AMP-activated protein kinase (AMPK) is a key enzyme in the regulation of cellular energy homeostasis. Recent studies demonstrated that AMPK also plays an important role in the modulation of inflammation, an energy-intensive molecular response. The commonly used AMPK activators include 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) and A-769662. In addition, the biological activities of metformin and adiponectin are closely related to activation of AMPK. Numerous studies have shown that these AMPK activators play an effectively protective role in animal models of acute lung injury, asthma, colitis, hepatitis, atherosclerosis and other inflammatory diseases. Therefore, AMPK activators may have promising potential for the prevention and treatment of inflammation related diseases.
AMP-Activated Protein Kinases ; physiology ; Adiponectin ; pharmacology ; Aminoimidazole Carboxamide ; pharmacology ; Animals ; Enzyme Activation ; Inflammation ; enzymology ; Metformin ; pharmacology ; Pyrones ; pharmacology ; Thiophenes ; pharmacology

Angiotensin II (Ang II) induces the pathological process of vascular structures, including renal glomeruli by hemodynamic and nonhemodynamic direct effects. In kidneys, Ang II plays an important role in the development of proteinuria by the modification of podocyte molecules. We have previously found that Ang II suppressed podocyte AMP-activated protein kinase (AMPK) via Ang II type 1 receptor and MAPK signaling pathway. In the present study, we investigated the roles of AMPK on the changes of p130Cas of podocyte by Ang II. We cultured mouse podocytes and treated them with various concentrations of Ang II and AMPK-modulating agents and analyzed the changes of p130Cas by confocal imaging and western blotting. In immunofluorescence study, Ang II decreased the intensity of p130Cas and changed its localization from peripheral cytoplasm into peri-nuclear areas in a concentrated pattern in podocytes. Ang II also reduced the amount of p130Cas in time and dose-sensitive manners. AMPK activators, metformin and AICAR, restored the suppressed and mal-localized p130Cas significantly, whereas, compound C, an AMPK inhibitor, further aggravated the changes of p130Cas. Losartan, an Ang II type 1 receptor antagonist, recovered the abnormal changes of p130Cas suppressed by Ang II. These results suggest that Ang II induces the relocalization and suppression of podocyte p130Cas by the suppression of AMPK via Ang II type 1 receptor, which would contribute to Ang II-induced podocyte injury.
AMP-Activated Protein Kinases/antagonists & inhibitors/chemistry/*metabolism ; Aminoimidazole Carboxamide/analogs & derivatives/pharmacology ; Angiotensin II/*pharmacology ; Angiotensin II Type 1 Receptor Blockers/pharmacology ; Animals ; Blotting, Western ; Cell Line ; Cell Nucleus/metabolism ; Crk-Associated Substrate Protein/*metabolism ; Cytoplasm/metabolism ; Focal Adhesion Kinase 1/metabolism ; Losartan/pharmacology ; Metformin/pharmacology ; Mice ; Microscopy, Confocal ; Podocytes/cytology/drug effects/metabolism ; Protein Kinase Inhibitors/*pharmacology ; Ribonucleotides/pharmacology ; Signal Transduction/*drug effects

