α-Mangostin induces mitochondrial dependent apoptosis in human hepatoma SK-Hep-1 cells through inhibition of p38 MAPK pathway

α-Mangostin is a dietary xanthone that has been shown to have anti-cancer and anti-proliferative properties in various types of human cancer cells. This study investigates the molecular mechanism of the apoptosis-inducing effects of α-mangostin on human hepatocellular carcinoma (HCC) cells. We observed that α-mangostin reduces the viability of HCC cells in a dose- and time-dependent manner. α-Mangostin mediated apoptosis of SK-Hep-1 cells is accompanied by nuclear chromatin condensation and cell cycle arrest in the sub-G1 phases as well as phosphatidylserine exposure. Furthermore, α-mangostin triggered the mitochondrial caspase apoptotic pathway, as indicated by the loss of mitochondrial membrane potential, the release of cytochrome c from mitochondria, and the regulation of B cell lymphoma 2 family member expression. Moreover, α-mangostin inhibited a sustained activation of p38 mitogen-activated protein kinase (MAPK) phosphorylation, and treatment with a p38 MAPK inhibitor enhanced α-mangostin-induced caspase activation and apoptosis in SK-Hep-1 cells. In vivo xenograft mice experiments revealed that α-mangostin significantly reduced tumor growth and weight in mice inoculated with SK-Hep-1 cells. These findings demonstrate that α-mangostin induces mitochondria-mediated apoptosis through inactivation of the p38 MAPK signaling pathway and that α-mangostin inhibits the in vivo tumor growth of SK-Hep-1 xenograft mice.     

Differences between integrin α5β1 and EGRF receptor in signal pathways controlling proliferation and apoptosis of MCF-7/Dox human breast carcinoma cells

In MCF-7/Dox human breast carcinoma cells, down-regulation of integrin α5β1 and inhibition of epidermal growth factor receptor (EGFR) markedly reduced cell proliferation. Cell cycle analysis showed that α5β1 down-regulation resulted in cycle arrest at the S-phase, followed by a significant increase in the population of apoptotic cells (subG₁ population). Inhibition of EGFR activity also caused cell cycle arrest at the S-phase but without any increase in the subG₁ population. Down-regulation of α5β1 and EGFR inhibition resulted in a significant decrease of cell content of the active (phosphorylated) forms of FAK and Erk protein kinases. The data obtained suggest that α5β1 integrin is implicated in cell growth control via inhibition of apoptotic cell death and through EGFR activation.     

ATP citrate lyase inhibitor triggers endoplasmic reticulum stress to induce hepatocellular carcinoma cell apoptosis via p-eIF2α/ATF4/CHOP axis

ATP citrate lyase (ACLY), a key enzyme in the metabolic reprogramming of many cancers, is widely expressed in various mammalian tissues. This study aimed to evaluate the effects and mechanisms of ACLY and its inhibitor BMS-303141 on hepatocellular carcinoma (HCC). In this study, ACLY was highly expressed in HCC tissues, especially in HepG2 and Huh7 cells, but was down-regulated in Hep3B and HCC-LM3 cells. Besides, ACLY knockdown inhibited HepG2 proliferation and clone formation, while opposite result was noticed in HCC-LM3 cells with ACLY overexpression. Moreover, ACLY knockdown impeded the migration and invasion abilities of HepG2 cells. Similarly, BMS-303141 suppressed HepG2 and Huh-7 cell proliferation. The p-eIF2α, ATF4, CHOP p-IRE1α, sXBP1 and p-PERK were activated in HepG2 cells stimulated by BMS-303141. In cells where ER stress was induced, ATF4 was involved in BMS-303141-mediated cell death procession, and ATF4 knockdown reduced HCC cell apoptosis stimulated by BMS-303141. In a mouse xenograft model, combined treatment with BMS-303141 and sorafenib reduced HepG2 tumour volume and weight. In addition, ACLY expression was associated with HCC metastasis and tumour-node-metastases staging. Survival analysis and Cox proportional hazards regression model showed that overall survival was lower in HCC patients with high ACLY expression; AFP level, TNM staging, tumour size and ACLY expression level were independent risk factors affecting their overall survival. In conclusion, ACLY might represent a promising target in which BMS-303141 could induce ER stress and activate p-eIF2α/ATF4/CHOP axis to promote apoptosis of HCC cells, and synergized with sorafenib to enhance the efficacy of HCC treatment.     

