Localization of AMP kinase is regulated by stress, cell density, and signaling through the MEK-->ERK1/2 pathway

Hsp70 Negatively Regulates Autophagy via Governing AMPK Activation, and Dual Hsp70-Autophagy Inhibition Induces Synergetic Cell Death in NSCLC Cells

Proteostasis mechanisms, such as proteotoxic-stress response and autophagy, are increasingly recognized for their roles in influencing various cancer hallmarks such as tumorigenesis, drug resistance, and recurrence. However, the precise mechanisms underlying their coordination remain not fully elucidated. The aim of this study is to investigate the molecular interplay between Hsp70 and autophagy in lung adenocarcinoma cells and elucidate its impact on the outcomes of anticancer therapies in vitro. For this purpose, we utilized the human lung adenocarcinoma A549 cell line and genetically modified it by knockdown of Hsp70 or HSF1, and the H1299 cell line with knockdown or overexpression of Hsp70. In addition, several treatments were employed, including treatment with Hsp70 inhibitors (VER-155008 and JG-98), HSF1 activator ML-346, or autophagy modulators (SAR405 and Rapamycin). Using immunoblotting, we found that Hsp70 negatively regulates autophagy by directly influencing AMPK activation, uncovering a novel regulatory mechanism of autophagy by Hsp70. Genetic or chemical Hsp70 overexpression was associated with the suppression of AMPK and autophagy. Conversely, the inhibition of Hsp70, genetically or chemically, resulted in the upregulation of AMPK-mediated autophagy. We further investigated whether Hsp70 suppression-mediated autophagy exhibits pro-survival- or pro-death-inducing effects via MTT test, colony formation, CellTiter-Glo 3D-Spheroid viability assay, and Annexin/PI apoptosis assay. Our results show that combined inhibition of Hsp70 and autophagy, along with cisplatin treatment, synergistically reduces tumor cell metabolic activity, growth, and viability in 2D and 3D tumor cell models. These cytotoxic effects were exerted by substantially potentiating apoptosis, while activating autophagy via rapamycin slightly rescued tumor cells from apoptosis. Therefore, our findings demonstrate that the combined inhibition of Hsp70 and autophagy represents a novel and promising therapeutic approach that may disrupt the capacity of refractory tumor cells to withstand conventional therapies in NSCLC.

EGCG alleviates heat-stress-induced fat deposition by targeting HSP70 through activation of AMPK-SIRT1-PGC-1α in porcine subcutaneous preadipocytes

Obesity has emerged as a prominent global health concern, with heat stress posing a significant challenge to both human health and animal well-being. Despite a growing interest in environmental determinants of obesity, very few studies have examined the associations between heat stress-related environmental factors and adiposity. Consequently, there exists a clear need to understand the molecular mechanisms underlying the obesogenic effects of heat stress and to formulate preventive strategies. This study focused on culturing porcine subcutaneous preadipocytes at 41.5 ℃ to induce heat stress, revealing that this stressor triggered apoptosis and fat deposition. Analysis demonstrated an upregulation in the expression of HSP70, BAX, adipogenesis-related genes (PPARγ, AP2, CEBPα and FAS), the p-AMPK/AMPK ratio and SIRT1, PGC-1α in the heat stress group compared to the control group (P < 0.05). Conversely, the expression of lipid lysis-related genes (ATGL, HSL and LPL) and Bcl-2 decreased in the heat stress group compared to the control group (P < 0.05). Furthermore, subsequent activator and/or inhibitor experiments validated that heat stress modulated HSP70 and AMPK signalling pathways to enhance lipogenesis and inhibit lipolysis in porcine subcutaneous preadipocytes. Importantly, this study reveals, for the first time, that EGCG mitigates heat-stress-induced fat deposition by targeting HSP70 through the activation of AMPK-SIRT1-PGC-1α in porcine subcutaneous preadipocytes. These findings elucidate the molecular mechanisms contributing to heat stress-induced obesity and provide a foundation for the potential clinical utilisation of EGCG as a preventive measure against both heat stress and obesity.

Pifithrin-µ Induces Stress Granule Formation, Regulates Cell Survival, and Rewires Cellular Signaling

(1) Background: Stress granules (SGs) are cytoplasmic protein-RNA condensates that assemble in response to various insults. SG production is driven by signaling pathways that are relevant to human disease. Compounds that modulate SG characteristics are therefore of clinical interest. Pifithrin-µ is a candidate anti-tumor agent that inhibits members of the hsp70 chaperone family. While hsp70s are required for granulostasis, the impact of pifithrin-µ on SG formation is unknown. (2) Methods: Using HeLa cells as model system, cell-based assays evaluated the effects of pifithrin-µ on cell viability. Quantitative Western blotting assessed cell signaling events and SG proteins. Confocal microscopy combined with quantitative image analyses examined multiple SG parameters. (3) Results: Pifithrin-µ induced bona fide SGs in the absence of exogenous stress. These SGs were dynamic; their properties were determined by the duration of pifithrin-µ treatment. The phosphorylation of eIF2α was mandatory to generate SGs upon pifithrin-µ exposure. Moreover, the formation of pifithrin-µ SGs was accompanied by profound changes in cell signaling. Pifithrin-µ reduced the activation of 5'-AMP-activated protein kinase, whereas the pro-survival protein kinase Akt was activated. Long-term pifithrin-µ treatment caused a marked loss of cell viability. (4) Conclusions: Our study identified stress-related changes in cellular homeostasis that are elicited by pifithrin-µ. These insights are important knowledge for the appropriate therapeutic use of pifithrin-µ and related compounds.

Proposed molecular mechanism of non-competitive inhibition using molecular dynamics simulations between α-glucosidase enzyme and mangostin compound as antidiabetic

CONTEXT

Further understanding of the molecular mechanisms is necessary since it is important for designing new drugs. This study aimed to understand the molecular mechanisms involved in the design of drugs that are inhibitors of the α-glucosidase enzyme. This research aims to gain further understanding of the molecular mechanisms underlying antidiabetic drug design. The molecular docking process yielded 4 compounds with the best affinity energy, including γ-Mangostin, 1,6-dimethyl-ester-3-isomangostin, 1,3,6-trimethyl-ester-α-mangostin, and 3,6,7-trimethyl-ester-γ-mangostin. Free energy calculation with molecular mechanics with generalized born and surface area solvation indicated that the 3,6,7-trimethyl-γ-mangostin had a better free energy value compared to acarbose and simulated maltose together with 3,6,7-trimethyl-γ-mangostin compound. Based on the analysis of electrostatic, van der Waals, and intermolecular hydrogen interactions, 3,6,7-trimethyl-γ-mangostin adopts a noncompetitive inhibition mechanism, whereas acarbose adopts a competitive inhibition mechanism. Consequently, 3,6,7-trimethyl-ester-γ-mangostin, which is a derivative of γ-mangostin, can provide better activity in silico with molecular docking approaches and molecular dynamics simulations.

METHOD

This research commenced with retrieving protein structures from the RCSB database, generating the formation of ligands using the ChemDraw Professional software, conducting molecular docking with the Autodock Vina software, and performing molecular dynamics simulations using the Amber software, along with the evaluation of RMSD values and intermolecular hydrogen bonds. Free energy, electrostatic interactions, and Van der Waals interaction were calculated using MM/GBSA. Acarbose, used as a positive control, and maltose are simulated together with test compound that has the best free energy. The forcefields used for molecular dynamics simulations are ff19SB, gaff2, and tip3p.

