Opposing actions of intact and N-terminal fragments of the human prolactin/growth hormone family members on angiogenesis: an efficient mechanism for the regulation of angiogenesis

Immunometric and functional measurement of endogenous vasoinhibin in human sera

Introduction

Circulating levels of the antiangiogenic protein vasoinhibin, a fragment of prolactin, are of interest in vasoproliferative retinopathies, preeclampsia, and peripartum cardiomyopathy; however, it is difficult to determine the circulating levels of vasoinhibin due to the lack of quantitative assays.

Methods

This study used human serum samples to assess the concentration and bioactivity of vasoinhibin using a novel enzyme-linked immunosorbent assay (ELISA) for human vasoinhibin, which employs an anti-vasoinhibin monoclonal antibody, a human umbilical vein endothelial cell (HUVEC) proliferation assay, and a chick chorioallantoic membrane (CAM) angiogenesis assay.

Results

Serum samples from 17 pregnant women without (one group) and with preeclampsia and pregnancy induced hypertension (another group) demonstrated endogenous vasoinhibin concentrations in the range of 5-340 ng/ml. Immunoactive vasoinhibin levels were significantly higher in preeclampsia serum compared to healthy pregnancy serum (mean 63.09 ± 22.15 SD vs. 19.67 ± 13.34 ng/ml, p = 0.0003), as was the bioactive vasoinhibin level as determined by the HUVEC proliferation assay (56.12 ± 19.83 vs. 13.38 ± 4.88 ng/ml, p < 0.0001). There was a correlation between the concentration of vasoinhibin measured by ELISA and the HUVEC proliferation assay (Pearson r = 0.95, p < 0.0001). Healthy serum demonstrated a proangiogenic effect in the CAM assay (p < 0.05, compared to control), while serum from preeclamptic patients demonstrated an antiangiogenic effect (p < 0.05 vs. control), as did recombinant human vasoinhibin and a synthetic circular retro-inverse vasoinhibin analogue (CRIVi45-51). The antiangiogenic effects in the CAM assay and the inhibition of HUVEC proliferation were abolished by addition of the ELISA anti-vasoinhibin monoclonal antibody, but not by mouse IgG.

Discussion

These results demonstrate the first quantitation of endogenous vasoinhibin in human sera and the elevation of it levels and antiangiogenic activity in sera from women with preeclampsia. The development and implementation of a quantitative assay for vasoinhibin overcomes a long-standing barrier and suggests the thorough clinical verification of vasoinhibin as a relevant biomarker.

The prolactin receptor: A cross-species comparison of gene structure, transcriptional regulation, tissue-specificity, and genetic variation

The conserved and multifaceted functions of prolactin (PRL) are coordinated through varied distribution and expression of its cell-surface receptor (PRLR) across a range of tissues and physiological states. The resultant heterogeneous expression of PRLR mRNA and protein across different organs and cell types supports a wide range of PRL-regulated processes including reproduction, lactation, development, and homeostasis. Genetic variation within the PRLR gene also accounts for several phenotypes impacting agricultural production and human pathology. The goal of this review is to highlight the many elements that control differential expression of the PRLR across tissues, and the various phenotypes that exist across species due to variation in the PRLR gene.

Homeostatic Regulation of Pro-Angiogenic and Anti-Angiogenic Proteins via Hedgehog, Notch Grid, and Ephrin Signaling in Tibial Dyschondroplasia

Precise coupling of two fundamental mechanisms, chondrogenesis and osteogenesis via angiogenesis, plays a crucial role during rapid proliferation of growth plates, and alteration in their balance might lead to pathogenic conditions. Tibial dyschondroplasia (TD) is characterized by an avascular, non-mineralized, jade-white "cartilaginous wedge" with impaired endochondral ossification and chondrocyte proliferation at the proximal end of a tibial bone in rapidly growing poultry birds. Developing vascular structures are dynamic with cartilage growth and are regulated through homeostatic balance among pro and anti-angiogenic proteins and cytokines. Pro-angiogenic factors involves a wide spectrum of multifactorial mitogens, such as vascular endothelial growth factors (VEGF), platelet-derived growth factors (PDGF), basic fibroblast growth factor (bFGF), placental growth factors, transforming growth factor-β (TGF-β), and TNF-α. Considering their regulatory role via the sonic hedgehog, notch-gridlock, and ephrin-B2/EphB4 pathways and inhibition through anti-angiogenic proteins like angiostatin, endostatin, decoy receptors, vasoinhibin, thrombospondin, PEX, and troponin, their possible role in persisting inflammatory conditions like TD was studied in the current literature review. Balanced apoptosis and angiogenesis are vital for physiological bone growth. Any homeostatic imbalance among apoptotic, angiogenetic, pro-angiogenic, or anti-angiogenic proteins ultimately leads to pathological bone conditions like TD and osteoarthritis. The current review might substantiate solid grounds for developing innovative therapeutics for diseases governed by the disproportion of angiogenesis and anti-angiogenesis proteins.

Interference of B lymphocyte tolerance by prolactin in rheumatic autoimmune diseases

Systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and systemic sclerosis (SSc) are the most common rheumatic autoimmune diseases/disorders (RADs) that affect autologous connective tissues as a result of the breakdown of the self-tolerance mechanisms of the immune system. Prolactin, a glycoprotein hormone, has been known for its crucial role in the pathogenesis of these rheumatic autoimmune diseases. In addition to regulating lymphocyte proliferation and antibody synthesis, prolactin is also responsible for regulating cytokine production. Moreover, it contributes to the breakdown of central and peripheral tolerance mechanisms of B lymphocytes. Given the crucial role of prolactin in the pathogenesis of the mentioned RADs, prolactin may contribute to their pathogenesis by the breakdown of tolerance. In the present study, the key role of prolactin to the breakdown of B lymphocyte tolerance and its possible implication for the pathogenesis of these diseases is discussed. Current literature supports prolactin's role in the breakdown of B lymphocyte central and peripheral tolerance mechanisms, such apoptosis, receptor editing, and also anergy. Therefore, prolactin may contribute to the pathogenesis of RADs by the breakdown of B lymphocyte tolerance. However, more investigations, particularly in RA and SSc animal models, are required to precisely address the pathologic role of prolactin.

The 14-Kilodalton Human Growth Hormone Fragment a Potent Inhibitor of Angiogenesis and Tumor Metastasis

The 14-kilodalton human growth hormone (14 kDa hGH) N-terminal fragment derived from the proteolytic cleavage of its full-length counterpart has been shown to sustain antiangiogenic potentials. This study investigated the antitumoral and antimetastatic effects of 14 kDa hGH on B16-F10 murine melanoma cells. B16-F10 murine melanoma cells transfected with 14 kDa hGH expression vectors showed a significant reduction in cellular proliferation and migration associated with an increase in cell apoptosis in vitro. In vivo, 14 kDa hGH mitigated tumor growth and metastasis of B16-F10 cells and was associated with a significant reduction in tumor angiogenesis. Similarly, 14 kDa hGH expression reduced human brain microvascular endothelial (HBME) cell proliferation, migration, and tube formation abilities and triggered apoptosis in vitro. The antiangiogenic effects of 14 kDa hGH on HBME cells were abolished when we stably downregulated plasminogen activator inhibitor-1 (PAI-1) expression in vitro. In this study, we showed the potential anticancer role of 14 kDa hGH, its ability to inhibit primary tumor growth and metastasis establishment, and the possible involvement of PAI-1 in promoting its antiangiogenic effects. Therefore, these results suggest that the 14 kDa hGH fragment can be used as a therapeutic molecule to inhibit angiogenesis and cancer progression.

