Activating AMP-activated protein kinase by an α1 selective activator compound 13 attenuates dexamethasone-induced osteoblast cell death

TRIM21 silencing inhibits the apoptosis and expedites the osteogenic differentiation of dexamethasone‑induced MC3T3‑E1 cells by activating the Keap1/Nrf2 pathway

Steroid-induced osteonecrosis of the femoral head (ONFH) is a serious complication caused by long-term or excessive use of glucocorticoids. The present study aimed to ascertain the effects of tripartite motif-containing protein 21 (TRIM21) on the process of steroid-induced ONFH and its hidden action mechanism. TRIM21 expression in dexamethasone (Dex)-treated mouse MC3T3-E1 preosteoblast cells was examined using reverse transcription-quantitative PCR and western blotting. The Cell Counting Kit-8 (CCK-8) method and lactate dehydrogenase release assay were used to respectively measure cell viability and injury. Flow cytometry analysis was used to assay cell apoptosis. Caspase 3 activity was evaluated using a specific assay, while alkaline phosphatase and Alizarin red S staining were used to evaluate osteogenesis. 2,7-dichloro-dihydrofluorescein diacetate fluorescence probe was used to estimate reactive oxygen species generation. Specific assay kits were used to appraise oxidative stress levels. In addition, the expression of apoptosis-, osteogenic differentiation- and Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2) signaling-associated proteins was assessed using western blotting. In Nrf2 inhibitor (ML385)-pretreated MC3T3-E1 cells exposed to Dex, cell apoptosis, osteogenesis and oxidative stress were detected again as aforementioned. Results revealed that TRIM21 expression was raised in Dex-induced MC3T3-E1 cells and TRIM21 deletion improved the viability and osteogenic differentiation, whereas it hampered the oxidative stress and apoptosis in MC3T3-E1 cells with Dex induction. In addition, silencing of TRIM21 activated Keap1/Nrf2 signaling. Moreover, ML385 partially abrogated the effects of TRIM21 depletion on the oxidative stress, apoptosis and osteogenic differentiation in MC3T3-E1 cells exposed to Dex. In conclusion, TRIM21 silencing might activate Keap1/Nrf2 signaling to protect against steroid-induced ONFH.

Dexamethasone-induced mitochondrial ROS-mediated inhibition of AMPK activity facilitates osteoblast necroptosis

Long-term or high-dose glucocorticoid use can lead to serious orthopedic complications, including femoral head necrosis. Both basic and clinical studies have shown that high doses dexamethasone (Dex) can directly induce osteoblasts death. This study investigated the mechanism underlying Dex induced osteoblast death. In this study, we showed that Dex induces osteoblast necroptosis, rather than apoptosis, through the inhibition of AMP-activated protein kinase (AMPK) activity. We also demonstrated that inactivation of AMPK-mediated necroptosis is through receptor-interacting protein kinase 3 (RIP3), but not RIP1. Furthermore, we found that Dex-induced necroptosis is dependent on mitochondrial reactive oxygen species (ROS) following with directly activation of RIP1 and inactivation of AMPK. These findings provide new insights into the mechanism of Dex-induced osteoblast death and may have implications for the development of new therapies for osteoporosis and other bone-related diseases.

Therapeutic perspectives of exosomes in glucocorticoid-induced osteoarthrosis

Exosomes are widely involved in a variety of physiological and pathological processes. These important roles are also hidden in the physiological processes related to bone. Chondrocytes, osteoblasts, synovial fibroblasts, and bone marrow mesenchymal stem cells produce and secrete exosomes, thereby affecting the biology process of target cells. Furthermore, in the primary pathogenesis of osteoarthrosis induced by steroid hormones, mainly involve glucocorticoid (GC), the exosomes have also widely participated. Therefore, exosomes may also play an important role in glucocorticoid-induced osteoarthrosis and serve as a promising treatment for early intervention of osteoarthrosis in addition to playing a regulatory role in malignant tumors. This review summarizes the previous results on this direction, systematically combs the role and therapeutic potential of exosomes in GC-induced osteoarthrosis, discusses the potential role of exosomes in the treatment and prevention of GC-induced osteoarthrosis, and reveals the current challenges we confronted.

PFKP alleviates glucose starvation-induced metabolic stress in lung cancer cells via AMPK-ACC2 dependent fatty acid oxidation

Cancer cells adopt metabolic reprogramming to promote cell survival under metabolic stress. A key regulator of cell metabolism is AMP-activated protein kinase (AMPK) which promotes catabolism while suppresses anabolism. However, the underlying mechanism of AMPK in handling metabolic stress in cancer remains to be fully understood. In this study, by performing a proteomics screening of AMPK-interacting proteins in non-small-cell lung cancer (NSCLC) cells, we discovered the platelet isoform of phosphofructokinase 1 (PFKP), a rate-limiting enzyme in glycolysis. Moreover, PFKP was found to be highly expressed in NSCLC patients associated with poor survival. We demonstrated that the interaction of PFKP and AMPK was greatly enhanced upon glucose starvation, a process regulated by PFKP-associated metabolites. Notably, the PFKP-AMPK interaction promoted mitochondrial recruitment of AMPK which subsequently phosphorylated acetyl-CoA carboxylase 2 (ACC2) to enhance long-chain fatty acid oxidation, a process helping maintenance of the energy and redox homeostasis and eventually promoting cancer cell survival under glucose starvation. Collectively, we revealed a critical non-glycolysis-related function of PFKP in regulating long-chain fatty acid oxidation via AMPK to alleviate glucose starvation-induced metabolic stress in NSCLC cells.

Endocrine Fibroblast Growth Factors in Relation to Stress Signaling

Fibroblast growth factors (FGFs) play important roles in various growth signaling processes, including proliferation, development, and differentiation. Endocrine FGFs, i.e., atypical FGFs, including FGF15/19, FGF21, and FGF23, function as endocrine hormones that regulate energy metabolism. Nutritional status is known to regulate the expression of endocrine FGFs through nuclear hormone receptors. The increased expression of endocrine FGFs regulates energy metabolism processes, such as fatty acid metabolism and glucose metabolism. Recently, a relationship was found between the FGF19 subfamily and stress signaling during stresses such as endoplasmic reticulum stress and oxidative stress. This review focuses on endocrine FGFs and the recent progress in FGF studies in relation to stress signaling. In addition, the relevance of the stress-FGF pathway to disease and human health is discussed.

Inhibition of hypoxia-induced Mucin 1 alters the proteomic composition of human osteoblast-produced extracellular matrix, leading to reduced osteogenic and angiogenic potential

The bone microenvironment is one of the most hypoxic regions of the human body and in experimental models; hypoxia inhibits osteogenic differentiation of mesenchymal stromal cells (MSCs). Our previous work revealed that Mucin 1 (MUC1) was dynamically expressed during osteogenic differentiation of human MSCs and upregulated by hypoxia. Upon stimulation, its C‐terminus (MUC1‐CT) is proteolytically cleaved, translocases to the nucleus, and binds to promoters of target genes. Therefore, we assessed the MUC1‐mediated effect of hypoxia on the proteomic composition of human osteoblast‐derived extracellular matrices (ECMs) and characterized their osteogenic and angiogenic potentials in the produced ECMs. We generated ECMs from osteogenically differentiated human MSC cultured in vitro under 20% or 2% oxygen with or without GO‐201, a MUC1‐CT inhibitor. Hypoxia upregulated MUC1, vascular endothelial growth factor, and connective tissue growth factor independent of MUC1 inhibition, whereas GO‐201 stabilized hypoxia‐inducible factor 1‐alpha. Hypoxia and/or MUC1‐CT inhibition reduced osteogenic differentiation of human MSC by AMP‐activated protein kinase/mTORC1/S6K pathway and dampened their matrix mineralization. Hypoxia modulated ECMs by transforming growth factor‐beta/Smad and phosphorylation of NFκB and upregulated COL1A1, COL5A1, and COL5A3. The ECMs of hypoxic osteoblasts reduced MSC proliferation and accelerated their osteogenic differentiation, whereas MUC1‐CT‐inhibited ECMs counteracted these effects.