Targeted Inhibition of Hsp90 in Combination with Metformin Modulates Programmed Cell Death Pathways in A549 Lung Cancer Cells

The pathophysiology of lung cancer is dependent on the dysregulation in the apoptotic and autophagic pathways. The intricate link between apoptosis and autophagy through shared signaling pathways complicates our understanding of how lung cancer pathophysiology is regulated. As drug resistance is the primary reason behind treatment failure, it is crucial to understand how cancer cells may respond to different therapies and integrate crosstalk between apoptosis and autophagy in response to them, leading to cell death or survival. Thus, in this study, we have tried to evaluate the crosstalk between autophagy and apoptosis in A549 lung cancer cell line that could be modulated by employing a combination therapy of metformin (6 mM), an anti-diabetic drug, with gedunin (12 µM), an Hsp90 inhibitor, to provide insights into the development of new cancer therapeutics. Our results demonstrated that metformin and gedunin were cytotoxic to A549 lung cancer cells. Combination of metformin and gedunin generated ROS and promoted MMP loss and DNA damage. The combination further increased the expression of AMPKα1 and promoted the nuclear localization of AMPKα1/α2. The expression of Hsp90 was downregulated, further decreasing the expression of its clients, EGFR, PIK3CA, AKT1, and AKT3. Inhibition of the EGFR/PI3K/AKT pathway upregulated TP53 and inhibited autophagy. The combination was promoting nuclear localization of p53; however, some cytoplasmic signals were also detected. Further increase in the expression of caspase 9 and caspase 3 was observed. Thus, we concluded that the combination of metformin and gedunin upregulates apoptosis by inhibiting the EGFR/PI3K/AKT pathway and autophagy in A549 lung cancer cells.

DNA Damage and Nuclear Morphological Changes in Cardiac Hypertrophy Are Mediated by SNRK Through Actin Depolymerization

BACKGROUND

Proper nuclear organization is critical for cardiomyocyte function, because global structural remodeling of nuclear morphology and chromatin structure underpins the development and progression of cardiovascular disease. Previous reports have implicated a role for DNA damage in cardiac hypertrophy; however, the mechanism for this process is not well delineated. AMPK (AMP-activated protein kinase) family of proteins regulates metabolism and DNA damage response (DDR). Here, we examine whether a member of this family, SNRK (SNF1-related kinase), which plays a role in cardiac metabolism, is also involved in hypertrophic remodeling through changes in DDR and structural properties of the nucleus.

METHODS

We subjected cardiac-specific Snrk-/- mice to transaortic banding to assess the effect on cardiac function and DDR. In parallel, we modulated SNRK in vitro and assessed its effects on DDR and nuclear parameters. We also used phosphoproteomics to identify novel proteins that are phosphorylated by SNRK. Last, coimmunoprecipitation was used to verify Destrin (DSTN) as the binding partner of SNRK that modulates its effects on the nucleus and DDR.

RESULTS

Cardiac-specific Snrk-/- mice display worse cardiac function and cardiac hypertrophy in response to transaortic banding, and an increase in DDR marker pH2AX (phospho-histone 2AX) in their hearts. In addition, in vitro Snrk knockdown results in increased DNA damage and chromatin compaction, along with alterations in nuclear flatness and 3-dimensional volume. Phosphoproteomic studies identified a novel SNRK target, DSTN, a member of F-actin depolymerizing factor proteins that directly bind to and depolymerize F-actin. SNRK binds to DSTN, and DSTN downregulation reverses excess DNA damage and changes in nuclear parameters, in addition to cellular hypertrophy, with SNRK knockdown. We also demonstrate that SNRK knockdown promotes excessive actin depolymerization, measured by the increased ratio of G-actin to F-actin. Last, jasplakinolide, a pharmacological stabilizer of F-actin, rescues the increased DNA damage and aberrant nuclear morphology in SNRK-downregulated cells.

CONCLUSIONS

These results indicate that SNRK is a key player in cardiac hypertrophy and DNA damage through its interaction with DSTN. This interaction fine-tunes actin polymerization to reduce DDR and maintain proper cardiomyocyte nuclear shape and morphology.

Thrap3 promotes nonalcoholic fatty liver disease by suppressing AMPK-mediated autophagy

Autophagy functions in cellular quality control and metabolic regulation. Dysregulation of autophagy is one of the major pathogenic factors contributing to the progression of nonalcoholic fatty liver disease (NAFLD). Autophagy is involved in the breakdown of intracellular lipids and the maintenance of healthy mitochondria in NAFLD. However, the mechanisms underlying autophagy dysregulation in NAFLD remain unclear. Here, we demonstrate that the hepatic expression level of Thrap3 was significantly increased in NAFLD conditions. Liver-specific Thrap3 knockout improved lipid accumulation and metabolic properties in a high-fat diet (HFD)-induced NAFLD model. Furthermore, Thrap3 deficiency enhanced autophagy and mitochondrial function. Interestingly, Thrap3 knockout increased the cytosolic translocation of AMPK from the nucleus and enhanced its activation through physical interaction. The translocation of AMPK was regulated by direct binding with AMPK and the C-terminal domain of Thrap3. Our results indicate a role for Thrap3 in NAFLD progression and suggest that Thrap3 is a potential target for NAFLD treatment.

DNA damage and nuclear morphological changes in cardiac hypertrophy are mediated by SNRK through actin depolymerization

BACKGROUND

Proper nuclear organization is critical for cardiomyocyte (CM) function, as global structural remodeling of nuclear morphology and chromatin structure underpins the development and progression of cardiovascular disease. Previous reports have implicated a role for DNA damage in cardiac hypertrophy, however, the mechanism for this process is not well delineated. AMPK family of proteins regulate metabolism and DNA damage response (DDR). Here, we examine whether a member of this family, SNF1-related kinase (SNRK), which plays a role in cardiac metabolism, is also involved in hypertrophic remodeling through changes in DDR and structural properties of the nucleus.

METHODS

We subjected cardiac specific (cs)- Snrk -/- mice to trans-aortic banding (TAC) to assess the effect on cardiac function and DDR. In parallel, we modulated SNRK in vitro and assessed its effects on DDR and nuclear parameters. We also used phospho-proteomics to identify novel proteins that are phosphorylated by SNRK. Finally, co-immunoprecipitation (co-IP) was used to verify Destrin (DSTN) as the binding partner of SNRK that modulates its effects on the nucleus and DDR.

RESULTS

cs- Snrk -/- mice display worse cardiac function and cardiac hypertrophy in response to TAC, and an increase in DDR marker pH2AX in their hearts. Additionally, in vitro Snrk knockdown results in increased DNA damage and chromatin compaction, along with alterations in nuclear flatness and 3D volume. Phospho-proteomic studies identified a novel SNRK target, DSTN, a member of F-actin depolymerizing factor (ADF) proteins that directly binds to and depolymerize F-actin. SNRK binds to DSTN, and DSTN downregulation reverses excess DNA damage and changes in nuclear parameters, in addition to cellular hypertrophy, with SNRK knockdown. We also demonstrate that SNRK knockdown promotes excessive actin depolymerization, measured by the increased ratio of globular (G-) actin to F-actin. Finally, Jasplakinolide, a pharmacological stabilizer of F-actin, rescues the increased DNA damage and aberrant nuclear morphology in SNRK downregulated cells.

