Erythropoietin enhancement of rat pancreatic tumor cell proliferation requires the activation of ERK and JNK signals

Transmembrane Protein ANTXR1 Regulates γ-Globin Expression by Targeting the Wnt/β-Catenin Signaling Pathway

Reactivation of fetal hemoglobin (HbF, α2γ2) alleviates clinical symptoms in patients with β-thalassemia and sickle cell disease, although the regulatory mechanisms of γ-globin expression have not yet been fully elucidated. Recent studies found that interfering with the expression of the membrane protein ANTXR1 gene upregulated γ-globin levels. However, the exact mechanism by which ANTXR1 regulates γ-globin levels remains unclear. Our study showed that overexpression and knockdown of ANTXR1 in K562, cord blood CD34⁺, and HUDEP-2 cells decreased and increased γ-globin expression, respectively. ANTXR1 regulates the reactivation of fetal hemoglobin (HbF, α2γ2) in K562, cord blood CD34⁺, and adult peripheral blood CD34⁺ cells through interaction with LRP6 to promote the nuclear entry of β-catenin and activate the Wnt/β-catenin signaling pathway. The overexpression or knockdown of ANTXR1 on γ-globin and Wnt/β-catenin signaling in K562 cells was reversed by the inhibitor XAV939 and the activator LiCl, respectively, where XAV939 inhibits the transcription of β-catenin in the Wnt pathway, but LiCl inhibits GSK3-β. We also showed that the binding ability of the rank4 site in the transcriptional regulatory region of the SOX6 gene to c-Jun was significantly increased after overexpression of ANTXR1 in K562 cells. SOX6 protein expression was increased significantly after overexpression of the c-Jun gene, indicating that the transcription factor c-Jun initiated the transcription of SOX6, thereby silencing γ-globin. Our findings may provide a new intervention target for the treatment of β-hemoglobinopathies.

Activin B Stimulates Mouse Vibrissae Growth and Regulates Cell Proliferation and Cell Cycle Progression of Hair Matrix Cells through ERK Signaling

Activins and their receptors play important roles in the control of hair follicle morphogenesis, but their role in vibrissae follicle growth remains unclear. To investigate the effect of Activin B on vibrissae follicles, the anagen induction assay and an in vitro vibrissae culture system were constructed. Hematoxylin and eosin staining were performed to determine the hair cycle stages. The 5-ethynyl-2′-deoxyuridine (EdU) and Cell Counting Kit-8 (CCK-8) assays were used to examine the cell proliferation. Flow cytometry was used to detect the cell cycle phase. Inhibitors and Western blot analysis were used to investigate the signaling pathway induced by Activin B. As a result, we found that the vibrissae follicle growth was accelerated by 10 ng/mL Activin B in the anagen induction assay and in an organ culture model. 10 ng/mL Activin B promoted hair matrix cell proliferation in vivo and in vitro. Moreover, Activin B modulates hair matrix cell growth through the ERK–Elk1 signaling pathway, and Activin B accelerates hair matrix cell transition from the G1/G0 phase to the S phase through the ERK–Cyclin D1 signaling pathway. Taken together, these results demonstrated that Activin B may promote mouse vibrissae growth by stimulating hair matrix cell proliferation and cell cycle progression through ERK signaling.

Epiregulin promotes the migration and chemotaxis ability of adipose-derived mesenchymal stem cells via mitogen-activated protein kinase signaling pathways

To investigate the function of epiregulin (EREG) in the migration and chemotaxis ability of mesenchymal stem cells. Adipose-derived stem cells (ADSCs) were used in this investigation. Lentiviral EREG short hairpin RNA was applied to silence EREG expression in ADSCs. Human recombinant EREG protein (rhEREG) was used to perform a gain-of-function study. Scratch-simulated wound migration and transwell chemotaxis assays were used to examine the migration and chemotaxis capacity of ADSCs in vitro. Using a Western blot assay, the expressions of p38 mitogen-activated protein kinase (p38 MAPK), c-Jun N-terminal kinase (JNK), extracellular signal-regulated protein kinases 1 and 2 (Erk1/2), and protein kinase B were detected. Depletion of EREG caused by specific short hairpin RNA restrained the migration and chemotaxis ability of ADSCs and inhibited the expressions of phosphorylated p38 MAPK, JNK, and Erk1/2. rhEREG improved ADSCs migration and chemotaxis capacity, which was repressed by knockdown of EREG and rescued the expressions of phosphorylated p38 MAPK, JNK, and Erk1/2 impaired by silencing EREG. Furthermore, rhEREG-improved migration and chemotaxis ability in EREG-depleted-ADSCs was restricted by a specific inhibitor, SB203580, for blocking p38 MAPK signaling, PD98059 for blocking Erk1/2 signaling, or SP600125 for blocking JNK signaling in ADSCs separately. EREG promotes migration and chemotaxis ability of ADSCs through MAPK signaling pathways.

