Stimulatory effects of lipopolysaccharide on endothelial cell activin and follistatin

Hints on transcriptional control of essential players in heterotopic ossification of Fibrodysplasia Ossificans Progressiva

Signaling of the Bone Morphogenetic Protein (BMP) pathway is influenced by the level of expression of its components, in particular receptors, intracellular molecules and target genes which largely depends on gene transcription. One peculiar aspect of Fibrodysplasia Ossificans Progressiva (FOP) relates to the cell types in which the genetic mutation exerts its effects, then not only those involved in the heterotopic ossification processes but also others that participate in the inflammatory phases preceding and triggering heterotopic ossification. Such effects are in part detectable as variation in gene expression, which is also variably manifesting in term of time of appearance in different phases of the inflammatory or ossification processes.

Activin A regulates activation of mouse neutrophils by Smad3 signalling

Activin A, a member of the transforming growth factor beta superfamily, acts as a pro-inflammatory factor in acute phase response, and influences the pathological progress of neutrophil-mediated disease. However, whether activin A can exert an effect on the activities of neutrophils remains unclear. In this study, we found that the release of activin A was enhanced from neutrophils of mouse when stimulated with lipopolysaccharide. Furthermore, neutrophils were not only the source of activin A but also the target cells in response to activin A, in which canonical activin signalling components existed, and levels of ACTRIIA, SMAD3 and p-SMAD3 proteins were elevated in activin A-treated neutrophils. Next, the role of activin A was determined in regulation of neutrophils activities. Our data revealed that activin A induced O₂⁻ release and reactive oxygen species production, promoted IL-6 release, and enhanced phagocytosis, but failed to attract neutrophils migrating across the trans-well membrane. Moreover, we found that effect of activin A on IL-6 release from the peritoneal neutrophils of mouse was significantly attenuated by in vivo Smad3 knockdown. In summary, these data demonstrate that activin A can exert an effect on neutrophils activation in an autocrine/paracrine manner through Smad3 signalling, suggesting that activin A is an important regulator of neutrophils.

Tight interplay in early pregnancy between follistatin and anti-mullerian hormone in women with polycystic ovarian syndrome (PCOS)

PURPOSE

Follistatin levels increase during the course of pregnancy and may play a role in ovarian arrest, reflected by the simultaneous decrease of anti-mullerian-hormone (AMH) levels. The aim of the study was to investigate AMH and follistatin levels during the hormonal window at the beginning of pregnancy. Since both parameters are described as deregulated in polycystic ovarian syndrome (PCOS), subgroup analysis of PCOS patients may additionally elucidate their interplay and effects on ovarian activity.

METHODS

Serum samples were retrospectively analyzed using the AMH Gen II ELISA and the Human Follistatin Quantikine ELISA Kit. Samples were collected longitudinally from 57 patients (32 with PCOS and 25 controls) before conception and during the first trimester. In 18 patients, measurements from the early and the late first trimester were available. Potential associations of AMH and follistatin levels with PCOS-related parameters were compared between the subgroups as well as longitudinally before and in the first trimester of pregnancy. For statistical analysis, the Spearman's correlation, Wilcoxon test, t test, Friedman test and multiple linear regression analysis was performed.

RESULTS

In contrast to AMH, follistatin levels differed not between controls and PCOS patients before and in pregnancy. In both subgroups, AMH levels significantly decreased and follistatin levels significantly increased in longitudinally performed measurements before conceiving and in the first trimester of pregnancy.

CONCLUSION

Follistatin levels are not suited as a biomarker for PCOS, but could be involved in suppressing ovarian activity, as reflected by AMH levels at the beginning of pregnancy.

Molecular targets of dietary phytochemicals for possible prevention and therapy of uterine fibroids: Focus on fibrosis

Uterine fibroids (myomas or leiomyomas) are common benign tumors of reproductive aged women. Fibroids are clinically apparent in 20-50% of women, and cause abnormal uterine bleeding, abdominal pain and discomfort, pregnancy complications and infertility. Unfortunately, limited numbers of medical treatment are available but no effective preventive strategies exist. Moreover, the benefits of medical treatments are tempered by lack of efficacy or serious adverse side effects. Fibrosis has recently been recognized as a key pathological event in leiomyoma development and growth. It is defined by the excessive deposition of extracellular matrix (ECM). ECM plays important role in making bulk structure of leiomyoma, and ECM-rich rigid structure is believed to be a cause of abnormal bleeding and pelvic pain/pressure. Dietary phytochemicals are known to regulate fibrotic process in different biological systems, and being considered as potential tool to manage human health. At present, very few dietary phytochemicals have been studied in uterine leiomyoma, and they are mostly known for their antiproliferative effects. Therefore, in this review, our aim was to introduce some dietary phytochemicals that could target fibrotic processes in leiomyoma. Thus, this review could serve as useful resource to develop antifibrotic drugs for possible prevention and treatment of uterine fibroids.

