Pharmacological Activation Of AMPK Research Articles

Abstract 2873: Radiation therapy promotes polyunsaturated fatty acid mediated ferroptosis in cervical cancer: Role of AMPK/xCT/GPX4 axis

Abstract Purpose: Previously, we found that mono-and di-unsaturated fatty acids can sensitize cervical cancer to radiotherapy (RT) through a p53 dependent apoptotic mechanism that is distinct from ferroptosis (Muhammad et al., Cancer Res. 2022; 82: 4515-27). Polyunsaturated fatty acids (PUFAs) enhance therapeutic response in preclinical tumor models by increasing lipid peroxidation (L-ROS) and induction of ferroptosis. Ferroptosis is a form of cell death that requires abundant cytosolic labile iron to promote membrane lipid peroxidation. The objective of the present study is to test whether the combination of RT + PUFAs promotes cell death via increased membrane lipid peroxidation and ferroptosis in cervical cancer, and to determine the impact of RT + PUFAs on cervix tumor cell metabolism and mitochondrial function. Experimental Procedures: Cell viability and clonogenic cell survival assays were performed using 8 human cervical cancer cell lines including normal cervix epithelial controls incubated with PUFAs (EPA, DHA and AA), before and after RT. Western blotting, siRNA-mediated knockdown, pharmacologic inhibition and activation were performed to determine whether ferroptosis dependent signals were mediating PUFA-induced RT sensitivity. Oxidative stress parameters were quantified using mass spectrometry and fluorometric dyes. Flow cytometry was used to quantify total cell ROS, lipid ROS, mitochondrial ROS and labile iron pool. Mitochondrial morphology and function were characterized using microscopy and the Seahorse assay. Summary: PUFAs + RT increased total ROS and LROS accumulation followed by a ferroptotic tumor cell death, which was iron-dependent and could be prevented by the addition of iron chelator and lipophilic antioxidants, Ferrostatin-1 and Liproxstatin-1. GPX4, a thiol dependent enzyme that eliminates lipid peroxides, and the cystine-glutamate antiporter (xCT) a key source of cystine for reduced glutathione (GSH) synthesis, were downregulated in response to PUFAs + RT. PUFAs + RT induced increased mitochondrial ROS and subsequent metabolic dysfunction. Mechanistically, the expression of AMPK, a key regulator of metabolic/energy homeostasis and mitochondrial biogenesis, was upregulated by PUFAs + RT. Pharmacological activation and inhibition of AMPK further enhanced and abrogated the effect of PUFA + RT, respectively. Conclusions: PUFAs modify the RT sensitivity of cervical cancer cells by inducing cell death through ferroptosis and mitochondrial dysfunction via AMPK activation. In vivo experiments are ongoing in immunocompromised and immunodeficient mouse tumor models to confirm this finding and determine the impact of PUFAs on RT induced tumor cell death and anti-tumor immunity. Citation Format: Naoshad Muhammad, Nishanth Gabriel, Louise M. Bengtsson, Tyler McKinnish, Naomi Msengi, Kevin Cho, Gary Patti, Julie K. Schwarz. Radiation therapy promotes polyunsaturated fatty acid mediated ferroptosis in cervical cancer: Role of AMPK/xCT/GPX4 axis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2873.

Phytochemical gallic acid alleviates nonalcoholic fatty liver disease via AMPK-ACC-PPARa axis through dual regulation of lipid metabolism and mitochondrial function