In addition, ECMs generated under MUC1‐CT inhibition reduced the angiogenic potential independent of oxygen concentration. We claim here that MUC1 is critical for hypoxia‐mediated changes during osteoblastogenesis, which not only alters the proteomic landscape of the ECM but thereby also modulates its osteogenic and angiogenic potentials.

PF-06409577 Activates AMPK Signaling and Inhibits Osteosarcoma Cell Growth

Osteosarcoma (OS) is a common primary bone malignancy. We here investigated the potential activity of PF-06409577, a novel, potent, and direct activator of AMP-activated protein kinase (AMPK), against human OS cells. In established (U2OS, MG-63, and SaOs-2 lines) and primary human OS cells, PF-06409577 inhibited cell viability and proliferation, while inducing cell apoptosis and cell cycle arrest. PF-06409577 induced AMPK activation, mTORC1 inhibition, autophagy induction, and downregulation of multiple receptor tyrosine kinase inOS cells. AMPK inactivation by AMPKα1 shRNA, CRISPR/Cas9 knockout, or dominant negative mutation (T172A) was able to abolish PF-06409577-induced activity in OS cells. In vivo, PF-06409577 oral administration at well-tolerated doses potently inhibited growth of U2OS cells and primary human OS cells in severe combined immunodeficient mice. AMPK activation, mTORC1 inhibition, autophagy induction, as well as RTK degradation and apoptosis activation were detected in PF-06409577-treated xenografts. In conclusion, activation of AMPK by PF-06409577 inhibits OS cell growth.

AMPK activation by ASP4132 inhibits non-small cell lung cancer cell growth

Activation of adenosine monophosphate-activated protein kinase (AMPK) is able to produce significant anti-non-small cell lung cancer (NSCLC) cell activity. ASP4132 is an orally active and highly effective AMPK activator. The current study tested its activity against NSCLC cells. In primary NSCLC cells and established cell lines (A549 and NCI-H1944) ASP4132 potently inhibited cell growth, proliferation and cell cycle progression as well as cell migration and invasion. Robust apoptosis activation was detected in ASP4132-treated NSCLC cells. Furthermore, ASP4132 treatment in NSCLC cells induced programmed necrosis, causing mitochondrial p53-cyclophilin D (CyPD)-adenine nucleotide translocase 1 (ANT1) association, mitochondrial depolarization and medium lactate dehydrogenase release. In NSCLC cells ASP4132 activated AMPK signaling, induced AMPKα1-ACC phosphorylation and increased AMPK activity. Furthermore, AMPK downstream events, including mTORC1 inhibition, receptor tyrosine kinases (PDGFRα and EGFR) degradation, Akt inhibition and autophagy induction, were detected in ASP4132-treated NSCLC cells. Importantly, AMPK inactivation by AMPKα1 shRNA, knockout (using CRISPR/Cas9 strategy) or dominant negative mutation (T172A) almost reversed ASP4132-induced anti-NSCLC cell activity. Conversely, a constitutively active AMPKα1 (T172D) mimicked and abolished ASP4132-induced actions in NSCLC cells. In vivo, oral administration of a single dose of ASP4132 largely inhibited NSCLC xenograft growth in SCID mice. AMPK activation, mTORC1 inhibition and EGFR-PDGFRα degradation as well as Akt inhibition and autophagy induction were detected in ASP4132-treated NSCLC xenograft tumor tissues. Together, activation of AMPK by ASP4132 potently inhibits NSCLC cell growth in vitro and in vivo.

Study on the molecular mechanism of BuShenHuoXue capsule in treatment of steroid-induced osteonecrosis of the femoral head

BACKGROUND

Steroid-induced osteonecrosis of the femoral head (SONFH) is the pathological process caused by the death of the active components of the head of the femur due to the high dose of hormones, which has become a common public health problem. BuShenHuoXue capsule (BSHXC) has been clinically proven to be effective against the SONFH, the main pharmacological action of BSHXC is tonifying kidney and promoting blood circulation, but the mechanism remains to be explored.

METHODS

We established a rat SONFH model by injecting Methylprednisolone (MPS) into the right gluteus muscle 30 mg/kg/d, 3 days of continuous injection every week, 4 weeks in total. According to the clinical dosage of BSHXC (Herba epimedium 3 g, Eucommia ulmoides 15 g, Salvia miltiorrhizae 30 g, Chuanxiong 15 g, Paeonia lactiflora Pall 15 g, Poria cocos 12 g, Achyranthes bidentata 12 g, antler gum 10 g, Cyperus rotundus L. Nine g and Radix Glycyrrhizae 9 g), it was converted into the equivalent dose of rats, and gavage was performed at the weight of 10 mL/kg, once per day. The BSHXC was subjected to experiments in vivo, SONFH pharmacodynamics, bioinformatics, and network of pharmacology to determine the active ingredients, and its protective role against SONFH, Enrichment analysis was performed to explore the possible mechanism of BSHXC, and cell experiments were undertaken to analyze the impact of BSHXC on the hormones associated with bone marrow mesenchymal stem cells (BMSCs) between osteogenesis and apoptosis.

RESULTS

Experiments confirmed that BSHXC could effectively reduce bone loss in SONFH rat models. From bioinformatics and a network constructed from 10 drugs-208 pharmacology-126 targets, the enrichment analysis showed that the core targets were inflammatory reaction, steroid hormones, estrogen receptors, osteoporosis, and adjustment of osteogenesis and osteoclast differentiation, among others. The cell proliferation and staining supported that the mechanism of BSHXC promoted osteogenesis and intervening in apoptosis.

CONCLUSIONS

The BSHXC reduced the inflammatory response, changed steroid response, regulated estrogen receptors, delayed osteoporosis, regulated osteoblast and osteoclast differentiation by regulating related targets, and improved the local microenvironment by a multi-component, multi-target, and multi-link process to delay or reverse the progression of SONFH.

FGF23 protects osteoblasts from dexamethasone-induced oxidative injury

Dexamethasone (DEX) can exert a cytotoxic effect on cultured osteoblasts. The current study explored the potential osteoblast cytoprotective effect of fibroblast growth factor 23 (FGF23). In OB-6 human osteoblastic cells and primary murine osteoblasts, FGF23 induced phosphorylation of the receptor FGFR1 and activated the downstream Akt-S6K1 signaling. FGF23-induced FGFR1-Akt-S6K phosphorylation was largely inhibited by FGFR1 shRNA, but augmented with ectopic FGFR1 expression in OB-6 cells. FGF23 attenuated DEX-induced death and apoptosis in OB-6 cells and murine osteoblasts. Its cytoprotective effects were abolished by FGFR1 shRNA, Akt inhibition or Akt1 knockout. Conversely, forced activation of Akt inhibited DEX-induced cytotoxicity in OB-6 cells. Furthermore, FGF23 activated Akt downstream nuclear-factor-E2-related factor 2 (Nrf2) signaling to alleviate DEX-induced oxidative injury. On the contrary, Nrf2 shRNA or knockout almost reversed FGF23-induced osteoblast cytoprotection against DEX. Collectively, FGF23 activates FGFR1-Akt and Nrf2 signaling cascades to protect osteoblasts from DEX-induced oxidative injury and cell death.