Seminal fluid factors regulate activin A and follistatin synthesis in female cervical epithelial cells

Seminal fluid induces pro-inflammatory cytokines and elicits an inflammation-like response in the cervix. Here, Affymetrix microarray and qPCR was utilised to identify activin A (INHBA) and its inhibitor follistatin (FST) amongst the cytokines induced by seminal plasma in Ect1 ectocervical epithelial cells, and a similar response was confirmed in primary ectocervical epithelial cells. TGFB is abundant in seminal plasma and all three TGFB isoforms induced INHBA in Ect1 and primary cells, and neutralisation of TGFB in seminal plasma suppressed the INHBA response. Bacterial lipopolysaccharide in seminal plasma also elicited INHBA, but potently suppressed FST production. There was moderate reciprocal inhibition between FST and INHBA, and cross-attenuating effects were seen. These data identify TGFB and potentially LPS as factors mediating seminal plasma-induced INHBA synthesis in cervical cells. INHBA and FST induced by seminal fluid in cervical tissues may thus contribute to regulation of the post-coital response in women.

Pegylated Interferon-α Modulates Liver Concentrations of Activin-A and Its Related Proteins in Normal Wistar Rat

AIMS

To measure the expression of activin βA-subunit, activin IIA and IIB receptors, Smad4, Smad7, and follistatin in the liver and the liver and serum concentrations of mature activin-A and follistatin in normal rat following treatment with pegylated interferon-α (Peg-INF-α) and ribavirin (RBV).

MATERIALS AND METHODS

40 male Wistar rats were divided equally into 4 groups: "control," "Peg-only" receiving 4 injections of Peg-INF-α (6 µg/rat/week), "RBV-only" receiving ribavirin (4 mg/rat/day) orally, and "Peg & RBV" group receiving both drugs. The expression of candidate molecules in liver was measured by immunohistochemistry and quantitative PCR. The concentrations of mature proteins in serum and liver homogenate samples were measured using ELISA.

RESULTS

Peg-INF-α  ± RBV altered the expression of all candidate molecules in the liver at the gene and protein levels (P < 0.05) and decreased activin-A and increased follistatin in serum and liver homogenates compared with the other groups (P < 0.05). There were also significant correlations between serum and liver activin-A and follistatin.

CONCLUSION

Peg-INF-α modulates the hepatic production of activin-A and follistatin, which can be detected in serum. Further studies are needed to explore the role of Peg-INF-α on the production of activins and follistatin by the liver and immune cells.

The effects of pegylated interferon-α and ribavirin on liver and serum concentrations of activin-A and follistatin in normal Wistar rat: a preliminary report

BACKGROUND

Activin-A and follistatin regulate the liver and the immune system.

AIMS

To measure the effects of treatment with pegylated-interferon-α (Peg-IFN-α) and ribavirin on the concentrations of mature activin-A and follistatin in serum and liver tissue homogenates in rats.

METHODS

A total of 28 male Wistar rats were divided equally into four groups as follow: 'Control group' (n = 7), 'PEG only group' consisted of those that only received a weekly injection of Peg-IFN-α (6 µg/rat) for 4 weeks, 'RBV only group' received ribavirin only (4 mg/rat/day) orally for 35 days and the last group received both Peg-IFN-α and ribavirin 'PEG & RBV group'. The concentrations of candidate proteins in serum and liver samples were measured using ELISA.

RESULTS

Pegylated-interferon-α decreased activin-A and increased follistatin significantly in serum and liver of 'PEG only' and 'PEG & RBV' groups compared with the 'Control' and 'RBV only' groups (P < 0.05). There was no significant difference between the 'RBV only' and 'Control' groups (P > 0.05) in the concentrations of candidate proteins. A significant positive correlations between serum and liver activin-A (r = 0.727; P = 0.02 × 10(-3)) and follistatin (r = 0.540; P = 0.01) was also detected.

