Extracellular Signal-related Kinase Activation Research Articles

Chronic Kidney Disease-associated Lung Injury Is Mediated by Phosphate-induced MAPK/AKT Signaling.

Chronic kidney disease (CKD) is associated with systemic phosphate elevations, called hyperphosphatemia. Translational studies have shown that hyperphosphatemia contributes to CKD-associated inflammation and injury in various tissues, including the kidney, heart, liver, and parathyroid gland. Mechanisms underlying pathologic actions of elevated phosphate on cells are not well understood but seem to involve uptake of phosphate through sodium-phosphate cotransporters and phosphate-induced signaling via fibroblast growth factor receptor (FGFR) 1. Clinical studies indicate CKD patients are more likely to develop inflammatory and restrictive lung diseases, such as fibrotic interstitial lung diseases, and here we aimed to determine whether hyperphosphatemia can cause lung injury. We found that a mouse model of CKD and hyperphosphatemia, induced by an adenine-rich diet, develops lung fibrosis and inflammation. Elevation of systemic phosphate levels by administration of a high-phosphate diet in a mouse model of primary lung inflammation and fibrosis, induced by bleomycin, exacerbated lung injury in the absence of kidney damage. Our in vitro studies identified increases of proinflammatory cytokines in human lung fibroblasts exposed to phosphate elevations. Phosphate activated extracellular signal related kinase (ERK) 1/2 and protein kinase B (PKB/AKT) signaling, and pharmacological inhibition of ERK, AKT, FGFR1, or sodium-phosphate cotransporters prevented phosphate-induced proinflammatory cytokine upregulation. Additionally, inhibition of FGFR1 or sodium-phosphate cotransporters decreased the phosphate-induced activation of ERK and AKT. Our study suggests that phosphate can directly target lung fibroblasts and induce an inflammatory response and that hyperphosphatemia in CKD and non-CKD models contributes to lung injury. Phosphate-lowering strategies might protect from CKD-associated lung injury.

Mechanosensitive hormone signaling promotes mammary progenitor expansion and breast cancer risk

Tissue stem-progenitor cell frequency has been implicated in tumor risk and progression, but tissue-specific factors linking these associations remain ill-defined. We observed that stiff breast tissue from women with high mammographic density, who exhibit increased lifetime risk for breast cancer, associates with abundant stem-progenitor epithelial cells. Using genetically engineered mouse models of elevated integrin mechanosignaling and collagen density, syngeneic manipulations, and spheroid models, we determined that a stiff matrix and high mechanosignaling increase mammary epithelial stem-progenitor cell frequency and enhance tumor initiation invivo. Augmented tissue mechanics expand stemness by potentiating extracellular signal-related kinase (ERK) activity to foster progesterone receptor-dependent RANK signaling. Consistently, we detected elevated phosphorylated ERK and progesterone receptors and increased levels of RANK signaling in stiff breast tissue from women with high mammographic density. The findings link fibrosis and mechanosignaling to stem-progenitor cell frequency and breast cancer risk and causally implicate epidermal growth factor receptor-ERK-dependent hormone signaling in this phenotype.

Role of MAPKs in TGF-β1-induced maturation and mineralization in human osteoblast-like cells

Objectives: Our study aimed to clarify the role of mitogen-activated protein kinases (MAPKs) in transforming growth factor (TGF)-β1-stimulated mineralization in the human osteoblast-like MG63 cells. MethodsThe viability of MG63 cells under TGF-β1 stimulation was assessed by MTS assay. Western blotting determined TGF-β1-mediated activation of extracellular signal-related protein kinase (ERK), p38, and c-Jun amino-terminal kinase (JNK). Mineralization-related gene expression was examined by quantitative real-time PCR, and mineral deposition levels were evaluated by alizarin red S staining. ResultsTGF-β1 had no effect on MG63 cell proliferation. Activation of p38 was observed at 3 h post TGF-β1 stimulation. Moreover, JNK phosphorylation was upregulated by TGF-β1 from 1 to 6 h post stimulation, but had no activation on ERK phosphorylation throughout the experimental period. Treatment with JNK inhibitor diminished the alizarin red S-stained area in a dose-dependent manner. Mineral deposition was unaffected by MEK inhibitor, whereas p38 inhibitor increased the red-stained area. Gene expression levels of ALP and BSP were significantly decreased under treatment with JNK inhibitor and p38 inhibitor. The MEK inhibitor had no effect on the TGF-β1–mediated upregulation of ALP and BSP. Although all three inhibitors suppressed expression of COL I, none were found to stimulate expression of OCN. ConclusionsHuman osteoblast-like MG63 cells maturation and mineralization are induced through JNK activation of MAPK signaling in response to TGF-β1.