miR-107 inhibition upregulates CAB39 and activates AMPK-Nrf2 signaling to protect osteoblasts from dexamethasone-induced oxidative injury and cytotoxicity

To human osteoblasts dexamethasone (DEX) treatment induces significant oxidative injury and cytotoxicity. Inhibition of CAB39 (calcium binding protein 39)-targeting microRNA can induce CAB39 upregulation, activating AMP-activated protein kinase (AMPK) signaling and offering osteoblast cytoprotection. Here we identified a novel CAB39-targeting miRNA: the microRNA-107 (miR-107). RNA-Pull down assay results demonstrated that the biotinylated-miR-107 directly binds to CAB39 mRNA in OB-6 human osteoblastic cells. Forced overexpression of miR-107, by infection of pre-miR-107 lentivirus or transfection of wild-type miR-107 mimic, largely inhibited CAB39 expression in OB-6 cells and primary human osteoblasts. Contrarily, miR-107 inhibition, by antagomiR-107, increased its expression, resulting in AMPK cascade activation. AntagomiR-107 largely attenuated DEX-induced cell death and apoptosis in OB-6 cells and human osteoblasts. Importantly, osteoblast cytoprotection by antagomiR-107 was abolished with AMPK in-activation by AMPKα1 dominant negative mutation, silencing or knockout. Further studies demonstrated that antagomiR-107 activated AMPK downstream Nrf2 cascade to inhibit DEX-induced oxidative injury. Conversely, Nrf2 knockout almost abolished antagomiR-107-induced osteoblast cytoprotection against DEX. Collectively, miR-107 inhibition induced CAB39 upregulation and activated AMPK-Nrf2 signaling to protect osteoblasts from DEX-induced oxidative injury and cytotoxicity.

Compound 13 activates AMPK-Nrf2 signaling to protect neuronal cells from oxygen glucose deprivation-reoxygenation

Oxygen glucose deprivation-reoxygenation (OGD-R) causes the production of reactive oxygen species (ROS) and oxidative injury in neuronal cells. We tested the potential neuroprotective function of compound 13 (C13), a novel AMP-activated protein kinase (AMPK) activator, against OGD-R. We show that C13 pretreatment protected SH-SY5Y neuronal cells and primary hippocampal neurons from OGD-R. C13 activated AMPK signaling in SH-SY5Y cells and primary neurons. It significantly inhibited OGD-R-induced apoptosis activation in neuronal cells. Conversely, AMPKα1 shRNA or knockout reversed C13-mediated neuroprotection against OGD-R. C13 potently inhibited OGD-R-induced ROS production and oxidative stress in SH-SY5Y cells and primary neurons. Furthermore, C13 induced Keap1 downregulation and Nrf2 activation, causing Nrf2 stabilization, nuclear accumulation, and expression of Nrf2-dependent genes. Nrf2 silencing or knockout in SH-SY5Y cells abolished C13-mediated neuroprotection against OGD-R. In conclusion, C13 activates AMPK-Nrf2 signaling to protect neuronal cells from OGD-R.

PGK1 depletion activates Nrf2 signaling to protect human osteoblasts from dexamethasone

Activation of nuclear-factor-E2-related factor 2 (Nrf2) cascade can alleviate dexamethasone (DEX)-induced oxidative injury and death of human osteoblasts. A recent study has shown that phosphoglycerate kinase 1 (PGK1) inhibition/depletion will lead to Kelch-like ECH-associated protein 1 (Keap1) methylglyoxal modification, thereby activating Nrf2 signaling cascade. Here, in OB-6 osteoblastic cells and primary human osteoblasts, PGK1 silencing, by targeted shRNA, induced Nrf2 signaling cascade activation, causing Nrf2 protein stabilization and nuclear translocation, as well as increased expression of ARE-dependent genes (HO1, NQO1, and GCLC). Functional studies demonstrated that PGK1 shRNA largely attenuated DEX-induced oxidative injury and following death of OB-6 cells and primary osteoblasts. Furthermore, PGK1 knockout, by the CRISPR/Cas9 method, similarly induced Nrf2 signaling activation and protected osteoblasts from DEX. Importantly, PGK1 depletion-induced osteoblast cytoprotection against DEX was almost abolished by Nrf2 shRNA. In addition, Keap1 shRNA mimicked and nullified PGK1 shRNA-induced anti-DEX osteoblast cytoprotection. At last we show that PGK1 expression is downregulated in human necrotic femoral head tissues of DEX-taking patients, correlating with HO1 depletion. Collectively, these results show that PGK1 depletion protects human osteoblasts from DEX via activation of Keap1-Nrf2 signaling cascade.

Activation of GPR30 promotes osteogenic differentiation of MC3T3-E1 cells: An implication in osteoporosis

Osteoporosis is an age-related disease characterized by reduced bone volume and disturbed bone metabolism. Novel therapies to rescue or prevent reduced bone mass by guiding the differentiation of pluripotent bone marrow stromal cells away from adipocyte differentiation and toward osteoblastic differentiation may serve as a valuable treatment option against osteoporosis. Estrogen has long been recognized as a key effector of bone formation and mineralization, but the exact mechanisms involved remain poorly understood. In the present study, we investigated the role of the estrogen-specific G protein-coupled receptor 30 (GPR30/GPER) using its specific agonist G1 in MC3T3-E1 preosteoblast cells. Our findings demonstrate that expression of GPR30 is upregulated during osteoblast differentiation and that agonism of GPR30 significantly increases some key markers of mineralization including alkaline phosphatase, osteocalcin, osterix, and type I collagen. We also demonstrate that GPR30 agonism upregulates expression of Runx2, which is recognized as an essential transcription factor involved in bone formation. Additionally, through a series of adenosine monophosphate-activated protein kinase (AMPK)-inhibition experiments using compound C, we show that the positive effects of GPR30 on mineralization and differentiation of preosteoblasts are mediated through the AMPK/anti-acetyl-CoA carboxylase (ACC) pathway. Taken together, the findings of the present study demonstrate the potential of GPR30 as a novel target for the treatment and prevention of osteoporosis.

Dexamethasone-induced cytotoxicity in human osteoblasts is associated with circular RNA HIPK3 downregulation

Dexamethasone (DEX) exerts potent cytotoxicity against cultured human osteoblasts. The current study examined the role of the circular RNA HIPK3 (circHIPK3) in the mechanism of cell death. We found that circHIPK3 expression was downregulated in DEX-treated human osteoblasts and circHIPK3 levels decreased in human necrotic femoral head tissues. In OB-6 osteoblastic cells and primary human osteoblasts ectopic overexpression of circHIPK3 potently suppressed DEX-induced apoptosis and programmed necrosis. Conversely, knockdown of circHIPK3by targeted siRNAs enhanced DEX-induced cytotoxicity in human osteoblasts. We further observed that microRNA-124 (miR-124), a key miRNA sponged by circHIPK3, accumulated following DEX treatment in OB-6 cells and primary osteoblasts. Confirming the role of miR-124 in DEX-induced cytotoxicity, miR-124 inhibitor attenuated cell death in human osteoblasts. Conversely, forced overexpression of miR-124 mimicked DEX-induced actions and induced cytotoxicity in human osteoblasts. We conclude that DEX-induced cytotoxicity in human osteoblasts is associated with circHIPK3 downregulation.