BackgroundNonalcoholic fatty liver disease (NAFLD) usually includes NAFL called simple hepatosteatosis and nonalcoholic steatohepatitis (NASH) called more steatohepatitis. The latter is a leading pathogenic promotor of hepatocellular carcinoma (HCC). Phytochemical gallic acid (GA) has been proved to exert positive efficacy in HCC in our work, but it remains unclear whether its hepatoprotective effect attributes to the controlled transition from simple steatosis to steatohepatitis. PurposeThis work aims to provide mechanistic evidence that the therapeutic application of GA in NAFLD is indispensable for GA-meliorated NASH progression. MethodsThe high-fat diet (HFD)-fed mice and palmitic acid (PA) and oleic acid (OA)-treated hepatocytes were used collectively in this study. Bioinformatic analysis, clinical subjects, RNA-Seq, molecular docking, and confirmatory experiments were performed comprehensively to uncover the pathological link between the AMPK-ACC-PPARα axis and the treatment of NAFLD. ResultsBy analyzing the clinical subjects and GEO database, we find a close link between the activation of AMPK-ACC-PPARα axis and the progression of NAFLD in human fatty liver. Subsequent assays show that GA exhibits pharmacological activation of AMPK, reprogramming lipid metabolism, and reversing mitochondrial function in cellular and murine fatty liver models. AMPK activation conferred substantial protection against murine NASH and fibrosis in the context of HFD-induced NAFLD. In contrast, silencing AMPK badly aggravates lipid deposition in hepatocytes, boosting NASH and NAFLD-associated HCC progression. The in silico docking, in vitro surface plasmon resonance and in vivo cellular thermal shift assay collectively reveal that GA directly interacts with AMPKα, which inactivates the ACC-PPARα axis signaling. Notably, GA repairs the liver damage, lipotoxicity, and mitochondrial respiratory capacity caused by excessive mtROS, while showing minimal effects in other major organs in mice. ConclusionOur work identifies GA as an important suppressor of NAFLD-HCC progression, and underscores the AMPK-ACC-PPARα signal axis as a potential therapeutic target for NAFLD treatment.

The Degradation of TMEM166 by Autophagy Promotes AMPK Activation to Protect SH-SY5Y Cells Exposed to MPP.

Neuronal oxidative stress caused by mitochondrial dysfunction plays a crucial role in the development of Parkinson’s disease (PD). Growing evidence shows that autophagy confers neuroprotection in oxidative-stress-associated PD. This work aims to investigate the involvement of TMEM166, an endoplasmic-reticulum-localized autophagy-regulating protein, in the process of PD-associated oxidative stress through the classic cellular PD model of neuroblastoma SH-SY5Y cells exposed to 1-methyl-4-phenylpyridinium (MPP+). Reactive oxygen species (ROS) production and mitochondrial membrane potential were checked to assess the oxidative stress induced by MPP+ and the cellular ATP generated was determined to evaluate mitochondrial function. The effect on autophagy induction was evaluated by analyzing p62 and LC3-II/I expression and by observing the LC3 puncta and the colocalization of LC3 with LAMP1/ LAMP2. The colocalization of mitochondria with LC3, the colocalization of Tom20 with LAMP1 and Tom20 expression were analyzed to evaluate mitophagy. We found that TMEM166 is up-regulated in transcript levels, but up-regulated first and then down-regulated by autophagic degradation in protein levels upon MPP+-treatment. Overexpression of TMEM166 induces mitochondria fragmentation and dysfunction and exacerbates MPP+-induced oxidative stress and cell viability reduction. Overexpression of TMEM166 is sufficient to induce autophagy and mitophagy and promotes autophagy and mitophagy under MPP+ treatment, while knockdown of TMEM166 inhibits basal autophagic degradation. In addition, overexpressed TMEM166 suppresses AMPK activation, while TMEM166 knockdown enhances AMPK activation. Pharmacological activation of AMPK alleviates the exacerbation of oxidative stress induced by TMEM166 overexpression and increases cell viability, while pharmacological inhibition mitophagy aggravates the oxidative stress induced by MPP+ treatment combined with TMEM166 overexpression. Finally, we find that overexpressed TMEM166 partially localizes to mitochondria and, simultaneously, the active AMPK in mitochondria is decreased. Collectively, these findings suggest that TMEM166 can translocate from ER to mitochondria and inhibit AMPK activation and, in response to mitochondrial oxidative stress, neuronal cells choose to up-regulate TMEM166 to promote autophagy/mitophagy; then, the enhancing autophagy/mitophagy degrades the TMEM166 to activate AMPK, by the two means to maintain cell survival. The continuous synthesis and degradation of TMEM166 in autophagy/mitochondria flux suggest that TMEM166 may act as an autophagy/mitochondria adaptor.

Inhibition of basal and glucagon-induced hepatic glucose production by 991 and other pharmacological AMPK activators.

