Elevated Activin Research Articles

Cutaneous Deficiency of Filaggrin and STAT3 Exacerbates Vaccinia Disease In Vivo

RationaleDefects in filaggrin and STAT3 are associated with atopic dermatitis (AD) and susceptibility to severe skin infection.MethodsWe evaluated skin infection with the current smallpox vaccine, ACAM-2000, in immunosuppressed mice with combined cutaneous deficiency in filaggrin and STAT3. In parallel, early events post-infection with ACAM-2000 were investigated in cultured keratinocytes in which filaggrin expression was knocked down via siRNA.ResultsImmunosuppressed, filaggrin-deficient mice, treated with the topical STAT3 inhibitor Stattic® prior to ACAM-2000 infection, demonstrated rapid weight loss, prolonged vaccinia burden in skin, and dermatitis. The TGF-β family ligand activin A was upregulated ten-fold in infected skin. Topically-applied ALK5/TGβR1 signaling inhibitor synergized with vaccinia immune globulin (VIG) to promote vaccinia clearance and limit weight loss. In cultured keratinocytes, filaggrin-directed siRNA inhibited programmed necrosis and inflammatory cytokine release induced by ACAM-2000, while viral growth was increased.ConclusionsOur findings may point to a novel role for filaggrin in early antiviral responses in skin. In wounded skin with underlying barrier defects, chronically elevated activin A levels may contribute to skin remodeling and cutaneous pathogen persistence. Inhibition of ALK5/TGFβR1 signaling may provide a novel co-therapeutic approach, together with VIG, to limit cutaneous spread of vaccinia.

Ligand trap of the activin receptor type IIA inhibits osteoclast stimulation of bone remodeling in diabetic mice with chronic kidney disease

Dysregulation of skeletal remodeling is a component ofrenal osteodystrophy. Previously, we showed that activinreceptor signaling is differentially affected in various tissues in chronic kidney disease (CKD). We tested whether a ligand trap for the activin receptor type 2A (RAP-011) is an effective treatment of the osteodystrophy of the CKD-mineral bone disorder. With a 70% reduction inthe glomerular filtration rate, CKD was induced at 14weeks of age in the ldlr-/- high fat-fed mouse modelofatherosclerotic vascular calcification and diabetes. Twenty mice with CKD, hyperphosphatemia, hyperparathyroidism, and elevated activin A were treated with RAP-011, wherease 19 mice were given vehicle twice weekly from week 22 until the mice were killed at 28 weeks of age. The animals were then evaluated by skeletal histomorphometry, micro-computed tomography, mechanical strength testing, and exvivo bone cell culture. Results in the CKD groups were compared with those of the 16 sham-operated ldlr-/- high fat-fed mice. Sham-operated mice had low-turnover osteodystrophy and skeletal frailty. CKD stimulated bone remodeling with significant increases in osteoclast and osteoblast numbers and bone resorption. Compared with mice with CKD andsham-operated mice, RAP-011 treatment eliminated the CKD-induced increase in these histomorphometric parameters and increased trabecular bone fraction. RAP-011 significantly increased cortical bone area and thickness. Activin A-enhanced osteoclastogenesis was mediated through p-Smad2 association with c-fos and activation of nuclear factor of activated T cells c1 (NFATc1). Thus, an ActRIIA ligand trap reversed CKD-stimulated bone remodeling, likely through inhibition ofactivin-A induced osteoclastogenesis.

Regulation of epithelial to mesenchymal transition in bovine conceptuses through the interaction between follistatin and activin A

Dynamic changes in bovine conceptus and endometrium occur during early gestation, in which the conceptus undergoes epithelial to mesenchymal transition (EMT) after the conceptus attachment to endometrium. To characterize EMT inducing factors, we initially undertook iTRAQ analysis with bovine uterine flushing (UF) obtained from pregnant animals on days 17 (P17: pre-attachment) and 20 (P20: post-attachment). The iTRAQ analysis demonstrated that follistatin (FST), an inhibitor of activin A, increased in P20 UF. We then found that FST decreased in P22 conceptuses, whereas elevated activin A found in P20 UF and endometria was further increased on P22. In addition, phosphorylated SMAD2 increased in P22 conceptuses. In bovine trophoblast cells, the treatment with P22 UF or activin An up-regulated EMT marker expressions, which were inhibited by FST. These results suggest that the initiation of bovine conceptus EMT could be regulated through the spatiotemporal expression of FST or activin A during the peri-attachment period.

