Placental antiangiogenic prolactin fragments are increased in human and rat maternal diabetes

Identification of PCPE-2 as the endogenous specific inhibitor of human BMP-1/tolloid-like proteinases

BMP-1/tolloid-like proteinases (BTPs) are major players in tissue morphogenesis, growth and repair. They act by promoting the deposition of structural extracellular matrix proteins and by controlling the activity of matricellular proteins and TGF-β superfamily growth factors. They have also been implicated in several pathological conditions such as fibrosis, cancer, metabolic disorders and bone diseases. Despite this broad range of pathophysiological functions, the putative existence of a specific endogenous inhibitor capable of controlling their activities could never be confirmed. Here, we show that procollagen C-proteinase enhancer-2 (PCPE-2), a protein previously reported to bind fibrillar collagens and to promote their BTP-dependent maturation, is primarily a potent and specific inhibitor of BTPs which can counteract their proteolytic activities through direct binding. PCPE-2 therefore differs from the cognate PCPE-1 protein and extends the possibilities to fine-tune BTP activities, both in physiological conditions and in therapeutic settings.

Paternal obesity induces epigenetic aberrations and gene expression changes in placenta and fetus

Paternal epigenome regulates placental and fetal growth. However, the effect of paternal obesity on placenta and its subsequent effect on the fetus via sperm remains unknown. We previously discovered abnormal methylation of imprinted genes involved in placental and fetal development in the spermatozoa of obese rats. In the present study, elaborate epigenetic characterization of sperm, placenta, and fetus was performed. For 16 weeks, male rats were fed either control or a high-fat diet. Following mating studies, sperm, placenta, and fetal tissue were collected. Significant changes were observed in placental weights, morphology, and cell populations. Methylation status of imprinted genes-Igf2, Peg3, Cdkn1c, and Gnas in spermatozoa, correlated with their expression in the placenta and fetus. Placental DNA methylating enzymes and 5-methylCytosine levels increased. Furthermore, in spermatozoa, DNA methylation of a few genes involved in pathways associated with placental endocrine function-gonadotropin-releasing hormone, prolactin, estrogen, and vascular endothelial growth factor, correlated with their expression in placenta and fetus. Changes in histone-modifying enzymes were also observed in the placenta. Histone marks H3K4me3, H3K9me3, and H4ac were downregulated, while H3K27me3 and H3ac were upregulated in placentas derived from obese male rats. This study shows that obesity-related changes in sperm methylome translate into abnormal expression in the F1-placenta fathered by the obese male, presumably affecting placental and fetal development.

Cathepsin D Inhibits Angiogenesis in Pituitary Neuroendocrine Tumors

Prolactin and growth hormone can acquire anti-angiogenic properties after undergoing proteolytic cleavage by Cathepsin D and bone morphogenetic protein 1 (BMP-1) into fragments known as vasoinhibins. Little is known about the effect of vasoinhibins on angiogenesis through the involvement of key cleavage enzymes Cathepsin D and BMP-1 in pituitary neuroendocrine tumors (PitNETs, formerly pituitary adenomas). The purpose of this study was to investigate the mechanism of action of Cathepsin D and BMP-1 on angiogenesis in PitNETs compared with that of pro-angiogenic factors, including vascular endothelial growth factor (VEGF) and basic fibroblast growth factor-2 (FGF2). A total of 43 patients were enrolled in a retrospective analysis and 22 samples were suitable for RNA extraction, including 16 nonfunctional PitNETs and six somatotroph tumors. The mRNA and protein levels of Cathepsin D, BMP-1, VEGF, and FGF2 were compared with those of von Willebrand factor, which was assessed to determine the vascularization of PitNETs. Cathepsin D and FGF2 were significantly correlated with vascularization in PitNETs. Both Cathepsin D and FGF2 are highly involved in angiogenesis in PitNETs, although the effect of Cathepsin D as an anti-angiogenic factor is dominant over that of FGF2 as a pro-angiogenic factor.