CONCLUSIONS

These results indicate that SNRK is a key player in cardiac hypertrophy and DNA damage through its interaction with DSTN. This interaction fine-tunes actin polymerization to reduce DDR and maintain proper CM nuclear shape and morphology.

Clinical Perspective

What is new? Animal hearts subjected to pressure overload display increased SNF1-related kinase (SNRK) protein expression levels and cardiomyocyte specific SNRK deletion leads to aggravated myocardial hypertrophy and heart failure.We have found that downregulation of SNRK impairs DSTN-mediated actin polymerization, leading to maladaptive changes in nuclear morphology, higher DNA damage response (DDR) and increased hypertrophy. What are the clinical implications? Our results suggest that disruption of DDR through genetic loss of SNRK results in an exaggerated pressure overload-induced cardiomyocyte hypertrophy.Targeting DDR, actin polymerization or SNRK/DSTN interaction represent promising therapeutic targets in pressure overload cardiac hypertrophy.

Combined chronic copper exposure and aging lead to neurotoxicity in vivo

The environment, containing pollutants, toxins, and transition metals (copper, iron, manganese, and zinc), plays a critical role in neurodegenerative disease development. Copper occupational exposure increases Parkinson's disease (PD) risk. Previously, we determined the mechanisms by which copper induces dopaminergic cell death in vitro. The copper transporter protein 1 (Ctr1) overexpression led to intracellular glutathione depletion potentiating caspase-3 mediated cell death; oxidative stress was primarily cytosolic, and Nrf2 was upregulated mediating an antioxidant response; and protein ubiquitination, AMPK-Ulk1 signaling, p62, and Atg5-dependent autophagy were increased as a protective mechanism. However, the effect of chronic copper exposure on the neurodegenerative process has not been explored in vivo. We aimed to elucidate whether prolonged copper treatment reproduces PD features and mechanisms during aging. Throughout 40 weeks, C57BL/6J male mice were treated with copper at 0, 100, 250, and 500 ppm in the drinking water. Chronic copper exposure altered motor function and induced dopaminergic neuronal loss, astrocytosis, and microgliosis in a dose-dependent manner. α-Synuclein accumulation and aggregation were increased in response to copper, and the proteasome and autophagy alterations, previously observed in vitro, were confirmed in vivo, where protein ubiquitination, AMPK phosphorylation, and the autophagy marker LC3-II were also increased by copper exposure. Finally, nitrosative stress was induced by copper in a concentration-dependent fashion, as evidenced by increased protein nitration. To our knowledge, this is the first study combining chronic copper exposure and aging, which may represent an in vivo model of non-genetic PD and help to assess potential prophylactic and therapeutic approaches. DATA AVAILABILITY: The data underlying this article are available in the article.

In Silico Study of Mangostin Compounds and Its Derivatives as Inhibitors of α-Glucosidase Enzymes for Anti-Diabetic Studies

Diabetes is a chronic disease with a high mortality rate worldwide and can cause other diseases such as kidney damage, narrowing of blood vessels, and heart disease. The concomitant use of drugs such as metformin, sulfonylurea, miglitol, and acarbose may cause side effects with long-term administration. Therefore, natural ingredients are the best choice, considering that their long-term side effects are not significant. One of the compounds that can be used as a candidate antidiabetic is mangostin; however, information on the molecular mechanism needs to be further analyzed through molecular docking, simulating molecular dynamics, and testing the in silico antidiabetic potential. This study focused on modeling the protein structure, molecular docking, and molecular dynamics simulations and analyses. This process produces RMSD values, free energies, and intermolecular hydrogen bonding. Based on the analysis results, all molecular dynamics simulations can occur under physiological conditions, and γ-mangostin is the best among the test compounds.

Molecular inhibition of RAS signalling to target ageing and age-related health

The RAS/MAPK pathway is a highly conserved signalling pathway with a well-established role in cancer. Mutations that hyperactivate this pathway are associated with unregulated cell proliferation. Evidence from a range of model organisms also links RAS/MAPK signalling to ageing. Genetic approaches that reduce RAS/MAPK signalling activity extend lifespan and also improve healthspan, delaying the onset and/or progression of age-related functional decline. Given its role in cancer, therapeutic interventions that target and inhibit this pathway's key components are under intense investigation. The consequent availability of small molecule inhibitors raises the possibility of repurposing these compounds to ameliorate the deleterious effects of ageing. Here, we review evidence that RAS/MAPK signalling inhibitors already in clinical use, such as trametinib, acarbose, statins, metformin and dihydromyricetin, lead to lifespan extension and to improved healthspan in a range of model systems. These findings suggest that the repurposing of small molecule inhibitors of RAS/MAPK signalling might offer opportunities to improve health during ageing, and to delay or prevent the development of age-related disease. However, challenges to this approach, including poor tolerance to treatment in older adults or development of drug resistance, first need to be resolved before successful clinical implementation.

Summary: This Review critically discusses the links between RAS signalling and ageing, and how RAS inhibitors could extend lifespan and enhance healthspan.

AMPK signaling and its targeting in cancer progression and treatment

The intrinsic mechanisms sensing the imbalance of energy in cells are pivotal for cell survival under various environmental insults. AMP-activated protein kinase (AMPK) serves as a central guardian maintaining energy homeostasis by orchestrating diverse cellular processes, such as lipogenesis, glycolysis, TCA cycle, cell cycle progression and mitochondrial dynamics. Given that AMPK plays an essential role in the maintenance of energy balance and metabolism, managing AMPK activation is considered as a promising strategy for the treatment of metabolic disorders such as type 2 diabetes and obesity. Since AMPK has been attributed to aberrant activation of metabolic pathways, mitochondrial dynamics and functions, and epigenetic regulation, which are hallmarks of cancer, targeting AMPK may open up a new avenue for cancer therapies. Although AMPK is previously thought to be involved in tumor suppression, several recent studies have unraveled its tumor promoting activity. The double-edged sword characteristics for AMPK as a tumor suppressor or an oncogene are determined by distinct cellular contexts. In this review, we will summarize recent progress in dissecting the upstream regulators and downstream effectors for AMPK, discuss the distinct roles of AMPK in cancer regulation and finally offer potential strategies with AMPK targeting in cancer therapy.

Stress-responsive AMP Kinase like protein regulates encystation of Entamoeba invadens

Starvation is always accompanied by an increase in the ratio of AMP/ATP followed by activation of AMPK. It is one of the sensors for cellular energy status and is highly conserved across various species. Its role in the stage differentiation process of protozoan species like Giardia, Plasmodium, Trypanosome, and Toxoplasma has been reported. Since Entamoeba undergoes encystation in glucose-starved conditions; it intrigued us to investigate the existence and role of AMPK during the differentiation of trophozoites to the cyst. By employing in silico approaches, we have identified an AMPK homologue which is denominated here as EiAMPK (AMPK-like protein in Entamoeba invadens). Sequence and structural analysis indicate that EiAMPK is sequentially and structurally similar to the AMPK alpha subunit of other organisms. The recombinant form of EiAMPK was functionally active and in accordance, its activity was inhibited by an AMPK-specific inhibitor (eg. Compound C). The increased expression of EiAMPK during different stresses indicated that EiAMPK is a stress-responsive gene. To further investigate, whether EiAMPK has any role in encystation, we employed RNAi-mediated gene silencing that demonstrated its active involvement in encystation. It is known that Entamoeba maintains a flow of glucose from the glycolytic pathway to chitin synthesis for cyst wall formation during encystation. It is conceivable that EiAMPK might have a command over such glucose metabolism. As anticipated, the chitin synthesis was found greatly inhibited in both EiAMPK knockdown and Compound C treated cells, indicating that EiAMPK regulates the cyst wall chitin synthesis.