Murine Inhibin α-Subunit Haploinsufficiency Causes Transient Abnormalities in Prepubertal Testis Development Followed by Adult Testicular Decline.

Activin production and signaling must be strictly regulated for normal testis development and function. Inhibins are potent activin inhibitors; mice lacking the inhibin-α gene (Inha-/- mice) cannot make inhibin and consequently have highly elevated activin and FSH serum concentrations and excessive activin signaling, resulting in somatic gonadal tumors and infertility. Dose-dependent effects of activin in testicular biology have been widely reported; hence, we hypothesized that male mice lacking one copy of the Inha gene would produce less inhibin and have an abnormal reproductive phenotype. To test this, we compared hormone concentrations, testis development, and sperm production in Inha+/+ and Inha+/- mice. Serum and testicular inhibin-α concentrations in adult Inha+/- mice were approximately 33% lower than wild type, whereas activin A, activin B, FSH, LH, and T were normal. Sixteen-day-old Inha+/- mice had a mixed phenotype, with tubules containing extensive germ cell depletion juxtaposed to tubules with advanced Sertoli and germ cell development. This abnormal phenotype resolved by day 28. By 8 weeks, Inha+/- testes were 11% larger than wild type and supported 44% greater daily sperm production. By 26 weeks of age, Inha+/- testes had distinct abnormalities. Although still fertile, Inha+/- mice had a 27% reduction in spermatogenic efficiency, a greater proportion of S-phase Sertoli cells and lower Leydig cell CYP11A1 expression. This study is the first to identify an intratesticular role for inhibin/inhibin-α subunit, demonstrating that a threshold level of this protein is required for normal testis development and to sustain adult somatic testicular cell function.

Elevated Activin A urine levels are predictors of intraventricular haemorrhage in preterm newborns

Intraventricular haemorrhage (IVH) is the most common variety of cerebral haemorrhage and cause of neurological disabilities in preterm newborns. We evaluated the usefulness of urine Activin A concentrations for the early detection of perinatal IVH. We conducted a case-control study on 100 preterm newborns (20 with IVH and 80 without IVH) in whom urine Activin A was measured at five predetermined time-points in the first 72 h after birth. IVH diagnosis and the extension of the lesion were performed by ultrasound scanning within the first 72 h and at 1 week after birth, respectively. Urine Activin A in infants who developed IVH was significantly higher than in controls at all monitoring time-points (p < 0.01 for all), increasing progressively from first urination to 24 h when it reached the highest peak (p < 0.001). At a cut-off 0.08 ng/L, at the first void, Activin A sensitivity and specificity were 68.7% (CI: 41.3-89%) and 84.5% (CI: 75-91.5%). Activin A measurements in urine soon after birth can constitute a promising tool for identifying preterm infants at risk of IVH.

Effects of a soluble activin type 2B receptor Fc fusion protein (STM 217) in TOV-21G, a mouse xenograft model of clear cell ovarian cancer.

2541 Background: Response rate and survival with the clear cell subtype of ovarian cancer is has not been improved by the introduction of platinum and taxane chemotherapy. Elevated serum activin is associated with inferior ovarian cancer survival, suggesting that activin inhibition may provide a new treatment strategy. STM 217 (recombinant hu-sActR2B-Fc) is a potent (IC50 &lt; 1nM) inhibitor of activin and myostatin signaling that was tested for anti-ovarian tumor activity. Methods: Athymic nude mice received TOV-21g (clear cell ovarian cancer model) xenografts in the abdominal flank region and after 14 days, weekly subcutaneous STM 217 was administered alone or in combination with 5-fluorouracil (5-FU). Mice were monitored for body weight and tumor volume. Results: After 52 days from tumor cell injection, STM 217 treatment resulted in a statistically significant 43% (p&lt;0.0001) tumor growth reduction, versus the vehicle-treated tumor bearing group tested using ANOVA. In the combination efficacy experiment, 5-FU monotherapy resulted in a 47% (p&lt;0.0001) tumor growth reduction, and the combination of STM217 and 5-FU together resulted in a 73% (p&lt;0.0001) tumor growth reduction. During the course of the study, body weight of the mice receiving STM 217 increased by 26%, mice receiving STM 217 and 5-FU increased by 22%, while control tumor bearing mice receiving vehicle exhibited a 10% body weight loss. Conclusions: Our study demonstrates that inhibition of activin signaling by use of a ligand trap results in antitumor activity, both as a monotherapy, and that additive activity was observed in combination with chemotherapy. Increases in body weight were not impaired by concomitant administration of 5-FU chemotherapy. This study suggests that a phase 1 clinical trial of activin inhibition in metastatic ovarian cancer is warranted.

