Proadrenomedullin NH(2)-terminal 20 peptide (PAMP) and adrenomedullin bind to teratocarcinoma cells.

Proadrenomedullin NH(2-)terminal 20 peptide (PAMP) and adrenomedullin (ADM) bind to teratocarcinoma cells. The effects of PAMP and ADM on teratocarcinoma cells were investigated. (125)I-PAMP bound to PA1 cells with moderate affinity (K(d) = 110 nM) to a single class of sites (B(max) = 110 000/cell). Specific (125)I-PAMP binding was inhibited by PAMP (IC(50) of 100 nM) but not ADM, calcitonin gene-related peptide (CGRP), or amylin. Specific (125)I-ADM binding was inhibited with high affinity by ADM, CGRP, and CGRP(8-37) (IC(50) values of 10, 10, and 15 nM respectively) but not PAMP or amylin. ADM elevated cAMP (ED(50) value of 100 nM), whereas PAMP had no effect on basal cAMP but inhibited the increase in cAMP caused by 10 nM ADM. Also, the increase in cAMP caused by ADM was inhibited CGRP(8-37), suggesting that ADM is binding to CGRP receptors. ADM (100 nM) stimulated transiently c-fos mRNA, whereas PAMP (1000 nM) had little effect; however, PAMP inhibited the increase in c-fos mRNA caused by ADM. ADM stimulated [(3)H]thymidine uptake into PA1 cells, whereas PAMP inhibited the increase in thymidine uptake caused by ADM. These results indicate that ADM and PAMP are both biologically active in teratocarcinoma cells

Adrenomedullin in mammalian embryogenesis

Here are summarized data supporting that adrenomedullin (AM) is a multifunctional factor involved in the complex regulatory mechanisms of mammalian development. During rodent embryogenesis, AM is first expressed in the heart, followed by a broader but also defined spatio-temporal pattern of expression in vascular, neural, and skeletal-forming tissues as well as in the main embryonic internal organs. AM pattern of expression is suggestive of its involvement in the control of embryonic invasion, proliferation, and differentiation processes, probably through autocrine or paracrine modes of action. AM levels in fetoplacental tissues, uterus, maternal and umbilical plasma are highly increased during normal gestation. These findings in addition to other physiological and gene targeting studies support the importance of AM as a vasorelaxant factor implicated in the regulation of maternal vascular adaptation to pregnancy, as well as of fetal and fetoplacental circulations. AM is also present in amniotic fluid and milk, which is suggestive of additional functions in the maturation and immunological protection of the fetus. Altered expression of AM has been found in some gestational pathologies, although it is not yet clear whether this corresponds to causative or compensatory mechanisms. Future studies in regard to the distribution and expression levels of the molecules known to function as AM receptors, together with data on the action of complement factor H (an AM binding protein), may help to better define the roles of AM during embryonic development

The role of adrenomedullin as a growth regulatory peptide in the normal and malignant setting

Adrenomedullin (AM ) is a recently discovered pluripo1ent peptide initially isolated fraro a human adrenal gland tumor (pheochromocytoma). Adrenomedullin has been shown to have an ancient origin with immunoreactive species fOWld in maromals, birds, reptiles, amphibians, fish , and eemnoderms (s t a r fish ). Given its highly conserved evolutionary expression, AM is thought te playa critica! !•ole in spedes survival. This peptide has been show lo mediate a variety of physiological fu netlons, of which iis involvement in growth r egulation wil1 be tbe central focus of this papero In the following text, we will review the cited Iiterature in this area and inelude our own observations regarding AM express10n in carcinogenesis, embryogenesis, and wound r epair. Adrenomedullin will be shown to induce both growth promotian or growth suppression depending on the taTget cell examined aud the sUITounding nutritional environment in which the analysis was done. Its implied role as a mitogen, aogiogenic fador, and apoplosis survival factor will be critiqued and evaluated relative to its impor tance in the cel! proHferation process. Finally, we will review the a ntimicrobiaJ effect AM has on severa1 human pathogens ( Es•cherichia coli and Candidn albi.cans) and demonstrate its partieipation in the host immune response syslem as a first line defense peptide