Pharmacological AMPK activation represents an attractive approach for the treatment of type 2 diabetes (T2D). AMPK activation increases skeletal muscle glucose uptake, but there is controversy as to whether AMPK activation also inhibits hepatic glucose production (HGP) and pharmacological AMPK activators can have off-target effects that contribute to their anti-diabetic properties. The main aim was to investigate the effects of 991 and other direct AMPK activators on HGP and determine whether the observed effects were AMPK-dependent. In incubated hepatocytes, 991 substantially decreased gluconeogenesis from lactate, pyruvate and glycerol, but not from other substrates. Hepatocytes from AMPKβ1-/- mice had substantially reduced liver AMPK activity, yet the inhibition of glucose production by 991 persisted. Also, the glucose-lowering effect of 991 was still seen in AMPKβ1-/- mice subjected to an intraperitoneal pyruvate tolerance test. The AMPK-independent mechanism by which 991 treatment decreased gluconeogenesis could be explained by inhibition of mitochondrial pyruvate uptake and inhibition of mitochondrial sn-glycerol-3-phosphate dehydrogenase-2. However, 991 and new-generation direct small-molecule AMPK activators antagonized glucagon-induced gluconeogenesis in an AMPK-dependent manner. Our studies support the notion that direct pharmacological activation of hepatic AMPK as well as inhibition of pyruvate uptake could be an option for the treatment of T2D-linked hyperglycemia.

Perfluorooctanoic acid alters the developmental trajectory of female germ cells and embryos in rodents and its potential mechanism

The epidemiological studies regarding perfluorooctanoic acid (PFOA) suggests that its exposure causes reproductive health issues, the underlying mechanisms of which are still in its infancy. Here, we report that PFOA deteriorates female reproduction at multiple development stages. Oocyte meiosis and preimplantation development are severely impaired by PFOA with oxidative stress being a contributor. Supplementing with antioxidant melatonin partially rescues oocyte meiotic maturation and non-apoptotic demise. The attenuation in ovarian follicle development however can be improved by metformin but not melatonin. Importantly, metformin blunts PFOA-induced fetal growth retardation (FGR) and such protective effect could be recapitulated by transplantation of fecal material and pharmacological activation of AMPK. Mechanistically, PFOA causes gut microbiota dysbiosis, which might thereby rewire host metabolism of L-phenylalanine, histamine and L-palmitoylcarnitine that triggers hyperphenylalaninaemia, inflammation and ferroptosis to initiate FGR. Deregulated serine metabolism by the gut microbe constitutes an alternative mechanism underlying PFOA-induced FGR in that modulation of serine in dam’s diet phenocopied the FGR. Our study expands the understanding of risk factors that impair human reproductive health, and proposes restoration of gut microbiota diversity and intervention of metabolism as therapeutics mitigating health risks predisposed by environmental perturbation.

Effect of inflammation-mediated endothelial metabolic shift on endothelial barrier function

Abstract Background The integrity of the endothelial cell barrier of the microvasculature is compromised by inflammation. The increased vascular permeability leads to tissue injury and organ dysfunction. In recent years, considerable advances have been made in the understanding of signalling mechanisms regulating the endothelial barrier integrity. The role of endothelial metabolism as a modulator of endothelial barrier integrity is not yet well-studied. The aim of the present study was to investigate the effect of inflammation on endothelial metabolism and its role in the maintenance of endothelial barrier integrity. Methods The study was carried out on cultured human umbilical vein endothelial cells and rat coronary microvascular endothelial cells. Inflammatory condition was simulated by treating cells with low concentrations (1 ng/mL) of TNFα for 24h. Endothelial barrier function was analysed by measuring the flux of albumen through endothelial monolayers cultured on filter membranes. Gene expression was analysed by qPCR-based assays. The capacity of endothelial cells for maximal ATP synthesis rate was investigated by the real-time live-cell imaging using FRET-based ATP-biosensor (live cell FRET). Total cellular ATP concentration was measured using luminescence-based commercial kit (ATPLite, PerkinElmer). Mitochondrial mass was analysed by the ratio of mitochondrial DNA (mtDNA) to nuclear DNA (nDNA). The cellular glucose uptake was measured by fluorescent microscopy using a fluorescent analogue of glucose (2-NBDG). Results Treatment of human endothelial cells with TNFα resulted in significant suppression of mitochondrial and upregulation of glycolytic ATP synthesis rate, suggesting a metabolic switch. This was accompanied by a reduction in mitochondrial content (mtDNA/nDNA), reduction in total cellular ATP levels, an enhanced expression of glycolytic enzymes 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) and phosphofructokinase 1 (PFK1), and enhanced glucose uptake by endothelial cells (n=5; p<0.05 for all parameters tested). Moreover, TNFα caused a 3-fold increase in endothelial permeability. Pharmacological inhibition of glycolysis either by partial replacement of glucose with 2-deoxy glucose (2DG) or an inhibition of PFKFB3 resulted in further worsening (a 5-fold increase in permeability) of TNFα-induced endothelial barrier failure. On the other hand pharmacological activation of AMPK, a potent inducer of mitochondrial biogenesis, could attenuate TNFα-induced but not 2DG-induced endothelial hyperpermeability. Conclusion The study demonstrates that TNFα induces metabolic switch towards glycolysis in endothelial cells. Moreover, the data suggest that upregulation of glycolysis may serve as an endogenous metabolic adaptation to the TNFα-induced suppression of mitochondrial ATP synthesis, which protects endothelial barrier integrity. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Justus-Liebig University GiessenDZHK (German Centre for Cardiovascular Research), partner site Rhein-Main, Bad Nauheim, Germany