IGFBP5 enhances osteogenic differentiation potential of periodontal ligament stem cells and Wharton's jelly umbilical cord stem cells, via the JNK and MEK/Erk signalling pathways

OBJECTIVES

Mesenchymal stem cell (MSC)-mediated tissue regeneration represents a promising strategy for repair of tissue defects, but its molecular mechanisms remain unclear, restricting the use of MSCs. Our previous study indicated that insulin-like growth factor-binding protein 5 (IGFBP5) exerted a valuable effect on osteogenic differentiation of MSCs, but its molecular mechanisms underlying directed differentiation remained unclear. In this study, we have investigated the molecular role of IGFBP5 in regulating this osteogenic differentiation potential.

MATERIALS AND METHODS

Periodontal ligament stem cells (PDLSCs) were isolated from periodontal ligament tissue. Wharton's jelly of umbilical cord stem cells (WJCMSCs) was obtained commercially. Lentiviral IGFBP5 shRNA was used to silence IGFBP5. Retroviruses expressing wild-type IGFBP5 were used to overexpress IGFBP5 in the WJCMSCs. Recombinant human IGFBP5 protein (rhIGFBP5) was used to treat PDLSCs for 24 h. Western blot analysis was used to detect the MAPK signalling pathway, and alkaline phosphatase (ALP) activity, Alizarin Red staining and quantitative calcium analysis were used to study osteogenic differentiation potentials.

RESULTS

Overexpression of IGFBP5 or rhIGFBP5 increased expression levels of phosphorylated c-Jun N-terminal kinase (p-JNK), phosphorylated mitogen-activated protein kinase 1 and 2 (p-MEK1/2) and phosphorylated extracellular regulated protein kinases (p-Erk1/2) in both WJCMSCs and PDLSCs. Consistently, silenced IGFBP5 was found to effectively inhibit expression of p-JNK, p-Erk1/2 and p-MEK1/2 in PDLSCs and WJCMSCs. Furthermore, inhibition of JNK by its inhibitor, SP600125, or MEK/Erk signalling by its inhibitor, PD98059, dramatically blocked IGFBP5-enhanced ALP activity and in vitro mineralization in both PDLSCs and WJCMSCs.

CONCLUSIONS

Our results demonstrated that IGFBP5 promoted osteogenic differentiation potentials of PDLSCs and WJCMSCs via the JNK and MEK/Erk signalling pathways.

Cell signaling pathways involved in drug-mediated fetal hemoglobin induction: Strategies to treat sickle cell disease

The developmental regulation of globin gene expression has shaped research efforts to establish therapeutic modalities for individuals affected with sickle cell disease and β-thalassemia. Fetal hemoglobin has been shown to block sickle hemoglobin S polymerization to improve symptoms of sickle cell disease; moreover, fetal hemoglobin functions to replace inadequate hemoglobin A synthesis in β-thalassemia thus serving as an effective therapeutic target. In the perinatal period, fetal hemoglobin is synthesized at high levels followed by a decline to adult levels by one year of age. It is known that naturally occurring mutations in the γ-globin gene promoters and distant cis-acting transcription factors produce persistent fetal hemoglobin synthesis after birth to ameliorate clinical symptoms. Major repressor proteins that silence γ-globin during development have been targeted for gene therapy in β-hemoglobinopathies patients. In parallel effort, several classes of pharmacological agents that induce fetal hemoglobin expression through molecular and cell signaling mechanisms have been identified. Herein, we reviewed the progress made in the discovery of signaling molecules targeted by pharmacologic agents that enhance γ-globin expression and have the potential for future drug development to treat the β-hemoglobinopathies.