Prolactin and its significance in the placenta

Prolactin, a pituitary hormone that was discovered about 80 years ago and is primarily known for its functions in mammary gland development and lactation, is now known to participate in numerous functions across different phylogenetic groups. Fundamentally known for its secretion from lactotroph cells in adenohypophysis region of pituitary gland, newer studies have demonstrated a number of extrapituitary sites which secrete prolactin, where it acts in an autocrine, paracrine, and endocrine manner to regulate essential physiological and biochemical processes. These sites include lymphocytes, epithelial cells of lactating mammary glands, breast cancer cells of epithelial origin, and the placenta. The placenta is one of the most important organs secreting prolactin; however, its role in placental biology has not to date been reviewed comprehensively. This review elaborates upon the various facets of prolactin hormone, including prolactin production and its post-translational modifications and signaling. Major emphasis is placed on placental prolactin and its potential roles, ranging from the role of prolactin in angiogenesis, preeclampsia, maternal diabetes, and anti-apoptosis, among others.

A comparative phylogenetic analysis of prolactin cleavage sites for the generation of vasoinhibin in vertebrates

Vasoinhibin is a pleiotropic protein hormone with endocrine, autocrine, and paracrine effects on blood vessel growth, permeability, and dilation, and a role in several human diseases. It is generated by proteolytic cleavage of the pituitary hormone prolactin by cathepsin D. Several isoforms with a variation in the number of amino acids and corresponding molecular mass exist. This in silico study investigated the cathepsin D cleavage sites in prolactin responsible for the generation of vasoinhibin in vertebrate species. Ninety-one prolactin protein sequences from species of the taxa primates, rodents, laurasiatheria, mammals, sauropsida, and fish were retrieved, and a multiple sequence alignment was performed. Each sequence was investigated for the presence of a vasoinhibin-generating cathepsin D cleavage site and its corresponding substrate affinity using a scoring system. Primates demonstrated the highest substrate affinity for the generation of the 15 kDa vasoinhibin isoform, and fish the highest affinity for the 16.8 kDa isoform. In both cases, this associates to the presence of leucine in the cleavage site, which is not present in species of the other taxa. In primate evolution, the presence of leucine in the cleavage site occurs with the emergence of simiiformes 42 million years ago and is conserved in higher primates across all subsequent speciation nodes. The 17.2 kDa vasoinhibin isoform has a constant substrate affinity in all taxa. The presence of leucine in vasoinhibin generating cleavage sites appears as an important feature of the molecular evolution of vasoinhibin.

Plasmin generates vasoinhibin-like peptides by cleaving prolactin and placental lactogen

Vasoinhibin is an antiangiogenic, profibrinolytic peptide generated by the proteolytic cleavage of the pituitary hormone prolactin by cathepsin D, matrix metalloproteinases, and bone morphogenetic protein-1. Vasoinhibin can also be generated when placental lactogen or growth hormone are enzymatically cleaved. Here, it is investigated whether plasmin cleaves human prolactin and placental lactogen to generate vasoinhibin-like peptides. Co-incubation of prolactin and placental lactogen with plasmin was performed and analyzed by gel electrophoresis and Western blotting. Mass spectrometric analyses were carried out for sequence validation and precise cleavage site identification. The cleavage sites responsible for the generation of the vasoinhibin-like peptides were located at K170-E171 in prolactin and R160-T161 in placental lactogen. Various genetic variants of the human prolactin and placental lactogen genes are projected to affect proteolytic generation of the vasoinhibin-like peptides. The endogenous counterparts of the vasoinhibin-like peptides generated by plasmin may represent vasoinhibin-isoforms with inhibitory effects on vasculature and coagulation.

BMP-1 disrupts cell adhesion and enhances TGF-β activation through cleavage of the matricellular protein thrombospondin-1