Naturally derived cytokine peptides limit virus replication and severe disease during influenza A virus infection

Objectives

Novel host‐targeted therapeutics could treat severe influenza A virus (IAV) infections, with reduced risk of drug resistance. LAT8881 is a synthetic form of the naturally occurring C‐terminal fragment of human growth hormone. Acting independently of the growth hormone receptor, it can reduce inflammation‐induced damage and promote tissue repair in an animal model of osteoarthritis. LAT8881 has been assessed in clinical trials for the treatment of obesity and neuropathy and has an excellent safety profile. We investigated the potential for LAT8881, its metabolite LAT9991F and LAT7771 derived from prolactin, a growth hormone structural homologue, to treat severe IAV infection.

Methods

LAT8881, LAT9991F and LAT7771 were evaluated for their effects on cell viability and IAV replication in vitro, as well as their potential to limit disease in a preclinical mouse model of severe IAV infection.

Results

In vitro LAT8881 treatment enhanced cell viability, particularly in the presence of cytotoxic stress, which was countered by siRNA inhibition of host lanthionine synthetase C‐like proteins. Daily intranasal treatment of mice with LAT8881 or LAT9991F, but not LAT7771, from day 1 postinfection significantly improved influenza disease resistance, which was associated with reduced infectious viral loads, reduced pro‐inflammatory cytokines and increased abundance of protective alveolar macrophages. LAT8881 treatment in combination with the antiviral oseltamivir phosphate led to more pronounced reduction in markers of disease severity than treatment with either compound alone.

Conclusion

These studies provide the first evidence identifying LAT8881 and LAT9991F as novel host‐protective therapies that improve survival, limit viral replication, reduce local inflammation and curtail tissue damage during severe IAV infection. Evaluation of LAT8881 and LAT9991F in other infectious and inflammatory conditions of the airways is warranted.

Biological aspects in controlling angiogenesis: current progress

All living beings continue their life by receiving energy and by excreting waste products. In animals, the arteries are the pathways of these transfers to the cells. Angiogenesis, the formation of the arteries by the development of pre-existed parental blood vessels, is a phenomenon that occurs naturally during puberty due to certain physiological processes such as menstruation, wound healing, or the adaptation of athletes' bodies during exercise. Nonetheless, the same life-giving process also occurs frequently in some patients and, conversely, occurs slowly in some physiological problems, such as cancer and diabetes, so inhibiting angiogenesis has been considered to be one of the important strategies to fight these diseases. Accordingly, in tissue engineering and regenerative medicine, the highly controlled process of angiogenesis is very important in tissue repairing. Excessive angiogenesis can promote tumor progression and lack of enough angiogensis can hinder tissue repair. Thereby, both excessive and deficient angiogenesis can be problematic, this review article introduces and describes the types of factors involved in controlling angiogenesis. Considering all of the existing strategies, we will try to lay out the latest knowledge that deals with stimulating/inhibiting the angiogenesis. At the end of the article, owing to the early-reviewed mechanical aspects that overshadow angiogenesis, the strategies of angiogenesis in tissue engineering will be discussed.

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.

Human Placental Tissue Contains a Placental Lactogen Derived Vasoinhibin

Hormonal factors affecting the vascular adaptions of the uteroplacental unit in noncomplicated and complicated pregnancies are of interest. Here, 4 human placentas from women with and without preeclampsia (PE) were investigated for the presence of placental lactogen (PL)-derived, antiangiogenic vasoinhibin. Western blotting and mass spectrometry of placental tissue revealed the presence of a 9-kDa PL-derived vasoinhibin, the normal 22-kDa full-length PL, and a 28-kDa immunoreactive protein of undetermined nature. The sequence of the 9-kDa vasoinhibin includes the antiangiogenic determinant of vasoinhibin and could constitute a relevant factor in normal pregnancy and PE.

The brain as a source and a target of prolactin in mammals

Prolactin is a polypeptide hormone associated with an extensive variety of biological functions. Among the roles of prolactin in vertebrates, some were preserved throughout evolution. This is the case of its function in the brain, where prolactin receptors, are expressed in different structures of the central nervous system. In the brain, prolactin actions are principally associated with reproduction and parental behavior, and involves the modulation of adult neurogenesis, neuroprotection, and neuroplasticity, especially during pregnancy, thereby preparing the brain to parenthood. Prolactin is mainly produced by specialized cells in the anterior pituitary gland. However, during vertebrate evolution many other extrapituitary tissues do also produce prolactin, like the immune system, endothelial cells, reproductive structures and in several regions of the brain. This review summarizes the relevance of prolactin for brain function, the sources of prolactin in the central nervous system, as well as its local production and secretion. A highlight on the impact of prolactin in human neurological diseases is also provided.

Prolactin and vasoinhibin are endogenous players in diabetic retinopathy revisited

Diabetic retinopathy (DR) and diabetic macular edema (DME) are major causes for visual loss in adults. Nearly half of the world's population with diabetes has some degree of DR, and DME is a major cause of visual impairment in these patients. Severe vision loss occurs because of tractional retinal detachment due to retinal neovascularization, but the most common cause of moderate vision loss occurs in DME where excessive vascular permeability leads to the exudation and accumulation of extracellular fluid and proteins in the macula. Metabolic control stands as an effective mean for controlling retinal vascular alterations in some but not all patients with diabetes, and the search of other modifiable factors affecting the risk for diabetic microvascular complications is warranted. Prolactin (PRL) and its proteolytic fragment, vasoinhibin, have emerged as endogenous regulators of retinal blood vessels. PRL acquires antiangiogenic and anti-vasopermeability properties after undergoing proteolytic cleavage to vasoinhibin, which helps restrict the vascularization of ocular organs and, upon disruption, promotes retinal vascular alterations characteristic of DR and DME. Evidence is linking PRL (and other pituitary hormones) and vasoinhibin to DR and recent preclinical and clinical evidence supports their translation into novel therapeutic approaches.

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.

Performance of a validated spontaneous preterm delivery predictor in South Asian and Sub-Saharan African women: a nested case control study

OBJECTIVES

To address the disproportionate burden of preterm birth (PTB) in low- and middle-income countries, this study aimed to (1) verify the performance of the United States-validated spontaneous PTB (sPTB) predictor, comprised of the IBP4/SHBG protein ratio, in subjects from Bangladesh, Pakistan and Tanzania enrolled in the Alliance for Maternal and Newborn Health Improvement (AMANHI) biorepository study, and (2) discover biomarkers that improve performance of IBP4/SHBG in the AMANHI cohort.

STUDY DESIGN

The performance of the IBP4/SHBG biomarker was first evaluated in a nested case control validation study, then utilized in a follow-on discovery study performed on the same samples. Levels of serum proteins were measured by targeted mass spectrometry. Differences between the AMANHI and U.S. cohorts were adjusted using body mass index (BMI) and gestational age (GA) at blood draw as covariates. Prediction of sPTB < 37 weeks and < 34 weeks was assessed by area under the receiver operator curve (AUC). In the discovery phase, an artificial intelligence method selected additional protein biomarkers complementary to IBP4/SHBG in the AMANHI cohort.