GLP-1 and GIP receptors signal through distinct β-arrestin 2-dependent pathways to regulate pancreatic β cell function

Glucagon-like peptide 1 (GLP-1R) and glucose-dependent insulinotropic polypeptide (GIPR) receptors are G-protein-coupled receptors involved in glucose homeostasis. Diabetogenic conditions decrease β-arrestin 2 (ARRB2) levels in human islets. In mouse β cells, ARRB2 dampens insulin secretion by partially uncoupling cyclic AMP (cAMP)/protein kinase A (PKA) signaling at physiological doses of GLP-1, whereas at pharmacological doses, the activation of extracellular signal-related kinase (ERK)/cAMP-responsive element-binding protein (CREB) requires ARRB2. In contrast, GIP-potentiated insulin secretion needs ARRB2 in mouse and human islets. The GIPR-ARRB2 axis is not involved in cAMP/PKA or ERK signaling but does mediate GIP-induced F-actin depolymerization. Finally, the dual GLP-1/GIP agonist tirzepatide does not require ARRB2 for the potentiation of insulin secretion. Thus, ARRB2 plays distinct roles in regulating GLP-1R and GIPR signaling, and we highlight (1) its role in the physiological context and the possible functional consequences of its decreased expression in pathological situations such as diabetes and (2) the importance of assessing the signaling pathways engaged by the agonists (biased/dual) for therapeutic purposes.

Inhibition of oxidative stress-induced epithelial-mesenchymal transition in retinal pigment epithelial cells of age-related macular degeneration model by suppressing ERK activation

IntroductionEpithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells is related to the pathogenesis of various retinopathies including age-related macular degeneration (AMD). Oxidative stress is the major factor that induces degeneration of RPE cells associated with the etiology of AMD. ObjectivesSodium iodate (NaIO3) generates intracellular reactive oxygen species (ROS) and is widely used to establish a model of AMD due to the selective induction of retinal degeneration. This study was performed to clarify the effects of multiple NaIO3-stimulated signaling pathways on EMT in RPE cells. MethodsThe EMT characteristics in NaIO3-treated human ARPE-19 cells and RPE cells of the mouse eyes were analyzed. Multiple oxidative stress-induced modulators were investigated and the effects of pre-treatment with Ca2+ chelator, extracellular signal-related kinase (ERK) inhibitor, or epidermal growth factor receptor (EGFR) inhibitor on NaIO3-induced EMT were determined. The efficacy of post-treatment with ERK inhibitor on the regulation of NaIO3-induced signaling pathways was dissected and its role in retinal thickness and morphology was evaluated by using histological cross-sections and spectral domain optical coherence tomography. ResultsWe found that NaIO3 induced EMT in ARPE-19 cells and in RPE cells of the mouse eyes. The intracellular ROS, Ca2+, endoplasmic reticulum (ER) stress marker, phospho-ERK, and phospho-EGFR were increased in NaIO3-stimulated cells. Our results showed that pre-treatment with Ca2+ chelator, ERK inhibitor, or EGFR inhibitor decreased NaIO3-induced EMT, interestingly, the inhibition of ERK displayed the most prominent effect. Furthermore, post-treatment with FR180204, a specific ERK inhibitor, reduced intracellular ROS and Ca2+ levels, downregulated phospho-EGFR and ER stress marker, attenuated EMT of RPE cells, and prevented structural disorder of the retina induced by NaIO3. ConclusionsERK is a crucial regulator of multiple NaIO3-induced signaling pathways that coordinate EMT program in RPE cells. Inhibition of ERK may be a potential therapeutic strategy for the treatment of AMD.

The iron chelator deferriferrichrysin induces paraptosis via extracellular signal-related kinase activation in cancer cells.