Renal GPNMB Is Highly Upregulated in Rodent Models of AKI and Is Further Elevated with Pharmacological AMPK Activation

Renal GPNMB Is Highly Upregulated in Rodent Models of AKI and Is Further Elevated with Pharmacological AMPK Activation

AXIN1 knockout does not alter AMPK/mTORC1 regulation and glucose metabolism in mouse skeletal muscle.

Tamoxifen-inducible skeletal muscle-specific AXIN1 knockout (AXIN1 imKO) in mouse does not affect whole-body energy substrate metabolism. AXIN1 imKO does not affect AICAR or insulin-stimulated glucose uptake in adult skeletal muscle. AXIN1 imKO does not affect adult skeletal muscle AMPK or mTORC1 signalling during AICAR/insulin/amino acid incubation, contraction and exercise. During exercise, α2/β2/γ3AMPK and AMP/ATP ratio show greater increases in AXIN1 imKO than wild-type in gastrocnemius muscle. AXIN1 is a scaffold protein known to interact with >20 proteins in signal transduction pathways regulating cellular development and function. Recently, AXIN1 was proposed to assemble a protein complex essential to catabolic-anabolic transition by coordinating AMPK activation and inactivation of mTORC1 and to regulate glucose uptake-stimulation by both AMPK and insulin. To investigate whether AXIN1 is permissive for adult skeletal muscle function, a phenotypic in vivo and ex vivo characterization of tamoxifen-inducible skeletal muscle-specific AXIN1 knockout (AXIN1 imKO) mice was conducted. AXIN1 imKO did not influence AMPK/mTORC1 signalling or glucose uptake stimulation at rest or in response to different exercise/contraction protocols, pharmacological AMPK activation, insulin or amino acids stimulation. The only genotypic difference observed was in exercising gastrocnemius muscle, where AXIN1 imKO displayed elevated α2/β2/γ3 AMPK activity and AMP/ATP ratio compared to wild-type mice. Our work shows that AXIN1 imKO generally does not affect skeletal muscle AMPK/mTORC1 signalling and glucose metabolism, probably due to functional redundancy of its homologue AXIN2.

Local delivery of simvastatin maintains tooth anchorage during mechanical tooth moving via anti-inflammation property and AMPK/MAPK/NF-kB inhibition.

Simvastatin (SMV) could increase tooth anchorage during orthodontic tooth movement (OTM). However, previous studies on its bone‐specific anabolic and anti‐inflammation properties were based on static in vitro and in vivo conditions. AMPK is a stress‐activated kinase that protects tissue against serious damage from overloading inflammation. Rat periodontal ligament cells (PDLCs) were subjected to a serial of SMV concentrations to investigate the optimization that promoted osteogenic differentiation. The PDLCs in static and/or tensile culturing conditions then received the proper concentration SMV. Related factors expression was measured by the protein array, real‐time PCR and Western blot. The 0.05UM SMV triggered osteogenic differentiation of PDLCs. The inhibition of AMPK activation through a pharmacological approach (Compound C) caused dramatic decrease in osteogenic/angiogenic gene expression and significant increase in inflammatory NF‐κB phosphorylation. In contrast, pharmacological activation of AMPK by AICAR significantly inhibited inflammatory factors expression and activated ERK1/2, P38 MAPK phosphorylation. Moreover, AMPK activation induced by SMV delivery significantly attenuated the osteoclastogenesis and decreased the expression of pro‐inflammatory TNF‐α and NF‐κB in a rodent model of OTM. The current studies suggested that SMV could intrigue intrinsic activation of AMPK in PDLCs that promote attenuate the inflammation which occurred under tensile irritation through AMPK/MAPK/NF‐kB Inhibition.