Silencing FOXO1 attenuates dexamethasone-induced apoptosis in osteoblastic MC3T3-E1 cells

Dexamethasone (DEX), a widely used glucocorticoid with strong anti-inflammatory and immunosuppressive activities, has been reported to induce apoptosis in osteoblasts, but the underlying mechanisms are still not comprehensively investigated. FOXO1 plays an important role in the regulation of cell proliferation and apoptosis. Our study aims to explore the role of FOXO1 in DEX-induced apoptosis of osteoblastic MC3T3-E1 cells through bioinformatics and experiments. We first employed bioinformatics to identify DEX-related genes and revealed their functions by GO enrichment analysis including FOXO1 associated biological processes. Expression level of FOXO1 was validated by GEO data. Then, experiments were performed to verify the hypothesis. CCK8 was used to detect cell viability and apoptosis was detected by flow cytometry. SiRNA was used to silence FOXO1 and western-blot was employed to detect protein expression. Results demonstrated DEX-related genes involved in cell proliferation, apoptosis and angiogenesis and FOXO1 was a regulator of apoptosis. DEX could up-regulate FOXO1 expression, inhibit cell viability, promote apoptosis. SiRNA-FOXO1 could attenuate DEX-induced apoptosis in MC3T3-E1. These findings suggested DEX could affect some vital biological processes of MC3T3-E1 and FOXO1 played an essential role in DEX-induced apoptosis in MC3T3-E1.

Mitochondrial Dynamics Impairment in Dexamethasone-Treated Neuronal Cells

Dexamethasone is an approved steroid for clinical use to activate or suppress cytokines, chemokines, inflammatory enzymes and adhesion molecules. It enters the brain, by-passing the blood brain barrier, and acts through genomic mechanisms. High levels of dexamethasone are able to induce neuronal cell loss, reduce neurogenesis and cause neuronal dysfunction. The exact mechanisms of steroid, especially the dexamethasone contribute to neuronal damage remain unclear. Therefore, the present study explored the mitochondrial dynamics underlying dexamethasone-induced toxicity of human neuroblastoma SH-SY5Y cells. Neuronal cells treatment with the dexamethasone resulted in a marked decrease in cell proliferation. Dexamethasone-induced neurotoxicity also caused upregulation of mitochondrial fusion and cleaved caspase-3 proteins expression. Mitochondria fusion was found in large proportions of dexamethasone-treated cells. These results suggest that dexamethasone-induced hyperfused mitochondrial structures are associated with a caspase-dependent death process in dexamethasone-induced neurotoxicity. These findings point to the high dosage of dexamethasone as being neurotoxic through impairment of mitochondrial dynamics.

Adiponectin attenuates lipopolysaccharide-induced cell injury of H9c2 cells by regulating AMPK pathway

Adiponectin, an adipokine synthesized and secreted majorly by adipose tissue, is reported to exert cardioprotective properties via anti-inflammation and antiapoptosis. Lipopolysaccharide (LPS) is a common inflammation and apoptosis inducer of cardiomyocytes. However, few studies have reported the roles of adiponectin on LPS-induced inflammation as well as apoptosis of H9c2 cells, and the possible mechanisms of these effects. In the present study, we found that adiponectin significantly relieved LPS-induced cytotoxicity including decreased viability and elevated LDH release, inhibited LPS-triggered inflammation, which is evidenced by increases in release of TNF-α, IL-1β as well as IL-6, and attenuated the enhanced rates of apoptotic cells as well as increased caspase-3 activity caused by LPS in H9c2 cells. In addition, our data demonstrated that adiponectin upregulated AMP-activated protein kinase (AMPK) activation of H9c2 cells with or without LPS administration. Moreover, we found that blocking AMPK pathway by compound c attenuated the protective effects of adiponectin against the cytotoxicity, inflammatory response, and apoptosis of H9c2 cells resulted from LPS. Our observations bring novel insights for understanding the mediatory role of AMPK pathway implicated in the protective effects of adiponectin against LPS-induced cardiotoxicity.

Flubendiamide Enhances Adipogenesis and Inhibits AMPKα in 3T3-L1 Adipocytes

Flubendiamide, a ryanoid class insecticide, is widely used in agriculture. Several insecticides have been reported to promote adipogenesis. However, the potential influence of flubendiamide on adipogenesis is largely unknown. The current study was therefore to determine the effects of flubendiamide on adipogenesis utilizing the 3T3-L1 adipocytes model. Flubendiamide treatment not only enhanced triglyceride content in 3T3-L1 adipocytes, but also increased the expression of cytosine-cytosine-adenosine-adenosine-thymidine (CCAAT)/enhancer-binding protein α and peroxisome proliferator-activated receptor gamma-γ, two important regulators of adipocyte differentiation. Moreover, the expression of the most important regulator of lipogenesis, acetyl coenzyme A carboxylase, was also increased after flubendiamide treatment. Further study revealed that 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) or A769662, two Adenosine 5′-monophosphate (AMP)-activated protein kinase α activators, subverted effects of flubendiamide on enhanced adipogenesis. Together, these results suggest that flubendiamide promotes adipogenesis via an AMPKα-mediated pathway.

Zoledronic Acid, Bevacizumab and Dexamethasone-Induced Apoptosis, Mitochondrial Oxidative Stress, and Calcium Signaling Are Decreased in Human Osteoblast-Like Cell Line by Selenium Treatment

Increased intracellular free calcium ion (Ca²⁺) concentration induces excessive oxidative stress and apoptosis. Medical procedures such as zoledronic acid (Zol), bevacizumab (Bev), and dexamethasone (Dex) are usually used in the treatment of bone diseases (osteoporosis, Paget's disease, etc.) and to prevent metastasis in the bone although the procedures induce osteonecrosis of the jaw through excessive production of reactive oxygen species (ROS). Recently, we observed regulator roles of selenium (Se) on apoptosis and Ca²⁺ entry through transient receptor potential vanilloid 1 (TRPV1) channels in the cancer cell lines. Therefore, Se may modulate Zol, Bev, and Dex-induced oxidative stress and apoptosis through regulation of TRPV1 channel. In the current study, we investigated the protective effects of Se on apoptosis and oxidative stress through TRPV1 in Zol, Bev, and Dex-induced osteoblast-like cell line. We used human osteoblast-like cell line (Saos-2), and the cells were divided into 12 groups as control, Zol, Bev, Dex, Se, Zol+Se, Bev+Se, Dex+Se, Zol+Dex, Zol+Dex+Se, Zol+Bev, and Zol+Bev+Se which were incubated with drugs (Zol, Bev, Dex, and Se) for 24 h. The cytosolic free Ca²⁺ concentration was increased by Zol, Bev, Dex, Zol+Bev, and Zol+Dex, although it was reduced by Se treatment. However, Zol, Bev, and Dex-induced increase in apoptosis, caspase 3, caspase 9, poly (ADP-ribose) polymerase 1 expression levels, and intracellular ROS production values in the cells were decreased by Se treatments. In conclusion, we observed that Zol, Bev, and Dex-induced apoptosis, mitochondrial oxidative stress, and calcium signaling are decreased in human osteoblast-like cell line by the Se treatment. Our findings may be relevant to the etiology and treatment of Zol, Bev, and Dex-induced osteonecrosis by Se.