Iron overload induces apoptosis of osteoblast cells via eliciting ER stress-mediated mitochondrial dysfunction and p-eIF2α/ATF4/CHOP pathway in vitro

Iron is an essential element for crucial biological function; whereas excess iron sedimentation impairs the main functions of tissues or organs. Cumulative researches have shown that the disturbances in iron metabolism, especially iron overload is closely concatenating with bone loss. Nevertheless, the specific process of iron overload-induced apoptosis in osteoblasts has not been thoroughly studied. In this study, our purpose is to elucidate the mechanism of osteoblast apoptosis induced by iron overload via the MC3T3-E1 cell line. Ferric ammonium citrate (FAC) was utilized to simulate iron overload conditions in vitro. These results showed that treatment with FAC dose-dependently induced the apoptosis of MC3T3-E1 cells at 48 h, dysfunction of iron metabolism, and increased intracellular reactive oxygen species (ROS) levels. Following, FAC does-dependently caused the calcium dyshomeostasis, decreased the calcium concentration in endoplasmic reticulum (ER), but increased the crosstalk between ER and mitochondria, and calcium concentration in the mitochondria. Moreover, FAC dose-dependently decreased mitochondrial membrane potential (MMP) and enhanced the expression of apoptosis related proteins (Bax, Cyto-C and C-caspase3). We furthermore revealed that FAC treatment activated the ER-mediated cell apoptosis via p-eIF2α/ATF4/CHOP pathway in MC3T3-E1 osteoblasts cells. In addition, pretreatment with the N-acetylcysteine (NAC) or Tauroursodeoxycholate Sodium (TUDC) attenuated cell apoptosis, ROS levels, mitochondria fragmentation and ER stress-related protein expression, and recovered the protein expression related to iron metabolism. In conclusion, our finding suggested that iron overload induced apoptosis via eliciting ER stress, which resulted in mitochondrial dysfunction and activated p-eIF2α/ATF4/CHOP pathway.     

Atiprimod triggered apoptotic cell death via acting on PERK/eIF2α/ATF4/CHOP and STAT3/NF-ΚB axis in MDA-MB-231 and MDA-MB-468 breast cancer cells

Molecular Biology Reports - The constitutive activation of STAT3 through receptor tyrosine kinases triggered breast cancer cell growth and invasion-metastasis. Atiprimod impacts anti-proliferative,...     

Regulation of human lung alveolar multipotent cells by a novel p38α MAPK/miR-17-92 axis

The cellular and molecular mechanisms that control lung homeostasis and regeneration are still poorly understood. It has been proposed that a population of cells exists in the mouse lung with the potential to differentiate into all major lung bronchioalveolar epithelium cell types in homeostasis or in response to virus infection. A new population of E-Cad/Lgr6(+) putative stem cells has been isolated, and indefinitely expanded from human lungs, harbouring both, self-renewal capacity and the potency to differentiate in vitro and in vivo. Recently, a putative population of human lung stem cells has been proposed as being c-Kit(+). Unlike Integrin-α6(+) or c-Kit(+) cells, E-Cad/Lgr6(+) single-cell injections in the kidney capsule produce differentiated bronchioalveolar tissue, while retaining self-renewal, as they can undergo serial transplantations under the kidney capsule or in the lung. In addition, a signalling network involving the p38α pathway, the activation of p53 and the regulation of the miR-17-92 cluster has been identified. Disruption of the proper cross-regulation of this signalling axis might be involved in the promotion of human lung diseases.     

Nogo-A-Δ20/EphA4 interaction antagonizes apoptosis of neural stem cells by integrating p38 and JNK MAPK signaling

Journal of Molecular Histology - Nogo-A protein consists of two main extracellular domains: Nogo-66 (rat amino acid [aa] 1019–1083) and Nogo-A-Δ20 (extracellular, active 180 amino acid...     