Preservation of microvascular barrier function requires CD31 receptor-induced metabolic reprogramming

Endothelial barrier (EB) breaching is a frequent event during inflammation, and it is followed by the rapid recovery of microvascular integrity. The molecular mechanisms of EB recovery are poorly understood. Triggering of MHC molecules by migrating T-cells is a minimal signal capable of inducing endothelial contraction and transient microvascular leakage. Using this model, we show that EB recovery requires a CD31 receptor-induced, robust glycolytic response sustaining junction re-annealing. Mechanistically, this response involves src-homology phosphatase activation leading to Akt-mediated nuclear exclusion of FoxO1 and concomitant β-catenin translocation to the nucleus, collectively leading to cMyc transcription. CD31 signals also sustain mitochondrial respiration, however this pathway does not contribute to junction remodeling. We further show that pathologic microvascular leakage in CD31-deficient mice can be corrected by enhancing the glycolytic flux via pharmacological Akt or AMPK activation, thus providing a molecular platform for the therapeutic control of EB response.

Exercise enhances skeletal muscle regeneration by promoting senescence in fibro-adipogenic progenitors

Idiopathic inflammatory myopathies cause progressive muscle weakness and degeneration. Since high-dose glucocorticoids might not lead to full recovery of muscle function, physical exercise is also an important intervention, but some exercises exacerbate chronic inflammation and muscle fibrosis. It is unknown how physical exercise can have both beneficial and detrimental effects in chronic myopathy. Here we show that senescence of fibro-adipogenic progenitors (FAPs) in response to exercise-induced muscle damage is needed to establish a state of regenerative inflammation that induces muscle regeneration. In chronic inflammatory myopathy model mice, exercise does not promote FAP senescence or resistance against tumor necrosis factor–mediated apoptosis. Pro-senescent intervention combining exercise and pharmacological AMPK activation reverses FAP apoptosis resistance and improves muscle function and regeneration. Our results demonstrate that the absence of FAP senescence after exercise leads to muscle degeneration with FAP accumulation. FAP-targeted pro-senescent interventions with exercise and pharmacological AMPK activation may constitute a therapeutic strategy for chronic inflammatory myopathy.

Abstract 923: Pharmacological Activation of Ampk With a Direct Pan-ampk Activator Results in a Worsening of a Hf Phenotype in Mice

The absence of effective therapeutic treatments that can restore function in patients with heart failure necessitates the identification of new mechanisms and strategies to improve outcomes. Strategies that directly target the cardiomyocyte and have potential to increase metabolic capacity hold promise as treatment modalities. We sought to evaluate direct activators of the AMP-Activated Protein Kinase (AMPK) in a model of HF to test for improvements. The pan-AMPK activator PF-739 resulted in activation of AMPK, phosphorylation of the downstream target ACC, and increases in glucose uptake after a single dose in vivo. PF-739 resulted in an increase in the gene expression of relevant transcriptional regulators PGC1α and NR4a1, suggesting potential for beneficial effects on substrate metabolism in a HF model. PF-739 and the ACE inhibitor Enalipril were used in a combined TAC/MI model of mouse HF. 4 weeks after injury the animals treated with PF-739 had an increase in end systolic and diastolic volume and ejection fraction compared to vehicle animals. Enalipril treatment resulted in modest improvements in echo heart assessments and a reduction in heart weight compared to vehicle animals. To understand the mechanism for impaired heart function in HF we assessed the impact of PF-739 on systemic blood pressure, reasoning this could impact HF progression in the model. PF-739 caused an increase in blood pressure after acute dosing in mice and rats. A small molecule analogue of PF-739 differing in one methyl group with dramatically reduced AMPK activity was shown to have no detectable blood pressure effect, suggesting the blood pressure effects are related to AMPK activity. Contrary to expectation, treatment with PF-739 caused impairment in heart function in a mouse model of HF, an effect that may be the result of a systemic blood pressure effect of the compound.

