood pressure and their potential role in preeclampsia.

Ligand-mediated endocytosis and intracellular sequestration of guanylyl cyclase/natriuretic peptide receptors: role of GDAY motif

The guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA), also referred to as GC-A, is a single polypeptide molecule having a critical function in blood pressure regulation and cardiovascular homeostasis. GC-A/NPRA, which resides in the plasma membrane, consists of an extracellular ligand-binding domain, a single transmembrane domain, and an intracellular cytoplasmic region containing a protein kinase-like homology domain (KHD) and a guanylyl cyclase (GC) catalytic domain. After binding with atrial and brain natriuretic peptides (ANP and BNP), GC-A/NPRA is internalized and sequestered into intracellular compartments. Therefore, GC-A/NPRA is a dynamic cellular macromolecule that traverses different subcellular compartments through its lifetime. This review describes the roles of short-signal sequences in the internalization, trafficking, and intracellular redistribution of GC-A/NPRA from cell surface to cell interior. Evidence indicates that, after internalization, the ligand-receptor complexes dissociate inside the cell and a population of GC-A/NPRA recycles back to the plasma membrane. Subsequently, the disassociated ligands are degraded in the lysosomes. However, a small percentage of the ligand escapes the lysosomal degradative pathway, and is released intact into culture medium. Using pharmacologic and molecular perturbants, emphasis has been placed on the cellular regulation and processing of ligand-bound GC-A/NPRA in terms of receptor trafficking and down-regulation in intact cells. The discussion is concluded by examining the functions of short-signal sequence motifs in the cellular life-cycle of GC-A/NPRA, including endocytosis, trafficking, metabolic processing, inactivation, and/or down-regulation in model cell systems.

Hypertension in mice lacking the proatrial natriuretic peptide convertase corin

Atrial natriuretic peptide (ANP) is a cardiac hormone that regulates blood pressure. In cardiomyocytes, the hormone is synthesized as a precursor, proatrial natriuretic peptide (pro-ANP), which is proteolytically converted to active ANP. Corin is a cardiac transmembrane serine protease that has been shown to process pro-ANP in vitro, but its physiological importance had not been established. Here, we show that corin-deficient (Cor-/-) mice develop normally during embryogenesis and survive to postnatal life. Cor-/- mice have elevated levels of pro-ANP but no detectable levels of ANP as compared with WT littermates. Infusion of an active recombinant soluble corin transiently restores pro-ANP conversion, resulting in the release of circulating biologically active ANP. Using radiotelemetry to assess blood pressure, we find that Cor-/- mice have spontaneous hypertension as compared with WT mice, and it is enhanced after dietary salt loading. Pregnant Cor-/- mice demonstrate late-gestation proteinuria and enhanced high blood pressure during pregnancy. In addition, Cor-/- mice exhibit cardiac hypertrophy resulting in a mild decline in cardiac function later in life. Thus, our data establish corin as the physiological pro-ANP convertase and indicate that corin deficiency may contribute to hypertensive heart disease.

Distinct regulation of nitric oxide and cyclic guanosine monophosphate production by steroid hormones in the rat uterus

It has previously been reported that uterine nitric oxide (NO) production is enhanced during rat pregnancy compared to non-pregnant, labouring or postpartum states. The present hypothesis is that these changes in uterine NO production during pregnancy are caused by the interplay of oestrogen and progesterone. It is further postulated that changes in cyclic guanosine monophosphate (cGMP) production closely follow the changes in uterine NO synthesis. To test these hypotheses a variety of hormonal regimens (17beta-oestradiol, progesterone and combinations) were applied to different rat models (prepubertal, non-pregnant intact and ovariectomized as well as pregnant rats). The production of nitric oxide (NO) as well as basal and in-vitro NO-stimulated cGMP tissue content were measured in parallel. NO production was measured by the accumulation of nitrites and nitrates in a 24 h incubation medium as analysed by Greiss reaction. cGMP content was measured by radioimmunoassay. Diethylenetriamine/NO (DETA/NO) was used as NO donor. NO production in the rat uterus was markedly increased by pregnancy compared to other physiological (prepubertal, or cycling dioestrus) and experimentally induced (OVX) states. In contrast, uterine cGMP was significantly decreased in pregnancy. Pregnancy also inhibited the elevation in uterine cGMP after in-vitro NO challenge. Chronic 17beta-oestradiol treatment in prepubertal and/or OVX models increased NO production and also mimicked the effect of pregnancy on cGMP. Administration of progesterone in prepubertal rats induced a parallel decrease in both uterine NO and cGMP. In conclusion, sex steroid hormones distinctly regulate uterine NO and cGMP production depending upon the dose and regimen used, as well as the animal's reproductive state.