β-Elemonic acid inhibits the growth of human Osteosarcoma through endoplasmic reticulum (ER) stress-mediated PERK/eIF2α/ATF4/CHOP activation and Wnt/β-catenin signal suppression

BackgroundOsteosarcoma (OS) is a significant threat to the lives of children and young adults. Although neoadjuvant chemotherapy is the first choice of treatment for OS, it is limited by serious side-effects and cancer metastasis. β-Elemonic acid (β-EA), an active component extracted from Boswellia carterii Birdw., has been reported to exhibit potential anti-inflammatory and anticancer activities. However, the anti-tumor effects and underlying mechanisms on OS as well as pharmacokinetic characteristics of β-EA remain unknown.PurposeThis study was aimed to investigating the anti-tumor effects of β-EA on human OS, the underlying mechanisms, and the pharmacokinetic and tissue distribution characteristics.Study design and methodsCell viability and colony formation assays were performed to determine the effect of β-EA cell on cell proliferation. Apoptosis rates, mitochondrial membrane potential and cell cycle features were analyzed by flow cytometry. qRT-PCR, Western blot, immunofluorescence and immunohistochemical assays were conducted to evaluate the expression levels of genes or proteins related to the pathways affected by β-EA in vitro and in vivo. Cell migration and invasion were evaluated in wound healing and Transwell chamber assays. The effects and pharmacokinetic characteristics of β-EA in vivo were evaluated by analyzing tumor suppression, pharmacokinetics and tissue distribution.ResultsExplorations indicated that endoplasmic reticulum (ER) stress conditions provoked by β-EA activated the PERK/eIF2α/ATF4 branch of the unfolded protein reaction (UPR), stimulating C/EBP homologous protein (CHOP)-regulated apoptosis and inducing Ca²⁺ leakage leading to caspase-dependent apoptosis. Furthermore, β-EA induced G0/G1 cell cycle arrest and inhibited metastasis of HOS and 143B cells by attenuating Wnt/β-catenin signaling effects, which included decreased levels of p-Akt(Ser473), p-Gsk3β (Ser9), Wnt/β-catenin target genes (c-Myc and CyclinD1) along with a decline in nuclear β-catenin accumulation. The fast absorption, short elimination half-life, and linear pharmacokinetic characteristics of β-EA were also revealed. The distribution of β-EA was detected in the tumor and bone tissues.ConclusionsOverall, both in vitro and in vivo investigations showed the potential of β-EA for the treatment of human OS. The pharmacokinetic profile and considerable distribution in the tumor and bone tissues warrant further preclinical or even clinical studies.     

Telmisartan,a possible PPAR-δ agonist,reduces TNF-α-stimulated VEGF-C production by inhibiting the p38MAPK/HSP27 pathway in human proximal renal tubular cells

Vascular endothelial growth factor-C (VEGF-C) is a main inducer of inflammation-associated lymphangiogenesis in various inflammatory disorders including chronic progressive kidney diseases, for which angiotensin II receptor type 1 blockers (ARBs) are widely used as the main treatment. Although proximal renal tubular cells may affect the formation of lymphatic vessels in the interstitial area by producing VEGF-C, the molecular mechanisms of VEGF-C production and its manipulation by ARB have not yet been examined in human proximal renal tubular epithelial cells (HPTECs).     

Mycobacterium bovis Bacillus Calmette-Guérin (BCG) stimulates IL-10 production via the PI3K/Akt and p38 MAPK pathways in human lung epithelial cells

Infection of human cells with mycobacteria has been shown to result in the production of anti-inflammatory cytokines. However, the signaling pathways that regulate the Mycobacterium bovis BCG-induced interleukin (IL)-10 production are currently unknown. In the present study, we investigated the involvement of phosphatidylinoditol 3-kinase (PI3K)/Akt and the p38 MAPK signaling pathways in the secretion of IL-10 in human lung epithelial cells (A549) after infection with M. bovis BCG. Treatment of A549 cells with LY 294002 (2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one) and wortmannin, two PI3K inhibitors, inhibited M. bovis BCG-induced IL-10 production. Stimulation of cells with M. bovis BCG caused an increase in Akt phosphorylation in a time-dependent manner, which was inhibited by wortmannin. In addition, treatment of A549 cells with an Akt inhibitor significantly blocked M. bovis BCG-induced IL-10 production. Moreover, the p38 inhibitor SB203580 significantly decreased IL-10 production in a dose-dependent manner, whereas M. bovis BCG-induced IL-10 secretion was completely unaffected by the MEK inhibitor PD98059. Finally, the inhibition of PI3K did not significantly affect p38 MAPK activation in M. bovis BCG-infected cells, indicating that PI3K activity is not required for the M. bovis BCG-induced phosphorylation of p38 MAPK. Collectively, these data suggest that the PI3K/Akt and p38 MAPK signaling pathways play an important role in the regulation of M. bovis BCG-induced IL-10 secretion in A549 cells.