CONCLUSION

Pegylated-interferon-α modulates the production of activin-A and follistatin by the liver, which is reflected and can be detected at the serum level. Further studies are needed to explore the role of Peg-IFN-α based therapy on the production of activins and follistatin by the liver and immune cells.

Activins and Follistatin in Chronic Hepatitis C and Its Treatment with Pegylated-Interferon-α Based Therapy

Pegylated-interferon-α based therapy for the treatment of chronic hepatitis C (CHC) is considered suboptimal as not all patients respond to the treatment and it is associated with several side effects that could lead to dose reduction and/or termination of therapy. The currently used markers to monitor the response to treatment are based on viral kinetics and their performance in the prediction of treatment outcome is moderate and does not combine accuracy and their values have several limitations. Hence, the development of new sensitive and specific predictor markers could provide a useful tool for the clinicians and healthcare providers, especially in the new era of interferon-free therapy, for the classification of patients according to their response to the standard therapy and only subscribing the novel directly acting antiviral drugs to those who are anticipated not to respond to the conventional therapy and/or have absolute contraindications for its use. The importance of activins and follistatin in the regulation of immune system, liver biology, and pathology has recently emerged. This review appraises the up-to-date knowledge regarding the role of activins and follistatin in liver biology and immune system and their role in the pathophysiology of CHC.

The activins and their binding protein, follistatin-Diagnostic and therapeutic targets in inflammatory disease and fibrosis

The activins, as members of the transforming growth factor-β superfamily, are pleiotrophic regulators of cell development and function, including cells of the myeloid and lymphoid lineages. Clinical and animal studies have shown that activin levels increase in both acute and chronic inflammation, and are frequently indicators of disease severity. Moreover, inhibition of activin action can reduce inflammation, damage, fibrosis and morbidity/mortality in various disease models. Consequently, activin A and, more recently, activin B are emerging as important diagnostic tools and therapeutic targets in inflammatory and fibrotic diseases. Activin antagonists such as follistatin, an endogenous activin-binding protein, offer considerable promise as therapies in conditions as diverse as sepsis, liver fibrosis, acute lung injury, asthma, wound healing and ischaemia-reperfusion injury.

Activin, neutrophils, and inflammation: just coincidence?

During the 26 years that have elapsed since its discovery, activin-A, a member of the transforming growth factor β super-family originally discovered from its capacity to stimulate follicle-stimulating hormone production by cultured pituitary gonadotropes, has been established as a key regulator of various fundamental biological processes, such as development, homeostasis, inflammation, and tissue remodeling. Deregulated expression of activin-A has been observed in several human diseases characterized by an immuno-inflammatory and/or tissue remodeling component in their pathophysiology. Various cell types have been recognized as sources of activin-A, and plentiful, occasionally contradicting, functions have been described mainly by in vitro studies. Not surprisingly, both harmful and protective roles have been postulated for activin-A in the context of several disorders. Recent findings have further expanded the functional repertoire of this molecule demonstrating that its ectopic overexpression in mouse airways can cause pathology that simulates faithfully human acute respiratory distress syndrome, a disorder characterized by strong involvement of neutrophils. This finding when considered together with the recent discovery that neutrophils constitute an important source of activin-A in vivo and earlier observations of upregulated activin-A expression in diseases characterized by strong activation of neutrophils may collectively imply a more intimate link between activin-A expression and neutrophil reactivity. In this review, we provide an outline of the functional repertoire of activin-A and suggest that this growth factor functions as a guardian of homeostasis, a modulator of immunity and an orchestrator of tissue repair activities. In this context, a relationship between activin-A and neutrophils may be anything but coincidental.

The roles of activin A and its binding protein, follistatin, in inflammation and tissue repair

Activin A, a member of the transforming growth factor-β superfamily of cytokines, is a critical controller of inflammation, immunity and fibrosis. It is rapidly released into the blood following a lipopolysaccharide challenge in experimental animals, through activation of the Toll-like receptor 4 signalling pathway. Blocking activin action by pre-treatment with its binding protein, follistatin, modifies the inflammatory cytokine cascade, and reduces the severity of the subsequent inflammatory response and mortality. Likewise, high serum levels of activin A are predictive of death in patients with septicaemia. However, activin A has complex immunomodulatory actions. It is produced by inflammatory macrophages, but can regulate either pro- or anti-inflammatory responses in these cells, depending on their prior activation status. Activin A is also produced by Th2 cells, and stimulates antibody production by B cells and the development of regulatory T cells. Production of activin A during inflammatory responses stimulates fibrosis and tissue remodelling, and follistatin inhibits these actions of activin A. The modulation of activin by follistatin may represent an important therapeutic target for the modulation and amelioration of inflammatory and fibrotic disorders.