Assessment of GSK1904529A as a promising anti-osteosarcoma agent

The insulin growth factor-I receptor (IGF1R) signaling is a key mechanism for osteosarcoma (OS) cell proliferation. GSK1904529A is a novel small molecule IGF1R kinase inhibitor. Its activity against OS cells was tested. In both established OS cell lines (Saos-2 and MG-63) and primary human OS cells, treatment with GSK1904529A (at nM concentrations) significantly inhibited cell proliferation. At the molecular level, GSK1904529A almost completely blocked IGF1R activation in OS cells, and inhibited downstream AKT-ERK activation. IGF1R silence by targeted shRNA also inhibited AKT-ERK activation and Saos-2 cell proliferation. Significantly, GSK1904529A was unable to further inhibit proliferation of IGF1R-silenced Saos-2 cells. In vivo, GSK1904529A administration orally inhibited Saos-2 tumor growth in nude mice. Together, these results suggest that targeting IGF1R by GSK1904529A inhibits OS cell growth in vitro and in vivo.

Itraconazole-Induced Inhibition on Human Esophageal Cancer Cell Growth Requires AMPK Activation

We here evaluated the antiesophageal cancer cell activity by the antifungal drug itraconazole. Our results show that μg/mL concentrations of itraconazole potently inhibited survival and proliferation of established (TE-1 and Eca-109) and primary human esophageal cancer cells. Itraconazole activated AMPK signaling, which was required for subsequent esophageal cancer cell death. Pharmacologic AMPK inhibition, AMPKα1 shRNA, or dominant negative mutation (T172A) almost completely abolished itraconazole-induced cytotoxicity against esophageal cancer cells. Significantly, itraconazole induced AMPK-dependent autophagic cell death (but not apoptosis) in esophageal cancer cells. Furthermore, AMPK activation by itraconazole induced multiple receptor tyrosine kinases (RTKs: EGFR, PDGFRα, and PDGFRβ), lysosomal translocation, and degradation to inhibit downstream Akt activation. In vivo, itraconazole oral gavage potently inhibited Eca-109 tumor growth in SCID mice. It was yet ineffective against AMPKα1 shRNA-expressing Eca-109 tumors. The in vivo growth of the primary human esophageal cancer cells was also significantly inhibited by itraconazole administration. AMPK activation, RTK degradation, and Akt inhibition were observed in itraconazole-treated tumors. Together, itraconazole inhibits esophageal cancer cell growth via activating AMPK signaling. Mol Cancer Ther; 17(6); 1229-39. ©2018 AACR.

miR-135b-5p inhibits LPS-induced TNFα production via silencing AMPK phosphatase Ppm1e

AMPK activation in monocytes could suppress lipopolysaccharide (LPS)-induced tissue-damaging TNFa production. We are set to provoke AMPK activation via microRNA (“miRNA”) downregulating its phosphatase Ppm1e. In human U937 and THP-1 monocytes, forced expression of microRNA-135b-5p (“miR-135b-5p”) downregulated Ppm1e and activated AMPK signaling. Further, LPS-induced TNFα production in above cells was dramatically attenuated. Ppm1e shRNA knockdown in U937 cells also activated AMPK and inhibited TNFα production by LPS. AMPK activation is required for miR-135b-induced actions in monocytes, AMPKα shRNA knockdown or T172A dominant negative mutation almost abolished miR-135b-5p's suppression on LPS-induced TNFα production. Significantly, miR-135b-5p inhibited LPS-induced reactive oxygen species (ROS) production, NFκB activation and TNFα mRNA expression in human macrophages. AMPKα knockdown or mutation again abolished above actions by miR-135b-5p. We conclude that miR-135b-5p expression downregulates Ppm1e to activate AMPK signaling, which inhibits LPS-induced TNFα production via suppressing ROS production and NFκB activation.

Improvement of dexamethasone sensitivity by chelation of intracellular Ca2+ in pediatric acute lymphoblastic leukemia cells through the prosurvival kinase ERK1/2 deactivation

Previous studies have demonstrated that glucocorticoid hormones, including dexamethasone, induced alterations in intracellular calcium homeostasis in acute lymphoblastic leukemia (ALL) cells. However, the mechanism by which intracellular calcium homeostasis participates in dexamethasone sensitivity and resistance on ALL cells remains elusive. Here, we found that treatment of cells with dexamethasone resulted in increased intracellular calcium concentrations through store-operated calcium entry stimulation, which was curtailed by store-operated calcium channel blockers. We show that BAPTA-AM, an intracellular Ca2+ chelator, synergistically enhances dexamethasone lethality in two human ALL cell lines and in three primary specimens. This effect correlated with the inhibition of the prosurvival kinase ERK1/2 signaling pathway. Chelating intracellular calcium with Bapta-AM or inhibiting ERK1/2 with PD98059 significantly potentiated dexamethasone-induced mitochondrial membrane potential collapse, reactive oxygen species production, cytochrome c release, caspase-3 activity, and cell death. Moreover, we show that thapsigargin elevates intracellular free calcium ion level, and activates ERK1/2 signaling, resulting in the inhibition of dexamethasone-induced ALL cells apoptosis. Together, these results indicate that calcium-related ERK1/2 signaling pathway contributes to protect cells from dexamethasone sensitivity by limiting mitochondrial apoptotic pathway. This report provides a novel resistance pathway underlying the regulatory effect of dexamethasone on ALL cells.

microRNA-25 targets PKCζ and protects osteoblastic cells from dexamethasone via activating AMPK signaling

AMP-activated protein kinase (AMPK) activation could protect osteoblasts from dexamethasone (Dex). This study aims to provoke AMPK activation via microRNA downregulation of its negative regulator protein kinase C ζ (PKCζ). Results show that microRNA-25-5p (miR-25-5p) targets PKCζ's 3’ untranslated regions (UTRs). Forced-expression of miR-25 downregulated PKCζ and activated AMPK in human osteoblastic cells (OB-6 and hFOB1.19 lines), which thereafter protected cells from Dex. Reversely, expression of antagomiR-25, the miR-25 inhibitor, upregulated PKCζ and inhibited AMPK activation, exacerbating Dex damages. Notably, PKCζ shRNA knockdown similarly activated AMPK and protected osteoblastic cells from Dex. AMPK activation was required for miR-25-induced osteoblastic cell protection. AMPKα shRNA or dominant negative mutation almost completely blocked miR-25-induced cytoprotection against Dex. Further studies showed that miR-25 expression increased NADPH activity and suppressed Dex-induced oxidative stress in osteoblastic cells. Such effects by miR-25 were abolished with AMPKα knockdown or mutation. Significantly, miR-25-5p level was increased in patients’ necrotic femoral head tissues, which was correlated with PKCζ downregulation and AMPK hyper-activation. These results suggest that miR-25-5p targets PKCζ and protects osteoblastic cells from Dex possibly via activating AMPK signaling.

miR-135b expression downregulates Ppm1e to activate AMPK signaling and protect osteoblastic cells from dexamethasone

Activation of AMP-activated protein kinase (AMPK) could potently protect osteoblasts/osteoblastic cells from dexamethasone (Dex). We aim to induce AMPK activation via microRNA ("miRNA") downregulation of its phosphatase Ppm1e. We discovered that microRNA-135b ("miR-135b") targets the 3' untranslated regions (UTRs) of Ppm1e. In human osteoblasticOB-6 cells and hFOB1.19 cells, forced-expression of miR-135b downregulated Ppm1e and activated AMPK signaling. miR-135b also protected osteoblastic cells from Dex. shRNA-induced knockdown of Ppm1e similarly activated AMPK and inhibited Dex-induced damages. Intriguingly, in the Ppm1e-silenced osteoblastic cells, miR-135b expression failed to offer further cytoprotection against Dex. Notably, AMPK knockdown (via shRNA) or dominant negative mutation abolished miR-135b-induced AMPK activation and cytoprotection against Dex. Molecularly, miR-135b, via activating AMPK, increased nicotinamide adenine dinucleotide phosphate (NADPH) activity and inhibited Dex-induced oxidative stress. At last, we found that miR-135b level was increased in human necrotic femoral head tissues, which was correlated with Ppm1e downregulation and AMPK activation. There results suggest that miR-135b expression downregulates Ppm1e to activate AMPK signaling, which protects osteoblastic cells from Dex.