RESULTS

The IBP4/SHBG biomarker significantly predicted sPTB < 37 weeks (n = 88 vs. 171 terms ≥ 37 weeks) after adjusting for BMI and GA at blood draw (AUC= 0.64, 95% CI: 0.57-0.71, p < .001). Performance was similar for sPTB < 34 weeks (n = 17 vs. 184 ≥ 34 weeks): AUC = 0.66, 95% CI: 0.51-0.82, p = .012. The discovery phase of the study showed that the addition of endoglin, prolactin, and tetranectin to the above model resulted in the prediction of sPTB < 37 with an AUC= 0.72 (95% CI: 0.66-0.79, p-value < .001) and prediction of sPTB < 34 with an AUC of 0.78 (95% CI: 0.67-0.90, p < .001).

CONCLUSION

A protein biomarker pair developed in the U.S. may have broader application in diverse non-U.S. populations.

The HGR motif is the antiangiogenic determinant of vasoinhibin: implications for a therapeutic orally active oligopeptide

The hormone prolactin acquires antiangiogenic and antivasopermeability properties after undergoing proteolytic cleavage to vasoinhibin, an endogenous prolactin fragment of 123 or more amino acids that inhibits the action of multiple proangiogenic factors. Preclinical and clinical evidence supports the therapeutic potential of vasoinhibin against angiogenesis-related diseases including diabetic retinopathy, peripartum cardiomyopathy, rheumatoid arthritis, and cancer. However, the use of vasoinhibin in the clinic has been limited by difficulties in its production. Here, we removed this barrier to using vasoinhibin as a therapeutic agent by showing that a short linear motif of just three residues (His46-Gly47-Arg48) (HGR) is the functional determinant of vasoinhibin. The HGR motif is conserved throughout evolution, its mutation led to vasoinhibin loss of function, and oligopeptides containing this sequence inhibited angiogenesis and vasopermeability with the same potency as whole vasoinhibin. Furthermore, the oral administration of an optimized cyclic retro-inverse vasoinhibin heptapeptide containing HGR inhibited melanoma tumor growth and vascularization in mice and exhibited equal or higher antiangiogenic potency than other antiangiogenic molecules currently used as anti-cancer drugs in the clinic. Finally, by unveiling the mechanism that obscures the HGR motif in prolactin, we anticipate the development of vasoinhibin-specific antibodies to solve the on-going challenge of measuring endogenous vasoinhibin levels for diagnostic and interventional purposes, the design of vasoinhibin antagonists for managing insufficient angiogenesis, and the identification of putative therapeutic proteins containing HGR.

The Relevant Participation of Prolactin in the Genesis and Progression of Gynecological Cancers

Prolactin (PRL) is a hormone produced by the pituitary gland and multiple non-pituitary sites, vital in several physiological processes such as lactation, pregnancy, cell growth, and differentiation. However, PRL is nowadays known to have a strong implication in oncogenic processes, making it essential to delve into the mechanisms governing these actions. PRL and its receptor (PRLR) activate a series of effects such as survival, cellular proliferation, migration, invasion, metastasis, and resistance to treatment, being highly relevant in developing certain types of cancer. Because women produce high levels of PRL, its influence in gynecological cancers is herein reviewed. It is interesting that, other than the 23 kDa PRL, whose mechanism of action is endocrine, other variants of PRL have been observed to be produced by tumoral tissue, acting in a paracrine/autocrine manner. Because many components, including PRL, surround the microenvironment, it is interesting to understand the hormone's modulation in cancer cells. This work aims to review the most important findings regarding the PRL/PRLR axis in cervical, ovarian, and endometrial cancers and its molecular mechanisms to support carcinogenesis.

Prolactin stimulates the vascularisation of the retina in newborn mice under hyperoxia conditions

The hormone prolactin (PRL) is emerging as an important regulator of ocular blood vessels. PRL is pro-angiogenic and acquires anti-angiogenic properties after undergoing proteolytic cleavage to the PRL fragment, vasoinhibin. The vascularisation of the rodent retina develops after birth when it rapidly expands until completion at the end of the first postnatal week. Exposure of newborn mice to high oxygen levels lowers the rate of blood vessel growth. In the present study, we investigated whether PRL treatment modifies the vascularisation of the retina in newborn mice exposed to high oxygen or to normoxia and whether the retinal conversion of PRL to vasoinhibin may be altered in the neonate. Newborn mice and their nursing mothers were subjected to 75% oxygen or to normoxia from postnatal day (P) 6 to P8 (group 1) or from P2 to P5 (group 2). PRL (2 µg g-1 , i.p., twice a day) or vehicle was injected from P5 to P8 in group 1 and from P1 to P5 in group 2. PRL treatment reduced the retinal inhibition of blood vessel growth and the increase in vascular regression induced by hyperoxia as revealed by immunofluorescence staining of blood vessels and the expression of angiogenesis and apoptosis markers. The pro-angiogenic effect may involve a reduced conversion of PRL to vasoinhibin. Incubation of PRL with retinal extracts showed reduced activity of the PRL-cleaving protease, cathepsin D, in the neonate vs the adult retina that was further reduced under hyperoxia. PRL and the PRL receptor mRNA were expressed at higher levels in the retina at P8 than in the adult, whereas endogenous PRL was undetectable in the circulation at P8. We conclude that PRL has a pro-angiogenic effect in the neonate retina as a result of its reduced conversion to vasoinhibin and that PRL produced by the retina may help promote physiological vascularisation after birth.

Vasoinhibin generation and effect on neuronal apoptosis in the hippocampus of late mouse embryos

Morphological and behavioral evidence suggests that vasoinhibin is present in the central nervous system (CNS), triggering neuroendocrine and behavioral responses to stress. Moreover, vasoinhibin reduces neuronal survival and differentiation of primary sensory neurons of the peripheral nervous system. To address the functional role played by vasoinhibin at the CNS, and to better understand the underlying mechanisms involved in its actions, we treated primary cultured hippocampal neurons obtained from embryonic day 16 (E16) mice with a human recombinant vasoinhibin. We examined the resulting cellular changes, focusing on neuronal cell death, and explored the local generation of vasoinhibin within the hippocampus. Our results show that vasoinhibin significantly reduced neuronal cell density and increased immunoreactive activated caspase-3 and TUNEL-positive staining at 72, 16, and 24 h, respectively. Furthermore, vasoinhibin increased the expression of proapoptotic genes BAX, BAD, BIM, and PUMA and decreased that of the antiapoptotic gene BCL-2 at 24 h, as assessed by quantitative real-time reverse transcription-polymerase chain reaction. Vasoinhibin effects were blocked by coincubation with a vasoinhibin antibody or with prolactin. Immunoreactive bands consistent with vasoinhibin were observed in hippocampal extracts by Western blot analysis, and a prolactin standard was cleaved to vasoinhibin by a hippocampal lysate in a heat- and cathepsin D inhibitor pepstatin A-dependent fashion. Taken together, these data support the notion that vasoinhibin is locally produced by cathepsin D within the embryonic mouse hippocampus, a brain region that plays a critical role in emotional regulation, resulting in decreased neuronal cell viability via the activation of the intrinsic apoptosis pathway.