Expression of adrenomedullin and its receptor during embryogenesis suggests autocrine or paracrine modes of action

The present study reports the developmental patterns of expression of adrenomedullin (AM) in rat and mouse embryos. AM is a novel multifunctional peptide recently isolated from a human pheochromocytoma, which has been shown to promote growth in a variety of mammalian cell lines. We have applied several techniques to investigate the localization of both the AM peptide and its receptor throughout development. Immunocytochemical detection has been performed using different specific antibodies against AM and its gene-related peptide pro-AM N-terminal 20 peptide. In situ hybridization showed the localization of the messenger RNAs for AM and its receptor. Western blot analysis together with reverse transcription-PCR gave further support to the localization of AM and its receptor in a variety of embryonic tissues. The localization of the receptor paralleled that of AM itself, suggesting an autocrine or paracrine mode of action. The spatio-temporal pattern of expression of AM in cardiovascular, neural, and skeletal-forming tissues as well as in the main embryonic internal organs is described. The primitive placenta, especially the giant trophoblastic cells, shows high levels of AM and AM receptor. The heart is the first organ that expresses AM during development. The kidney, lung, and developing tooth, in which epithelial-mesenchymal interactions are taking place, show specific patterns of AM expression. In several regions of the embryo, the patterns of AM expression correspond to the degree of differentiation. The possible involvement of AM in the control of embryonic invasion, proliferation, and differentiation is discussed

Adrenomedullin expression in the mouse mammary gland: evidence for the mature form in milk

Adrenomedullin (AM) is a recently identified amidated peptide produced by a variety of tissue types. We have investigated the involvement of AM and its receptor (AM-R) in developing mouse mammary glands and have examined what influence ovarian hormones have on AM and AM-R expression in this system. Tissues from ductal morphogenesis, virgin adult, pregnancy, and lactation stages were assessed for AM and AM-R by molecular, biochemical and immunohistochemical techniques. Results from these studies indicated that messenger RNA for AM and AM-R and immunoreactivity for AM were expressed in the luminal epithelium of small and large ducts and in terminal end buds. Immunoreactive AM was identified as a cytoplasm component of ductal cells, with some cells also having nuclear staining. Western blot analysis of mammary gland tissues yielded two molecular mass species (M(r) 14,000 and 18,500) of AM immunoreactivity in the mammary gland for the above developmental stages, consistent with processed intermediate and prohormone forms respectively. Ovariectomy alone or followed by hormonal treatments did not alter the expression pattern for these two proteins. By Western blot, the fully processed AM form (M(r) 6000) was identified in milk extracts from lactating glands. These data suggest a potential role for AM and its receptor in the maintenance of mammary gland homeostasis and suggests a potential role for AM in development of the newborn

Expression of adrenomedullin and proadrenomedullin N-terminal 20 peptide in human and rat prostate

Adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP) are two recently discovered hypotensive peptides translated from the same message transcript (preproAM mRNA). In this article we report the presence of AM, PAMP, and their mRNA in human and rat prostate and of AM receptor mRNA in rat prostate. PreproAM mRNA was found in the epithelium of normal human and rat prostate glands by in situ hybridization. In humans, it was mainly expressed in the basal cells. In rat, its expression was higher in the ducts than in the acini of all the prostate lobes. Immunocytochemistry identified a similar distribution pattern for AM compared with its mRNA but showed different locations for AM and PAMP immunoreactivity. The former was widespread in the epithelia, whereas the latter was almost exclusively found in neuroendocrine cells. In rat, Western blot analysis confirmed the presence of high levels of AM peptide in the ventral lobe and of its precursor in the ventral and dorsolateral lobes. Immunoreactivity for serotonin, chromogranin A, PAMP, and AM defined four subpopulations of prostate neuroendocrine-like cells in rat, a cell type that has not been previously described

Concurrent and distinct transcription and translation of transforming growth factor-beta type I and type II receptors in rodent embryogenesis