Cancer cells generally exhibit increased iron uptake, which contributes to their abnormal growth and metastatic ability. Iron chelators have thus recently attracted attention as potential anticancer agents. Here, we show that deferriferrichrysin (Dfcy), a natural product from Aspergillus oryzae acts as an iron chelator to induce paraptosis (a programmed cell death pathway characterized by ER dilation) in MCF-7 human breast cancer cells and H1299 human lung cancer cells. We first examined the anticancer efficacy of Dfcy in cancer cells and found that Dfcy induced ER dilation and reduced the number of viable cells. Extracellular signal-related kinase (ERK) was activated by Dfcy treatment, and the MEK inhibitor U0126, a small molecule commonly used to inhibit ERK activity, prevented the increase in ER dilation in Dfcy-treated cells. Concomitantly, the decrease in the number of viable cells upon treatment with Dfcy was attenuated by U0126. Taken together, these results demonstrate that the iron chelator Dfcy exhibits anticancer effects via induction of ERK-dependent paraptosis.

Lpar1-mediated Effects in Endothelial Progenitor Cells Are Crucial for Lung Repair in Acute Respiratory Distress Syndrome/Acute Lung Injury.

Acute respiratory distress syndrome/acute lung injury (ARDS/ALI) involves acute respiratory failure characterized by vascular endothelial and lung alveolar epithelial injury. Endothelial progenitor cells (EPCs) can mediate vasculogenesis. However, the limitations of EPCs, such as low survival and differentiation, are believed to inhibit the effectiveness of autologous cell therapies. This study demonstrated that lysophosphatidic acid (LPA), a bioactive small molecule without immunogenicity, is involved in the survival and antiapoptotic effects in human umbilical cord mesenchymal stem cells. This study aimed to explore whether LPA improves the survival of EPCs, enhancing the cellular therapeutic efficacy in ARDS, and these results will expand the application of LPA in stem cells and regenerative medicine. LPA promoted the colony formation, proliferation, and migration of EPCs and upregulated the expression of vascular endothelial-derived growth factor (VEGF) in EPCs. LPA pretreatment of transplanted EPCs improved the therapeutic effect by increasing EPC numbers in the rat lungs. LPA enhanced EPC proliferation and migration through Lpar1 coupled to Gi/o and Gq/11, respectively. Activation of extracellular signal-related kinase 1/2, or ERK1/2, was related to LPA-induced EPC proliferation but not migration. LPA/Lpar1-mediated Gi/o protein was also shown to be involved in promoting VEGF expression and inhibiting IL-1α expression in EPCs. Low LPA concentrations are present after lung injury; thus, the restoration of LPA may promote endothelial cell homeostasis and lung repair in ARDS. Inhalation of LPA significantly promoted the homing of endogenous EPCs to the lung and reduced lung injury in both rats with LPS-induced ALI and Streptococcus pneumoniae-infected mice. Taken together, these data indicated that LPA/Lpar1-mediated effects in EPCs are involved in maintaining endothelial cell homeostasis and lung tissue repair under physiological conditions.

Effects of dabrafenib and erlotinib combination treatment on anaplastic thyroid carcinoma.

Dabrafenib is a BRAF kinase inhibitor approved for treatment of BRAF-mutated anaplastic thyroid carcinoma (ATC) in combination with trametinib. Erlotinib is a tyrosine kinase inhibitor of EGF receptor (EGFR). We evaluated effects of dabrafenib and erlotinib combination treatment on ATC cells in vitro and in vivo. Cell proliferation, colony formation, apoptosis, and migration of ATC cells harboring a BRAF mutation (BHT101, 8505C, and SW1736) were evaluated after treatment with dabrafenib in combination with erlotinib or trametinib. The changes in activation of mitogen extracellular kinase (MEK) and extracellular signal-related kinase (ERK) signaling were also evaluated by Western blot analysis. Effects of these combinations were also evaluated using an in vivo xenograft model. First, we detected EGFR activation in dabrafenib-resistant SW1736 cells using a phospho-receptor tyrosine kinase array. A dabrafenib and erlotinib combination synergistically inhibited cell proliferation, colony formation, and migration, with an induction of apoptotic cell death in all three ATC cells, compared with dabrafenib or erlotinib alone. This synergistic effect was comparable with a dabrafenib and trametinib combination. The dabrafenib and erlotinib combination effectively inhibited phosphorylated (p)-MEK, p-ERK, and p-EGFR expressions compared with dabrafenib or erlotinib alone, while the dabrafenib and trametinib combination only inhibited p-MEK and p-ERK expressions. The dabrafenib with erlotinib or trametinib combinations also significantly suppressed tumor growth and induced apoptosis in a BHT101 xenograft model. The dabrafenib and erlotinib combination could be a potential novel treatment regimen to overcome drug resistance to dabrafenib alone in patients with BRAF-mutated ATC.