Prolactin and its receptor as therapeutic targets in glioblastoma multiforme

Although prolactin (PRL) and its receptor (PRLR) have been detected in glioblastoma multiforme (GBM), their role in its pathogenesis remains unclear. Our aim was to explore their contribution in GBM pathogenesis. We detected PRL and PRLR in all GBM cell lines tested. PRLR activation or overexpression using plasmid transfection increased proliferation, viability, clonogenicity, chemoresistance and matrix metalloproteinase activity in GBM cells, while PRLR antagonist ∆1–9-G129R-hPRL reduced their proliferation, viability, chemoresistance and migration. Meta-analysis of transcriptomic data indicated that PRLR was expressed in all grade II-III glioma (GII-III) and GBM samples. PRL was upregulated in GBM biopsies when compared to GII-III. While in the general population tumour PRL/PRLR expression did not correlate with patient survival, biological sex-stratified analyses revealed that male patients with PRL⁺/PRLR^HIGH GBM performed worse than PRL⁺/PRLR^LOW GBM. In contrast, all male PRL⁺/PRLR^HIGH GII-III patients were alive whereas only 30% of PRL⁺/PRLR^LOW GII-III patients survived after 100 months. Our study suggests that PRLR may be involved in GBM pathogenesis and could constitute a therapeutic target for its treatment. Our findings also support the notion that sexual dimorphism should be taken into account to improve the care of GBM patients.

Synergy Between Low Dose Metronomic Chemotherapy and the pH-centered Approach Against Cancer

Low dose metronomic chemotherapy (MC) is becoming a mainstream treatment for cancer in veterinary medicine. Its mechanism of action is anti-angiogenesis by lowering vascular endothelial growth factor (VEGF) and increasing trombospondin-1 (TSP1). It has also been adopted as a compassionate treatment in very advanced human cancer. However, one of the main limitations of this therapy is its short-term effectiveness: 6 to 12 months, after which resistance develops. pH-centered cancer treatment (pHT) has been proposed as a complementary therapy in cancer, but it has not been adopted or tested as a mainstream protocol, in spite of existing evidence of its advantages and benefits. Many of the factors directly or indirectly involved in MC and anti-angiogenic treatment resistance are appropriately antagonized by pHT. This led to the testing of an association between these two treatments. Preliminary evidence indicates that the association of MC and pHT has the ability to reduce anti-angiogenic treatment limitations and develop synergistic anti-cancer effects. This review will describe each of these treatments and will analyze the fundamentals of their synergy.

Large uremic toxins: an unsolved problem in end-stage kidney disease

Patients with end-stage kidney disease (ESKD) on maintenance hemodialysis are subject to a high burden of inflammation and cardiovascular disease, driven at least in part by retention of uremic solutes. Existing dialysis technologies using high-flux membranes offer limited clearance of solutes >15 kDa. New approaches to improve the removal of large uremic toxins include the novel medium cut-off dialysis membranes with pores larger than those in high-flux membranes. These new membranes provide the potential to improve the clearance of large middle molecules up to 50 kDa. In this review, we discuss 18 uremic toxins with molecular weights between 15 and 60 kDa that are retained in ESKD, for which there is evidence of a link to inflammation and/or cardiovascular disease. These include inflammatory proteins, cytokines, adipokines and other signaling proteins. Improved clearance of this group of difficult to remove molecules has the potential to lead to improved outcomes in dialysis patients by reducing the burden of cardiovascular disease, which now needs to be assessed in robust clinical trials.

Therapeutic strategies for enhancing angiogenesis in wound healing

The enhancement of wound healing has been a goal of medical practitioners for thousands of years. The development of chronic, non-healing wounds is a persistent medical problem that drives patient morbidity and increases healthcare costs. A key aspect of many non-healing wounds is the reduced presence of vessel growth through the process of angiogenesis. This review surveys the creation of new treatments for healing cutaneous wounds through therapeutic angiogenesis. In particular, we discuss the challenges and advancement that have been made in delivering biologic, pharmaceutical and cell-based therapies as enhancers of wound vascularity and healing.

Differential activity of 16K rat prolactin in different organic systems

The 16K isoform of rat prolactin (16K rPRL) performs multiple functions in various systems including angiogenesis, tumorigenesis, and reproduction. Recently, 16K rPRL has attained prominence as a possible therapeutic target in pathophysiological conditions. However, the integral function and mechanism of 16K rPRL in various systems has not been elucidated. To this end, a transient gain-of-function animal model was adopted. An expression DNA plasmid containing 16K rPRL or rPRL gene was introduced into the muscle of adult mice by direct injection. The mRNA and protein expression levels of 16K rPRL were detected by initial RT–PCR and subsequent Southern blot and western blot, respectively. When the expression vector was introduced, the results were as follows: First, 16K rPRL combined with rPRL reduced angiogenesis in the testis whereas rPRL alone induced angiogenesis. Second, 16K rPRL combined with rPRL reduced WBC proliferation, whereas rPRL alone increased WBC proliferation. Third, 16K rPRL combined with rPRL reduced diestrus, whereas rPRL alone extended diestrus. Fourth, 16K rPRL combined with rPRL unexpectedly increased testosterone (T) levels, whereas rPRL alone did not increase T levels. Taken together, our data suggest that the 16K rPRL isoform performs integral functions in angiogenesis in the testis, WBC proliferation, and reproduction, although the action of 16K rPRL is not always antagonistic.

The Endothelium in Acromegaly

Growth hormone (GH) and insulin like growth factor-1 (IGF-1) excess induce well-known deleterious effects on the cardiovascular system, especially after long-term exposition. Acromegaly, a condition of chronic GH and IGF-1 hypersecretion, is frequently associated to cardiovascular complications, although recent studies have shown a reduction in the prevalence of these comorbidities in well-controlled patients and a mortality risk similar to normal aging population. Many factors could contribute to the increased cardiovascular risk of acromegaly patients. Among these factors, the endothelium plays a key role in the pathogenesis of atherosclerotic plaques and could be considered an early marker of atherosclerosis and cardiovascular dysfunction. In this review we examined the relationship between GH/IGF-1 excess and the endothelium, from basic studies to clinical evidence. Many studies involving various arterial districts (microvascular arteries of retina, kidney and brain, and major vessels as carotid and aorta) showed that GH/IGF-1 excess promotes endothelial dysfunction via several different mechanisms. Increased endothelial proliferation, dysfunction of endothelial progenitor cells, increased oxidative stress, and compromised oxidative defenses are the main factors that are associated with endothelial dysfunction. In the general population, these alterations are associated with the development of atherosclerosis with an increased incidence of coronary artery disease and cerebrovascular complications. However, in acromegaly this is still a debated issue, despite the presence of many pro-atherogenic factors and comorbidities, such as hypertension, diabetes, sleep apnoea, and metabolic syndrome. Preclinical markers of atherosclerosis as arterial intima media thickness, pulse wave velocity and flow mediated dilation seem to be impaired in acromegaly and partly mediated by the endothelium dysfunction. In conclusion, the pathophysiology of endothelial dysfunction in the condition of GH and IGF-1 excess remains a crucial area of investigation to fully dissect the association of acromegaly with cardiovascular disease complications.

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.

