Rapid actions of plasma membrane estrogen receptors regulate motility of mouse embryonic stem cells through a profilin-1/cofilin-1-directed kinase signaling pathway

Estrogen inhibits TGF‑β1‑stimulated cardiac fibroblast differentiation and collagen synthesis by promoting Cdc42

17β‑estradiol (E2) can inhibit cardiac fibrosis in female patients with heart failure (HF) and activate cell division cycle 42 (Cdc42), however it is unknown whether 17β‑estradiol (E2) can ameliorate differentiation and collagen synthesis in TGF‑β1‑stimulated mouse cardiac fibroblasts (MCFs) by regulating cell division cycle 42 (Cdc42). The present study aimed to investigate the roles of estrogen and Cdc42 in preventing myocardial fibrosis and the underlying molecular mechanisms. An ELISA was used to measure the levels of E2 and Cdc42 in the serum of patients with heart failure (HF), and western blotting was used to measure the expression levels of Cdc42 in TGF‑β1‑stimulated immortalized MCFs. MCFs were transfected with a Cdc42 overexpression (OE) lentivirus or small interfering RNA (siRNA), or treated with a Cdc42 inhibitor (MLS‑573151), and the function of Cdc42 was assessed by western blotting, immunofluorescence staining, reverse transcription‑quantitative PCR and dual‑luciferase reporter assays. Western blotting and immunofluorescence staining were performed to verify the protective effect of E2 on TGF‑β1‑stimulated MCFs, and the association between the protective effect and Cdc42. The results demonstrated that Cdc42 levels were increased in the serum of patients with HF and were positively correlated with the levels of E2; however, Cdc42 levels were decreased in TGF‑β1‑stimulated MCFs. Cdc42 inhibited MCF differentiation and collagen synthesis, as indicated by the protein expression of α‑smooth muscle actin, collagen I and collagen III. Mechanistically, Cdc42 inhibited the transcription of TGF‑β1 by promoting the expression of p21 (RAC1)‑activated kinase 1 (Pak1)/JNK/c‑Jun signaling pathway proteins and inhibiting the activity of the Tgfb1 gene promoter. In addition, E2 inhibited the differentiation and collagen synthesis of TGF‑β1‑stimulated MCFs, and promoted the protein expression of Pak1, JNK and c‑Jun, consistent with the effects of Cdc42, whereas the effects of E2 were abolished when Cdc42 was knocked down. The aforementioned findings suggested that E2 could inhibit differentiation and collagen synthesis in TGF‑β1‑stimulated MCFs by regulating Cdc42 and the downstream Pak1/JNK/c‑Jun signaling pathway.

Caveolin1: its roles in normal and cancer stem cells

PURPOSE

Stem cells are characterized by the capability of self-renewal and multi-differentiation. Normal stem cells, which are important for tissue repair and tissue regeneration, can be divided into embryonic stem cells (ESCs) and somatic stem cells (SSCs) depending on their origin. As a subpopulation of cells within cancer, cancer stem cells (CSCs) are at the root of therapeutic resistance. Tumor-initiating cells (TICs) are necessary for tumor initiation. Caveolin1 (Cav1), a membrane protein located at the caveolae, participates in cell lipid transport, cell migration, cell proliferation, and cell signal transduction. The purpose of this review was to explore the relationship between Cav1 and stem cells.

RESULTS

In ESCs, Cav1 is beneficial for self-renewal, proliferation, and migration. In SSCs, Cav1 exhibits positive or/and negative effects on stem cell self-renewal, differentiation, proliferation, migration, and angiogenic capacity. Cav1 deficiency impairs normal stem cell-based tissue repair. In CSCs, Cav1 inhibits or/and promotes CSC self-renewal, differentiation, invasion, migration, tumorigenicity ability, and CSC formation. And suppressing Cav1 promotes chemo-sensitivity in CSCs and TICs.

CONCLUSION

Cav1 shows dual roles in stem cell biology. Targeting the Cav1-stem cell axis would be a new way for tissue repair and cancer drug resistance.