The transforming growth factor-betas (TGF-betas) are multifunctional regulatory polypeptides that play a crucial role in many cell processes and function through a set of cell surface protein receptors that includes TGF-beta type I (RI) and type II (RII). The present study reports a comprehensive comparison of the patterns of expression of TGF-beta RI and RII proteins and mRNAs in the developing mouse embryo using immunohistochemical and in situ hybridization analyses. Although widespread expression of both TGF-beta receptors was detected throughout the embryonic development period so that many similarities occur in localization of the TGF-beta receptors, TGF-beta RI was expressed in a well-defined, non-uniform pattern that was different in many respects from that of TGF-beta RII. Whereas higher levels of TGF-beta RI compared to TGF-beta RII were detected in some tissues of the embryo at the beginning of organogenesis, the level of TGF-beta RII increased more dramatically than that of TGF-beta RI during late organogenesis; this was especially true in many neural structures where TGF-beta RI and RII were comparable by day 16. The lung, kidney and intestine, in which epithelial-mesenchymal interactions occur, showed a complex pattern of TGF-beta RI and Rll expression. Additionally, northern blot hybridization and reverse transcription-polymerase chain reaction (RT-PCR) amplification showed non-uniform expression of the transcripts for TGF-beta RI and RII in embryonic and adult mouse and rat tissues. These data show that regulation of TGF-beta1 RI and RII occurs concurrently, but distinctly, in a spatial and temporal manner in rodent embryogenesis which may allow control of signal transduction of TGF-beta during development

Adrenomedullin functions as an important tumor survival factor in human carcinogenesis

Adrenomedullin (AM) is a pluripotent regulatory peptide initially isolated from a human pheochromocytoma (adrenal tumor) and subsequently shown to play a critical role in cancer cell division, tumor neovascularization, and circumvention of programmed cell death, thus it is an important tumor cell survival factor underlying human carcinogenesis. A variety of neural and epithelial cancers have been shown to produce abundant amounts of AM. Recent findings have implicated elevation of serum AM with the onset of malignant expression. In addition, patients with tumors producing high levels of this peptide have a poor prognostic clinical outcome. Given that most human epithelial cancers display a microenvironment of reduced oxygen tension, it is interesting to note that AM and several of its receptors are upregulated during hypoxic insult. The existence of such a regulatory pathway has been implicated as the basis for the overexpression of AM/AM-R in human malignancies, thereby generating a subsequent autocrine/paracrine growth advantage for the tumor cell. Furthermore, AM has been implicated as a potential immune suppressor substance, inhibiting macrophage function and acting as a newly identified negative regulator of the complement cascade, protective properties which may help cancer cells to circumvent immune surveillance. Hence, AM's traditional participation in normal physiology (cited elsewhere in this issue) can be extended to a primary player in human carcinogenesis and may have clinical relevance as a biological target for the intervention of tumor progression

The aryl hydrocarbon receptor repressor is a putative tumor suppressor gene in multiple human cancers

The aryl hydrocarbon receptor repressor (AHRR) is a bHLH/Per-ARNT-Sim transcription factor located in a region of chromosome 5 (5p15.3) that has been proposed to contain one or more tumor suppressor genes. We report here consistent downregulation of AHRR mRNA in human malignant tissue from different anatomical origins, including colon, breast, lung, stomach, cervix, and ovary, and demonstrate DNA hypermethylation as the regulatory mechanism of AHRR gene silencing. Knockdown of AHRR gene expression in a human lung can- cer cell line using siRNA significantly enhanced in vitro anchorage-dependent and -independent cell growth as well as cell growth after transplantation into immunocompromised mice. In addition, knockdown of AHRR in non-clonable normal human mammary epithelial cells enabled them to grow in an anchorage-independent manner. Further, downregulation of AHRR expression in the human lung cancer cell line conferred resistance to apoptotic signals and enhanced motility and invasion in vitro and angiogenic potential in vivo. Ectopic expression of AHRR in tumor cells resulted in diminished anchorage-dependent and -independent cell growth and reduced angiogenic potential. These results therefore demonstrate that AHRR is a putative new tumor suppressor gene in multiple types of human cancers