Somatolactogens and diabetic retinopathy

IMPORTANCE

Diabetic retinopathy (DR) is one of the most common of all diabetic complications. The number of people with DR in the United States is expected to increase to 16 million by 2050. DR is the leading cause of blindness among working-age adults in many different countries, including the United States. In later DR stages, neovascularization is associated with extensive retinal capillary non-perfusion and vitreo-proliferation leading to retinal detachment. This neovascularization is orchestrated by an imbalance of growth factors in the retina from which somatolactogens (pituitary growth hormone, GH-N; placental growth hormone, GH-V; prolactin, PRL; and placental lactogen, PL, also referred as chorionic somatomammotropin, CSH), may play an important role.

OBSERVATIONS

Somatolactogens are a group of hormones that share many structural and functional features. They are important for physiological changes in pregnancy, for adequate development of the fetus, and in the case of GH-N, for promoting growth after birth. GH-N is synthesized by the anterior pituitary, GH-V and PL are secreted by the placenta, whereas, PRL is synthesized by the anterior pituitary and uterine decidua. However, in recent years the expression of GH-N and PRL and their receptors have been detected in other tissues including the retina, acting as neuroprotective and pro-angiogenic agents. The relationship of GH-N and diabetic retinopathy (DR) was established many years ago when it was observed that its deficiency was related to regression of DR while an increase in serum levels of GH-N, GH-V, and PL promoted DR. While more studies are needed to define the potential implications of GH-V and PL in DR pathogenesis, it has been demonstrated that GH-N and PRL participate in DR by enhancing neovascularization. Some PRL isoforms, however, have shown an anti-angiogenic activity rather than pro-angiogenesis and appears to be PRL's main role in the regulation of retinal vasculature.

CONCLUSIONS

Somatolactogens are a group of hormones with a significant role in neuroprotection and angiogenesis regulation in the eye. Understanding the mechanisms of angiogenesis regulation by somatolactogens will potentially lead to the development of new drugs for DR.

A missing piece: the spiny mouse and the puzzle of menstruating species

We recently discovered the first known menstruating rodent. With the exception of four bats and the elephant shrew, the common spiny mouse (Acomys cahirinus) is the only species outside the primate order to exhibit menses. There are few widely accepted theories on why menstruation developed as the preferred reproductive strategy of these select mammals, all of which reference the evolution of spontaneous decidualisation prior to menstrual shedding. Though menstruating species share several reproductive traits, there has been no identifiable feature unique to menstruating species. Such a feature might suggest why spontaneous decidualisation, and thus menstruation, evolved in these species. We propose that a ≥3-fold increase in progesterone during the luteal phase of the reproductive cycle is a unique characteristic linking menstruating species. We discuss spontaneous decidualisation as a consequence of high progesterone, and the potential role of prolactin in screening for defective embryos in these species to aid in minimising implantation of abnormal embryos. We further explore the possible impact of nutrition in selecting species to undergo spontaneous decidualisation and subsequent menstruation. We summarise the current knowledge of menstruation, discuss current pre-clinical models of menstruation and how the spiny mouse may benefit advancing our understanding of this rare biological phenomenon.

Human Placental Growth Hormone Variant in Pathological Pregnancies

Growth hormone (GH), an endocrine hormone, primarily secreted from the anterior pituitary, stimulates growth, cell reproduction, and regeneration and is a major regulator of postnatal growth. Humans have two GH genes that encode two versions of GH proteins: a pituitary version (GH-N/GH1) and a placental GH-variant (GH-V/GH2), which are expressed in the syncytiotrophoblast and extravillous trophoblast cells of the placenta. During pregnancy, GH-V replaces GH-N in the maternal circulation at mid-late gestation as the major circulating form of GH. This remarkable change in spatial and temporal GH secretion patterns is proposed to play a role in mediating maternal adaptations to pregnancy. GH-V is associated with fetal growth, and its circulating concentrations have been investigated across a range of pregnancy complications. However, progress in this area has been hindered by a lack of readily accessible and reliable assays for measurement of GH-V. This review will discuss the potential roles of GH-V in normal and pathological pregnancies and will touch on the assays used to quantify this hormone.

16 kDa vasoinhibin binds to integrin alpha5 beta1 on endothelial cells to induce apoptosis

Many functions of vasoinhibins have been reported, but its receptor has not been clarified yet. Vasoinhibins, 11-18 kDa N-terminal fragments of prolactin, have anti-angiogenic activity and act on endothelial cells to induce apoptosis and to inhibit migration and proliferation, which are opposite to the effects of prolactin. Although vasoinhibins bind to the prolactin receptor, its binding activity is very weak compared to prolactin. Therefore, in this study, we evaluated the binding activity between 16 kDa vasoinhibin and integrin beta1, alpha5 beta1, alpha1 beta1 and alphaV beta3 to identify a specific receptor for vasoinhibins. Moreover, we examined whether 16 kDa vasoinhibin induced apoptosis through integrin beta1 and alpha5 beta1 in endothelial cells. In this study, binding assays and co-immunoprecipitation experiments demonstrated that 16 kDa vasoinhibin could bind strongly to integrin beta1 and alpha5 beta1. Moreover, neutralizing with integrin beta1 and alpha5 beta1 antibody could inhibit 16 kDa vasoinhibin-induced apoptosis in endothelial cells. These findings suggest that vasoinhibins can act on endothelial cells through integrin alpha5 beta1 to induce apoptosis.

Chronic limb-threatening ischemia could benefit from growth hormone therapy for wound healing and limb salvage

Revascularization for chronic limb-threatening ischemia (CLTI) is necessary to alleviate symptoms and wound healing. When it fails or is not possible, there are few alternatives to avoid limb amputation in these patients. Although experimental studies with stem cells and growth factors have shown promise, clinical trials have demonstrated inconsistent results because CLTI patients generally need arteriogenesis rather than angiogenesis. Moreover, in addition to the perfusion of the limb, there is the need to improve the neuropathic response for wound healing, especially in diabetic patients. Growth hormone (GH) is a pleiotropic hormone capable of boosting the aforementioned processes and adds special benefits for the redox balance. This hormone has the potential to mitigate symptoms in ischemic patients with no other options and improves the cardiovascular complications associated with the disease. Here, we discuss the pros and cons of using GH in such patients, focus on its effects on peripheral arteries, and analyze the possible benefits of treating CLTI with this hormone.

PEG hydrogel containing calcium-releasing particles and mesenchymal stromal cells promote vessel maturation

The use of human mesenchymal stromal cells (hMSC) for treating diseased tissues with poor vascularization has received significant attention, but low cell survival has hampered its translation to the clinic. Bioglasses and glass-ceramics have also been suggested as therapeutic agents for stimulating angiogenesis in soft tissues, but these effects need further evaluation in vivo. In this study, calcium-releasing particles and hMSC were combined within a hydrogel to examine their vasculogenic potential in vitro and in vivo. The particles provided sustained calcium release and showed proangiogenic stimulation in a chorioallantoic membrane (CAM) assay. The number of hMSC encapsulated in a degradable RGD-functionalized PEG hydrogel containing particles remained constant over time and IGF-1 release was increased. When implanted in the epidydimal fat pad of immunocompromised mice, this composite material improved cell survival and stimulated vessel formation and maturation. Thus, the combination of hMSC and calcium-releasing glass-ceramics represents a new strategy to achieve vessel stabilization, a key factor in the revascularization of ischemic tissues.