Counteracting the Ramifications of UVB Irradiation and Photoaging with Swietenia macrophylla King Seed

In this day and age, the expectation of cosmetic products to effectively slow down skin photoaging is constantly increasing. However, the detrimental effects of UVB on the skin are not easy to tackle as UVB dysregulates a wide range of molecular changes on the cellular level. In our research, irradiated keratinocyte cells not only experienced a compromise in their redox system, but processes from RNA translation to protein synthesis and folding were also affected. Aside from this, proteins involved in various other processes like DNA repair and maintenance, glycolysis, cell growth, proliferation, and migration were affected while the cells approached imminent cell death. Additionally, the collagen degradation pathway was also activated by UVB irradiation through the upregulation of inflammatory and collagen degrading markers. Nevertheless, with the treatment of Swietenia macrophylla (S. macrophylla) seed extract and fractions, the dysregulation of many genes and proteins by UVB was reversed. The reversal effects were particularly promising with the S. macrophylla hexane fraction (SMHF) and S. macrophylla ethyl acetate fraction (SMEAF). SMHF was able to oppose the detrimental effects of UVB in several different processes such as the redox system, DNA repair and maintenance, RNA transcription to translation, protein maintenance and synthesis, cell growth, migration and proliferation, and cell glycolysis, while SMEAF successfully suppressed markers related to skin inflammation, collagen degradation, and cell apoptosis. Thus, in summary, our research not only provided a deeper insight into the molecular changes within irradiated keratinocytes, but also serves as a model platform for future cosmetic research to build upon. Subsequently, both SMHF and SMEAF also displayed potential photoprotective properties that warrant further fractionation and in vivo clinical trials to investigate and obtain potential novel bioactive compounds against photoaging.

Increased intracellular pH is necessary for adult epithelial and embryonic stem cell differentiation

Despite extensive knowledge about the transcriptional regulation of stem cell differentiation, less is known about the role of dynamic cytosolic cues. We report that an increase in intracellular pH (pHi) is necessary for the efficient differentiation of Drosophila adult follicle stem cells (FSCs) and mouse embryonic stem cells (mESCs). We show that pHi increases with differentiation from FSCs to prefollicle cells (pFCs) and follicle cells. Loss of the Drosophila Na⁺-H⁺ exchanger DNhe2 lowers pHi in differentiating cells, impairs pFC differentiation, disrupts germarium morphology, and decreases fecundity. In contrast, increasing pHi promotes excess pFC cell differentiation toward a polar/stalk cell fate through suppressing Hedgehog pathway activity. Increased pHi also occurs with mESC differentiation and, when prevented, attenuates spontaneous differentiation of naive cells, as determined by expression of microRNA clusters and stage-specific markers. Our findings reveal a previously unrecognized role of pHi dynamics for the differentiation of two distinct types of stem cell lineages, which opens new directions for understanding conserved regulatory mechanisms.

Letrozole regulates actin cytoskeleton polymerization dynamics in a SRC-1 dependent manner in the hippocampus of mice

In the hippocampus, local estrogens (E₂) derived from testosterone that is catalyzed by aromatase play important roles in the regulation of hippocampal neural plasticity, but the underlying mechanisms remain unclear. The actin cytoskeleton contributes greatly to hippocampal synaptic plasticity; however, whether it is regulated by local E₂ and the related mechanisms remain to be elucidated. In this study, we first examined the postnatal developmental profiles of hippocampal aromatase and specific proteins responsible for actin cytoskeleton dynamics. Then we used aromatase inhibitor letrozole (LET) to block local E₂ synthesis and examined the changes of these proteins and steroid receptor coactivator-1 (SRC-1), the predominant coactivator for steroid nuclear receptors. Finally, SRC-1 specific RNA interference was used to examine the effects of SRC-1 on the expression of these actin remodeling proteins. The results showed a V-type profile for aromatase and increased profiles for actin cytoskeleton proteins in both male and female hippocampus without obvious sex differences. LET treatment dramatically decreased the F-actin/G-actin ratio, the expression of Rictor, phospho-AKT (ser473), Profilin-1, phospho-Cofilin (Ser3), and SRC-1 in a dose-dependent manner. In vitro studies demonstrated that LET induced downregulation of these proteins could be reversed by E₂, and E₂ induced increase of these proteins were significantly suppressed by SRC-1 shRNA interference. These results for the first time clearly demonstrated that local E₂ inhibition could induce aberrant actin polymerization; they also showed an important role of SRC-1 in the mediation of local E₂ action on hippocampal synaptic plasticity by regulation of actin cytoskeleton dynamics.

Autotaxin-LPA axis regulates hMSC migration by adherent junction disruption and cytoskeletal rearrangement via LPAR1/3-dependent PKC/GSK3β/β-catenin and PKC/Rho GTPase pathways