Icariside II activates EGFR-Akt-Nrf2 signaling and protects osteoblasts from dexamethasone

The potential effect of icariside II on dexamethasone-induced osteoblast cell damages was evaluated here. In MC3T3-E1 osteoblastic cells and the primary murine osteoblasts, co-treatment with icariside II dramatically attenuated dexamethasone- induced cell death and apoptosis. Icariside II activated Akt signaling, which is required for its actions in osteoblasts. Akt inhibitors (LY294002, perifosine and MK-2206) almost abolished icariside II-induced osteoblast cytoprotection against dexamethasone. Further studies showed that icariside II activated Nrf2 signaling, downstream of Akt, to inhibit dexamethasone-induced reactive oxygen species (ROS) production in MC3T3-E1 cells and primary osteoblasts. On the other hand, Nrf2 shRNA knockdown inhibited icariside II-induced anti-dexamethasone cytoprotection in MC3T3-E1 cells. Finally, we showed that icariside II induced heparin-binding EGF (HB-EGF) production and EGFR trans-activation in MC3T3-E1 cells. EGFR inhibition, via anti-HB-EGF antibody, EGFR inhibitor AG1478 or EGFR shRNA knockdown, almost blocked icariside II-induced Akt-Nrf2 activation in MC3T3-E1 cells. Collectively, we conclude that icariside II activates EGFR-Akt-Nrf2 signaling and protects osteoblasts from dexamethasone. Icariside II might have translational value for the treatment of dexamethasone-associated osteoporosis/osteonecrosis.

Targeted activation of AMPK by GSK621 ameliorates H2O2-induced damages in osteoblasts

GSK621 is a novel AMP-activated protein kinase (AMPK) activator. This study tested its potential cytoprotective effect in hydrogen peroxide (H₂O₂)-treated osteoblasts. In cultured MC3T3-E1 osteoblastic cells and primary murine osteoblasts, GSK621 significantly attenuated H₂O₂-induced cell death and apoptosis. AMPK activation was required for GSK621-induced osteoblast cytoprotection. Inhibition of AMPK, by AMPKα1 T172A mutation or shRNA silence, almost completely blocked GSK621-induced osteoblast cytoprotection. Reversely, introduction of a constitutively-active AMPKα1 (T172D) alleviated H₂O₂ injuries in MC3T3-E1 cells. Further, GSK621 increased nicotinamide adenine dinucleotide phosphate (NADPH) content in osteoblasts to inhibit H₂O₂-induced reactive oxygen species (ROS) production. Meanwhile, GSK621 activated cytoprotective autophagy in the osteoblasts. On the other hand, pharmacological inhibition of autophagy alleviated GSK621-mediated osteoblast cytoprotection against H₂O₂. These results suggest that targeted activation of AMPK by GSK621 ameliorates H₂O₂-induced osteoblast cell injuries.

AntogomiR-451 protects human gastric epithelial cells from ethanol via activating AMPK signaling

The prevention and treatment efficiency of ethanol-induced gastric epithelial injury are not satisfied. We have previously shown that AMP-activated protein kinase (AMPK) activation exerts a pro-survival function in human gastric epithelial cells (GECs). miroRNA-451 ("miR-451")'s inhibitor, antagomiR-451, can activate AMPK signaling. In the present study, we show that forced-expression of antagomiR-451 via a lentiviral vector depleted miR-451, leading to AMPK activation in established GES-1 cells and primary human GECs. AntagomiR-451 efficiently protected GES-1 cells and primary human GECs from ethanol-induced viability reduction and apoptosis. AMPK activation is required for antagomiR-451-induced GEC protection. AMPKα1 knockdown (by targeted-shRNAs) or knockout (by CRISPR-Cas-9 KO plasmid) blocked antagomiR-451-induced AMPK activation, and GEC protection against ethanol. Further experimental results show that antagomiR-451 significantly attenuated ethanol-induced reactive oxygen species (ROS) production, lipid peroxidation and DNA damage. Collectively, antagomiR-451 protects human GECs from ethanol via activating AMPK signaling.

AMPK activation by Tanshinone IIA protects neuronal cells from oxygen-glucose deprivation

The current study tested the potential neuroprotective function of Tanshinone IIA (ThIIA) in neuronal cells with oxygen-glucose deprivation (ODG) and re-oxygenation (OGDR). In SH-SY5Y neuronal cells and primary murine cortical neurons, ThIIA pre-treatment attenuated OGDR-induced viability reduction and apoptosis. Further, OGDR-induced mitochondrial depolarization, reactive oxygen species production, lipid peroxidation and DNA damages in neuronal cells were significantly attenuated by ThIIA. ThIIA activated AMP-activated protein kinase (AMPK) signaling, which was essential for neuroprotection against OGDR. AMPKα1 knockdown or complete knockout in SH-SY5Y cells abolished ThIIA-induced AMPK activation and neuroprotection against OGDR. Further studies found that ThIIA up-regulated microRNA-135b to downregulate the AMPK phosphatase Ppm1e. Notably, knockdown of Ppm1e by targeted shRNA or forced microRNA-135b expression also activated AMPK and protected SH-SY5Y cells from OGDR. Together, AMPK activation by ThIIA protects neuronal cells from OGDR. microRNA-135b-mediated silence of Ppm1e could be the key mechanism of AMPK activation by ThIIA.

microRNA-19a protects osteoblasts from dexamethasone via targeting TSC1

Activation of mTOR complex 1 (mTORC1) could protect human osteoblasts from dexamethasone. Tuberous sclerosis complex 1 (TSC1) is mTORC1 upstream inhibitory protein. We demonstrate here that microRNA-19a (“miR-19a”, -3p) targets the 3' untranslated regions of TSC1 mRNA. Expression of miR-19a downregulated TSC1 in OB-6 osteoblastic cells and primary human osteoblasts. miR-19a activated mTORC1 and protected human osteoblasts from dexamethasone. mTORC1 inhibition, by RAD001 or Raptor shRNA, almost completely abolished miR-19a-induced osteoblast cytoprotection against dexamethasone. Knockdown of TSC1 by targeted shRNA similarly induced mTORC1 activation and protected osteoblasts. Moreover, miR-19a activated mTORC1-dependent NF-E2-related factor 2 (Nrf2) signaling and inhibited dexamethasone-induced reactive oxygen species production in osteoblasts. Together, miR-19a protects human osteoblasts from dexamethasone possibly via targeting TSC1-mTORC1 signaling.

Jujube leaf green tea extracts inhibits hepatocellular carcinoma cells by activating AMPK

Here we evaluated the anti-hepatocellular carcinoma activity by the Jujube leaf green tea extracts (JLGTE). We showed that JLGTE exerted anti-proliferative, cytotoxic and pro-apoptotic activities against HepG2 and primary human hepatocellular carcinoma cells. It was however non-cytotoxic to the normal hepatocytes. JLGTE activated AMP-activated protein kinase (AMPK) signaling, which was required for its cytotoxicity against hepatocellular carcinoma cells. Silence of AMPKα1, via targeted short hairpin RNAs or CRISPR-Cas9 genome editing, inhibited JLGTE-induced AMPK activation and HepG2 cell apoptosis. Further, in-activation of AMPK by a dominant negative AMPKα1 (T172A) also alleviated JLGTE's cytotoxicity against HepG2 cells. On the other hand, forced-activation of AMPK by introduction of a constitutively-active AMPKα1 (T172D) mimicked JLGTE's actions and led to HepG2 cell apoptosis. These results suggest that JLGTE inhibits human hepatocellular carcinoma cells possibly via activating AMPK.