Protocadherin 15 suppresses oligodendrocyte progenitor cell proliferation and promotes motility through distinct signalling pathways

Oligodendrocyte progenitor cells (OPCs) express protocadherin 15 (Pcdh15), a member of the cadherin superfamily of transmembrane proteins. Little is known about the function of Pcdh15 in the central nervous system (CNS), however, Pcdh15 expression can predict glioma aggression and promote the separation of embryonic human OPCs immediately following a cell division. Herein, we show that Pcdh15 knockdown significantly increases extracellular signal-related kinase (ERK) phosphorylation and activation to enhance OPC proliferation in vitro. Furthermore, Pcdh15 knockdown elevates Cdc42-Arp2/3 signalling and impairs actin kinetics, reducing the frequency of lamellipodial extrusion and slowing filopodial withdrawal. Pcdh15 knockdown also reduces the number of processes supported by each OPC and new process generation. Our data indicate that Pcdh15 is a critical regulator of OPC proliferation and process motility, behaviours that characterise the function of these cells in the healthy CNS, and provide mechanistic insight into the role that Pcdh15 might play in glioma progression.

The Nuclear Pore Complex 62 Suppression Inhibits Coxsackievirus B Replication and Inflammatory Response.

Coxsackievirus B3 (CVB3) is one of the major viruses associated with human viral myocarditis, in members of the Picornaviridae order. Cellular localization depends on the activity of nuclear pore complexes, which are composed of nucleoporins (Nups), including Nup62. To better understand interactions between Nup62 and CVB3, we investigated the impact of CVB3 infection on Nup62 levels and the impact of Nup62 production on CVB3 replication in cultured cells. We found that CVB3 infection correlated with decreased Nup62 expression in vitro and that lower levels of Nup62 led to inhibition of CVB3 replication and to decreased activation of AKT and extracellular signal-related kinase. Our study reveals that Nup62 regulates the CVB3 replication during infection.

B-Raf inhibitor vemurafenib counteracts sulfur mustard-induced epidermal impairment through MAPK/ERK signaling

The chemical warfare agent sulfur mustard (SM) causes severe cutaneous lesions characterized by epidermal cell death, apoptosis, and inflammation. At present, the molecular mechanisms underlying SM-induced injury are not well understood, and there is no standard treatment protocol for SM-exposed patients. Here, we conducted a high-content screening of the Food and Drug Administration (FDA)-approved drug library of 1018 compounds against SM injury on an immortal human keratinocyte HaCaT cell line, focusing on cell survival. We found that the B-Raf inhibitor vemurafenib had an apparent therapeutic effect on HaCaT cells and resisted SM toxicity. Other tested B-Raf inhibitors, both type-I (dabrafenib and encorafenib) and type-II (RAF265 and AZ628), also exhibited potent therapeutic effects on SM-exposed HaCaT cells. Both SM and vemurafenib triggered extracellular signal-related kinase (ERK) activation. The therapeutic effect of vemurafenib in HaCaT cells during SM injury was ERK-dependent, indicating a specific role of ERK in keratinocyte regulatory mechanisms. Furthermore, vemurafenib partially improved cutaneous damage in a mouse ear vesicant model. Collectively, our results provide evidence that the B-Raf inhibitor vemurafenib is a potential therapeutic agent against SM injury, and oncogenic B-Raf might be an exciting new therapeutic target following exposure to mustard vesicating agents.

Strontium sintered calcium sulfate bone graft for enhancing osteogenesis in a rat femoral defect model

