Active vitamin D activates chondrocyte autophagy to reduce osteoarthritis via mediating the AMPK–mTOR signaling pathway

2020 ◽  
Vol 98 (3) ◽  
pp. 434-442 ◽  
Author(s):  
Chunyu Kong ◽  
Changlei Wang ◽  
Yuquan Shi ◽  
Lei Yan ◽  
Junhua Xu ◽  
...  
Keyword(s):  
Vitamin D ◽  
Signaling Pathway ◽  
Therapeutic Option ◽  
Serum Levels ◽  
Mtor Signaling ◽  
Mtor Signaling Pathway ◽  
Ampk Signaling ◽  
Hydroxyvitamin D ◽  
Compound C ◽  
Safranin O

Osteoarthritis (OA) is a common joint degenerative disease. Vitamin D (VD) is essential for bone health. We hypothesized that active VD could be used as a therapeutic treatment for OA. Low serum levels of 25-hydroxyvitamin D [25(OH)D] have been found in patients with OA, and thus the serum level of VD could be diagnostic of OA. To test this, we established a mouse model of OA. The results from staining with hematoxylin–eosin and Safranin O – Fast Green indicated that active VD reduced the symptoms of OA in mice. The results from Western blotting indicated that treatment with VD increased the activity of the p-AMPK–AMPK signaling pathway and decreased the p-mTOR–mTOR pathway; it also increased the ratio of LC3II:LC3I antibodies and the protein expression levels of Beclin-1, but decreased the level of p62. Further, treatment with VD reduced the levels of tumor necrosis factor-α and interleukin-6 both in cartilage tissues and in chondrocytes. Administration of the AMPK inhibitor compound C and autophagy inhibitor 3-methyladenine (3-MA) reversed these changes following VD treatment. In addition, the results from transfection with mRFP-GFP-LC3 indicated that active VD led to autophagosome aggregation in OA chondrocytes. 3-MA inhibited cell autophagy and promoted inflammation in OA. This study provides evidence that active VD activate chondrocyte autophagy to reduce OA inflammation via activating the AMPK–mTOR signaling pathway. Treatment with active VD could be a novel therapeutic option for OA.

Emodin Ameliorate High Glucose-induced Podocyte Apoptosis via Regulating AMPK/mTOR- mediated Autophagy Signaling Pathway

2021 ◽  
Author(s):  
Hong Liu ◽  
Yanglin Hu ◽  
Ge Shi ◽  
Wenqiang Yang ◽  
Fei Xiong ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
High Glucose ◽  
Cell Apoptosis ◽  
Caspase 3 ◽  
Therapeutic Option ◽  
Mtor Signaling ◽  
Mtor Signaling Pathway ◽  
Trypan Blue Exclusion ◽  
Compound C

Abstract Background: Podocyte apoptosis and autophagy dysfunction have been considered to be one of the important causes of diabetic nephropathy (DN). Emodin has the function of regulating autophagy. The present study was performed to investigate the effect of emodin on high glucose (HG)-induced podocyte apoptosis and whether the potential anti-apoptotic mechanism of emodin is related to the induction of AMPK/mTOR-mediated autophagy in MPC5 cells in vitro.Methods: The viability and apoptosis of podocytes (MPC5 cells) were detected using CCK-8 assay, trypan blue exclusion assay and flow cytometry analysis, respectively. The expression levels of Cleaved caspase-3, autophagy maker LC3 I/II, and AMPK/mTOR signaling pathway-related proteins were evaluated with western blot analysis. The changes of morphology and RFP-LC3 fluorescence were observed under microscopy.Results: HG (20-160 mmol/L) dose-dependently induced cell apoptosis in MPC5 cells, whereas emodin (4 μmol/L) significantly ameliorated HG-induced cell apoptosis and caspase-3 cleavage. Emodin (4 μmol/L) significantly increased LC3-II levels and induced RFP-LC3-containing punctate structures in MPC5 cells. Furthermore, the protective effects of emodin were mimicked by rapamycin (100 nmol/L). Moreover, emodin increased the phosphorylation of AMPK and suppressed the phosphorylation of mTOR. The AMPK inhibitor compound C (10 μmol/L) abolished emodin-induced autophagy activation.Conclusion: Emodin ameliorated HG-induced apoptosis of MPC5 cells in vitro that involved induction of autophagy through the AMPK/mTOR signaling pathway, which might provide a potential therapeutic option for DN.

scholarly journals NOX2-Derived Hydrogen Peroxide Impedes the AMPK/Akt-mTOR Signaling Pathway in Parkinson's Disease in Vitro Models