Bone morphogenetic protein 1 (BMP-1) is an important metalloproteinase that synchronizes growth factor activation with extracellular matrix assembly during morphogenesis and tissue repair. The mechanisms by which BMP-1 exerts these effects are highly context dependent. Because BMP-1 overexpression induces marked phenotypic changes in two human cell lines (HT1080 and 293-EBNA cells), we investigated how BMP-1 simultaneously affects cell-matrix interactions and growth factor activity in these cells. Increasing BMP-1 led to a loss of cell adhesion that depended on the matricellular glycoprotein thrombospondin-1 (TSP-1). BMP-1 cleaved TSP-1 between the VWFC/procollagen-like domain and the type 1 repeats that mediate several key TSP-1 functions. This cleavage induced the release of TSP-1 C-terminal domains from the extracellular matrix and abolished its previously described multisite cooperative interactions with heparan sulfate proteoglycans and CD36 on HT1080 cells. In addition, BMP-1-dependent proteolysis potentiated the TSP-1-mediated activation of latent transforming growth factor-β (TGF-β), leading to increased signaling through the canonical SMAD pathway. In primary human corneal stromal cells (keratocytes), endogenous BMP-1 cleaved TSP-1, and the addition of exogenous BMP-1 enhanced cleavage, but this had no substantial effect on cell adhesion. Instead, processed TSP-1 promoted the differentiation of keratocytes into myofibroblasts and stimulated production of the myofibroblast marker α-SMA, consistent with the presence of processed TSP-1 in human corneal scars. Our results indicate that BMP-1 can both trigger the disruption of cell adhesion and stimulate TGF-β signaling in TSP-1-rich microenvironments, which has important potential consequences for wound healing and tumor progression.

Prolactin activates IRF1 and leads to altered balance of histone acetylation: Implications for systemic lupus erythematosus

Objectives: Prolactin is known to be associated with autoimmune disease; however, the mechanisms are incompletely understood. Previous studies have highlighted the effects on B-cell tolerance and monocyte/macrophage activation. One study found that prolactin could activate IRF1, a transcription factor implicated in SLE and interferon responses. We hypothesized that prolactin elicited transcriptional regulation though an epigenetic process related to IRF1 activation in monocytes. This study examined IRF1 activation and downstream epigenetic effects.Methods: Protein analysis, qRT-PCR, and ChIP assays were used in a human monocytic cell line and primary monocytes to define changes related to acute and chronic prolactin exposure.Results: We found that prolactin acutely induced both expression and activation of IRF1. Prolactin induced interactions of IRF1 with the histone acetyltransferase co-activators CBP and p300. Chronic prolactin induced expression of multiple histone modifying proteins and genes within the interferon signature suggesting that the prolonged exposure to prolactin resets the landscape and balance of chromatin modifying enzymes.Conclusion: These data provide insight into the mechanism of the association of prolactin with autoimmunity. We found effects at the level of epigenetics, an area not previously explored. Our data support a role for chronic prolactin regulating the expression of genes setting the landscape of chromatin modifying enzymes and driving the interferon signature. This novel finding is of relevance in systemic lupus erythematosus, where clinical effects of hyperprolactinemia have been recognized.

A Dysregulation of the Prolactin/Vasoinhibin Axis Appears to Contribute to Preeclampsia

Preeclampsia is a hypertensive disorder affecting 3-5% of all pregnancies. The only curative treatment is delivery of the placenta and the pathophysiology is poorly understood. Studies have demonstrated altered levels of antiangiogenic factors in patients with preeclampsia. One such factor is the antiangiogenic and antivasodilatatory peptide hormone vasoinhibin, which is higher in the circulation, urine, and amniotic fluid of women with preeclampsia. Normal pregnancy is characterized by elevated circulating prolactin and placental lactogen levels, both of which can serve as vasoinhibin precursors when they are enzymatically cleaved. A dysregulation of vasoinhibin generation during preeclampsia is indicated by higher vasoinhibin, prolactin, placental lactogen, and vasoinhibin-generating enzymes levels and activity. The present article integrates known vasoinhibin levels, effects, and signaling mechanisms to the clinical characteristics of preeclampsia to substantiate the notion that vasoinhibin dysregulation can be causally linked to the development of preeclampsia. If this view is demonstrated, assessment of vasoinhibin levels and regulation of its activity could help estimate the risk of preeclampsia and improve its treatment.

Principles of the prolactin/vasoinhibin axis

The hormonal family of vasoinhibins, which derive from the anterior pituitary hormone prolactin, are known for their inhibiting effects on blood vessel growth, vasopermeability, and vasodilation. As pleiotropic hormones, vasoinhibins act in multiple target organs and tissues. The generation, secretion, and regulation of vasoinhibins are embedded into the organizational principle of an axis, which integrates the hypothalamus, the pituitary, and the target tissue microenvironment. This axis is designated as the prolactin/vasoinhibin axis. Disturbances of the prolactin/vasoinhibin axis are associated with the pathogenesis of retinal and cardiac diseases and with diseases occurring during pregnancy. New phylogenetical, physiological, and clinical implications are discussed.