The present study was aimed to explore the effect of AMP-activated protein kinase (AMPK) on monocyte adhesion to vascular endothelial cells and underlying molecular mechanism. Tumor necrosis factor α (TNFα)-activated human aortic endothelial cells (HAECs) were treated with different concentrations of AMPK agonist 5-Aminoimidazole-4-carboxamide-1-β-D-ribonucleotide (AICAR) or AMPK inhibitor compound C. And other HAECs were overexpressed with constitutive active or dominant negative AMPK protein and then treated with TNFα. The rates of monocytes adhering to endothelial cells were detected by fluorescent staining. Intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) mRNA levels and protein secretions were detected by quantitative PCR and ELISA, respectively. Acetylation of NF-κB p65 at lysine 221 site was assessed by Western blot. NF-κB p65 DNA binding activity was analyzed by an ELISA-based method. By using small interfering RNA based strategy, p300 expression in HAECs was down-regulated and then cells were incubated with TNFα. NF-κB p65 DNA binding activity, ICAM-1 and VCAM-1 expressions and adhesion rates were detected, respectively. The activity of p300 was also detected by ELISA. The results showed that AICAR treatment significantly reduced monocyte-endothelial adhesion rate, as well as ICAM-1 and VCAM-1 mRNA levels and protein secretions, in TNFα-activated HAECs. Moreover, transfection of constitutive active AMPKα but not dominant negative AMPKα strongly diminished TNFα-induced upregulation of ICAM-1 and VCAM-1 mRNA expressions and secretions, as well as monocyte-endothelial adhesion. Furthermore, AMPK activation decreased TNFα-mediated acetylation of NF-κB p65 at Lys221 site and reduced NF-κB p65 DNA binding activity. Silencing p300 by siRNA significantly abolished the effect of TNFα- induced adhesion molecules expression and monocyte-endothelial adhesion. Blocking AMPK activation by compound C almost completely reversed the effect of AICAR exerted on HAECs. These results suggest AMPK activation suppresses monocyte-endothelial adhesion, and the underlying mechanism is relevant to the inhibition of p300 activity and NF-κB p65 transcriptional activity.
AMP-Activated Protein Kinases ; Aminoimidazole Carboxamide ; analogs & derivatives ; Aorta ; Cell Adhesion ; Cell Adhesion Molecules ; Cells, Cultured ; E1A-Associated p300 Protein ; Endothelial Cells ; Enzyme Activation ; Humans ; Intercellular Adhesion Molecule-1 ; Monocytes ; NF-kappa B ; Ribonucleotides ; Tumor Necrosis Factor-alpha ; Vascular Cell Adhesion Molecule-1

AMP activated protein kinase (AMPK) is a pivotal metabolic regulatory enzyme and novel target of controlling inflammation. Our previous studies had demonstrated that 5-amino-4-imidazolecarboxamide riboside (AICAR), an AMPK activator, attenuated lipopolysaccharide (LPS)/D-galactosamine (D-gal)-induced fulminant hepatitis via suppressing inflammatory response. Since inflammation usually activates the coagulation response and aggravates inflammation-induced tissue injury, the present study was to explore the effects of AICAR on inflammation-induced activation of coagulation. Male BALB/c mice received LPS/D-gal intraperitoneal injection were used as fulminant hepatitis model. Western blot was used to detect tissue factor (TF) and hypoxia-inducible factor 1α (HIF-1α) protein expressions in hepatic tissue, as well as nuclear factor kappa B (NF-κB) p65 translocation into the nucleus. Real-time quantitative PCR was used to analyze erythropoietin (EPO) mRNA expression level. Lactic acid (LA) level in hepatic tissue was detected by kit. The results showed that LPS/D-gal induced the enhanced expression of TF, elevation of NF-κB p65 nuclear translocation, up-regulation of HIF-1α and EPO expressions, and increased LA level. These above alterations could be suppressed by AICAR. These results suggest that AICAR may down-regulate LPS/D-gal-induced TF expression (coagulation activity), and relieve hepatic hypoxia and metabolic disorder via suppressing the activity of NF-κB, which may be a novel mechanism of the beneficial effect of AICAR on LPS/D-gal-induced fulminant hepatitis.
AMP-Activated Protein Kinases ; Aminoimidazole Carboxamide ; analogs & derivatives ; Animals ; Down-Regulation ; Erythropoietin ; Hepatitis ; Hypoxia-Inducible Factor 1, alpha Subunit ; Inflammation ; Lipopolysaccharides ; Male ; Mice ; NF-kappa B ; Thromboplastin ; Up-Regulation

OBJECTIVETo investigate the effects of AMPK agonist Acadesine (AICAR) on growth inhibition of K562 cells and their sensitivity to imatinib (IM).