2021 ◽  
Author(s):  
Ruijie Zhang ◽  
Nana Zhang ◽  
Xiaoqing Dong ◽  
Xin Chen ◽  
Jing Ma ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Parkinson’S Disease ◽  
Hydrogen Peroxide ◽  
Parkinson's Disease ◽  
Signaling Pathway ◽  
Neuronal Apoptosis ◽  
Mtor Signaling ◽  
Regulatory Proteins ◽  
Mtor Signaling Pathway ◽  
Compound C

Abstract Oxidative stress is closely related to the pathogenesis of Parkinson's disease (PD), a typical neurodegenerative disease. NADPH oxidase 2 (NOX2) is involved in hydrogen peroxide (H2O2) generation. Recently, we have reported that H2O2 and PD toxins, including 6-hydroxydopamine (6-OHDA), 1-Methyl-4-phenylpyridin-1-ium (MPP+) and rotenone, induce neuronal apoptosis by inhibiting mTOR pathway. Here, we show that 6-OHDA, MPP+ or rotenone induced H2O2 generation by upregulation of NOX2 and its regulatory proteins (p22phox, p40phox, p47phox, p67phox, and Rac1), leading to apoptotic cell death in PC12 cells and primary neurons. Pretreatment with catalase, a H2O2-scavenging enzyme, significantly blocked PD toxins-evoked NOX2-derived H2O2, thereby hindering activation of AMPK, inhibition of Akt/mTOR, induction of apoptosis in neuronal cells. Similar events were also seen in the cells pretreated with Mito-TEMPO, a mitochondria-specific superoxide scavenger, implying a mitochondrial H2O2-dependent mechanism involved. Further research revealed that inhibiting NOX2 with apocynin or silencing NOX2 attenuated the effects of PD toxins on AMPK/Akt/mTOR and apoptosis in the cells. Of importance, ectopic expression of constitutively active Akt or dominant negative AMPKα, or inhibition of AMPK with compound C suppressed PD toxins-induced expression of NOX2 and its regulatory proteins, as well as consequential H2O2 and apoptosis in the cells. Taken together, these results indicate that certain PD toxins can impede the AMPK/Akt-mTOR signaling pathway leading to neuronal apoptosis by eliciting NOX2-derived H2O2. Our findings suggest that neuronal loss in PD may be prevented by regulating of NOX2, AMPK/Akt-mTOR signaling and/or administering antioxidants to ameliorate oxidative stress.

scholarly journals Apelin-13 Regulates Angiotensin II-Induced Cx43 Downregulation and Autophagy via the AMPK/mTOR Signaling Pathway in HL-1 Cells

2020 ◽  
pp. 813-822
Author(s):  
Y CHEN ◽  
X QIAO ◽  
L ZHANG ◽  
X LI ◽  
Q LIU
Keyword(s):  
Atrial Fibrillation ◽  
Angiotensin Ii ◽  
Signaling Pathway ◽  
Connexin 43 ◽  
Mtor Signaling ◽  
Atrial Remodeling ◽  
Mtor Signaling Pathway ◽  
Cx43 Expression ◽  
Compound C ◽  
Cell Hypertrophy

Atrial fibrillation is associated with atrial remodeling, in which connexin 43 (Cx43) and cell hypertrophy play important roles. In this study, apelin-13, an aliphatic peptide, was used to explore the protective effects of the adenosine monophosphate-activated protein kinase (AMPK)/mTOR signaling pathway on Cx43 expression and autophagy, using murine atrial HL-1 cells. The expression of Cx43, AMPK, B-type natriuretic peptide (BNP) and pathway-related proteins was detected by Western blot analysis. Cellular fluorescence imaging was used to visualize Cx43 distribution and the cytoskeleton. Our results showed that the Cx43 expression was significantly decreased in HL-1 cells treated with angiotensin II but increased in cells additionally treated with apelin-13. Meanwhile, apelin-13 decreased BNP expression and increased AMPK expression. However, the expression of Cx43 and LC3 increased by apelin-13 was inhibited by treatment with compound C, an AMPK inhibitor. In addition, rapamycin, an mTOR inhibitor, promoted the development of autophagy, further inhibited the protective effect on Cx43 expression and increased cell hypertrophy. Thus, apelin-13 enhances Cx43 expression and autophagy via the AMPK/mTOR signaling pathway, and serving as a potential therapeutic target for atrial fibrillation.

scholarly journals Oleanolic Acid Induces Autophagy and Apoptosis via the AMPK-mTOR Signaling Pathway in Colon Cancer