Erythropoietin protects against hemorrhagic blood-brain barrier disruption through the effects of aquaporin-4

Erythropoietin (EPO) has protective effects against many neurological diseases, including intracerebral hemorrhage (ICH). Here, we aimed to test EPO's effects on blood-brain barrier (BBB) disruption morphologically and functionally following ICH, which has not been well investigated. We also examined whether the effects were dependent on aquaporin-4 (AQP4). We detected the expression of perihematomal AQP4 and EPO receptor (EPOR) induced by EPO injection at 1, 3 and 7 days after ICH. We also examined the effects of EPO on BBB disruption by ICH in wild-type mice, and tested whether such effects were AQP4 dependent by using AQP4 knock-out mice. Furthermore, we assessed the related signal transduction pathways via astrocyte cultures. We found that EPO highly increased perihematomal AQP4 and EPOR expression. Specifically, EPO led to BBB protection in both types of mice by functionally reducing brain edema and BBB permeability, as well as morphologically suppressing tight junction (TJ) opening and endothelial cell swelling, and increasing expression of the TJ proteins occludin and zonula occluden-1 (ZO-1). Statistical analysis indicated that AQP4 was required for these effects. In addition, EPO upregulated phosphorylation of C-Jun amino-terminal kinase (JNK) and p38-mitogen-activated protein kinase (MAPK) as well as EPOR and AQP4 proteins in cultured astrocytes. The latter was inhibited by JNK and p38-MAPK inhibitors. Our data suggest that EPO protects BBB from disruption after ICH and that the main targets are the TJ proteins occludin and ZO-1. The effects of EPO are associated with increased levels of AQP4, and may occur through activation of JNK and p38-MAPK pathways after binding to EPOR.

Epiregulin can promote proliferation of stem cells from the dental apical papilla via MEK/Erk and JNK signalling pathways

OBJECTIVES

Mesenchymal stem cells (MSCs) are a reliable resource for tissue regeneration, but their molecular mechanisms of differentiation and proliferation remain unclear; this situation has restricted use of MSCs to a limited number of applications. A previous study of ours found a member of the epidermal growth factor family, epiregulin (EREG), to be involved in regulation of MSC differentiation. In the present study, we have used human dental stem cells from the apical papilla (SCAPs) to investigate the role of EREG on proliferation of MSCs.

MATERIALS AND METHODS

SCAPs were isolated from apical papillae of immature third molars. Retroviral short hairpin RNA (shRNA) was used to silence EREG gene expression, and human recombinant EREG protein was used to stimulate SCAPs. SCAP proliferation was examined using tetrazolium dye colorimetric assay/cell growth curve. Western blotting was performed to detect expressions of extracellular signal-regulated protein kinases 1 and 2 (Erk1/2), mitogen-activated protein kinases 1 and 2 (MEK1/2), protein kinase B (Akt), p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun N-terminal kinase (JNK).

RESULTS

Depletion of EREG with shRNA inhibited SCAP proliferation and repressed phosphorylation of Erk1/2 and JNK. Human recombinant EREG protein promoted cell proliferation and enhanced Erk1/2, MEK and JNK phosphorylation in SCAPs. Furthermore, blocking MEK/Erk signalling with specific Erk1/2 inhibitor PD98059, or JNK signalling with specific inhibitor SP600125, abolished effects of EREG on cell proliferation.

CONCLUSION

These findings indicate that EREG could enhance cell proliferation in dental tissue-derived MSCs by activating MEK/Erk and JNK signalling pathways.

Erythropoietin-driven signalling and cell migration mediated by polyADP-ribosylation

Background:

Recombinant human erythropoietin (EPO) is the leading biotechnology engineered hormone for treatment of anaemia associated with chronic conditions including kidney failure and cancer. The finding of EPO receptors on cancer cells has raised the concern that in addition to its action in erythropoiesis, EPO may promote tumour cell growth. We questioned whether EPO-induced signalling and consequent malignant cell manifestation is mediated by polyADP-ribosylation.

Methods:

Erythropoietin-mediated PARP (polyADP-ribose polymerase-1) activation, gene expression and core histone H4 acetylation were examined in UT7 cells, using western blot analysis, RT–PCR and immunofluorescence. Erythropoietin-driven migration of the human breast epithelial cell line MDA-MB-435 was determined by the scratch assay and in migration chambers.