Activin A is stimulated by tumor necrosis factor-alpha and modulates collagen gene expression in human amniotic cells

Accumulating evidence supports the idea of activin A as a modulator of inflammation. In human pregnancy, elevated activin A concentrations in amniotic fluid are reported in women with intra-amniotic infection and inflammation- induced pre-term birth. To test the hypothesis that activin A was involved in the pathophysiology of amnionitis, we evaluated the effects of tumor necrosis factor-α and lipopolysaccharide on activin A production in human amniotic epithelial cells, and the effects of activin A on the expression of collagen mRNA in amniotic mesenchymal cells. Amniotic membranes were obtained from patients without systemic disease, signs of premature delivery or fetal complications, during elective cesarean sections at term. Amniotic epithelial cells and mesenchymal cells were separately obtained by enzymatic digestion and cultured. Activin A was measured by enzyme-linked immunosorbent assay and collagen mRNA levels were assessed by quantitative PCR. Amniotic epithelial cells produced activin A in a cell density- and time-dependent manner. Tumor necrosis factor- α enhanced activin A production in a time-dependent (48-120 h) and dose-dependent (10-300 ng/ml) manner in amniotic epithelial cells. Lipopolysaccharide also stimulated activin A production, but the effect was less prominent. In amniotic mesenchymal cells, the effect of activin A on the expression of type I and type III collagen mRNA was suppressive. Tumor necrosis factor-α and lipopolysaccharide stimulated activin A production in amniotic epithelial cells, and activin A modulated expression of collagen mRNA in amniotic mesenchymal cells. These results support the idea that activin A is involved in the pathophysiology of amnionitis.

640: Elevated activin A and soluble endoglin serum levels in first trimester harald pre-eclampsia

640: Elevated activin A and soluble endoglin serum levels in first trimester harald pre-eclampsia

Elevated pretreatment serum activin A and progression-free and overall survival in trastuzumab-treated metastatic breast cancer.

38 Background: About half of HER2-positive metastatic breast cancer patients will respond tofirst-line trastuzumab-containing therapy, but most will progress within a year. Trastuzumab resistance remains a vexing clinical problem, and better predictive and prognostic biomarkers are needed. Activin A is a TGF-B superfamily member and regulates cell proliferation, apoptosis, differentiation, and immune response. Methods: Serum activin A was measured using ELISA (R&amp;D Systems, Minneapolis, MN) in 60 metastatic breast cancer patients before starting first-line trastuzumab-containing therapy. Progression-free survival (PFS) and overall survival (OS) were analyzed using the Kaplan-Meier method and Cox modeling with both continuous and dichotomous (median) serum activin A analyses. Results: Pretreatment serum activin A levels averaged 2376 pg/ml, and had a median of 629 pg/ml and 25th and 75th quartile values of 406 and 1791 pg/ml, respectively. Patients who were hormone receptor negative had significantly higher activin A levels (median 1287 vs 450 pg/ml, p=0.002). Higher serum activin A was significant on a continuous basis for predicting reduced PFS to first-line trastuzumab-containing therapy (p&lt;0.003), and for predicting shorter OS (p&lt;0.0001). When analyzed using a dichotomous (median) cutpoint, the elevated serum activin A cohort had a significantly reduced PFS (HR 2.79, p &lt;0. 002) (median 6.6 mo vs. 31.1 mo) and OS (HR 5.24, p &lt;0.0001) (median 19.6 mo vs. median not reached). In multivariate analysis for PFS with other covariates (age, line of therapy, CA 15-3, and hormone receptor status), activin A was the only significant covariate (p=0.021). In multivariate analysis for OS, activin A (p=0.002) and CA 15-3 (p=0.03) remained significant as prognostic factors. Conclusions: Elevated pretreatment serum activin A predicts reduced PFS and overall survival in metastatic breast cancer patients treated with first-line trastuzumab-containing therapy. Activin A deserves further study as an adverse biomarker, and to select patients most likely to respond to activin A-targeted therapy.