Spatial regulation of AMPK signaling revealed by a sensitive kinase activity reporter

AMP-activated protein kinase (AMPK) is a master regulator of cellular energetics which coordinates metabolism by phosphorylating a plethora of substrates throughout the cell. But how AMPK activity is regulated at different subcellular locations for precise spatiotemporal control over metabolism is unclear. Here we present a sensitive, single-fluorophore AMPK activity reporter (ExRai AMPKAR), which reveals distinct kinetic profiles of AMPK activity at the mitochondria, lysosome, and cytoplasm. Genetic deletion of the canonical upstream kinase liver kinase B1 (LKB1) results in slower AMPK activity at lysosomes but does not affect the response amplitude at lysosomes or mitochondria, in sharp contrast to the necessity of LKB1 for maximal cytoplasmic AMPK activity. We further identify a mechanism for AMPK activity in the nucleus, which results from cytoplasmic to nuclear shuttling of AMPK. Thus, ExRai AMPKAR enables illumination of the complex subcellular regulation of AMPK signaling.

Caspase cleavage and nuclear retention of the energy sensor AMPK-α1 during apoptosis

AMP-activated protein kinase (AMPK) coordinates energy homeostasis during metabolic and energy stress. We report that the catalytic subunit isoform AMPK-α1 (but not α2) is cleaved by caspase-3 at an early stage during induction of apoptosis. AMPK-α1 cleavage occurs following Asp529, generating an ∼58-kDa N-terminal fragment (cl-AMPK-α1) and leading to the precise excision of the nuclear export sequence (NES) from the C-terminal end. This cleavage does not affect (1) the stability of pre-formed heterotrimeric complexes, (2) the ability of cl-AMPK-α1 to become phosphorylated and activated by the upstream kinases LKB1 or CaMKK2, or (3) allosteric activation by AMP or A-769662. Importantly, cl-AMPK-α1 is only detectable in the nucleus, consistent with removal of the NES, and ectopic expression of cleavage-resistant D529A-mutant AMPK-α1 promotes cell death induced by cytotoxic agents. Thus, we have elucidated a non-canonical mechanism of AMPK activation within the nucleus, which protects cells against death induced by DNA damage.

Hemin-Induced Death Models Hemorrhagic Stroke and Is a Variant of Classical Neuronal Ferroptosis

Ferroptosis is a caspase-independent, iron-dependent form of regulated necrosis extant in traumatic brain injury, Huntington disease, and hemorrhagic stroke. It can be activated by cystine deprivation leading to glutathione depletion, the insufficiency of the antioxidant glutathione peroxidase-4, and the hemolysis products hemoglobin and hemin. A cardinal feature of ferroptosis is extracellular signal-regulated kinase (ERK)1/2 activation culminating in its translocation to the nucleus. We have previously confirmed that the mitogen-activated protein (MAP) kinase kinase (MEK) inhibitor U0126 inhibits persistent ERK1/2 phosphorylation and ferroptosis. Here, we show that hemin exposure, a model of secondary injury in brain hemorrhage and ferroptosis, activated ERK1/2 in mouse neurons. Accordingly, MEK inhibitor U0126 protected against hemin-induced ferroptosis. Unexpectedly, U0126 prevented hemin-induced ferroptosis independent of its ability to inhibit ERK1/2 signaling. In contrast to classical ferroptosis in neurons or cancer cells, chemically diverse inhibitors of MEK did not block hemin-induced ferroptosis, nor did the forced expression of the ERK-selective MAP kinase phosphatase (MKP)3. We conclude that hemin or hemoglobin-induced ferroptosis, unlike glutathione depletion, is ERK1/2-independent. Together with recent studies, our findings suggest the existence of a novel subtype of neuronal ferroptosis relevant to bleeding in the brain that is 5-lipoxygenase-dependent, ERK-independent, and transcription-independent. Remarkably, our unbiased phosphoproteome analysis revealed dramatic differences in phosphorylation induced by two ferroptosis subtypes. As U0126 also reduced cell death and improved functional recovery after hemorrhagic stroke in male mice, our analysis also provides a template on which to build a search for U0126's effects in a variant of neuronal ferroptosis.SIGNIFICANCE STATEMENT Ferroptosis is an iron-dependent mechanism of regulated necrosis that has been linked to hemorrhagic stroke. Common features of ferroptotic death induced by diverse stimuli are the depletion of the antioxidant glutathione, production of lipoxygenase-dependent reactive lipids, sensitivity to iron chelation, and persistent activation of extracellular signal-regulated kinase (ERK) signaling. Unlike classical ferroptosis induced in neurons or cancer cells, here we show that ferroptosis induced by hemin is ERK-independent. Paradoxically, the canonical MAP kinase kinase (MEK) inhibitor U0126 blocks brain hemorrhage-induced death. Altogether, these data suggest that a variant of ferroptosis is unleashed in hemorrhagic stroke. We present the first, unbiased phosphoproteomic analysis of ferroptosis as a template on which to understand distinct paths to cell death that meet the definition of ferroptosis.

Ca2+/Calmodulin-Dependent Protein Kinase II Inhibits Hepatitis B Virus Replication from cccDNA via AMPK Activation and AKT/mTOR Suppression

Ca2+/calmodulin-dependent protein kinase II (CaMKII), which is involved in the calcium signaling pathway, is an important regulator of cancer cell proliferation, motility, growth, and metastasis. The effects of CaMKII on hepatitis B virus (HBV) replication have never been evaluated. Here, we found that phosphorylated, active CaMKII is reduced during HBV replication. Similar to other members of the AMPK/AKT/mTOR signaling pathway associated with HBV replication, CaMKII, which is associated with this pathway, was found to be a novel regulator of HBV replication. Overexpression of CaMKII reduced the expression of covalently closed circular DNA (cccDNA), HBV RNAs, and replicative intermediate (RI) DNAs while activating AMPK and inhibiting the AKT/mTOR signaling pathway. Findings in HBx-deficient mutant-transfected HepG2 cells showed that the CaMKII-mediated AMPK/AKT/mTOR signaling pathway was independent of HBx. Moreover, AMPK overexpression reduced HBV cccDNA, RNAs, and RI DNAs through CaMKII activation. Although AMPK acts downstream of CaMKII, AMPK overexpression altered CaMKII phosphorylation, suggesting that CaMKII and AMPK form a positive feedback loop. These results demonstrate that HBV replication suppresses CaMKII activity, and that CaMKII upregulation suppresses HBV replication from cccDNA via AMPK and the AKT/mTOR signaling pathway. Thus, activation or overexpression of CaMKII may be a new therapeutic target against HBV infection.

Membrane polarization in non-neuronal cells as a potential mechanism of metabolic disruption by depolarizing insecticides

A significant rise in the incidence of obesity and type 2 diabetes has occurred worldwide in the last two decades. Concurrently, a growing body of evidence suggests a connection between exposure to environmental pollutants, particularly insecticides, and the development of obesity and type 2 diabetes. This review summarizes key evidence of (1) the presence of different types of neuronal receptors - target sites for neurotoxic insecticides - in non-neuronal cells, (2) the activation of these receptors in non-neuronal cells by membrane-depolarizing insecticides, and (3) changes in metabolic functions, including lipid and glucose accumulation, associated with changes in membrane potential. Based on these findings, we propose that changes in membrane potential (V_mem) by certain insecticides serve as a novel regulator of lipid and glucose metabolism in non-excitable cells associated with obesity and type 2 diabetes.