METHODSK562 cells were cultured with different concentrations of AICAR alone or its combination with IM for 48 hours, the CCK-8 assay was used to detect cell proliferation, the cell cycle distribution and apoptosis were analyzed by flow cytometry. The expression levels of Cyclin D1, Cyclin E1 and Caspase 3 protein were determined by Western blot.

RESULTSAICAR inhibited the proliferation of K562 cells in dose-dependent manner, and their IC50 value was 0.45 mmol/L at 48 hours. AICAR could induce arrest of K562 cells in G1 phase and down-regulated the protein expression levels of Cyclin D1 and Cyclin E1; whereas it didn't influence the cell apoptosis. Additionally, the growth inhibition of cells induced by IM was enhanced by AICAR.

CONCLUSIONAICAR can inhibit the proliferation of K562 cells by arresting the cell cycle and enhancing the sensitivity of K562 cells to IM.

Aminoimidazole Carboxamide ; analogs & derivatives ; pharmacology ; Apoptosis ; Caspase 3 ; metabolism ; Cell Cycle Checkpoints ; Cell Proliferation ; drug effects ; Cyclin D1 ; metabolism ; Cyclin E ; metabolism ; Humans ; Imatinib Mesylate ; pharmacology ; K562 Cells ; drug effects ; Oncogene Proteins ; metabolism ; Ribonucleosides ; pharmacology

BACKGROUND/AIMS: 5'-Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a cellular energy sensor that monitors intracellular AMP/adenosine triphosphate (ATP) ratios and is a key regulator of the proliferation and survival of diverse malignant cell types. In the present study, we investigated the effect of activating AMPK by 5-aminoimidazole-4-carboxamide-ribonucleotide (AICAR) in thyroid cancer cells. METHODS: We used FRO thyroid cancer cells harboring the BRAF(V600E) mutation to examine the effect of AICAR on cell proliferation and cell survival. We also evaluated the involvement of mitogen-activated protein kinase (MAPK) pathways in this effect. RESULTS: We found that AICAR treatment promoted AMPK activation and suppressed cell proliferation and survival by inducing p21 accumulation and activating caspase-3. AICAR significantly induced activation of p38 MAPK, and pretreatment with SB203580, a specific inhibitor of the p38 MAPK pathway, partially but significantly rescued cell survival. Furthermore, small interfering RNA targeting AMPK-alpha1 abolished AICAR-induced activation of p38 MAPK, p21 accumulation, and activation of caspase-3. CONCLUSIONS: Our findings demonstrate that AMPK activation using AICAR inhibited cell proliferation and survival by activating p38 MAPK and proapoptotic molecules in FRO thyroid cancer cells. These results suggest that the AMPK and p38 MAPK signaling pathways may be useful therapeutic targets to treat thyroid cancer.
AMP-Activated Protein Kinases/genetics/metabolism ; Aminoimidazole Carboxamide/*analogs & derivatives/pharmacology ; Antineoplastic Agents/*pharmacology ; Caspase 3/metabolism ; Cell Line, Tumor ; Cell Proliferation/drug effects ; Cell Survival/drug effects ; Cyclin-Dependent Kinase Inhibitor p21/metabolism ; Dose-Response Relationship, Drug ; Enzyme Activation ; Enzyme Activators/pharmacology ; Humans ; Mutation ; Protein Kinase Inhibitors/pharmacology ; Proto-Oncogene Proteins B-raf/genetics ; RNA Interference ; Ribonucleotides/*pharmacology ; Signal Transduction/*drug effects ; Thyroid Neoplasms/*enzymology/genetics/pathology ; Time Factors ; Transfection ; p38 Mitogen-Activated Protein Kinases/antagonists & inhibitors/*metabolism

OBJECTIVETo investigate the effect of AMPK agonist 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) on proliferation, differentiation and apoptosis of U937 cells and explore its possible mechanism.

METHODSU937 cells were cultured with different concentrations of AICAR for 24 h and 48 h. Cell proliferation was evaluated. Cell growth curve was analyzed by CCK-8; cell apoptosis was analyzed by cell morphology, Annexin V/7-AAD double labeling. The differentiation of U937 cells was evaluated by expression of CD11b. The Bcl-xL, Bax, Bim, caspase-3 mRNA expressions of U937 cells were determined by real time PCR.