Improved exercise capacity in cyclophilin-D knockout mice associated with enhanced oxygen utilization efficiency and augmented glucose uptake via AMPK-TBC1D1 signaling nexus.

We previously reported in HEK 293T cells that silencing the mitochondrial peptidyl prolyl isomerase cyclophilin-D (Cyp-D) reduces Vo2. We now report that in vivo Cyp-D ablation using constitutive Cyp-D knockout (KO) mice also reduces Vo2 both at rest (∼15%) and during treadmill exercise (∼12%). Yet, despite Vo2 reduction, these Cyp-D KO mice ran longer (1071 ± 77 vs. 785 ± 79 m; P = 0.002), for longer time (43 ± 3 vs. 34 ± 3 min; P = 0.004), and at higher speed (34 ± 1 vs. 29 ± 1 m/s; P ≤ 0.001), resulting in increased work (87 ± 6 vs. 58 ± 6 J; P ≤ 0.001). There were parallel reductions in carbon dioxide production, but of lesser magnitude, yielding a 2.3% increase in the respiratory exchange ratio consistent with increased glucose utilization as respiratory substrate. In addition, primary skeletal muscle cells of Cyp-D KO mice subjected to electrical stimulation exhibited higher glucose uptake (4.4 ± 0.55 vs. 2.6 ± 0.04 pmol/mg/min; P ≤ 0.001) with enhanced AMPK activation (0.58 ± 0.06 vs. 0.38 ± 0.03 pAMPK/β-tubulin ratio; P ≤ 0.01) and TBC1 (Tre-2/USP6, BUB2, Cdc16) domain family, member 1 (TBC1D1) inactivation. Likewise, pharmacological activation of AMPK also increased glucose uptake (3.2 ± 0.3 vs. 2.3 ± 0.2 pmol/mg/min; P ≤ 0.001). Moreover, lactate and ATP levels were increased in these cells. Taken together, Cyp-D ablation triggered an adaptive response resulting in increased exercise capacity despite less oxygen utilization associated with increased glucose uptake and utilization involving AMPK-TBC1D1 signaling nexus.-Radhakrishnan, J., Baetiong, A., Kaufman, H., Huynh, M., Leschinsky, A., Fresquez, A., White, C., DiMario, J. X., Gazmuri, R. J. Improved exercise capacity in cyclophilin-D knockout mice associated with enhanced oxygen utilization efficiency and augmented glucose uptake via AMPK-TBC1D1 signaling nexus.

Abstract LB-189: Pharmacological reactivation of MYC-dependent apoptosis cooperates with anti-PD1 immunotherapy

Abstract Elevated MYC levels sensitize tumor cells to apoptosis but the therapeutic potential of this mechanism remains unclear. We find, in a model of MYC-driven breast cancer, that pharmacological activation of AMPK dramatically synergizes with BCL-2/BCL-XL inhibitors to activate MYC-dependent apoptosis. We demonstrate the translational potential of an AMPK and BCL- 2/BCL-XL co-targeting strategy in ex vivo and in vivo models of MYC-high breast cancer. Metformin combined with either navitoclax or venetoclax efficiently inhibits tumor growth, confers survival benefits and induces tumor infiltration by immune cells. However, withdrawal of the drugs allowed tumor re- growth with presentation of PD1+/CD8+ T cell infiltrates, suggesting immune escape. A two-step treatment regimen, beginning with neoadjuvant metformin+venetoclax to induce apoptosis and followed by tumor resection and adjuvant metformin+venetoclax+anti-PD1 treatment to overcome immune escape, led to durable antitumor responses even after drug withdrawal. We demonstrate that pharmacological reactivation of MYC-dependent apoptosis is a powerful antitumor strategy involving both tumor cell depletion and immunosurveillance. Citation Format: Heidi M. Haikala, Johanna M. Anttila, Mariel Savelius, Elsa Marques, Tiina Raatikainen, Mette Ilander, Henna Hakanen, Johanna Mattson, Paivi Heikkila, Marjut Leidenius, Heikki Joensuu, Satu Mustjoki, Panu Kovanen, Martin Eilers, Joel D. Leverson, Juha T. Klefström. Pharmacological reactivation of MYC-dependent apoptosis cooperates with anti-PD1 immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-189.