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Changxiao Hu ◽  
Yibo Cao ◽  
Ping Li ◽  
Xiaorong Tang ◽  
Minhui Yang ◽  
...  
Keyword(s):  
Colon Cancer ◽  
Signaling Pathway ◽  
Oleanolic Acid ◽  
Mtor Signaling ◽  
Dependent Manner ◽  
Biological Functions ◽  
Mtor Signaling Pathway ◽  
Ampk Signaling ◽  
Apoptosis Rate ◽  
Hct 116

Aims. The purpose of this study was to explore the biological functions of the mTOR and AMPK signaling pathways in colon cancer (CC). The potential molecular mechanisms by which oleanolic acid (OA) induces autophagy and apoptosis were also investigated. Methods. The biological functions of mTOR were analyzed by GeneCards, the Search Tool for the Retrieval of Interacting Genes (STRING), and the Database for Annotation, Visualization and Integrated Discovery (DAVID). Least absolute shrinkage and selection operator (LASSO) regression analysis was used to obtain prognostic and survival data of CC patients from the Gene Expression Omnibus (GEO) database. The effects of OA on the CC cell lines HCT-116 and SW-480 were analyzed by CCK-8, colony formation assay, and high-content system (HCS) array scan. The apoptosis rate of SW-480 and HCT-116 cells was detected by flow cytometry. The mRNA and protein expression levels in HCT-116 and SW-480 cells and NCM-460 normal colonic epithelial cells were detected by RT-PCR and Western blotting. Results. mTOR was highly expressed in CC patients and acted as an oncogene. The AMPK signaling pathway mediated by mTOR predicted the poor prognosis of CC patients. OA effectively inhibited the proliferation and viability of CC cells. Furthermore, the apoptosis rate of CC cells was clearly increased following OA administration. Regarding the molecular mechanism of OA, the results indicated that mTOR and the antiapoptosis gene Bcl-2 were downregulated by OA. In addition, regulator genes of autophagy and apoptosis, including BAX, caspase-9, caspase-8, and caspase-3, were significantly upregulated by OA. Moreover, OA upregulated AMPK and its downstream proteins, including TSC2, BAX, Beclin 1, LC3B-II, and ULK1, to induce autophagy and apoptosis in CC cells. Conclusion. The findings from this study demonstrate that OA could effectively inhibit the proliferation and viability of CC cells. The anti-CC activity of OA is closely related to the activation of the AMPK-mTOR signaling pathway. Activation of AMPK and inhibition of mTOR are involved in the induction of autophagy and apoptosis by OA. OA induced autophagy and apoptosis mainly in an AMPK activation-dependent manner in CC cells.

Metformin Inhibits Abdominal Aortic Aneurysm Formation through the Activation of the AMPK/mTOR Signaling Pathway

2021 ◽  
pp. 1-11
Author(s):  
Jiaan He ◽  
Nan Li ◽  
Yichuan Fan ◽  
Xingzhi Zhao ◽  
Chengwei Liu ◽  
...  
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Signaling Pathway ◽  
Mtor Signaling ◽  
Protective Mechanism ◽  
Mtor Signaling Pathway ◽  
Sprague Dawley ◽  
Downstream Signaling ◽  
Compound C ◽  
Abdominal Aortic

Background and Objective: Epidemiological evidence suggests that the antidiabetic drug metformin (MET) can also inhibit abdominal aortic aneurysm (AAA) formation. However, the underlying protective mechanism remains unknown. It has been reported that phosphorylated AMP-activated protein kinase (AMPK) levels are significantly lower in AAA tissues than control aortic tissues. AMPK activation can inhibit the downstream signaling molecule called mechanistic target of rapamycin (mTOR), which has also been reported be upregulated in thoracic aneurysms. Thus, blocking mTOR signaling could attenuate AAA progression. MET is a known agonist of AMPK. Therefore, in this study, we investigated if MET could inhibit formation of AAA by activating the AMPK/mTOR signaling pathway. Materials and Methods: The AAA animal model was induced by intraluminal porcine pancreatic elastase (PPE) perfusion in male Sprague Dawley rats. The rats were treated with MET or compound C (C.C), which is an AMPK inhibitor. AAA formation was monitored by serial ultrasound. Aortas were collected 4 weeks after surgery and subjected to immunohistochemistry, Western blot, and transmission electron microscopy analyses. Results: MET treatment dramatically inhibited the formation of AAA 4 weeks after PPE perfusion. MET reduced the aortic diameter, downregulated both macrophage infiltration and matrix metalloproteinase expression, decreased neovascularization, and preserved the contractile phenotype of the aortic vascular smooth muscle cells. Furthermore, we detected an increase in autophagy after MET treatment. All of these effects were reversed by the AMPK inhibitor C.C. Conclusion: This study demonstrated that MET activates AMPK and suppresses AAA formation. Our study provides a novel mechanism for MET and suggests that MET could be potentially used as a therapeutic candidate for preventing AAA.