Bioactive molecules and stem cell-based regenerative engineering is emerging a promising approach for regenerating tissues. Autotaxin (ATX) is a key enzyme that regulates lysophosphatidic acid (LPA) levels in biological fluids, which exerts a wide range of cellular functions. However, the biological role of ATX in human umbilical cord blood-derived mesenchymal stem cells (hMSCs) migration remains to be fully elucidated. In this study, we observed that hMSCs, which were stimulated with LPA, accelerated wound healing, and LPA increased the migration of hMSCs into a wound site in a mouse skin wound healing model. In an experiment to investigate the effect of LPA on hMSC migration, ATX and LPA increased hMSC migration in a dose-dependent manner, and LPA receptor 1/3 siRNA transfections inhibited the ATX-induced cell migration. Furthermore, LPA increased Ca(2+) influx and PKC phosphorylation, which were blocked by Gαi and Gαq knockdown as well as by Ptx pretreatment. LPA increased GSK3β phosphorylation and β-catenin activation. LPA induced the cytosol to nuclear translocation of β-catenin, which was inhibited by PKC inhibitors. LPA stimulated the binding of β-catenin on the E-box located in the promoter of the CDH-1 gene and decreased CDH-1 promoter activity. In addition, the ATX and LPA-induced increase in hMSC migration was blocked by β-catenin siRNA transfection. LPA-induced PKC phosphorylation is also involved in Rac1 and CDC42 activation, and Rac1 and CDC42 knockdown abolished LPA-induced F-actin reorganization. In conclusion, ATX/LPA stimulates the migration of hMSCs through LPAR1/3-dependent E-cadherin reduction and cytoskeletal rearrangement via PKC/GSK3β/β-catenin and PKC/Rho GTPase pathways.

Regulation of cyclooxygenase-2 expression in rat oviductal epithelial cells: Evidence for involvement of GPR30/Src kinase-mediated EGFR signaling

The oviduct plays a crucial role in female reproduction by regulating gamete transport, providing a specific microenvironment for fertilization and early embryonic development. Cyclooxygenase (COX)-derived prostaglandins play essential role in carrying out these oviduct-specific functions. Estrogen upregulates COX-2 expression in rat oviduct; however, the mechanisms responsible for regulation of COX-2 expression in rat oviductal epithelial cells (OECs) remain unclear. In the present study, we proposed that estrogen induces COX-2 expression via G-protein coupled receptor i.e., GPR30 in OECs. To investigate this hypothesis, we examined the effects of E2-BSA, ICI 182,780, GPR30 agonist and GPR30 antagonist on COX-2 expression and explored potential signaling pathway leading to COX-2 expression. Co-localization experiments revealed GPR30 to be primarily located in the peri-nuclear space, which was also the site of E2-BSA-fluorescein isothiocyanate (E2-BSA-FITC) binding. The E2-BSA induced-COX-2 and prostaglandin release were subjected to regulation by both EGFR and PI3K signaling as inhibitors of c-Src kinase (PP2), EGFR (EGFR inhibitor) and PI-3 kinase (LY294002) attenuated E2-BSA mediated effect. These results suggest that EGFR transactivation leading to activation of PI-3K/Akt pathway participates in COX-2 expression in rat OECs. Interestingly, E2-BSA induced COX-2 expression and subsequent prostaglandin release were abolished by NF-κB inhibitor. In addition, E2-BSA induced the nuclear translocation of p65-NF-κB and up-regulated the NF-κB promoter activity in rat OECs. Taken together, results demonstrated that E2-BSA induced the COX-2 expression and consequent PGE2 and PGF2α release in rat OECs. These effects are mediated through GPR30-derived EGFR transactivation and PI-3K/Akt cascade leading to NF-κB activation.

Melatonin enhances the human mesenchymal stem cells motility via melatonin receptor 2 coupling with Gαq in skin wound healing

Melatonin, a circadian rhythm-promoting molecule, has a variety of biological functions, but the functional role of melatonin in the motility of mesenchymal stem cells (MSCs) has yet to be studied. In a mouse skin excisional wound model, we found that transplantation of umbilical cord blood (UCB)-MSCs pretreated with melatonin enhanced wound closure, granulation, and re-epithelialization at mouse skin wound sites, where relatively more UCB-MSCs which were engrafted onto the wound site were detected. Thus, we identified the signaling pathway of melatonin, which affects the motility of UCB-MSCs. Melatonin (1 μm) significantly increased the motility of UCB-MSCs, which had been inhibited by the knockdown of melatonin receptor 2 (MT2). We found that Gαq coupled with MT2 and that the binding of Gαq to MT2 uniquely stimulated an atypical PKC isoform, PKCζ. Melatonin induced the phosphorylation of FAK and paxillin, which were concurrently downregulated by blocking of the PKC activity. Melatonin increased the levels of active Cdc42 and Arp2/3, and it has the ability to stimulate cytoskeletal reorganization-related proteins such as profilin-1, cofilin-1, and F-actin in UCB-MSCs. Finally, a lack of MT2 expression in UCB-MSCs during a mouse skin transplantation experiment resulted in impaired wound healing and less engraftment of stem cells at the wound site. These results demonstrate that melatonin signaling via MT2 triggers FAK/paxillin phosphorylation to stimulate reorganization of the actin cytoskeleton, which is responsible for Cdc42/Arp2/3 activation to promote UCB-MSCs motility.