Activation of AMPK restricts Zika virus replication in endothelial cells by potentiating antiviral response and inhibiting viral-induced glycolysis

Abstract Viruses are known to perturb host cellular metabolism to enable their replication and spread. However, studies examining Zika virus (ZIKV) infection and metabolism are limited. Here, using primary human retinal vascular endothelial (HRvEC) cells and HUVEC cell line, we investigated the role of AMPK, a master regulator of energy metabolism, in response to ZIKV challenge. ZIKV infection caused a time-dependent reduction in the phosphorylation of AMPK and its downstream target ACC. Pharmacological activation of AMPK using AICAR or metformin attenuated ZIKV replication, and similar findings were observed using GSK621, a specific activator of AMPKα. This phenomenon was reversed by incubation of cells with an AMPK inhibitor, compound C. Lentivirus-mediated knockdown of AMPK and the use of AMPK−/− MEFs further supporting the notion that AMPK restricts ZIKV replication. Interestingly, AMPK activation potentiated the expression of genes with antiviral properties (e.g., IFNs, OAS2, ISG15, MX1) and inhibited inflammatory mediators (e.g., TNFα, CCL5). Bio-energetic analysis revealed that ZIKV infection evoked a glycolytic response, as evidenced by elevated ECAR (extracellular acidification rate) levels and increased expression of key glycolytic genes (GLUT1, HK1, TPI, MCT4); AICAR treatment reduced this response. Consistent with this, 2-deoxyglucose (2DG), an inhibitor of the glycolysis, augmented AMPK activity, and attenuated ZIKV replication. Collectively, our study demonstrates that AMPK activation restricts ZIKV replication by promoting an antiviral responses and inhibiting ZIKV-induced glycolysis in endothelial cells. AMPK signaling thus represents a new potential antiviral target for ZIKV infections.

IRSp53 coordinates AMPK and 14-3-3 signaling to regulate filopodia dynamics and directed cell migration.

Filopodia are actin-filled membrane protrusions that play essential roles in cell motility and cell–cell communication and act as precursors of dendritic spines. IRSp53 is an essential regulator of filopodia formation, which couples Rho-GTPase signaling to actin cytoskeleton and membrane remodeling. IRSp53 has three major domains: an N-terminal inverse-BAR (I-BAR) domain, a Cdc42- and SH3-binding CRIB-PR domain, and an SH3 domain that binds downstream cytoskeletal effectors. Phosphorylation sites in the region between the CRIB-PR and SH3 domains mediate the binding of 14-3-3. Yet the mechanism by which 14-­3-3 regulates filopodia formation and dynamics and its role in cell migration are poorly understood. Here, we show that phosphorylation-dependent inhibition of IRSp53 by 14-3-3 counters activation by Cdc42 and cytoskeletal effectors, resulting in down-regulation of filopodia dynamics and cancer cell migration. In serum-starved cells, increased IRSp53 phosphorylation triggers 14-3-3 binding, which inhibits filopodia formation and dynamics, irrespective of whether IRSp53 is activated by Cdc42 or downstream effectors (Eps8, Ena/VASP). Pharmacological activation or inhibition of AMPK, respectively, increases or decreases the phosphorylation of two of three sites in IRSp53 implicated in 14-3-3 binding. Mutating these phosphorylation sites reverses 14-3-3-dependent inhibition of filopodia dynamics and cancer cell chemotaxis.

AMP-activated protein kinase regulates glycocalyx impairment and macrophage recruitment in response to low shear stress.