Elevated serum activin A and survival in CRPC.

e15170 Background: The prognosis of castration-resistant prostate cancer (CRPC) varies widely. Activin A is a ligand in the TGF-B superfamily that regulates cell proliferation, apoptosis, differentiation, and immune responses. In patients with multiple myeloma, elevated activin A is associated with advanced disease and poorer overall survival (OS). Methods: 60 Metastatic CRPC patients whose serum samples were stored at the Dana-Farber Cancer Institute were used for this study. Plasma activin A levels were measured using ELISA (R&amp;D Systems, Minneapolis, MN). Levels of activin A within key patient and disease characteristics were analyzed using the Wilcoxon rank sum test. OS distributions by activin A tertile status were estimated with Kaplan-Meier (KM) and compared with the logrank test. Cox regression was used to produce hazard ratios (HR). Results: In this cohort of 60 patients with metastatic CRPC, median age at diagnosis was 62y, median PSA was 15.3 ng/mL and 37% had a biopsy Gleason score (GS) &gt;8. The index blood draw was a median of 32.9 mo from androgen-deprivation therapy. Median age and PSA at blood draw were 71y and 23.5 ng/mL. At the time of blood draw, 57% of patients had bone only metastasis, 30% were receiving primary or 38% secondary hormonal therapy, and 30% were receiving chemotherapy. Median survival follow-up was 17 months after blood collection (27 deaths). Activin A levels were 621.9 pg/mL (median) and 1382.7 pg/mL (mean). Activin A levels were elevated among older patients (&gt; 65y) and only within patients with higher PSA (&gt;20 ng/mL) at blood draw. KM estimates of median OS (months) for the low, mid and high serum activin A tertile groups were 19.7, 13.8 and 5.4, respectively (p&lt;0.001). The HR (referent low) was 1.4 (95% CI: 0.5-4.5) for the mid and 5.6 (95% CI: 2.1-14.9) for the high tertile. OS was significantly different within age and GS groups, but not within PSA groups. In multivariable analysis, tertile activin A remained significant (p&lt;0.02) when adjusted separately for age at diagnosis, biopsy Gleason score, and serum TIMP-1 (reported previously). Conclusions: Elevated serum activin A predicted for shortened OS in metastatic CRPC, and deserves further study as a biomarker of aggressive disease.

Elevated pretreatment serum activin A and progression-free and overall survival in trastuzumab-treated metastatic breast cancer.

607 Background: About half of HER2-positive metastatic breast cancer patients will respond tofirst-line trastuzumab-containing therapy, but most will progress within a year. Trastuzumab resistance remains a vexing clinical problem, and better predictive and prognostic biomarkers are needed. Activin A is a TGF-B superfamily member and regulates cell proliferation, apoptosis, differentiation, and immune response. Methods: Serum activin A was measured using ELISA (R&amp;D Systems, Minneapolis, MN) in 60 metastatic breast cancer patients before starting first-line trastuzumab-containing therapy. Progression-free survival (PFS) and overall survival (OS) were analyzed using the Kaplan-Meier method and Cox modeling with both continuous and dichotomous (median) serum activin A analyses. Results: Pretreatment serum activin A levels averaged 2376 pg/ml, and had a median of 629 pg/ml and 25th and 75th quartile values of 406 and 1791 pg/ml, respectively. Patients who were hormone receptor negative had significantly higher activin A levels (median 1287 vs 450 pg/ml, p=0.002). Higher serum activin A was significant on a continuous basis for predicting reduced PFS to first-line trastuzumab-containing therapy (p&lt;0.003), and for predicting shorter OS (p&lt;0.0001). When analyzed using a dichotomous (median) cutpoint, the elevated serum activin A cohort had a significantly reduced PFS (HR 2.79, p &lt;0. 002) (median 6.6 mo vs. 31.1 mo) and OS (HR 5.24, p &lt;0.0001) (median 19.6 mo vs. median not reached). In multivariate analysis for PFS with other covariates (age, line of therapy, CA 15-3, and hormone receptor status), activin A was the only significant covariate (p=0.021). In multivariate analysis for OS, activin A (p=0.002) and CA 15-3 (p=0.03) remained significant as prognostic factors. Conclusions: Elevated pretreatment serum activin A predicts reduced PFS and overall survival in metastatic breast cancer patients treated with first-line trastuzumab-containing therapy. Activin A deserves further study as an adverse biomarker, and to select patients most likely to respond to activin A-targeted therapy.