Nuclear UHRF1 is a gate-keeper of cellular AMPK activity and function

The AMP-activated protein kinase (AMPK) is a central regulator of energy homeostasis. Although much has been learned on how low energy status and glucose starvation activate AMPK, how AMPK activity is properly controlled in vivo is still poorly understood. Here we report that UHRF1, an epigenetic regulator highly expressed in proliferating and cancer cells, interacts with AMPK and serves to suppress AMPK activity under both basal and stressed conditions. As a nuclear protein, UHRF1 promotes AMPK nuclear retention and strongly suppresses nuclear AMPK activity toward substrates H2B and EZH2. Importantly, we demonstrate that UHRF1 also robustly inhibits AMPK activity in the cytoplasm compartment, most likely as a consequence of AMPK nucleocytoplasmic shuttling. Mechanistically, we found that UHRF1 has no obvious effect on AMPK activation by upstream kinases LKB1 and CAMKK2 but inhibits AMPK activity by acting as a bridging factor targeting phosphatase PP2A to dephosphorylate AMPK. Hepatic overexpression of UHRF1 showed profound effects on glucose and lipid metabolism in wild-type mice but not in those with the liver-specific knockout of AMPKα1/α2, whereas knockdown of UHRF1 in adipose tissue led to AMPK activation and reduced sizes of adipocytes and lipogenic activity, highlighting the physiological significance of this regulation in glucose and lipid metabolism. Thus, our study identifies UHRF1 as a novel AMPK gate-keeper with critical roles in cellular metabolism.

AMPK Localization: A Key to Differential Energy Regulation

As the central node between nutrition signaling input and the metabolic pathway, AMP-activated protein kinase (AMPK) is tightly regulated to maintain energy homeostasis. Subcellular compartmentalization of AMPK is one of the critical regulations that enables AMPK to access proper targets and generate appropriate responses to specific perturbations and different levels of stress. One of the characterized localization mechanisms is RanGTPase-driven CRM1 that recognizes the nuclear export sequence (NES) on the α subunit to translocate AMPK into the cytoplasm. Nuclear localization putatively employs RanGTPase-driven importin that might recognize the nuclear localization signal (NLS) present on the AMPKα2 kinase domain. Nucleo-cytoplasmic shuttling of AMPK is influenced by multiple factors, such as starvation, exercise, heat shock, oxidant, cell density, and circadian rhythm. Tissue-specific localization, which distributes AMPK trimers with different combinations, has also been shown to be vital in maintaining tissue-specific metabolism. Tissue-specific and subcellular distribution of AMPK might be attributed to differences in the expression of the subunit, the stabilization by protein regulators, tissue activity, and the localization of AMPK activators. Considering the importance of AMPK localization in coordinating signaling and metabolism, further research is due to fully elucidate the largely unknown complex mechanism underlying this regulation.

AMPK: restoring metabolic homeostasis over space and time

The evolution of AMPK and its homologs enabled exquisite responsivity and control of cellular energetic homeostasis. Recent work has been critical in establishing the mechanisms that determine AMPK activity, novel targets of AMPK action, and the distribution of AMPK-mediated control networks across the cellular landscape. The role of AMPK as a hub of metabolic control has led to intense interest in pharmacologic activation as a therapeutic avenue for a number of disease states, including obesity, diabetes, and cancer. As such, critical work on the compartmentalization of AMPK, its downstream targets, and the systems it influences has progressed in recent years. The variegated distribution of AMPK-mediated control of metabolic homeostasis has revealed key insights into AMPK in normal biology and future directions for AMPK-based therapeutic strategies.

Metformin and insulin-resistant related diseases: Emphasis on the role of microRNAs

Metformin is one of the most prescribed drugs in type II diabetes (T2DM) which has recently found new applications in the prevention and treatment of various illnesses, from metabolic disorders to cardiovascular and age-related diseases. Metformin improves insulin resistance (IR) by modulating metabolic mechanisms and mitochondrial biogenesis. Alternation of microRNAs (miRs) in the treatment of IR-related illnesses has been observed by metformin therapy. MiRs are small non-coding RNAs that play important roles in RNA silencing, targeting the 3'untranslated region (3'UTR) of most mRNAs and inhibiting the translation of related proteins. As a result, their dysregulation is associated with many diseases. Metformin may alter miRs levels in the treatment of various diseases by AMPK-dependent or AMPK-independent mechanisms. Here, we summarized the therapeutic role of metformin by modifying the aberrant expression of miRs as potential biomarkers or therapeutic targets in diseases in which IR plays a key role.

Heat stress promotes lipid accumulation by inhibiting the AMPK-PGC-1α signaling pathway in 3T3-L1 preadipocytes

Heat stress (HS) results in health problems in animals. This study was conducted to investigate the effect and the underlying mechanism of HS on the proliferation and differentiation process of 3T3-L1 preadipocytes. 3T3-L1 preadipocytes were treated at 37 °C or 41.5 °C. HS up-regulated the mRNA and protein expression level of heat shock protein 70 (HSP70). Furthermore, the proliferation of 3T3-L1 preadipocytes were significantly inhibited after HS treatment for 2 days. A large number of accumulated lipid droplets were observed under the microscope after HS treatment for 8 days. Notably, the result of oil red O staining showed that the number of lipid droplets increased significantly and the differentiation ability of the cells was enhanced after HS. Moreover, after 2 and 8 d of differentiation, HS increased the transcription levels of fat synthesis genes including peroxisome proliferators activated receptor γ (PPARγ), fatty acid binding protein 2 (AP2), fatty acid synthase (FAS) and CCAAT enhancer binding protein α (CEBPα) genes, while decreasing the transcription levels of lipid decomposition genes including ATGL and HSL genes. In addition, HS reduced the expression of AMPK and PGC-1α, as well as the dephosphorylation of AMPK. 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR) can eliminate HS induced lipogenesis by activating AMPK. These results indicated that HS inhibited the proliferation of 3T3-L1 preadipocytes and promoted lipid accumulation by inhibiting the AMPK-PGC-1α signaling pathway in 3T3-L1 preadipocytes. This work lays a theoretical foundation for improving the effect of HS on meat quality of livestock and provides a new direction for the prevention of obesity caused by HS.

AMPKβ1 and AMPKβ2 define an isoform-specific gene signature in human pluripotent stem cells, differentially mediating cardiac lineage specification

AMP-activated protein kinase (AMPK) is a key regulator of energy metabolism that phosphorylates a wide range of proteins to maintain cellular homeostasis. AMPK consists of three subunits: α, β, and γ. AMPKα and β are encoded by two genes, the γ subunit by three genes, all of which are expressed in a tissue-specific manner. It is not fully understood, whether individual isoforms have different functions. Using RNA-Seq technology, we provide evidence that the loss of AMPKβ1 and AMPKβ2 lead to different gene expression profiles in human induced pluripotent stem cells (hiPSCs), indicating isoform-specific function. The knockout of AMPKβ2 was associated with a higher number of differentially regulated genes than the deletion of AMPKβ1, suggesting that AMPKβ2 has a more comprehensive impact on the transcriptome. Bioinformatics analysis identified cell differentiation as one biological function being specifically associated with AMPKβ2. Correspondingly, the two isoforms differentially affected lineage decision toward a cardiac cell fate. Although the lack of PRKAB1 impacted differentiation into cardiomyocytes only at late stages of cardiac maturation, the availability of PRKAB2 was indispensable for mesoderm specification as shown by gene expression analysis and histochemical staining for cardiac lineage markers such as cTnT, GATA4, and NKX2.5. Ultimately, the lack of AMPKβ1 impairs, whereas deficiency of AMPKβ2 abrogates differentiation into cardiomyocytes. Finally, we demonstrate that AMPK affects cellular physiology by engaging in the regulation of hiPSC transcription in an isoform-specific manner, providing the basis for further investigations elucidating the role of dedicated AMPK subunits in the modulation of gene expression.