Strontium-containing calcium sulfate hemihydrate has been widely investigated in bone tissue engineering in recent years. The sensitive dose-dependent effect of strontium ions limits the clinical applications due to the uncontrollable release property of fabricated bone substitutes. The purpose of our study was to design a novel strontium sintered calcium sulfate anhydrate scaffold possessing a tailored released concentration and further in vivo bone regeneration. The in vitro biocompatibility, toxicity and differentiation of MC3T3E1 cells were evaluated by using different concentrations of SrCl2 and various weight ratios of strontium sintered calcium sulfate scaffolds. For the in vivo studies, we designed a critical-sized femoral defect model of rats transplanted with different weight ratios of strontium-substituted scaffolds to study new bone regeneration. In vitro data suggested that a Sr2+ concentration below 10−4 M had a positive effect on the osteogenic differentiation of MC3T3E1 cells. The enhanced cell viability, osteogenic profiles, bone mineralization and promising cellular proliferation were measured in 1% and 5% weight ratios of strontium-substituted scaffolds. Runt-related transcription factor 2 (RUNX2)-mediated osteogenesis was associated with the activation of extracellular signal-related kinase (ERK) signaling pathways in MC3T3E1 cells cultured in scaffold extracts. The in vivo experiments revealed that these sintered scaffolds showed acceptable biodegradability in X-ray and micro-CT images at the 12th week. Histological analysis showed intact surrounding bone regeneration, more osteoid formation, neovascularization and less fibrotic tissue in the 1% weight ratio of strontium sintered calcium sulfate scaffolds, suggesting that this sintered scaffolds weight ratio possesses potential for application in bone tissue engineering.

Evolution of MET and NRAS gene amplification as acquired resistance mechanisms in EGFR mutant NSCLC

EGFR mutant non-small cell lung cancer patients' disease demonstrates remarkable responses to EGFR-targeted therapy, but inevitably they succumb to acquired resistance, which can be complex and difficult to treat. Analyzing acquired resistance through broad molecular testing is crucial to understanding the resistance mechanisms and developing new treatment options. We performed diverse clinical testing on a patient with successive stages of acquired resistance, first to an EGFR inhibitor with MET gene amplification and then subsequently to a combination EGFR and MET targeted therapies. A patient-derived cell line obtained at the time of disease progression was used to identify NRAS gene amplification as an additional driver of drug resistance to combination EGFR/MET therapies. Analysis of downstream signaling revealed extracellular signal-related kinase activation that could only be eliminated by trametinib treatment, while Akt activation could be modulated by various combinations of MET, EGFR, and PI3K inhibitors. The combination of an EGFR inhibitor with a MEK inhibitor was identified as a possible treatment option to overcome drug resistance related to NRAS gene amplification.

Antimony-induced astrocyte activation via mitogen-activated protein kinase activation-dependent CREB phosphorylation

Recent studies suggest that the chemical element antimony (Sb) is neurotoxic; however, the molecular mechanisms behind Sb-related neuronal damage are currently unknown. In this study, we found that Sb exposure promoted astrocyte proliferation and increased the expression of inducible nitric oxide synthase (iNOS) and glial fibrillary acidic protein (GFAP), two key protein markers of reactive astrogliosis, at both the gene and protein level, suggesting that Sb induced astrocyte activation. Moreover, the p38 mitogen-activated protein kinase (p38 MAPK) and extracellular signal-related kinase (ERK) pathways were activated following Sb exposure. Inhibition of p38 MAPK reduced Sb-induced iNOS and GFAP upregulation, while inhibiting ERK reduced GFAP expression only, in Sb-exposed C6 cells. Sb treatment also induced the phosphorylation of cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB), and the inhibition of CREB caused a reduction in Sb-induced GFAP and iNOS expression. Furthermore, inhibiting both p38 MAPK and ERK effectively alleviated CREB phosphorylation in Sb-exposed C6 cells. Taken together, our results suggest that p38 MAPK and ERK activation mediate Sb-induced astrocyte activation through CREB phosphorylation. These results help to clarify the molecular mechanisms underlying Sb-associated neurotoxicity.

Anthocyanins Promote Learning through Modulation of Synaptic Plasticity Related Proteins in an Animal Model of Ageing.

Anthocyanin-rich foods, such as berries, reportedly ameliorate age-related cognitive deficits in both animals and humans. Despite this, investigation into the mechanisms which underpin anthocyanin-mediated learning and memory benefits remains relatively limited. The present study investigates the effects of anthocyanin intake on a spatial working memory paradigm, assessed via the cross-maze apparatus, and relates behavioural test performance to underlying molecular mechanisms. Six-week supplementation with pure anthocyanins (2% w/w), administered throughout the learning phase of the task, improved both spatial and psychomotor performances in aged rats. Behavioural outputs were accompanied by changes in the expression profile of key proteins integral to synaptic function/maintenance, with upregulation of dystrophin, protein kinase B (PKB/Akt) and tyrosine hydroxylase, and downregulation of apoptotic proteins B-cell lymphoma-extra-large (Bcl-xL) and the phosphorylated rapidly accelerated fibrosarcoma (p-Raf). Separate immunoblot analysis supported these observations, indicating increased activation of extracellular signal-related kinase (ERK1), Akt Ser473, mammalian target of rapamycin (mTOR) Ser2448, activity-regulated cytoskeleton-associated protein (Arc/Arg 3.1) and brain-derived neurotrophic factor (BDNF) in response to anthocyanin treatment, whilst α-E-catenin, c-Jun N-terminal kinase (JNK1) and p38 protein levels decreased. Together, these findings suggest that purified anthocyanin consumption enhances spatial learning and motor coordination in aged animals and can be attributed to the modulation of key synaptic proteins, which support integrity and maintenance of synaptic function.