Activin A and cardiovascular disease in type 2 diabetes mellitus

Silent coronary artery disease is a frequent complication of type 2 diabetes (T2DM). Based on its multiple roles in inflammation, atherogenesis and glucose homeostasis, we hypothesised that activin A could be related to coronary atherosclerosis in T2DM. Activin A and follistatin were measured in 102 patients with T2DM and 20 age- and sex-matched healthy controls. Coronary angiography was performed in a sub-population of patients and associations with activin A were examined using multiple linear regression. Serum activin A and the activin A/follistatin ratio were increased in patients with T2DM and coronary artery disease (CAD) compared with healthy volunteers and the elevated activin A was associated with the severity of coronary atherosclerotic burden as determined by the proportion of ≥2 vessel disease (p = 0.035) after multivariable-adjusted trend analysis. No significant association between presence of CAD or extent score and activin A was observed. In patients with T2DM, increased activin A may reflect chronic underlying pathophysiological processes involved in development of cardiovascular disease.

Generation of a Specific Activin Antagonist by Modification of the Activin A Propeptide

Elevated activin A levels in inhibin-deficient mice promote the development of gonadal tumors and induce cachexia by reducing muscle, liver, stomach, and fat mass. Because activin A is an important regulator of tissue growth, inhibiting the actions of this TGFβ family ligand may halt or reverse pathology in diseased tissues. In this study, we modified the activin A propeptide to generate a specific activin antagonist. Propeptides mediate the synthesis and secretion of all TGFβ ligands and, for some family members (e.g. TGFβ1), bind the mature growth factor with high enough affinity to confer latency. By linking the C-terminal region of the TGFβ1 propeptide to the N-terminal region of the activin A propeptide, we generated a chimeric molecule [activin/TGFβ1 propeptide (AT propeptide)] with increased affinity for activin A. The AT propeptide was 30-fold more potent than the activin A propeptide at suppressing activin-induced FSH release by LβT2 pituitary gonadotrope cells. Binding of the AT propeptide to activin A shields the type II receptor binding site, thereby reducing Smad2 phosphorylation and downstream signaling. In comparison with the commonly used activin antagonists, follistatin (IC(50) 0.42 nM), soluble activin type II receptor A-Fc (IC(50) 0.47 nM), and soluble activin type II receptor B-Fc (IC(50) 0.91 nM), the AT propeptide (IC(50) 2.6 nM) was slightly less potent. However, it was more specific, inhibiting activin A and activin B (IC(50) 10.26 nM) but not the closely related ligands, myostatin and growth differentiation factor-11. As such, the AT propeptide represents the first specific activin antagonist, and it should be an effective reagent for blocking activin actions in vivo.

Genetic evidence that SMAD2 is not required for gonadal tumor development in inhibin-deficient mice

BackgroundInhibin is a tumor-suppressor and activin antagonist. Inhibin-deficient mice develop gonadal tumors and a cachexia wasting syndrome due to enhanced activin signaling. Because activins signal through SMAD2 and SMAD3 in vitro and loss of SMAD3 attenuates ovarian tumor development in inhibin-deficient females, we sought to determine the role of SMAD2 in the development of ovarian tumors originating from the granulosa cell lineage.MethodsUsing an inhibin α null mouse model and a conditional knockout strategy, double conditional knockout mice of Smad2 and inhibin alpha were generated in the current study. The survival rate and development of gonadal tumors and the accompanying cachexia wasting syndrome were monitored.ResultsNearly identical to the controls, the Smad2 and inhibin alpha double knockout mice succumbed to weight loss, aggressive tumor progression, and death. Furthermore, elevated activin levels and activin-induced pathologies in the liver and stomach characteristic of inhibin deficiency were also observed in these mice. Our results indicate that SMAD2 ablation does not protect inhibin-deficient females from the development of ovarian tumors or the cachexia wasting syndrome.ConclusionsSMAD2 is not required for mediating tumorigenic signals of activin in ovarian tumor development caused by loss of inhibin.