Results:

We have found that EPO treatment induced PARP activation. Moreover, EPO-driven c-fos and Egr-1 gene expression as well as histone H4 acetylation were mediated via polyADP-ribosylation. Erythropoietin-induced cell migration was blocked by the PARP inhibitor, ABT-888, indicating an essential role for polyADP-ribosylation in this process.

Conclusions:

We have identified a novel pathway by which EPO-induced gene expression and breast cancer cell migration are regulated by polyADP-ribosylation. This study introduces new possibilities regarding EPO treatment for cancer-associated anaemia where combining systemic EPO treatment with targeted administration of PARP inhibitors to the tumour may allow safe treatment with EPO, minimising its possible undesirable proliferative effects on the tumour.

Erythropoietin protects intestinal epithelial barrier function and lowers the incidence of experimental neonatal necrotizing enterocolitis

The impermeant nature of the intestinal barrier is maintained by tight junctions (TJs) formed between adjacent intestinal epithelial cells. Disruption of TJs and loss of barrier function are associated with a number of gastrointestinal diseases, including neonatal necrotizing enterocolitis (NEC), the leading cause of death from gastrointestinal diseases in preterm infants. Human milk is protective against NEC, and the human milk factor erythropoietin (Epo) has been shown to protect endothelial cell-cell and blood-brain barriers. We hypothesized that Epo may also protect intestinal epithelial barriers, thereby lowering the incidence of NEC. Our data demonstrate that Epo protects enterocyte barrier function by supporting expression of the TJ protein ZO-1. As immaturity is a key factor in NEC, Epo regulation of ZO-1 in the human fetal immature H4 intestinal epithelial cell line was examined and demonstrated Epo-stimulated ZO-1 expression in a dose-dependent manner through the PI3K/Akt pathway. In a rat NEC model, oral administration of Epo lowered the incidence of NEC from 45 to 23% with statistical significance. In addition, Epo treatment protected intestinal barrier function and prevented loss of ZO-1 at the TJs in vivo. These effects were associated with elevated Akt phosphorylation in the intestine. This study reveals a novel role of Epo in the regulation of intestinal epithelial TJs and barrier function and suggests the possible use of enteral Epo as a therapeutic agent for gut diseases.

Association between pharmaceutical support and basic science research on erythropoiesis-stimulating agents

BACKGROUND

To our knowledge, no prior research has evaluated the association between pharmaceutical industry funding and basic science research results. When erythropoiesis-stimulating agents (ESAs) were licensed to treat chemotherapy-associated anemia, basic science concerns related to potential cancer stimulation were raised. We evaluated associations between pharmaceutical industry support and reported findings evaluating ESA effects on cancer cells.

METHODS

Articles identified in MEDLINE and EMBASE databases (1988-2008) investigating basic science findings related to ESA administration in the solid tumor setting were reviewed. Outcomes included information on erythropoietin receptors (EpoRs), Epo-induced signaling events, cellular function, and qualitative conclusions. Information on study funding (academic investigators with no reported funding from ESA manufacturers [64 studies], academic investigators with grant funding from ESA manufacturers [7 studies], and investigators employed by the ESA manufacturers [3 studies]) was evaluated. Some studies did not include information on each outcome.

RESULTS

Investigators without funding from ESA manufacturers were more likely than academic investigators with such funding or investigators employed by ESA manufacturers to identify EpoRs on solid tumor cells (100%, 60%, and 67%, respectively; P = .009), Epo-induced signaling events (94%, 0%, and 0%, respectively; P = .001), or changes in cellular function (57%, 0%, and 0%, respectively; P = .007) and to conclude that ESAs had potentially harmful effects on cancer cells (57%, 0%, and 0%, respectively; P = .008).

CONCLUSIONS

Researchers who do not have pharmaceutical industry support are more likely than those with pharmaceutical support to identify detrimental in vitro effects of ESAs. The potential for conflicts of interest to affect basic science research should be considered.

Intestinal hormones and growth factors: effects on the small intestine

There are various hormones and growth factors which may modify the intestinal absorption of nutrients, and which might thereby be useful in a therapeutic setting, such as in persons with short bowel syndrome. In part I, we focus first on insulin-like growth factors, epidermal and transferring growth factors, thyroid hormones and glucocorticosteroids. Part II will detail the effects of glucagon-like peptide (GLP)-2 on intestinal absorption and adaptation, and the potential for an additive effect of GLP2 plus steroids.