Acute regulation of activin A and its binding protein, follistatin, in serum and tissues following lipopolysaccharide treatment of adult male mice

Activin A, a member of the transforming growth factor-β family, increases in the circulation within 1 h after administration of bacterial LPS. To clarify the origins of this rapid increase, the distribution of activin A and its binding protein, follistatin, and their production following LPS treatment, were assessed in adult male mice. In untreated mice, activin A was detectable in all 23 tissues examined, with highest mRNA expression (as measured by quantitative RT-PCR) was found in the liver, and the largest concentration of activin A protein (by ELISA) was found in the bone marrow. Likewise, follistatin mRNA and protein were present in all tissues, with highest expression in the vas deferens. Activin A and follistatin mRNA did not increase significantly in any tissue within the first hour after LPS, but activin A protein decreased by 35% in the bone marrow and increased 5-fold in the lung. No significant changes were observed in any other tissue. Activin A reached a peak in the circulation 1 h following LPS, and then declined. Cycloheximide, an inhibitor of protein translation, reduced this increase of activin A by more than 50%. Actinomycin D, an inhibitor of mRNA transcription, had no effect. Circulating follistatin did not increase until 4 h after LPS and was not affected by either inhibitor. These data indicate that the rapid increase in circulating activin A during LPS-induced inflammation is regulated at the posttranscriptional level, apparently from newly translated and stored protein, and implicate bone marrow-derived cells, and, in particular, neutrophils, as a significant source of this preformed activin A.

The regulation and functions of activin and follistatin in inflammation and immunity

The activins are members of the transforming growth factor β superfamily with broad and complex effects on cell growth and differentiation. Activin A has long been known to be a critical regulator of inflammation and immunity, and similar roles are now emerging for activin B, with which it shares 65% sequence homology. These molecules and their binding protein, follistatin, are widely expressed, and their production is increased in many acute and chronic inflammatory conditions. Synthesis and release of the activins are stimulated by inflammatory cytokines, Toll-like receptor ligands, and oxidative stress. The activins interact with heterodimeric serine/threonine kinase receptor complexes to activate SMAD transcription factors and the MAP kinase signaling pathways, which mediate inflammation, stress, and immunity. Follistatin binds to the activins with high affinity, thereby obstructing the activin receptor binding site, and targets them to cell surface proteoglycans and lysosomal degradation. Studies on transgenic mice and those with gene knockouts, together with blocking studies using exogenous follistatin, have established that activin A plays critical roles in the onset of cachexia, acute and chronic inflammatory responses such as septicemia, colitis and asthma, and fibrosis. However, activin A also directs the development of monocyte/macrophages, myeloid dendritic cells, and T cell subsets to promote type 2 and regulatory immune responses. The ability of both endogenous and exogenous follistatin to block the proinflammatory and profibrotic actions of activin A has led to interest in this binding protein as a potential therapeutic for limiting the severity of disease and to improve subsequent damage associated with inflammation and fibrosis. However, the ability of activin A to sculpt the subsequent immune response as well means that the full range of effects that might arise from blocking activin bioactivity will need to be considered in any therapeutic applications.

Role of activin in bacterial infections: a potential target for immunointervention?

Severe bacterial infections such as sepsis and meningitis still kill or severely injure people despite the use of bactericidal antibiotics. Therefore, new strategies for a better therapy are needed. Activin A, a member of the TGF-β superfamily and its binding protein follistatin (FS) are released by various cell types during acute and chronic inflammatory processes. Until now, a clear definition of conditions in which activin A exerts either its pro- or anti-inflammatory functions is lacking. The activin/FS-system participates in the fine-tuning of the host’s inflammatory response upon infectious stimuli. This response is on the one hand necessary for fighting pathogens, but on the other hand can negatively affect the host. This article focuses on the role of activin A and FS in infection and after acute inflammatory stimuli. The therapeutic potentials of blocking or promoting activin actions are discussed.