Activation of AMP-activated protein kinase by compound 991 protects osteoblasts from dexamethasone

Dexamethasone (Dex) induces direct cytotoxicity to cultured osteoblasts. The benzimidazole derivative compound 991 ("C991") is a novel and highly-efficient AMP-activated protein kinase (AMPK) activator. Here, in both MC3T3-E1 osteoblastic cells and primary murine osteoblasts, treatment with C991 activated AMPK signaling, and significantly attenuated Dex-induced apoptotic and non-apoptotic cell death. AMPKα1 knockdown (by shRNA), complete knockout (by CRISPR/Cas9 method) or dominant negative mutation (T172A) not only blocked C991-mediated AMPK activation, but also abolished its pro-survival effect against Dex in osteoblasts. Further studies showed that C991 boosted nicotinamide adenine dinucleotide phosphate (NADPH) activity and induced mRNA expression of NF-E2-related factor 2 (Nrf2)-regulated genes (heme oxygenase-1 and NADPH quinone oxidoreductase 1). Additionally, C991 alleviated Dex-induced reactive oxygen species (ROS) production in osteoblasts. Notably, genetic AMPK inhibition reversed the anti-oxidant actions by C991 in Dex-treated osteoblasts. Together, we conclude that C991 activates AMPK signaling to protect osteoblasts from Dex.

Activation of Nrf2 by MIND4-17 protects osteoblasts from hydrogen peroxide-induced oxidative stress

MIND4-17 is a recently developed NF-E2-related factor 2 (Nrf2) activator, which uniquely causes Nrf2 disassociation from Keap1. Here, we showed that pretreatment with MIND4-17 significantly inhibited hydrogen peroxide (H₂O₂)-induced viability reduction of primary osteoblasts and OB-6 osteoblastic cells. Meanwhile, MIND4-17 inhibited both apoptotic and non-apoptotic osteoblast cell death by H₂O₂. MIND4-17 treatment induced Keap1-Nrf2 disassociation, causing Nrf2 stabilization, accumulation and nuclear translocation in osteoblasts, leading to transcription of several Nrf2-dependent genes, including heme oxygenase 1 (HO-1), NAD(P)H quinone oxidoreductase 1 (NQO1), γ-glutamylcysteine synthetase modifier subunit (GCLM) and catalytic subunit (GCLC). Additionally, MIND4-17 largely attenuated H₂O₂-reactive oxygen species (ROS) production, lipid peroxidation and DNA damages. Nrf2 knockdown by targeted short hairpin RNA (shRNA) exacerbated H₂O₂-induced cytotoxicity in OB-6 osteoblastic cells, and nullified MIND4-17-mediated cytoprotection against H₂O₂. Meanwhile, Keap1 shRNA took over MIND4-17′s actions and protected OB-6 cells from H₂O₂. Together, MIND4-17 activates Nrf2 signaling and protects osteoblasts from H₂O₂.

Activation of AMPK by OSU53 protects spinal cord neurons from oxidative stress

The present study tested the potential effect of OSU53, a novel AMPK activator, against hydrogen peroxide (H2O2)-induced spinal cord neuron damages. Treatment with OSU53 attenuated H2O2-induced death and apoptosis of primary murine spinal cord neurons. OSU53 activated AMPK signaling, which is required for its actions in spinal cord neurons. The AMPK inhibitor Compound C or AMPKα1 siRNA almost abolished OSU53-mediated neuroprotection against H2O2. On the other hand, sustained-activation of AMPK by introducing the constitutive-active AMPKα1 mimicked OSU53's actions, and protected spinal cord neurons from oxidative stress. OSU53 significantly attenuated H2O2-induced reactive oxygen species production, lipid peroxidation and DNA damages in spinal cord neurons. Additionally, OSU53 increased NADPH content and heme oxygenase-1 mRNA expression in H2O2-treated spinal cord neurons. Together, we indicate that targeted-activation of AMPK by OSU53 protects spinal cord neurons from oxidative stress.

MicroRNA-200a activates Nrf2 signaling to protect osteoblasts from dexamethasone

Treatment with dexamethasone in human osteoblasts leads to oxidative stress and cell injures. NF-E2-related factor 2 (Nrf2) is a key anti-oxidant signaling. We want to induce Nrf2 activation via microRNA-mediated silencing its suppressor Keap1. Our results show that microRNA-200a ("miR-200a") expression depleted Keap1, causing Nrf2 protein stabilization in OB-6 osteoblastic cells. Reversely, the miR-200a anti-sense led to Keap1 upregulation and Nrf2 degradation. miR-200a expression activated Nrf2 signaling, which inhibited dexamethasone-induced reactive oxygen species production and OB-6 cell death/apoptosis. Keap1 shRNA also activated Nrf2 and protected OB-6 cells from dexamethasone. Importantly, miR-200a was in-effective in Keap1-silenced (by shRNA) OB-6 cells. In the primary human osteoblasts, Keap1 silence by targeted-shRNA or miR-200a protected cells from dexamethasone. Significantly, miR-200a level was decreased in necrotic femoral head tissues, which was correlated with Keap1 mRNA upregulation. Together, miR-200a expression activates Nrf2 signaling and protects human osteoblasts from dexamethasone.

AMPK-autophagy inhibition sensitizes icaritin-induced anti-colorectal cancer cell activity

The current research studied the potential effect of autophagy on icaritin-induced anti-colorectal cancer (CRC) cell activity. Treatment of icaritin in both primary and established (HT-29) CRC cells induced feedback activation of autophagy, evidenced by p62 degradation, Beclin-1 and autophagy-related gene-5 (ATG-5) upregulation, as well as light chain 3B (LC3B)-GFP puncta formation. Pharmacological inhibiting of autophagy dramatically potentiated icaritin-induced CRC cell death and apoptosis. Meanwhile, shRNA-mediated knockdown of Beclin-1 or ATG-5 also sensitized icaritin-induced CRC cell death and apoptosis. Icaritin activated AMP-activated protein kinase (AMPK) signaling in CRC cells, functioning as the upstream signaling for autophagy activation. shRNA/siRNA-mediated knockdown of AMPKα1inhibited icaritin-induced autophagy activation, but exacerbated CRC cell death. On the other hand, the AMPK activator compound 13 (C13) or the autophagy activator MHY1485 attenuated icaritin-induced cytotoxicity. In nude mice, icaritin (oral administration)-induced HT-29 tumor growth inhibition was potentiated when combined with AMPKα1 shRNA knockdown in tumors. We conclude that feedback activation of AMPK-autophagy pathway could be a primary resistance factor of icaritin.

microRNA-455 targets cullin 3 to activate Nrf2 signaling and protect human osteoblasts from hydrogen peroxide

Over-production of hydrogen peroxide (H₂O₂) will lead to human osteoblast dysfunction and apoptosis, causing progression of osteoporosis and osteonecrosis. NF-E2-related factor 2 (Nrf2) is a well-characterized anti-oxidant signaling. Cullin 3 (Cul3) ubiquitin E3 ligase dictates Nrf2 degradation. We demonstrate that microRNA-455 ("miR-455") is a putative Cul3-targeting microRNA. Forced-expression of miR-455 in both hFOB1. 19 osteoblast cell line and primary human osteoblasts induced Cul3 degradation and Nrf2 protein stabilization, which led to subsequent transcription of ARE (anti-oxidant response element)-dependent genes (NQO1, HO1 and GCLC). Cul3 silencing, by expressing miR-455 or targeted-shRNA, protected human osteoblasts from H₂O₂. Reversely, miR-455 anti-sense caused Cul3 accumulation and Nrf2 degradation, which exacerbated H₂O₂ damages in hFOB1. 19 cells. Moreover, forced over-expression of Cul3 in hFOB1. 19 cells silenced Nrf2 and sensitized H₂O₂. Together, we propose that miR-455 activated Nrf2 signaling and protected human osteoblasts from oxidative stress possibly via targeting Cul3.