STATEMENT OF SIGNIFICANCE

Increasing blood vessel formation in diseased tissues with poor vascularization is a current clinical challenge. Cell therapy using human mesenchymal stem cells has received considerable interest, but low cell survival has hampered its translation to the clinic. Bioglasses and glass-ceramics have been explored as therapeutic agents for stimulating angiogenesis in soft tissues, but these effects need further evaluation in vivo. By incorporating both human mesenchymal stem cells and glass-ceramic particles in an implantable hydrogel, this study provides insights into the vasculogenic potential in soft tissues of the combined strategies. Enhancement of vessel formation and maturation supports further investigation of this strategy.

Human placental growth hormone in normal and abnormal fetal growth

Human placental growth hormone (PGH), encoded by the growth hormone (GH) variant gene on chromosome 17, is expressed in the syncytiotrophoblast and extravillous cytotrophoblast layers of the human placenta. Its maternal serum levels increase throughout pregnancy, and gradually replaces the pulsatile secreted pituitary GH. PGH is also detectable in cord blood and in the amniotic fluid. This placental-origin hormone stimulates glyconeogenesis, lipolysis and anabolism in maternal organs, and influences fetal growth, placental development and maternal adaptation to pregnancy. The majority of these actions are performed indirectly by regulating maternal insulin-like growth factor-I levels, while the extravillous trophoblast involvement indicates a direct effect on placental development, as it stimulates trophoblast invasiveness and function via a potential combination of autocrine and paracrine mechanisms. The current review focuses on the role of PGH in fetal growth. In addition, the association of PGH alterations in maternal circulation and placental expression in pregnancy complications associated with abnormal fetal growth is briefly reviewed.

Growth hormone modulates in vitro endothelial cell migration and formation of capillary-like structures

The generation of new blood vessels is a complex process mediated by a variety of growth factors, and the growth hormone (GH) has been shown to act as a proangiogenic factor. In fact, human GH deficiency or excess are associated with endothelial dysfunction. Moreover, mouse models have revealed the action of GH in both tissue repair and in the microvascular circulation of normal tissues. In this study, we investigated the in vitro effects of GH on endothelial cells. Using a murine endothelioma cell line (tEnd.1), we demonstrated that GH has a mitogenic effect. The hormone also affected the endothelial cellular morphology and augmented the deposition of the extracellular matrix molecules, laminin, and fibronectin, on tEnd.1 surface. GH could stimulate tEnd.1 cell fugetaxis, in transwell chambers migration assay, and increased the formation of capillary-like structures in Matrigel®-coated plates. Given the important role of angiogenesis during tissue injury, for example, at ischemic lesions, these findings shed light on therapeutic angiogenesis, particularly in pathologies where the cardiovascular system has been compromised.

From Bench to Bedside: Translating the Prolactin/Vasoinhibin Axis

The prolactin/vasoinhibin axis defines an endocrine system, in which prolactin (PRL) and vasoinhibins regulate blood vessel growth and function, the secretion of other hormones, inflammatory and immune processes, coagulation, and behavior. The core element of the PRL/vasoinhibin axis is the generation of vasoinhibins, which consists in the proteolytic cleavage of their precursor molecule PRL. Vasoinhibins can interact with multiple different partners to mediate their effects in various tissues and anatomical compartments, indicating their pleiotropic nature. Based on accumulating knowledge about the PRL/vasoinhibin axis, two clinical trials were initiated, in which vasoinhibin levels are the target of therapeutic interventions. One trial investigates the effect of levosulpiride, a selective dopamine D2-receptor antagonist, on retinal alterations in patients with diabetic macular edema and retinopathy. The rationale of this trial is that the levosulpiride-induced hyperprolactinemia resulting in increased retinal vasoinhibins could lead to beneficiary outcomes in terms of a vasoinhibin-mediated antagonization of diabetes-induced retinal alterations. Another trial investigated the effect of bromocriptine, a dopamine D2-receptor agonist, for the treatment of peripartum cardiomyopathy. The rationale of treatment with bromocriptine is the inhibition of vasoinhibin generation by substrate depletion to prevent detrimental effects on the myocardial microvascularization. The trial demonstrated that bromocriptine treatment was associated with a high rate of left ventricular recovery and low morbidity and mortality. Therapeutic interventions into the PRL/vasoinhibin axis bear the risk of side effects in the areas of blood coagulation, blood pressure, and alterations of the mental state.

Vasoinhibin, an N-terminal Prolactin Fragment, Directly Inhibits Cardiac Angiogenesis in Three-dimensional Heart Culture

Vasoinhibins (Vi) are fragments of the growth hormone/prolactin (PRL) family and have antiangiogenic functions in many species. It is considered that Vi derived from PRL are involved in the pathogenesis of peripartum cardiomyopathy (PPCM). However, the pathogenic mechanism of PPCM, as well as heart angiogenesis, is not yet clear. Therefore, the aim of the present study is to clarify whether Vi act directly on angiogenesis inhibition in heart blood vessels. Endothelial cell viability was decreased by Vi treatment in a culture experiment. Furthermore, expression of proangiogenic genes, such as vascular endothelial growth factor, endothelial nitric oxide synthase, and VE-cadherin, were decreased. On the other hand, apoptotic factor gene, caspase 3, and inflammatory factor genes, tumor necrosis factor α and interleukin 6, were increased by Vi treatment. In three-dimensional left ventricular wall angiogenesis assay in mice, Vi treatment also inhibited cell migration, neovessel sprouting, and growth toward collagen gel. These data demonstrate that Vi treatment directly suppresses angiogenesis of the heart and support the hypothesis that Vi induce PPCM.

Prolactin alters blood pressure by modulating the activity of endothelial nitric oxide synthase

Increased levels of a cleaved form of prolactin (molecular weight 16 kDa) have been associated with preeclampsia. To study the effects of prolactin on blood pressure (BP), we generated male mice with a single-copy transgene (Tg; inserted into the hypoxanthine-guanine phosphoribosyltransferase locus) that enables inducible hepatic production of prolactin and its cleavage product. The Tg is driven by the indole-3-carbinol (I3C)-inducible rat cytochrome P450 1A1 promoter. When the Tg mice were fed normal chow (NC), plasma prolactin concentrations were comparable to those in female WT mice in the last third of pregnancy, and BP was lower than in WT mice (∼95 mm Hg vs. ∼105 mm Hg). When the Tg mice were fed chow containing IC3, plasma prolactin concentrations increased threefold, BP increased to ∼130 mm Hg, and cardiac function became markedly impaired. IC3 chow did not affect the WT mice. Urinary excretion of nitrite/nitrate and the amount of Ser1177-phosphorylated endothelial nitric oxide (NO) synthase (eNOS) were significantly greater in the Tg mice fed NC than in WT mice, as they are during pregnancy. However, when I3C was fed, these indicators of NO production became significantly less in the Tg mice than in WT mice. The effects of increased plasma prolactin were abolished by a genetic absence of eNOS. Thus, a threefold increase in plasma prolactin is sufficient to increase BP significantly and to markedly impair cardiac function, with effects mediated by NO produced by eNOS. We suggest that pregnant women with abnormally high prolactin levels may need special attention.

Multiple Effects of Growth Hormone in the Body: Is it Really the Hormone for Growth?