Mitochondrial and Metabolic Pathways Regulate Nuclear Gene Expression to Control Differentiation, Stem Cell Function, and Immune Response in Leukemia

Mitochondria are involved in many biological processes including cellular homeostasis, energy generation, and apoptosis. Moreover, mitochondrial and metabolic pathways are interconnected with gene expression to regulate cellular functions such as cell growth, survival, differentiation, and immune recognition. Metabolites and mitochondrial enzymes regulate chromatin-modifying enzymes, chromatin remodeling, and transcription regulators. Deregulation of mitochondrial pathways and metabolism leads to alterations in gene expression that promote cancer development, progression, and evasion of the immune system. This review highlights how mitochondrial and metabolic pathways function as a central mediator to control gene expression, specifically on stem cell functions, differentiation, and immune response in leukemia. SIGNIFICANCE: Emerging evidence demonstrates that mitochondrial and metabolic pathways influence gene expression to promote tumor development, progression, and immune evasion. These data highlight new areas of cancer biology and potential new therapeutic strategies.

The landscape of alternative splicing reveals novel events associated with tumorigenesis and the immune microenvironment in gastric cancer

Alternative splicing (AS), contributing to vast protein diversity from a rather limited number of genes in eukaryotic transcripts, has emerged as an important signature for tumor initiation and progression. However, a systematic understanding of its functional impact and relevance to gastric cancer (GC) tumorigenesis is lacking. Differentially expressed AS (DEAS) was verified among GC-associated AS events based on RNA-seq profiles from the TCGA database. Functional enrichment analysis, unsupervised clustering analysis and prognostic models were used to infer the potential roles of DEAS events and their molecular, clinical and immune features. In total, 12,225 AS events were detected from 5,199 genes, among which 314 AS events were identified as DEAS events in GC. The parental genes of the DEAS events were significantly enriched in the regulation of GC-related processes. The splicing correlation network suggested a significant relationship between DEAS events and splicing factors (SFs). Three clusters of DEAS events were identified to be different in prognosis, cancer-specific signatures and immune features between distinct clusters. Univariate and multivariate analyses regarded 3 DEAS events as independent prognostic indicators. Profiling of the AS landscape in GC elucidated the functional roles of the splicing network in GC and might serve as a novel prognostic indicator and therapeutic target.

Molecular Signature of Multisystem Cardiometabolic Stress and Its Association With Prognosis

Importance

Cardiometabolic disease is responsible for decreased longevity and poorer cardiovascular outcomes in the modern era. Metabolite profiling provides a specific measure of global metabolic function to examine specific metabolic mechanisms and pathways of cardiometabolic disease beyond its clinical definitions.

Objectives

To define a molecular basis for cardiometabolic stress and assess its association with cardiovascular prognosis.

Design, Setting, and Participants

A prospective observational cohort study was conducted in a population-based setting across 2 geographically distinct centers (Boston Puerto Rican Health Study [BPRHS], an ongoing study of individuals enrolled between June 1, 2004, and October 31, 2009; and Atherosclerosis Risk in Communities [ARIC] study, whose participants were originally sampled between November 24, 1986, and February 10, 1990, and followed up through December 31, 2017). Participants in the BPRHS were 668 Puerto Rican individuals with metabolite profiling living in Massachusetts, and participants in the ARIC study were 2152 individuals with metabolite profiling and long-term follow-up for mortality and cardiovascular outcomes. Statistical analysis was performed from October 1, 2018, to March 13, 2020.

Exposure

The primary exposure was metabolite profiles across both cohorts.

Main Outcomes and Measures

Outcomes included associations with multisystem cardiometabolic stress and all-cause mortality and incident coronary heart disease (in the ARIC study).

Results

Participants in the BPRHS (N = 668; 491 women; mean [SD] age, 57.0 [7.4] years; mean [SD] body mass index [calculated as weight in kilograms divided by height in meters squared], 32.0 [6.5]) had higher prevalent cardiometabolic risk relative to those in the ARIC study (N = 2152; 599 African American individuals; 1213 women; mean [SD] age, 54.3 [5.7] years; mean [SD] body mass index, 28.0 [5.5]). Multisystem cardiometabolic stress was defined for 668 Puerto Rican individuals in the BPRHS as a multidimensional composite of hypothalamic-adrenal axis activity, sympathetic activation, blood pressure, proatherogenic dyslipidemia, insulin resistance, visceral adiposity, and inflammation. A total of 260 metabolites associated with cardiometabolic stress were identified in the BPRHS, involving known and novel pathways of cardiometabolic disease (eg, amino acid metabolism, oxidative stress, and inflammation). A parsimonious metabolite-based score associated with cardiometabolic stress in the BPRHS was subsequently created; this score was applied to shared metabolites in the ARIC study, demonstrating significant associations with coronary heart disease and all-cause mortality after multivariable adjustment at a 30-year horizon (per SD increase in metabolomic score: hazard ratio, 1.14; 95% CI, 1.00-1.31; P = .045 for coronary heart disease; and hazard ratio, 1.15; 95% CI, 1.07-1.24; P < .001 for all-cause mortality).

Conclusions and Relevance

Metabolites associated with cardiometabolic stress identified known and novel pathways of cardiometabolic disease in high-risk, community-based cohorts and were associated with coronary heart disease and survival at a 30-year time horizon. These results underscore the shared molecular pathophysiology of metabolic dysfunction, cardiovascular disease, and longevity and suggest pathways for modification to improve prognosis across all linked conditions.

Selenium-binding protein 1 alters energy metabolism in prostate cancer cells

OBJECTIVE

The broad goal of the research described in this study was to investigate the contributions of selenium-binding protein 1 (SBP1) loss in prostate cancer development and outcome.

METHODS

SBP1 levels were altered in prostate cancer cell lines and the consequences on oxygen consumption, expression of proteins associated with energy metabolism, and cellular transformation and migration were investigated. The effects of exposing cells to the SBP1 reaction products, H₂ O₂ and H₂ S were also assessed. In silico analyses identified potential HNF4α binding sites within the SBP1 promoter region and this was investigated using an inhibitor specific for that transcription factor.

RESULTS

Using in silico analyses, it was determined that the promoter region of SBP1 contains putative binding sites for the HNF4α transcription factor. The potential for HNF4α to regulate SBP1 expression was supported by data indicating that HNF4α inhibition resulted in a dose-response increase in the levels of SBP1 messenger RNA and protein, identifying HNF4α as a novel negative regulator of SBP1 expression in prostate cancer cells. The consequences of altering the levels of SBP1 were investigated by ectopically expressing SBP1 in PC-3 prostate cancer cells, where SBP1 expression attenuated anchorage-independent cellular growth and migration in culture, both properties associated with transformation. SBP1 overexpression reduced oxygen consumption in these cells and increased the activation of AMP-activated protein kinase (AMPK), a major regulator of energy homeostasis. In addition, the reaction products of SBP1, H₂ O₂ , and H₂ S also activated AMPK.