Vitamin D deficiency causes insulin resistance by provoking oxidative stress in hepatocytes

Vitamin D deficiency could cause insulin resistance. However, the underlying mechanisms are unclear. The 1α-Hydroxylase [“1α(OH)ase”] is a key enzyme for activate vitamin D3 synthesis. Here, we show that 1α(OH)ase stable knockdown by targeted shRNA led to vitamin D3 depletion in L02 hepatocytes. 1α(OH)ase silence also inhibited insulin-induced downstream signaling (IRS-1, ERK and AKT) transduction and glucose transporter 4 expression. Further, 1α(OH)ase shRNA in L02 hepatocytes led to significant reactive oxygen species production, p53-p21 activation and DNA damages. Such effects were almost completely reversed with co-treatment of n-acetylcysteine, which is an established anti-oxidant. Remarkably, insulin-induced downstream signaling transduction and glucose transporter 4 expression were recovered with n-acetylcysteine co-treatment in 1α(OH)ase-silenced L02 hepatocytes. Together, our results suggest that vitamin D deficiency-induced insulin resistance is possibly caused by oxidative stress in hepatocytes.

Insulin resistance in vitamin D-deficient mice is alleviated by n-acetylcysteine

Vitamin D deficiency will lead to insulin resistance. In the current study, vitamin D3 1α-Hydroxylase [“1α(OH)ase”] knockout mice were generated to mimic vitamin D deficiency in vivo. As compared to the wild-type mice, the liver tissues of the knockout mice showed impaired insulin signaling, decreased glucose transporter 4 expression and increased reactive oxygen species production. Meanwhile, p53-p21 activation, apoptosis intensity and pro-inflammatory cytokines (IL-6, IL-1 and MIP-1α) level were significantly increased in the knockout mice livers. Significantly, such effects in the knockout mice were largely attenuated by supplement with anti-oxidant n-acetylcysteine (NAC). Remarkably, insulin resistance and metabolic abnormalities in the knockout mice were largely alleviated after treatment of NAC. Therefore, inhibition of oxidative stress by NAC alleviated insulin resistance in vitamin D-deficient mice. Oxidative stress could be the primary cause of insulin resistance by vitamin D deficiency.

A novel AMPK activator hernandezine inhibits LPS-induced TNFα production

Here, we found that hernandezine, a novel AMPK activator, inhibited LPS-induced TNFα expression/production in human macrophage cells (THP-1 and U937 lines). Activation of AMPK is required for hernandezine-induced anti-LPS response. AMPKα shRNA or dominant negative mutation (T172A) blocked hernandezine-induced AMPK activation, which almost completely reversed anti-LPS activity by hernandezine. Exogenous expression of the constitutively activate AMPKα (T172D, caAMPKα) also suppressed TNFα production by LPS. Remarkably, hernandezine was unable to further inhibit LPS-mediated TNFα production in caAMPKα-expressing cells. Hernandezine inhibited LPS-induced reactive oxygen species (ROS) production and nuclear factor kappa B (NFκB) activation. Treatment of hernandezine in ex-vivo cultured primary human peripheral blood mononuclear cells (PBMCs) also largely attenuated LPS-induced TNFα production. Together, we conclude that AMPK activation by hernandezine inhibits LPS-induced TNFα production in macrophages/monocytes.

MHY1485 activates mTOR and protects osteoblasts from dexamethasone

Dexamethasone (Dex) exerts cytotoxic effects to cultured osteoblasts. The potential effect of MHY1485, a small-molecular mammalian target of rapamycin (mTOR) activator, against the process was studied here. In both osteoblastic MC3T3-E1 cells and primary murine osteoblasts, treatment with MHY1485 significantly ameliorated Dex-induced cell death and apoptosis. mTOR inhibition, through mTOR kinase inhibitor OSI-027 or mTOR shRNAs, abolished MHY1485-mediated osteoblast cytoprotection against Dex. Intriguingly, activation of mTOR complex (mTORC1), but not mTORC2, is required for MHY1485's anti-Dex activity. mTORC1 inhibitors (rapamycin and RAD001) or Raptor knockdown almost reversed MHY1485-induced osteoblast cytoprotection. mTORC2 inhibition, via shRNA knockdown of Rictor, failed to affect MHY1485's activity in MC3T3-E1 cells. Further studies showed that MHY1485 treatment in MC3T3-E1 cells and primary murine osteoblasts significantly inhibited Dex-induced mitochondrial death pathway activation, the latter was tested by mitochondrial depolarization, cyclophilin D-ANT-1 association and cytochrome C cytosol release. Together, these results suggest that MHY1485 activates mTORC1 signaling to protect osteoblasts from Dex.

Preclinical study of CC223 as a potential anti-ovarian cancer agent

Aberrant activation of mTOR contributes to ovarian cancer progression. CC223 is a novel and potent mTOR kinase inhibitor. The current study tested its activity against human ovarian cancer cells. We showed that CC223, at nM concentrations, inhibited survival and proliferation of established/primary human ovarian cancer cells. Further, significant apoptosis activation was observed in CC223-treated ovarian cancer cells. CC223 disrupted assembly of mTOR complex 1 (mTORC1) and mTORC2 in SKOV3 cells. Meanwhile, activation of mTORC1 and mTORC2 was almost completely blocked by CC223. Intriguingly, restoring mTOR activation by introduction of a constitutively-active Akt1 only partially inhibited CC223-induced cytotoxicity in SKOV3 cells. Further studies showed that CC223 inhibited sphingosine kinase 1 (SphK1) activity and induced reactive oxygen species (ROS) production in SKOV3 cells. At last, oral administration of CC223 potently inhibited SKOV3 xenografted tumor growth in nude mice. The results of this study imply that CC223 could be further studied as a potential anti-ovarian cancer agent.

PP2A catalytic subunit silence by microRNA-429 activates AMPK and protects osteoblastic cells from dexamethasone

Activation of AMP-activated protein kinase (AMPK) could efficiently protect osteoblasts from dexamethasone (Dex). Here, we aim to induce AMPK activation through miRNA-mediated downregulating its phosphatase, protein phosphatase 2A (PP2A). We discovered that microRNA-429 ("miR-429") targets the catalytic subunit of PP2A (PP2A-c). Significantly, expression of miR-429 downregulated PP2A-c and activated AMPK (p-AMPKα1 Thr172) in human osteoblastic cells (OB-6 and hFOB1.19 lines). Remarkably, miR-429 expression alleviated Dex-induced osteoblastic cell death and apoptosis. On the other hand, miR-429-induced AMPK activation and osteoblast cytoprotection were almost abolished when AMPKα1 was either silenced (by targeted shRNA) or mutated (T172A inactivation). Further studies showed that miR-429 expression in osteoblastic cells increased NADPH (nicotinamide adenine dinucleotide phosphate) content to significantly inhibit Dex-induced oxidative stress. Such effect by miR-429 was again abolished with AMPKα1 silence or mutation. Together, we propose that PP2A-c silence by miR-429 activates AMPK and protects osteoblastic cells from Dex.