scholarly journals Neferine Enhances Autophagy to Alleviate Cytotoxicity and Apoptosis Induced by CSE in AEC-II through AMPK/mTOR Signaling Pathway

2020 ◽  
Author(s):  
Mengmeng Wang ◽  
Haiyang Yu ◽  
Yuqing Sun ◽  
Pengpeng Cheng ◽  
Qian Wang ◽  
...  
Keyword(s):  
Protective Effect ◽  
Signaling Pathway ◽  
Cell Model ◽  
Cell Damage ◽  
Case Fatality ◽  
Chronic Respiratory Disease ◽  
Mtor Signaling ◽  
Autophagic Flux ◽  
Mtor Signaling Pathway ◽  
Compound C

Abstract COPD is a clinical common chronic respiratory disease, its incidence case fatality rate is higher, there is currently no cure drugs and methods. In this study, in order to make clear its role in the development of autophagy in COPD, COPD cell model is established.To further explore whether regulating autophagy could have a protective effect to fight against CSE-induced cytotoxicity and apoptosis, we choose neferine as an autophagy inducer. Neferine activated cell autophagy in an vitro CSE-induced COPD cell model and gradually attenuated CSE-induced cell apoptosis. Furthermore, this process happens largely through the AMPK/mTOR signaling pathway. As a autophagic flux inhibitor, chloroquine abolished the prosurvival autophagy effect, and AMPK inhibitor Compound C blocked neferine-mediated autophagy and then neferine failed to protect COPD cell model from CSE-induced apoptosis. Overall,our findings suggested that neferine possibly has a potentially protective effect in cell damage mechanisms caused by CSE. It hints that neferine has the prospect of turning into a potential therapeutics to cure CSE-induced cytotoxicity and apoptosis and even COPD patients.

scholarly journals 17β-Estradiol Induces Mitophagy Upregulation to Protect Chondrocytes via the SIRT1-Mediated AMPK/mTOR Signaling Pathway

2021 ◽  
Vol 11 ◽  
Author(s):  
Runhong Mei ◽  
Peng Lou ◽  
Guanchao You ◽  
Tianlong Jiang ◽  
Xuefeng Yu ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Western Blotting ◽  
Mtor Signaling ◽  
Sirtuin 1 ◽  
Mtor Signaling Pathway ◽  
Compound C ◽  
Transmission Electron ◽  
Sirt1 Inhibitor ◽  
17Β Estradiol ◽  
Related Proteins

Increasing evidence reveals that estrogen, especially 17β-estradiol (17β-E2), is associated with articular cartilage metabolism disorder and postmenopausal osteoarthritis (OA). SIRT1, AMPK, and mTOR are regarded as critical mitophagy regulators. Recent studies have shown that mitophagy displays a protective effect against OA, but the molecular mechanism is not well known. This study aimed to investigate the effect of 17β-E2 on Sirtuin-1 (SIRT1) expression and the induction of mitophagy upregulation by 17β-E2 via the SIRT1-mediated AMP-activated protein kinase (AMPK)/mammalian target of the rapamycin (mTOR) signaling pathway to protect chondrocytes. ATDC5 chondrocytes were treated with different concentrations of 17β-E2 (0 M, 1 × 10-9 M, 1 × 10-8 M, and 1 × 10-7 M) for 24 h or pretreatment with or without NAM (SIRT1 inhibitor), Compound C (AMPK inhibitor) and S1842 (mTOR inhibitor) for 30 min prior to treatment with 17β-E2 (1 × 10-7 M) for 24 in each groups. Expression of SIRT1 was evaluated by real-time PCR, Western blotting and confocal immunofluorescence staining. Then, the mitophagosomes in cells were observed under a transmission electron microscopy (TEM), and the AMPK/mTOR signaling pathway was detected by Western blotting. The mitophagy-related proteins, p-AMPK, p-mTOR, p-JNK, and p-p38 were also identified by Western blot analysis. The chondrocytes viability and proliferation were determined by MTT and 5-Bromo-2’-deoxyuridine (BrdU) assay. These experiments were independently repeated 3 times The study found that 17β-E2 increased the expression level of SIRT1, p-AMPK, and mitophagy-related proteins but decreased p-mTOR expression, and then induced mitophagy upregulation in chondrocytes. More mitochondrial autophagosomes were observed in 17β-E2-treated chondrocytes under a transmission electron microscope. Also, 17β-E2 improved cell viability and proliferation with the higher expression of SIRT1 and activation of the AMPK/mTOR signaling pathway. However, SIRT1 inhibitor nicotinamide (NAM) and AMPK inhibitor Compound C blocked the beneficial effect of 17β-E2. In summary, this study was novel in demonstrating that 17β-E2 induced mitophagy upregulation to protect chondrocytes via the SIRT1-mediated AMPK/mTOR signaling pathway.