CONCLUSIONS

Based on the obtained data, it is hypothesized that SBP1 negatively regulates oxidative phosphorylation (OXPHOS) in the healthy prostate cells by the production of H₂ O₂ and H₂ S and consequential activation of AMPK. The reduction of SBP1 levels in prostate cancer can occur due to increased binding of HNF4α, acting as a transcriptional inhibitor to the SBP1 promoter. Consequently, there is a reduction in H₂ O₂ and H₂ S-mediated signaling, inhibition of AMPK, and stimulation of OXPHOS and building blocks of biomolecules needed for tumor growth and progression. Other effects of SBP1 loss in tumor cells remain to be discovered.

Differential endothelial signaling responses elicited by chemogenetic H2O2 synthesis

Hydrogen peroxide (H2O2) modulates critical phosphorylation pathways in vascular endothelial cells, many of which affect endothelial nitric oxide synthase (eNOS) signal transduction. Both intracellular and extracellular sources of H2O2 have been implicated in eNOS regulation, yet the specific endothelial pathways remain incompletely understood. Here we exploited chemogenetic approaches and live-cell imaging methods to both generate and detect H2O2 in different subcellular compartments (cytosol, nucleus, and caveolae) of cultured EA.hy926 human endothelial cells. We developed novel recombinant constructs encoding differentially-targeted yeast d-amino acid oxidase (DAAO), which generates H2O2 only when its d-amino acid substrate is provided. DAAO was expressed as a fusion protein with the new H2O2 biosensor HyPer7.2, which allowed us to quantitate intracellular H2O2 levels by ratiometric imaging in living endothelial cells following the activation of DAAO by d-alanine. The addition of extracellular H2O2 to the HyPer-DAAO-transfected cells led to increases in H2O2 throughout different regions of the cell, as measured using the differentially-targeted HyPer biosensor for H2O2. The sensor response to extracellular H2O2 was more rapid than that quantitated following the addition of d-alanine to transfected cells to activate differentially-targeted DAAO. The maximal intracellular levels of H2O2 observed in response to the addition of extracellular H2O2 vs. intracellular (DAAO-generated) H2O2 were quantitatively similar. Despite these similarities in the measured levels of intracellular H2O2, we observed a remarkable quantitative difference in the activation of endothelial phosphorylation pathways between chemogenetically-generated intracellular H2O2 and the phosphorylation responses elicited by the addition of extracellular H2O2 to the cells. Addition of extracellular H2O2 had only a nominal effect on phosphorylation of eNOS, kinase Akt or AMP-activated protein kinase (AMPK). By contrast, intracellular H2O2 generation by DAAO caused striking increases in the phosphorylation of these same key signaling proteins. We also found that the AMPK inhibitor Compound C completely blocked nuclear H2O2-promoted eNOS phosphorylation. However, Compound C had no effect on eNOS phosphorylation following H2O2 generation from cytosol- or caveolae-targeted DAAO. We conclude that H2O2 generated in the cell nucleus activates AMPK, leading to eNOS phosphorylation; in contrast, AMPK activation by cytosol- or caveolae-derived H2O2 does not promote eNOS phosphorylation via AMPK. These findings indicate that H2O2 generated in different subcellular compartments differentially modulates endothelial cell phosphorylation pathways, and suggest that dynamic subcellular localization of oxidants may modulate signaling responses in endothelial cells.

The MAPK and AMPK signalings: interplay and implication in targeted cancer therapy

Cancer is characterized as a complex disease caused by coordinated alterations of multiple signaling pathways. The Ras/RAF/MEK/ERK (MAPK) signaling is one of the best-defined pathways in cancer biology, and its hyperactivation is responsible for over 40% human cancer cases. To drive carcinogenesis, this signaling promotes cellular overgrowth by turning on proliferative genes, and simultaneously enables cells to overcome metabolic stress by inhibiting AMPK signaling, a key singular node of cellular metabolism. Recent studies have shown that AMPK signaling can also reversibly regulate hyperactive MAPK signaling in cancer cells by phosphorylating its key components, RAF/KSR family kinases, which affects not only carcinogenesis but also the outcomes of targeted cancer therapies against the MAPK signaling. In this review, we will summarize the current proceedings of how MAPK-AMPK signalings interplay with each other in cancer biology, as well as its implications in clinic cancer treatment with MAPK inhibition and AMPK modulators, and discuss the exploitation of combinatory therapies targeting both MAPK and AMPK as a novel therapeutic intervention.

Insight on Transcriptional Regulation of the Energy Sensing AMPK and Biosynthetic mTOR Pathway Genes

The Adenosine Monophosphate-activated Protein Kinase (AMPK) and the Mechanistic Target of Rapamycin (mTOR) are two evolutionarily conserved kinases that together regulate nearly every aspect of cellular and systemic metabolism. These two kinases sense cellular energy and nutrient levels that in turn are determined by environmental nutrient availability. Because AMPK and mTOR are kinases, the large majority of studies remained focused on downstream substrate phosphorylation by these two proteins, and how AMPK and mTOR regulate signaling and metabolism in normal and disease physiology through phosphorylation of their substrates. Compared to the wealth of information known about the signaling and metabolic pathways modulated by these two kinases, much less is known about how the transcription of AMPK and mTOR pathway genes themselves are regulated, and the extent to which AMPK and mTOR regulate gene expression to cause durable changes in phenotype. Acute modification of cellular systems can be achieved through phosphorylation, however, induction of chronic changes requires modulation of gene expression. In this review we will assemble evidence from published studies on transcriptional regulation by AMPK and mTOR and discuss about the putative transcription factors that regulate expression of AMPK and mTOR complex genes.

Protective Effect of Metformin against Hydrogen Peroxide-Induced Oxidative Damage in Human Retinal Pigment Epithelial (RPE) Cells by Enhancing Autophagy through Activation of AMPK Pathway

Age-related macular degeneration (AMD) is a leading cause of blindness with limited effective treatment. Although the pathogenesis of this disease is complex and not fully understood, the oxidative damage caused by excessive reactive oxygen species (ROS) in retinal pigment epithelium (RPE) has been considered as a major cause. Autophagy is essential for the degradation of cellular components damaged by ROS, and its dysregulation has been implicated in AMD pathogenesis. Therefore, strategies aiming to boost autophagy could be effective in protecting RPE cells from oxidative damage. Metformin is the first-line anti-type 2 diabetes drug and has been reported to stimulate autophagy in many tissues. We therefore hypothesized that metformin may be able to protect RPE cells against H₂O₂-induced oxidative damage by autophagy activation. In the present study, we found that metformin attenuated H₂O₂-induced cell viability loss, apoptosis, elevated ROS levels, and the collapse of the mitochondria membrane potential in D407 cells. Autophagy was stimulated by metformin, and inhibition of autophagy by 3-methyladenine (3-MA) and chloroquine (CQ) or knockdown of Beclin1 and LC3B blocked the protective effects of metformin. In addition, we showed that metformin could activate the AMPK pathway, whereas both pharmacological and genetic inhibitions of AMPK blocked the autophagy-stimulating and protective effects of metformin. Metformin conferred a similar protection against H₂O₂-induced oxidative damage in primary cultured human RPE cells. Taken together, these results demonstrate that metformin could protect RPE cells from H₂O₂-induced oxidative damage by stimulating autophagy via the activation of the AMPK pathway, supporting its potential use in the prevention and treatment of AMD.