Low shear stress (LSS) increases degradation of the endothelial glycocalyx, leading to production of endothelial inflammation and atherosclerosis. However, the underlying mechanisms of how LSS diminishes the endothelial glycocalyx remain unclear. We showed that LSS inactivated AMPK, enhanced Na+-H+ exchanger (NHE)1 activity, and induced glycocalyx degradation. Activation of AMPK prevented LSS-induced NHE1 activity and endothelial glycocalyx impairment. We further identified hyaluronidase 2 (HYAL2) as a mediator of endothelial glycocalyx impairment in HUVECs exposed to LSS. Inactivation of AMPK by LSS up-regulates the activity of HYAL2, which acts downstream of NHE1. We characterized a left common carotid artery partial ligation (PL) model of LSS in C57BL/6 mice. The results showed decreased expression of hyaluronan (HA) in the endothelial glycocalyx and decreased thickness of the endothelial glycocalyx in PL mice. Pharmacological activation of AMPK by ampkinone not only attenuated glycocalyx impairment due to HA degradation but also blocked vascular cell adhesion molecule 1 and intercellular adhesion molecule 1 expression increase and macrophage recruitment in the endothelia of PL mice. Our results revealed that AMPK dephosphorylation induced by LSS activates NHE1 and HYAL2 to promote HA degradation and glycocalyx injury, which may contribute to endothelial inflammatory reaction and macrophage recruitment.-Zhang, J., Kong, X., Wang, Z., Gao, X., Ge, Z., Gu, Y., Ye, P., Chao, Y., Zhu, L., Li, X., Chen, S. AMP-activated protein kinase regulates glycocalyx impairment and macrophage recruitment in response to low shear stress.

Pharmacological AMPK activation induces transcriptional responses congruent to exercise in skeletal and cardiac muscle, adipose tissues and liver.

Physical activity promotes metabolic and cardiovascular health benefits that derive in part from the transcriptional responses to exercise that occur within skeletal muscle and other organs. There is interest in discovering a pharmacologic exercise mimetic that could imbue wellness and alleviate disease burden. However, the molecular physiology by which exercise signals the transcriptional response is highly complex, making it challenging to identify a single target for pharmacological mimicry. The current studies evaluated the transcriptome responses in skeletal muscle, heart, liver, and white and brown adipose to novel small molecule activators of AMPK (pan-activators for all AMPK isoforms) compared to that of exercise. A striking level of congruence between exercise and pharmacological AMPK activation was observed across the induced transcriptome of these five tissues. However, differences in acute metabolic response between exercise and pharmacologic AMPK activation were observed, notably for acute glycogen balances and related to the energy expenditure induced by exercise but not pharmacologic AMPK activation. Nevertheless, intervention with repeated daily administration of short-acting activation of AMPK was found to mitigate hyperglycemia and hyperinsulinemia in four rodent models of metabolic disease and without the cardiac glycogen accretion noted with sustained pharmacologic AMPK activation. These findings affirm that activation of AMPK is a key node governing exercise mediated transcription and is an attractive target as an exercise mimetic.

Pharmacological reactivation of MYC-dependent apoptosis induces susceptibility to anti-PD-1 immunotherapy

Elevated MYC expression sensitizes tumor cells to apoptosis but the therapeutic potential of this mechanism remains unclear. We find, in a model of MYC-driven breast cancer, that pharmacological activation of AMPK strongly synergizes with BCL-2/BCL-XL inhibitors to activate apoptosis. We demonstrate the translational potential of an AMPK and BCL-2/BCL-XL co-targeting strategy in ex vivo and in vivo models of MYC-high breast cancer. Metformin combined with navitoclax or venetoclax efficiently inhibited tumor growth, conferred survival benefits and induced tumor infiltration by immune cells. However, withdrawal of the drugs allowed tumor re-growth with presentation of PD-1+/CD8+ T cell infiltrates, suggesting immune escape. A two-step treatment regimen, beginning with neoadjuvant metformin+venetoclax to induce apoptosis and followed by adjuvant metformin+venetoclax+anti-PD-1 treatment to overcome immune escape, led to durable antitumor responses even after drug withdrawal. We demonstrate that pharmacological reactivation of MYC-dependent apoptosis is a powerful antitumor strategy involving both tumor cell depletion and immunosurveillance.

Metformin: An Old Dog with a New Trick?

Idiopathic pulmonary fibrosis (IPF) remains an important medical challenge, but recent translational data have provided clues implicating deficient AMPK signaling in persistently activated myelofibroblasts within fibrotic foci. A new study in Nature Medicine reports that pharmacological activation of AMPK with metformin can reverse established fibrosis by facilitating deactivation and apoptosis of myofibroblasts.