scholarly journals Rapamycin Antagonizes BCRP-Mediated Drug Resistance Through the PI3K/Akt/mTOR Signaling Pathway in mPRα-Positive Breast Cancer

2021 ◽  
Vol 11 ◽  
Author(s):  
Jing Zhang ◽  
Jing Hu ◽  
Weiwei Li ◽  
Chunyan Zhang ◽  
Peng Su ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Signaling Pathway ◽  
Therapeutic Option ◽  
Poor Response ◽  
Mtor Signaling ◽  
Cell Counting ◽  
Mtor Signaling Pathway ◽  
Potential Biomarker ◽  
Response To Chemotherapy

PurposeOverexpression of breast cancer (BCa) resistance protein (BCRP) is detected in approximately 30% of BCa cases. BCRP indicates a poor response to chemotherapy, and it has become a classic target to overcome drug-resistant tumor cells. In this study, we aimed to explore the mechanism of BCRP overexpression and a strategy to reverse this overexpression in invasive BCa.MethodsBCRP expression in BCa tissues was determined by immunohistochemistry. GSE25066 was downloaded from the NCBI GEO database. Western blot was used to determine the expression of key molecules in vitro. Cell counting kit-8 assays were used to assess the drug response of BCa cells.ResultsOur results suggested that BCRP is an independent risk factor for BCa. We further established that upon 17α-PG binding, membrane progesterone receptor α (mPRα) promoted BCRP expression via the PI3K/Akt/mTOR signaling pathway. mPRα physically interacted with p-Akt1 S473. Moreover, rapamycin, an inhibitor of mTOR complex 1 (mTORC1), downregulated BCRP expression and enhanced the effects of particular drugs, including doxorubicin and paclitaxel.ConclusionBCRP is a potential biomarker of poor prognosis in BCa. BCRP expression is regulated by 17α-PG in mPRα-positive BCa cells through the PI3K/Akt/mTOR signaling pathway. Rapamycin might enhance the therapeutic effect of chemotherapy agents in mPRα-positive MDA-MB-453/BCRP cells and might be a therapeutic option for mPRα-positive invasive BCa with BCRP overexpression.

scholarly journals Combined Inhibition of mTORC1 and mTORC2 Signaling Pathways Is a Promising Therapeutic Option in Inhibiting Pheochromocytoma Tumor Growth: In Vitro and In Vivo Studies in Female Athymic Nude Mice

Endocrinology ◽  
2013 ◽  
Vol 154 (2) ◽  
pp. 646-655 ◽  
Author(s):  
Alessio Giubellino ◽  
Petra Bullova ◽  
Svenja Nölting ◽  
Hana Turkova ◽  
James F. Powers ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Nude Mice ◽  
Therapeutic Option ◽  
Mammalian Target Of Rapamycin ◽  
Mtor Signaling ◽  
In Vivo Studies ◽  
Mtor Signaling Pathway ◽  
Athymic Nude Mice

Several lines of evidence, including the recent discovery of novel susceptibility genes, point out an important role for the mammalian target of rapamycin (mTOR) signaling pathway in the development of pheochromocytoma. Analyzing a set of pheochromocytomas from patients with different genetic backgrounds, we observed and confirmed a significant overexpression of key mTOR complex (mTORC) signaling mediators. Using selective ATP-competitive inhibitors targeting both mTORC1 and mTORC2, we significantly arrested the in vitro cell proliferation and blocked migration of pheochromocytoma cells as a result of the pharmacological suppression of the Akt/mTOR signaling pathway. Moreover, AZD8055, a selective ATP-competitive dual mTORC1/2 small molecular inhibitor, significantly reduced the tumor burden in a model of metastatic pheochromocytoma using female athymic nude mice. This study suggests that targeting both mTORC1 and mTORC2 is a potentially rewarding strategy and supports the application of selective inhibitors in combinatorial drug regimens for metastatic pheochromocytoma.

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