In this review, we analyze the effects of growth hormone on a number of tissues and organs and its putative role in the longitudinal growth of an organism. We conclude that the hormone plays a very important role in maintaining the homogeneity of tissues and organs during the normal development of the human body or after an injury. Its effects on growth do not seem to take place during the fetal period or during the early infancy and are mediated by insulin-like growth factor I (IGF-I) during childhood and puberty. In turn, IGF-I transcription is dependent on an adequate GH secretion, and in many tissues, it occurs independent of GH. We propose that GH may be a prohormone, rather than a hormone, since in many tissues and organs, it is proteolytically cleaved in a tissue-specific manner giving origin to shorter GH forms whose activity is still unknown.

Growth hormone and ocular dysfunction: Endocrine, paracrine or autocrine etiologies?

The eye is a target site for GH action and growth hormone has been implicated in diabetic retinopathy and other ocular dysfunctions. However, while this could reflect the hypersecretion of pituitary GH, the expression of the GH gene is now known to occur in ocular tissues and it could thus also reflect excess GH production within the eye itself. The possibility that ocular dysfunctions might arise from endocrine, autocrine or paracrine etiologies of GH overexpression is therefore the focus of this brief review.

Plasma prolactin and breast cancer risk: a meta- analysis

Breast cancer is the most common cancer among women, and its incidence is on a constant rise. Previous studies suggest that higher levels of plasma prolactin are associated with escalated risk of breast cancer, however, these results are contradictory and inconclusive. PubMed and Medline were used to search and identify published observational studies that assessed the relationship between plasma prolactin levels and the risk of breast cancer. The pooled relative risks (RRs) with 95% confidence intervals (CIs) were calculated using a fixed-effects or random-effects model. A total of 7 studies were included in our analysis. For the highest versus lowest levels of plasma prolactin, the pooled RR (95% CI) of breast cancer were 1.16 (1.04, 1.29). In subgroup analyses, we found a positive association between plasma prolactin levels and the risk of breast cancer among the patients who were postmenopausal, ER(+)/PR(+) or in situ and invasive carcinoma. However, this positive association was not detected in the premenopausal and ER(-)/PR(-) patients. In conclusion, the present study provides evidence supporting a significantly positive association between plasma prolactin levels and the risk of breast cancer.

The Placental Variant of Human Growth Hormone Reduces Maternal Insulin Sensitivity in a Dose-Dependent Manner in C57BL/6J Mice

The human placental GH variant (GH-V) is secreted continuously from the syncytiotrophoblast layer of the placenta during pregnancy and is thought to play a key role in the maternal adaptation to pregnancy. Maternal GH-V concentrations are closely related to fetal growth in humans. GH-V has also been proposed as a potential candidate to mediate insulin resistance observed later in pregnancy. To determine the effect of maternal GH-V administration on maternal and fetal growth and metabolic outcomes during pregnancy, we examined the dose-response relationship for GH-V administration in a mouse model of normal pregnancy. Pregnant C57BL/6J mice were randomized to receive vehicle or GH-V (0.25, 1, 2, or 5 mg/kg · d) by osmotic pump from gestational days 12.5 to 18.5. Fetal linear growth was slightly reduced in the 5 mg/kg dose compared with vehicle and the 0.25 mg/kg groups, respectively, whereas placental weight was not affected. GH-V treatment did not affect maternal body weights or food intake. However, treatment with 5 mg/kg · d significantly increased maternal fasting plasma insulin concentrations with impaired insulin sensitivity observed at day 18.5 as assessed by homeostasis model assessment. At 5 mg/kg · d, there was also an increase in maternal hepatic GH receptor/binding protein (Ghr/Ghbp) and IGF binding protein 3 (Igfbp3) mRNA levels, but GH-V did not alter maternal plasma IGF-1 concentrations or hepatic Igf-1 mRNA expression. Our findings suggest that at higher doses, GH-V treatment can cause hyperinsulinemia and is a likely mediator of the insulin resistance associated with late pregnancy.

Regulation and localization of vascular endothelial growth factor within the mammary glands during the transition from late gestation to lactation

The vascular network within the developing mammary gland (MG) grows in concert with the epithelium to prepare for lactation, although the mechanisms coordinating this vascular development are unresolved. Vascular endothelial growth factor A (VEGF-A) mediates angiogenesis and vascular permeability in the MG during pregnancy and lactation, where its expression is upregulated by prolactin. Given our previous finding that late-gestational hyperprolactinemia induced by domperidone (DOM) increased subsequent milk yield from gilts, we sought to establish changes in vascular development during late gestation and lactation in the MGs of these pigs and determine whether DOM altered MG angiogenesis and the factors regulating it. Gilts received either no treatment (n = 6) or DOM (n = 6) during late gestation, then had their MG biopsied from late gestation through lactation to assess microvessel density, VEGF-A distribution and messenger RNA expression, and aquaporin (AQP) gene expression. Microvessel density in the MG was unchanged during gestation then increased between days 2 and 21 of lactation (P < 0.05). The local expression of messenger RNA for VEGF-A120, VEGF-A147, VEGF-A164, VEGF-A164b, VEGF-A188, VEGF receptors-1 and -2, and AQP1 and AQP3 all generally increased during the transition from gestation to lactation (P < 0.05). Immunostaining localized VEGF-A to the apical cytoplasm of secretory epithelial cells, consistent with a far greater concentration of VEGF-A in colostrum and/or milk vs plasma (P < 0.0001). There was no effect of DOM on any of the variables analyzed. In summary, we found that vascular development in the MG increases during lactation in first-parity gilts and that VEGF-A is a part of the mammary secretome. Although late-gestational hyperprolactinemia increases milk yield, there was no evidence that it altered vascular development.

Placental Barrier and Autism Spectrum Disorders: The Role of Prolactin and Dopamine on the Developing Fetal Brain

Dopamine and prolactin exhibit opposite effects on lactation. However, a possible role for increased prolactin/dopamine ratio in postpartum mood and thought disorders and as a prognostic indicator of the mother's future mental health has not been well investigated. Postpartum depression is a serious condition with potentially devastating outcomes for both the mother and the infant. Early detection and treatment of this condition can have impressive results. Treatment options include antidepressant medications for mood disorders and use of antipsychotics and electroconvulsive therapy to address postpartum psychosis. Although there are obvious benefits of such treatments on the welfare of the mother and her child, broader implications of these treatments on lactation and child growth and development are not known. This review article explores a possible link between in-utero exposure to a high maternal prolactin/dopamine ratio and subsequent development of autism spectrum disorders. We hypothesize that a comprehensive, biologically oriented approach to the use of psychotropics in the regulation of neurotransmission during pre- and postpartum periods may result in better outcomes in this population.

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.

Depot-Based Delivery Systems for Pro-Angiogenic Peptides: A Review

Insufficient vascularization currently limits the size and complexity for all tissue engineering approaches. Additionally, increasing or re-initiating blood flow is the first step toward restoration of ischemic tissue homeostasis. However, no FDA-approved pro-angiogenic treatments exist, despite the many pre-clinical approaches that have been developed. The relatively small size of peptides gives advantages over protein-based treatments, specifically with respect to synthesis and stability. While many pro-angiogenic peptides have been identified and shown promising results in vitro and in vivo, the majority of biomaterials developed for pro-angiogenic drug delivery focus on protein delivery. This narrow focus limits pro-angiogenic therapeutics as peptides, similar to proteins, suffer from poor pharmacokinetics in vivo, necessitating the development of controlled release systems. This review discusses pro-angiogenic peptides and the biomaterials delivery systems that have been developed, or that could easily be adapted for peptide delivery, with a particular focus on depot-based delivery systems.