Netrin-1 induces MMP-12-dependent E-cadherin degradation via the distinct activation of PKCα and FAK/Fyn in promoting mesenchymal stem cell motility

Netrin-1 (Ntn-1) is a potent inducer of neuronal cell migration; however, its molecular mechanism that guides the migratory behavior of stem cells has not been characterized. In this study, we investigate the role of Ntn-1 in promoting the motility of human umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs) and its related signaling pathways. Ntn-1 (50 ng/mL) significantly increased motility of UCB-MSCs, which was inhibited by blocking antibodies for deleted in colorectal cancer (DCC) and integrin (IN) α6β4. Ntn-1 in DCC stimulated protein kinase Cα (PKCα) activation, but not PKCɛ, PKCθ, and PKCζ, while Ntn-1 in INα6β4 induced the phosphorylation of focal adhesion kinase (FAK) and Fyn. Notably, Ntn-1 induced phosphorylation of extracellular signal-regulated kinases (ERK), c-Jun N-terminal kinases (JNK), and nuclear factor kappa-B (NF-κB), but they were concurrently downregulated by blocking the activities of PKCα, FAK, and Fyn. Ntn-1 uniquely increased the MMP-12 expression of all the matrix metalloproteinase (MMP) isoforms present in UCB-MSCs, though this was significantly blocked by an NF-κB inhibitor. Finally, Ntn-1 induced the MMP-12-dependent degradation of E-cadherin (E-cad), while Ntn-1 abrogated the interaction between E-cad and p120-catenin. In addition, Ntn-1 has the ability to stimulate cytoskeletal reorganization-related proteins, such as Cdc42, Rac1, Profilin-1, Cofilin-1, α-Actinin-4, and filamentous actin (F-actin) in UCB-MSCs. These results demonstrate that Ntn-1 induces MMP-12-dependent E-cad degradation via the distinct activation of PKCα and FAK/Fyn, which is necessary to govern the activation of ERK, JNK, and NF-κB in promoting motility of UCB-MSCs.

Galectin-1 stimulates motility of human umbilical cord blood-derived mesenchymal stem cells by downregulation of smad2/3-dependent collagen 3/5 and upregulation of NF-κB-dependent fibronectin/laminin 5 expression

Galectin-1 (Gal-1) belongs to a family of endogenous lectins with conserved carbohydrate recognition domains binding β-galactosidase sugars and plays a vital role in regulating stem cell functions including determination of cell fate. However, our understanding of the functional roles of Gal-1 in human umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs) is still fragmentary and incomplete. Gal-1 significantly increased motility after a 24-h incubation, and this effect was inhibited by β-lactose. We analyzed 17 extracellular matrix (ECM) genes in UCB-MSCs. Gal-1 decreased the expression of collagen genes COL3A1 (COL-3) and COL5A1 (COL-5) but increased the expression of fibronectin (FN) and laminin 5 (LM-5), that were reversed by β-lactose. Gal-1 increased protein kinase C (PKC), c-Src, and caveolin-1 (Cav-1) phosphorylation that was attenuated by β-lactose and the Src inhibitor PP2. In addition, pretreatment with the lipid raft disruptor Mβ-CD and the PKC inhibitors inhibited Gal-1-induced UCB-MSC motility. In addition, Gal-1 reduced smad2/3 phosphorylation and induced nuclear factor (NF)-κB phosphorylation. Pretreatment with Mβ-CD attenuated Gal-1-reduced smad2/3 phosphorylation, COL-3, and COL-5 expression but did not affect NF-κB phosphorylation, FN, or LM-5 expression. In contrast, PKC inhibitors only attenuated NF-κB phosphorylation, FN, and LM-5 expression. Reconstructing Gal-1-induced genetic changes by replacing it with siRNA specific for COL-3 or COL-5, or treatment of the cells with FN and LM-5 proteins, increased motility and its related proteins such as focal adhesion kinase, Akt, Erk, integrins, and matrix metalloproteinase-2. A combined treatment with COL-3/COL-5 siRNA or FN/LM-5 compared with that of single treatments was synergistic. However, a single Gal-1 treatment maximally stimulated motility and related protein phosphorylation/expression. These results demonstrate that Gal-1 stimulated human UCB-MSC motility by decreasing COL-3/COL-5 expression and increasing FN/LM-5 expression through a PKC-dependent NF-κB and c-Src/Cav-1-dependent smad2/3 pathway that was critical for governing the activation of FAK, Akt, Erk, integrins, and MMP2.