Advantages of Tyrosine Kinase Anti-Angiogenic Cediranib over Bevacizumab: Cell Cycle Abrogation and Synergy with Chemotherapy.

Angiogenesis plays a crucial role in tumor development and metastasis. Both bevacizumab and cediranib have demonstrated activity as single anti-angiogenic agents in endometrial cancer, though subsequent studies of bevacizumab combined with chemotherapy failed to improve outcomes compared to chemotherapy alone. Our objective was to compare the efficacy of cediranib and bevacizumab in endometrial cancer models. The cellular effects of bevacizumab and cediranib were examined in endometrial cancer cell lines using extracellular signal-related kinase (ERK) phosphorylation, ligand shedding, cell viability, and cell cycle progression as readouts. Cellular viability was also tested in eight patient-derived organoid models of endometrial cancer. Finally, we performed a phosphoproteomic array of 875 phosphoproteins to define the signaling changes related to bevacizumab versus cediranib. Cediranib but not bevacizumab blocked ligand-mediated ERK activation in endometrial cancer cells. In both cell lines and patient-derived organoids, neither bevacizumab nor cediranib alone had a notable effect on cell viability. Cediranib but not bevacizumab promoted marked cell death when combined with chemotherapy. Cell cycle analysis demonstrated an accumulation in mitosis after treatment with cediranib + chemotherapy, consistent with the abrogation of the G2/M checkpoint and subsequent mitotic catastrophe. Molecular analysis of key controllers of the G2/M cell cycle checkpoint confirmed its abrogation. Phosphoproteomic analysis revealed that bevacizumab and cediranib had both similar and unique effects on cell signaling that underlie their shared versus individual actions as anti-angiogenic agents. An anti-angiogenic tyrosine kinase inhibitor such as cediranib has the potential to be superior to bevacizumab in combination with chemotherapy.

PKCβ/NF-κB pathway in diabetic atrial remodeling.

Atrial remodeling in diabetes is partially attributed to NF-κB/TGF-β signal transduction pathway activation. We examined whether the hyperglycemia-induced increased expression of NF-κB/TGF-β was dependent upon protein kinase C-β (PKCβ) and tested the hypothesis that selective inhibition of PKCβ using ruboxistaurin (RBX) can reduce NF-κB/TGF-β expression and inhibit abnormal atrial remodeling in streptozotocin (STZ)-induced diabetic rats. The effects of PKCβ inhibition on NF-κB/TGF-β signal transduction pathway-mediated atrial remodeling were investigated in STZ-induced diabetic rats. Mouse atrial cardiomyocytes (HL-1 cells) were cultured in low- or high-glucose or mannitol conditions in the presence or absence of small interference RNA that targeted PKCβ. PKCβ inhibition using ruboxistaurin (RBX, 1mg/kg/day) decreased the expression of NF-κBp65, p-IκB, P38MARK, TNF-α, TGF-β, Cav1.2, and NCX proteins and inducibility of atrial fibrillation (AF) in STZ-induced diabetic rats. Exposure of cardiomyocytes to high-glucose condition activated PKCβ and increased NF-κB/TGF-β expression. Suppression of PKCβ expression by small interference RNA decreased high-glucose-induced NF-κB and extracellular signal-related kinase activation in HL-1 cells. Pharmacological inhibition of PKCβ is an effective method to reduce AF incidence in diabetic rat models by preventing NF-κB/TGF-β-mediated atrial remodeling.