RESULTSAICAR significantly inhibited the growth of U937 cells in a time-and dose-dependent manner, with a 24 h IC50 value of 1.1 mmol/L and 48 h of 0.9 mmol/L. 1.0 mmol/L AICAR didn't induce differentiation of U937 cells with the increase of CD11b expression for 24 h (P > 0.05). The U937 cells apoptosis was confirmed by cell morphology and Annexin V/7-AAD labeling. AICAR induced apoptosis of U937 cells and the apoptosis rate was (6.81 ± 1.16)% at 1 mmol/L AICAR higher than control group (2.74 ± 0.32)% without AICAR for 24 h treatment (P < 0.05). The real time PCR assay revealed that as compared with control group, the expression of Bim and caspase-3 mRNA were increased, while Bcl-xL and Bax were unchanged on the AICAR treatment.

CONCLUSIONAICAR can effectively inhibit proliferation and induce apoptosis of U937 cells. However, it has no significant effect on differentiation of U937 cells. The mechanism may be related with up-regulating Bim and Caspase-3.

Aminoimidazole Carboxamide ; analogs & derivatives ; pharmacology ; Apoptosis ; drug effects ; Cell Differentiation ; drug effects ; Cell Proliferation ; drug effects ; Humans ; Ribonucleotides ; pharmacology ; U937 Cells

Alcoholic hepatitis is a leading cause of liver failure in which the increased production of tumor necrosis factor alpha (TNFalpha) plays a critical role in progression of alcoholic liver disease. In the present study, we investigated the effects of cilostazol, a selective inhibitor of type III phosphodiesterase on ethanol-mediated TNFalpha production in vitro and in vivo, and the effect of cilostazol was compared with that of pentoxifylline, which is currently used in clinical trial. RAW264.7 murine macrophages were pretreated with ethanol in the presence or absence of cilostazol then, stimulated with lipopolysacchride (LPS). Cilostazol significantly suppressed the level of LPS-stimulated TNFalpha mRNA and protein with a similar degree to that by pentoxifylline. Cilostazol increased the basal AMP-activated protein kinase (AMPK) activity as well as normalized the decreased AMPK by LPS. AICAR, an AMPK activator and db-cAMP also significantly decreased TNFalpha production in RAW264.7 cells, but cilostazol did not affect the levels of intracellular cAMP and reactive oxygen species (ROS) production. The in vivo effect of cilostazol was examined using ethanol binge drinking (6 g/kg) mice model. TNFalpha mRNA and protein decreased in liver from ethanol gavaged mice compared to that from control mice. Pretreatment of mice with cilostazol or pentoxifylline further reduced the TNFalpha production in liver. These results demonstrated that cilostazol effectively decrease the ethanol-mediated TNFalpha production both in murine macrophage and in liver from binge drinking mice and AMPK may be responsible for the inhibition of TNFalpha production by cilostazol.
Aminoimidazole Carboxamide ; AMP-Activated Protein Kinases ; Animals ; Binge Drinking ; Ethanol ; Hepatitis, Alcoholic ; Liver ; Liver Diseases, Alcoholic ; Liver Failure ; Macrophages ; Mice ; Pentoxifylline ; Reactive Oxygen Species ; Ribonucleotides ; RNA, Messenger ; Tetrazoles ; Tumor Necrosis Factor-alpha

BACKGROUNDEndothelial dysfunction is a key event in the onset and progression of atherosclerosis in diabetic patients. Apoptosis may lead to endothelial dysfunction and contribute to vascular complications. However, no study has addressed apoptosis in human umbilical vein endothelial cells (HUVECs) induced by an intermittent high-glucose media and its association with adiponectin receptor 1 (adipoR1), adipoR2, or adenosine monophosphate (AMP)-activated protein kinase (AMPK).