The relationship between follistatin and chronic low-grade inflammation in women with polycystic ovary syndrome

The circulating follistatin and high-sensitivity C-reactive protein (hsCRP) concentrations were significantly higher in 155 Taiwanese women with polycystic ovary syndrome (PCOS) than in 37 healthy controls. Follistatin and hsCRP levels in both the PCOS and control groups were significantly correlated with each other independent of obesity and insulin resistance.

The biology of activin: recent advances in structure, regulation and function

Activin was discovered in the 1980s as a gonadal protein that stimulated FSH release from pituitary gonadotropes and was thought of as a reproductive hormone. In the ensuing decades, many additional activities of activin were described and it was found to be produced in a wide variety of cell types at nearly all stages of development. Its signaling and actions are regulated intracellularly and by extracellular antagonists. Over the past 5 years, a number of important advances have been made that clarify our understanding of the structural basis for signaling and regulation, as well as the biological roles of activin in stem cells, embryonic development and in adults. These include the crystallization of activin in complex with the activin type II receptor ActRIIB, or with the binding proteins follistatin and follistatin-like 3, as well as identification of activin's roles in gonadal sex development, follicle development, luteolysis, beta-cell proliferation and function in the islet, stem cell pluripotency and differentiation into different cell types and in immune cells. These advances are reviewed to provide perspective for future studies.

Activin and related proteins in inflammation: not just interested bystanders

Activin A, a member of the transforming growth factor-beta superfamily, is released rapidly into the circulation during inflammation. This review examines the evidence that activin is a critical mediator of inflammation and immunity. Activin modulates several aspects of the inflammatory response, including release of pro-inflammatory cytokines, nitric oxide production and immune cell activity. Crucially, inhibiting activin with follistatin, a high affinity binding protein, alters the pattern of cytokines released and improves survival in a mouse model of endotoxic shock. Serum and tissue concentrations of activin are elevated in a wide range of pathological conditions. The utility of activin as a diagnostic marker of clinical inflammation and the use of follistatin to block activin actions therapeutically are also discussed.

Female infertility and disrupted angiogenesis are actions of specific follistatin isoforms

The circulating and tissue-bound forms of follistatin (FST315 and FST288, respectively) modulate the actions of activins. FST knockout (KO/null) mice, lacking both isoforms, die perinatally with defects in lung, skin, and the musculoskeletal system. Using constructs of the human FST gene engineered to enable expression of each isoform under the control of natural regulatory elements, transgenic mouse lines were created and crossed with FST null mice to attempt to rescue the neonatal lethality. FST288 expression alone did not rescue the neonatal lethality, but mice expressing FST315 on the KO background survived to adulthood with normal lung and skin morphology and partial reversal of the musculoskeletal defects noted in FST KO mice. The FST315 rescue mice displayed a short period of neonatal growth retardation, impaired tail growth, and female infertility. The latter may be due to failure of corpus luteum formation, a decline in the ovarian follicular population, and an augmented uterine inflammatory response to mating. Failure of corpus luteum formation and impaired tail growth indicate abnormal vascularization and suggest that FST288 is required for the promotion of angiogenesis. The augmented uterine inflammatory response may result from the failure of FST315 to modulate the proinflammatory actions of activin A in the uterus or may result from the altered steroid milieu associated with the ovarian abnormalities. Although we cannot definitively conclude that the remaining defects are due to the absence of a particular isoform or due to variable expression of each, these models have demonstrated novel physiological processes that are influenced by FST.

Activin A is a critical component of the inflammatory response, and its binding protein, follistatin, reduces mortality in endotoxemia

Activin A is a member of the transforming growth factor-beta superfamily, which we have identified as having a role in inflammatory responses. We show that circulating levels of activin increase rapidly after LPS-induced challenge through activation of Toll-like receptor 4 and the key adaptor protein, MyD88. Treatment with the activin-binding protein, follistatin, alters the profiles of TNF, IL-1beta, and IL-6 after LPS stimulation, indicating that activin modulates the release of several key proinflammatory cytokines. Further, mice administered one 10-mug dose of follistatin to block activin effects have increased survival after a lethal dose of LPS, and the circulating levels of activin correlate with survival outcome. These findings demonstrate activin A's crucial role in the inflammatory response and show that blocking its actions by the use of follistatin has significant therapeutic potential to reduce the severity of inflammatory diseases.