Activin A Enhances Prostate Cancer Cell Migration Through Activation of Androgen Receptor and Is Overexpressed in Metastatic Prostate Cancer

Bone metastasis is the major cause of mortality associated with prostate cancer. Whereas activin A is known to inhibit prostate cancer cell growth and promote apoptosis, the correlation of elevated activin A with increasing serum prostate-specific antigen (PSA) levels in bone metastatic stages of prostate cancer is well documented. The molecular mechanisms explaining these paradoxical effects of activin A and how activin A influences the progression of prostate cancer with bone metastasis remain unclear. By comparing expression profiles of primary prostate cancer biopsies, with and without bone metastasis, we discovered that the expression of activin A is increased in cases with bone metastatic propensity and correlates with increased androgen receptor (AR), PSA expression, and Gleason scores. Activin A promotes migration of prostate cancer cells to osteoblasts, elevates the AR gene transcription through Smads through binding to AR promoter, and induces nuclear translocation of AR to interact with Smad3. Knockdown of Smad3 by siRNA decreases activin A-promoted AR expression and cancer cell migration. Overexpression of AR reversed Smad3-siRNA suppression on activin A-mediated cell migration to osteoblasts. These data suggest that activation of the AR through Smads is required for activin A-promoted prostate cancer cell migration to bone matrix, thereby promoting the bone metastatic phenotype, and the activin A-Smad-AR axis may be considered a therapeutic target in bone metastatic diseases.

Activin A Promotes the TGF-β-Induced Conversion of CD4+CD25− T Cells into Foxp3+ Induced Regulatory T Cells

TGF-beta induces the conversion of CD4(+)CD25(-) T cells into CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg). Activin A is a pleiotropic TGF-beta family member and is expressed in response to inflammatory signals. In this study, we report on the effects of activin A on the conversion of CD4(+)CD25(-) T cells into Foxp3-expressing induced Treg (iTreg). Activin A was able to promote the conversion of CD4(+)CD25(-) T cells into iTreg in a dose-dependent manner in vitro. Activin A together with TGF-beta1 had synergistic effects on the rate of iTreg conversion in vitro. Intact TGF-beta1 signaling seemed to be essential for the effects of activin A on iTreg generation because cells overexpressing a dominant negative TGF-beta type II receptor could not be converted by activin A in vitro. In vivo, the frequency of peripheral, but not central, Treg was increased in transgenic mice with elevated activin A serum levels and the in vivo conversion rate of CD4(+)CD25(-) T cells into Foxp3-expressing iTreg was increased as compared with wild type mice. These data suggest a role for activin A as a promoter of the TGF-beta dependent conversion of CD4(+)CD25(-) T cells into iTreg in vitro and in vivo. Therefore, besides promoting inflammation, activin A may contribute to the regulation of inflammation via the expansion of peripheral Treg.

The Role of Activin A and Akt/GSK Signaling in Ovarian Tumor Biology

Elevated activin A levels in serum, cyst fluid, and peritoneal fluid of ovarian cancer patients suggest a role for this peptide hormone in disease development. We hypothesize that activin A plays a role in ovarian tumor biology, and analyzed activin-mediated pro-oncogenic signaling in vitro and the expression of activin signaling pathway molecules in vivo. Activin A regulation of Akt and GSK, and the effects of repressing the activities of these molecules (with pharmacological inhibitors) on cellular proliferation were assessed in the cell line, OVCA429. Activin A activated Akt, which phosphorylated GSK, repressing GSK activity in vitro. Activin A stimulated cellular proliferation and repression of GSK augmented activin-regulated proliferation. To validate in vitro observations, immunostaining of the betaA-subunit of activin A and phospho-GSKalpha/beta (Ser9/21) was performed, and the correlation between immunoreactivity levels of these markers and survival was evaluated in benign serous cystadenoma, borderline tumor, and cystadenocarcinoma microarrays. Analysis of tissue microarrays revealed that betaA expression in epithelia did not correlate with survival or malignancy, but expression was elevated in stromal cells from carcinomas when compared with benign tumors. Phospho-GSKalpha/beta (Ser9/21) staining was more intense in mitotically active carcinoma cells and exhibited a polarized localization in benign neoplasms that was absent in carcinomas. Notably, lower phospho-GSKalpha/beta (Ser9/21) immunoreactivity correlated with better survival for carcinoma patients (P=0.046). Our data are consistent with a model in which activin A may mediate ovarian oncogenesis by activating Akt and repressing GSK to stimulate cellular proliferation.