METHODSHUVECs were cultured in continuous normal glucose (5.5 mmol/L), continuous high glucose (25 mmol/L), alternating normal and high glucose and mannitol. In the alternating normal and high-glucose media, HUVECs were treated under different conditions. First, cells were transfected with the adipoR1-specific small-interfering RNA (siRNA) and then stimulated with globular adiponectin (gAD). Second, cells were cultured in both gAD and the AMPK activator 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR). Third, cells were cultured in the AMPK inhibitor adenine-9-β-D-arabino-furanoside (araA), gAD, and in AICAR.

RESULTSHUVEC apoptosis increased more significantly in an intermittent high-glucose medium than in a constant high-glucose medium. HUVEC apoptosis induced by an intermittent high-glucose medium was inhibited when the cells were pretreated with 3 µg/ml gAD, which rapidly activated AMPK and adipoR1 in HUVECs. However, adipoR2 was not activated.

CONCLUSIONSWe found that adipoR1, not adipoR2, is involved in mediating intermittent high-concentration glucose-evoked apoptosis in endothelial cells. gAD activated AMPK through adipoR1, leads to the partial inhibition of HUVEC apoptosis. A fluctuating glucose medium is more harmful than a constant high-glucose medium to endothelial cells.

AMP-Activated Protein Kinases ; antagonists & inhibitors ; genetics ; metabolism ; Adiponectin ; pharmacology ; Aminoimidazole Carboxamide ; analogs & derivatives ; pharmacology ; Apoptosis ; drug effects ; Glucose ; pharmacology ; Human Umbilical Vein Endothelial Cells ; cytology ; drug effects ; metabolism ; Humans ; RNA, Small Interfering ; Receptors, Adiponectin ; genetics ; metabolism ; Ribonucleotides ; pharmacology ; Signal Transduction ; drug effects ; genetics

BACKGROUNDMetformin has become a cornerstone in the treatment of patients with type-2 diabetes. Accumulated evidence suggests that metformin supports direct cardiovascular effects. The present study aimed to investigate if metformin has beneficial effects on primary cardiomyocytes damaged by H2O2, and reveal the potential mechanism of action of metformin.

METHODSCardiomyocytes were incubated in the presence of 100 µmol/L H2O2 for 12 hours. Cardiomyocytes were pretreated with metformin at different concentrations and time and with aminoimidazole carboxamide ribonucleotide (AICAR) (500 µmol/L), an adenosine monophophate (AMP)-activated protein kinase (AMPK) agonist for 60 minutes before the addition of H2O2. Other cells were preincubated with compound C (an AMPK antagonist, 20 µmol/L) for 4 hours. The viability and apoptosis of cells were analyzed. AMPK, endothelial nitric oxide synthase (eNOS), and transforming growth factor (TGF)-β1 were analyzed using immunblotting.

RESULTSMetformin had antagonistic effects on the influences of H2O2 on cell viability and attenuated oxidative stress-induced apoptosis. Metformin also increased phosphorylation of AMPK and eNOS, and reduced the expression of TGF-β1, basic fibroblast growth factor (bFGF), and tumor necrosis factor (TNF)-α.

CONCLUSIONSMetformin has beneficial effects on cardiomyocytes, and this effect involves activation of the AMPK-eNOS pathway. Metformin may be potentially beneficial for the treatment of heart disease.

AMP-Activated Protein Kinases ; physiology ; Aminoimidazole Carboxamide ; analogs & derivatives ; pharmacology ; Animals ; Apoptosis ; drug effects ; Cell Survival ; drug effects ; Cells, Cultured ; Hypoglycemic Agents ; pharmacology ; Metformin ; pharmacology ; Myocytes, Cardiac ; drug effects ; metabolism ; Nitric Oxide Synthase Type III ; genetics ; RNA, Messenger ; analysis ; Rats ; Rats, Wistar ; Ribonucleotides ; pharmacology ; Transforming Growth Factor beta1 ; genetics ; Tumor Necrosis Factor-alpha ; genetics