Tectorigenin enhances PDX1 expression and protects pancreatic β-cells by activating ERK and reducing ER stress

Pancreas/duodenum homeobox protein 1 (PDX1) is an important transcription factor that regulates islet β-cell proliferation, differentiation, and function. Reduced expression of PDX1 is thought to contribute to β-cell loss and dysfunction in diabetes. Thus, promoting PDX1 expression can be an effective strategy to preserve β-cell mass and function. Previously, we established a PDX1 promoter-dependent luciferase system to screen agents that can promote PDX1 expression. Natural compound tectorigenin (TG) was identified as a promising candidate that could enhance the activity of the promoter for the PDX1 gene. In this study, we first demonstrated that TG could promote the expression of PDX1 in β-cells via activating extracellular signal-related kinase (ERK), as indicated by increased phosphorylation of ERK; this effect was observed under either normal or glucotoxic/lipotoxic conditions. We then found that TG could suppress induced apoptosis and improved the viability of β-cells under glucotoxicity and lipotoxicity by activation of ERK and reduction of reactive oxygen species and endoplasmic reticulum (ER) stress. These effects held true in vivo as well: prophylactic or therapeutic use of TG could obviously inhibit ER stress and decrease islet β-cell apoptosis in the pancreas of mice given a high-fat/high-sucrose diet (HFHSD), thus dramatically maintaining or restoring β-cell mass and islet size, respectively. Accordingly, both prophylactic and therapeutic use of TG improved HFHSD-impaired glucose metabolism in mice, as evidenced by ameliorating hyperglycemia and glucose intolerance. Taken together, TG, as an agent promoting PDX1 expression exhibits strong protective effects on islet β-cells both in vitro and in vivo.

β-mercaptoethanol promotes osteogenesis of human mesenchymal stem cells via sirt1-ERK pathway.

Human umbilical cord-derived mesenchymal stem cells (hUMSCs) hold strong self-renewal capacity and low immunogenicity, which have attracted attention as potential candidates for bone repair and regeneration. However, insufficient osteogenic differentiation markedly hinders the clinical applications of hUMSCs. In the present study, the effect of β-mercaptoethanol (BME), a small molecule antioxidant which has been identified to regulate cell proliferation and differentiation, on osteogenic differentiation of hUMSCs and underlying signaling mechanism were investigated. The results indicated that under osteogenic induction conditions, BME treatment increased the alkaline phosphatase (ALP) activity and promoted calcium mineralization in hUMSCs. The gene and protein expression of osteogenesis-related markers such as ALP, osteopontin (OPN), osteocalcin (OCN) and collagen type I (COLI) were also significantly up-regulated. Besides, BME promoted the protein expression of silent information regulator type 1 (sirt1) and stimulated the activation of extracellular signal-related kinase (ERK), contributing to increased Runx2 expression. Furthermore, blocking the expression of sirt1 attenuated BME-enhanced ERK phosphorylation and osteogenic differentiation of hUMSCs. These results indicated that BME accelerated osteogenic differentiation of hUMSCs by activating the sirt1-ERK signaling pathway, thereby providing insights into the development of MSCs-based bone regeneration strategies.

Antiphotoaging Effect of (2′S)-Columbianetin from Corydalis heterocarpa in UVA-Irradiated Human Dermal Fibroblasts

Ultraviolet A (UVA)-induced detrimental effects in the skin, also known as photoaging, are mediated with several pathways including oxidative stress generation and extracellular matrix (ECM) degradation. UVA irradiation results in excessive production of matrix metalloproteinases (MMPs), enzymes responsible for the degradation of ECM components such as collagen. In this study, the protective effects of (2′S)-columbianetin against UVA-induced changes in matrix metalloproteinase-1 (MMP-1) and collagen production were investigated in human dermal fibroblasts (HDFs). The (2′S)-columbianetin was isolated from Corydalis heterocarpa. UVA exposure increased MMP-1 release from HDFs and diminished the release of type I pro-collagen. Treatment with (2′S)-columbianetin reversed these effects of UVA exposure. The (2′S)-columbianetin treatment also suppressed the intracellular expression of MMP-1 and increased type I pro-collagen expression. UVA exposure elevated the activation of p38, c-Jun-amino-terminal kinase (JNK) and extracellular signal-related kinase (ERK) as the mechanism to stimulate MMP-1 production. The (2′S)-columbianetin suppressed the phosphorylation of JNK and ERK. The (2′S)-columbianetin was also stimulated collagen production via TGFβ signaling cascade, relieving UVA-induced suppression of Smad2/3 phosphorylation and translocation. In conclusion, (2′S)-columbianetin was suggested to be a potential cosmeceutical lead compound with antiphotoaging properties against UVA-induced collagen degradation.