New insights in prolactin: pathological implications

Prolactin is a hormone that is mainly secreted by lactotroph cells of the anterior pituitary gland, and is involved in many biological processes including lactation and reproduction. Animal models have provided insights into the biology of prolactin proteins and offer compelling evidence that the different prolactin isoforms each have independent biological functions. The major isoform, 23 kDa prolactin, acts via its membrane receptor, the prolactin receptor (PRL-R), which is a member of the haematopoietic cytokine superfamily and for which the mechanism of activation has been deciphered. The 16 kDa prolactin isoform is a cleavage product derived from native prolactin, which has received particular attention as a result of its newly described inhibitory effects on angiogenesis and tumorigenesis. The discovery of multiple extrapituitary sites of prolactin secretion also increases the range of known functions of this hormone. This Review summarizes current knowledge of the biology of prolactin and its receptor, as well as its physiological and pathological roles. We focus on the role of prolactin in human pathophysiology, particularly the discovery of the mechanism underlying infertility associated with hyperprolactinaemia and the identification of the first mutation in human PRLR.

Tumor subtype-specific associations of hormone-related reproductive factors on breast cancer survival

PURPOSE

It is inconclusive whether reproductive factors, which are known as risk factors of breast cancer, also influence survival. We investigated overall and subtype-specific associations between reproductive factors and breast cancer survival.

METHODS

Among 3,430 incident breast cancer patients who enrolled in the Seoul Breast Cancer Study, 269 patients (7.8%) died and 528 patients (15.4%) recurred. The overall and subtype-specific associations of reproductive factors including age at menarche and menopause, duration of estrogen exposure, menstrual cycle, parity, age at first full-term pregnancy, number of children, age at last birth, time since the last birth, and duration of breastfeeding, on overall and disease-free survival (OS and DFS) were estimated by hazard ratios (HRs) and 95% confidence intervals (95% CIs) using a multivariate Cox proportional hazard model.

RESULTS

An older age at menarche (HR for OS=1.10, 95% CI=1.03-1.19), a greater number of children (≥ 4 vs. 2, HR for DFS=1.58, 95% CI=1.11-2.26), and a shorter time since last birth (<5 vs. ≥ 20 years, HR for DFS=1.67, 95% CI=1.07-2.62) were associated with worse survival while longer duration of estrogen exposure with better survival (HR for DFS=0.97, 95% CI=0.96-0.99). In the stratified analyses by subtypes, those associations were more pronounced among women with hormone receptor and human epidermal growth factor 2 positive (HR+ HER2+) tumors.

CONCLUSIONS

It is suggested that reproductive factors, specifically age at menarche, number of children, time since last birth, and duration of estrogen exposure, could influence breast tumor progression, especially in the HR+ HER2+ subtype.

Vascular endothelial growth factor (VEGF) levels in short, GH treated children: a distinct pattern of VEGF-C in Noonan syndrome

CONTEXT

Noonan syndrome (NS) is characterized by short stature and elevated risk of lymphedema. The mechanism underlying lymphedema may be mediated by vascular endothelial growth factors (VEGFs).

OBJECTIVE

To assess the effect of growth hormone (GH) treatment on plasma insulin-like growth factor (IGF)-1, VEGF-A and VEGF-C levels in patients with NS as compared to short GH-sufficient children.

DESIGN

Retrospective, comparative.

SETTING

Endocrinology department of a tertiary pediatric medical center.

PATIENTS AND METHODS

Plasma IGF-1, VEGF-A and VEGF-C levels were measured before and during GH treatment in 6 patients with NS and 18 age-matched short subjects (Turner, idiopathic short stature and small for gestational age).

MAIN OUTCOME MEASURES

Changes in plasma VEGF and IGF-1 levels.

RESULTS

Baseline IGF-1 SDS levels were slightly lower in NS patients compared with controls; IGF-1 response to GH therapy was markedly lower in NS patients compared with controls (p = 0.017). Mean baseline VEGF-A levels were similar in NS patients and controls whilst mean baseline VEGF-C levels were significantly lower in the NS group as compared with controls (p = 0.022). Plasma VEGF-A and VEGF-C levels did not significantly change during GH treatment in the study cohort. No correlation was found between VEGF-C levels and levels of IGF-1, VEGF-A and auxological parameters, either before or during GH administration.

CONCLUSION

Children with NS have a distinct growth factor profile including low basal VEGF-C and flattened IGF-1 response to GH. Further studies are needed to confirm our findings and to elucidate the interaction between VEGF-C levels and lymphedema.

Orphan nuclear receptor NR4A2 induces transcription of the immunomodulatory peptide hormone prolactin

Background

Nuclear receptor 4A2 (NR4A2) is an orphan nuclear receptor and constitutively active transcription factor expressed at elevated levels in inflamed joint tissues from patients with arthritis. Inflammatory mediators rapidly and potently induce NR4A2 expression in resident joint cells and infiltrating immune cells. This receptor promotes synovial hyperplasia by increasing proliferation of synoviocytes and inducing transcription of matrix degrading enzymes and pro-inflammatory mediators. In order to further elucidate the molecular mechanisms of NR4A2, we conducted a gene expression screen to identify novel transcriptional targets of NR4A2 that may contribute to arthritis progression.

Methods

NR4A2 was over-expressed in human synoviocytes by lentiviral transduction and gene expression changes were measured using qPCR arrays specific for inflammation, proliferation, adhesion, and migration pathways. Subsequent analysis focused on the most potently induced gene prolactin (PRL). Messenger RNA levels of PRL and PRL receptor (PRL-R) were measured by RT-qPCR and protein levels were measured by ELISA. PRL promoter studies were conducted in synoviocytes transiently transfected with NR4A2 and PRL reporter constructs. Molecular responses to PRL in synoviocytes were addressed using qPCR arrays specific for JAK/STAT signaling pathways.

Results

PRL was the most potently induced gene on the qPCR arrays, exhibiting a 68-fold increase in response to ectopic NR4A2. This gene encodes an immunomodulatory peptide hormone with roles in autoimmune diseases and inflammation. Induction of PRL mRNA and secreted protein by NR4A2 was confirmed in subsequent experiments, with increases of 300-fold and 18-fold respectively. Depletion of endogenous NR4A receptors with shRNA reduced basal and PGE₂-induced PRL levels by 95%. At the transcriptional level, NR4A2 requires a functional DNA binding domain to transactivate the distal PRL promoter. Deletional analysis indicates that NR4A2 targets a region of the distal PRL promoter spanning −270 to -32 bp. In synoviocytes, recombinant PRL regulates several genes involved in inflammation, proliferation, and cell survival, suggesting that NR4A2 induced PRL may also impact these pathways and contribute to arthritis progression.

Conclusions

These results provide the first evidence for transcriptional regulation of the immunomodulatory peptide hormone PRL by NR4A2 in synoviocytes, and highlight a novel molecular pathway in inflammatory arthritis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12950-015-0059-2) contains supplementary material, which is available to authorized users.