Effects of CDB-4022 on Leydig Cell Function in Adult Male Rats1

CDB-4022, an indenopryridine, suppresses spermatogenesis and decreases inhibin secretion in adult male rats. In the present study, we investigated the effects of CDB-4022 on Leydig cell function. A single oral dose of CDB-4022 (2.5 mg/kg) resulted in a 2-fold decrease in serum testosterone levels after 7 days that was paralleled by a decrease in Cyp17a1 mRNA and protein levels and 17alpha hydroxylase enzymatic activity compared with vehicle-treated rats. Consistent with the lower serum testosterone levels, pituitary Lhb and Fshb mRNA levels were increased 3.2- and 2.3-fold, respectively, by CDB-4022 treatment. Ultrastructural analysis of pituitary gonadotrophs showed distended endoplasmic reticulum (ER) and fewer secretory granules in CDB-4022-treated rats, characteristic of enhanced secretory activity. Conversely, CDB-4022 increased serum progesterone levels, testicular Star mRNA and protein expression, and the number of Leydig cells per testis. Serum inhibin B levels were undetectable in CDB-4022-treated rats, while serum activin A levels were similar to controls, indicating that the CDB-4022-treated rats have an elevated activin A:inhibin B ratio. In the presence of hCG stimulation, activin A directly suppressed testosterone secretion but enhanced progesterone secretion from rat Leydig cell primary cultures. Likewise, treatment of MA-10 cells with activin A was found to enhance cAMP-stimulated progesterone secretion and STAR expression. Together, our data indicate that CDB-4022 treatment inhibits CYP17A1 and stimulates STAR expression, thereby decreasing testosterone but increasing progesterone production. We propose that unopposed actions of activin A most likely contribute to the steroid profile in rats after CDB-4022 treatment. Our findings establish CDB-4022 as a new model to examine intratesticular control mechanisms that modulate Leydig cell gene expression and function.

Activin A Efficiently Specifies Definitive Endoderm from Human Embryonic Stem Cells Only When Phosphatidylinositol 3-Kinase Signaling Is Suppressed

Human ESCs (hESCs) respond to signals that determine their pluripotency, proliferation, survival, and differentiation status. In this report, we demonstrate that phosphatidylinositol 3-kinase (PI3K) antagonizes the ability of hESCs to differentiate in response to transforming growth factor beta family members such as Activin A and Nodal. Inhibition of PI3K signaling efficiently promotes differentiation of hESCs into mesendoderm and then definitive endoderm (DE) by allowing them to be specified by Activin/Nodal signals present in hESC cultures. Under conditions where hESCs are grown in mouse embryo fibroblast-conditioned medium under feeder-free conditions, approximately 70%-80% are converted into DE following 5 days of treatment with inhibitors of the PI3K pathway, such as LY 294002 and AKT1-II. Microarray and quantitative polymerase chain reaction-based gene expression profiling demonstrates that definitive endoderm formation under these conditions closely parallels that following specification with elevated Activin A and low fetal calf serum (FCS)/knockout serum replacement (KSR). Reduced insulin/insulin-like growth factor (IGF) signaling was found to be critical for cell fate commitment into DE. Levels of insulin/IGF present in FCS/KSR, normally used to promote self-renewal of hESCs, antagonized differentiation. In summary, we show that generation of hESC-DE requires two conditions: signaling by Activin/Nodal family members and release from inhibitory signals generated by PI3K through insulin/IGF. These findings have important implications for our understanding of hESC self-renewal and early cell fate decisions.

Microglial cells and peritoneal macrophages release activin A upon stimulation with Toll-like receptor agonists

Activin A levels are elevated in the cerebrospinal fluid (CSF) of patients with meningitis and in the sera of patients with sepsis. The source(s) of the elevated concentrations of activin A in CSF and serum have not yet been discovered. Here we demonstrate that primary mouse microglial cells and peritoneal macrophages release activin A after treatment with agonists of Toll-like receptor (TLR) 2, 4, and 9. These findings provide further evidence for a role of activin in the innate immune response and suggest that microglial cells and macrophages are a source of elevated activin A concentrations observed in the CSF during bacterial meningitis and in the systemic circulation during sepsis.