The Unusual Suspects in Cytokinesis: Fitting the Pieces Together

Cytokinesis is the step of the cell cycle in which the cell must faithfully separate the chromosomes and cytoplasm, yielding two daughter cells. The assembly and contraction of the contractile network is spatially and temporally coupled with the formation of the mitotic spindle to ensure the successful completion of cytokinesis. While decades of studies have elucidated the components of this machinery, the so-called usual suspects, and their functions, many lines of evidence are pointing to other unexpected proteins and sub-cellular systems as also being involved in cytokinesis. These we term the unusual suspects. In this review, we introduce recent discoveries on some of these new unusual suspects and begin to consider how these subcellular systems snap together to help complete the puzzle of cytokinesis.

Spatial control of AMPK signaling at subcellular compartments

AMP-activated protein kinase (AMPK) is a master regulator of energy homeostasis that functions to restore the energy balance by phosphorylating its substrates during altered metabolic conditions. AMPK activity is tightly controlled by diverse regulators including its upstream kinases LKB1 and CaMKK2. Recent studies have also identified the localization of AMPK at different intracellular compartments as another key mechanism for regulating AMPK signaling in response to specific stimuli. This review discusses the AMPK signaling associated with different subcellular compartments, including lysosomes, endoplasmic reticulum, mitochondria, Golgi apparatus, nucleus, and cell junctions. Because altered AMPK signaling is associated with various pathologic conditions including cancer, targeting AMPK signaling in different subcellular compartments may present attractive therapeutic approaches for treatment of disease.

TLR9 in MAFLD and NASH: At the Intersection of Inflammation and Metabolism

Toll-Like Receptor 9 (TLR9) is an ancient receptor integral to the primordial functions of inflammation and metabolism. TLR9 functions to regulate homeostasis in a healthy system under acute stress. The literature supports that overactivation of TLR9 under the chronic stress of obesity is a critical driver of the pathogenesis of NASH and NASH-associated fibrosis. Research has focused on the core contributions of the parenchymal and non-parenchymal cells in the liver, adipose, and gut compartments. TLR9 is activated by endogenous circulating mitochondrial DNA (mtDNA). Chronically elevated circulating levels of mtDNA, caused by the stress of overnutrition, are observed in obesity, metabolic dysfunction-associated fatty liver disease (MAFLD), and NASH. Clinical evidence is supportive of TLR9 overactivation as a driver of disease. The role of TLR9 in metabolism and energy regulation may have an underappreciated contribution in the pathogenesis of NASH. Antagonism of TLR9 in NASH and NASH-associated fibrosis could be an effective therapeutic strategy to target both the inflammatory and metabolic components of such a complex disease.

AMPK Activity Contributes to G2 Arrest and DNA Damage Decrease via p53/p21 Pathways in Oxidatively Damaged Mouse Zygotes

In zygotes, the capacity of G2/M checkpoint and DNA repair mechanisms to respond to DNA damage varies depending on different external stressors. In our previous studies, we found that mild oxidative stress induced a G2/M phase delay in mouse zygotes fertilized in vitro, due to the activation of the spindle assembly checkpoint. However, it is unclear whether the G2/M phase delay involves G2 arrest, triggered by activation of the G2/M checkpoint, and whether AMPK, a highly conserved cellular energy sensor, is involved in G2 arrest and DNA damage repair in mouse zygotes. Here, we found that mouse zygotes treated with 0.03 mM H₂O₂ at 7 h post-insemination (G1 phase), went into G2 arrest in the first cleavage. Furthermore, phosphorylated H2AX, a specific DNA damage and repair marker, can be detected since the early S phase. We also observed that oxidative stress induced phosphorylation and activation of AMPK. Oxidative stress-activated AMPK first localized in the cytoplasm of the mouse zygotes in the late G1 phase and then translocated to the nucleus from the early S phase. Overall, most of the activated AMPK accumulated in the nuclei of mouse zygotes arrested in the G2 phase. Inhibition of AMPK activity with Compound C and SBI-0206965 abolished oxidative stress-induced G2 arrest, increased the activity of CDK1, and decreased the induction of cell cycle regulatory proteins p53 and p21. Moreover, bypassing G2 arrest after AMPK inhibition aggravated oxidative stress-induced DNA damage at M phase, increased the apoptotic rate of blastocysts, and reduced the formation rate of 4-cell embryos and blastocysts. Our results suggest the G2/M checkpoint and DNA repair mechanisms are operative in coping with mild oxidative stress-induced DNA damage. Further, AMPK activation plays a vital role in the regulation of the oxidative stress-induced G2 arrest through the inhibition of CDK1 activity via p53/p21 pathways, thereby facilitating the repair of DNA damage and the development and survival of oxidative stress-damaged embryos. Our study provides insights into the molecular mechanisms underlying oxidative-stress induced embryonic developmental arrest, which is crucial for the development of novel strategies to ensure viable embryo generation.

Artemether Activation of AMPK/GSK3β(ser9)/Nrf2 Signaling Confers Neuroprotection towards β-Amyloid-Induced Neurotoxicity in 3xTg Alzheimer's Mouse Model

Alzheimer's disease is a severe neurodegenerative disease. Multiple factors involving neurofibrillary tangles and amyloid-β plaques lead to the progression of the AD, generated by aggregated hyperphosphorylated Tau protein. Inflammation, mitochondrial dysfunction, and oxidative stress play a significant role in the progression of AD. It has been therefore suggested that the multifactorial nature of AD pathogenesis requires the design of antioxidant drugs with a broad spectrum of neuroprotective activities. For this reason, the use of natural products, characterized by multiple pharmacological properties is advantageous as AD-modifying drugs over the single-targeted chemicals. Artemether, a peroxide sesquiterpenoid lipid-soluble compound, has been used in the clinic as an antimalarial drug. Also, it exhibits potent anti-inflammatory and antioxidant activities. Here, we report the neuroprotective effects of Artemether towards Aβ-induced neurotoxicity in neuronal cell cultures. A temporal correlation was found between Artemether neuroprotection towards Aβ-induced neurotoxicity and AMPK/GSK3β phosphorylation activity and increased expression of the activated Nrf2 signaling pathway. In 3xTg-AD mice, Artemether attenuated learning and memory deficits, inhibited cortical neuronal apoptosis and glial activation, inhibited oxidative stress through decrease of lipid peroxidation and increased expression of SOD, and reduced Aβ deposition and tau protein phosphorylation. Moreover, in 3xTg-AD mice, Artemether induced phosphorylation of the AMPK/GSK3β pathway which activated Nrf2, increasing the level of antioxidant protein HO-1. These activities probably produced the antioxidant and anti-inflammatory effects responsible for the neuroprotective effects of Artemether in the 3xTg-AD mouse model. These findings propose Artemether as a new drug for the treatment of AD disease.

Fluid flow-induced activation of subcellular AMPK and its interaction with FAK and Src

AMP-activated protein kinase (AMPK) is a metabolic energy sensor that plays a critical role in cancer cell survival and growth. While the physical microenvironment is believed to influence tumor growth and progression, its role in AMPK regulation remains largely unknown. In the present study, we evaluated AMPK response to mechanical forces and its interaction with other mechano-responsive signaling proteins, FAK and Src. Using genetically encoded biosensors that can detect AMPK activities at different subcellular locations (cytosol, plasma membrane, nucleus, mitochondria, and Golgi apparatus), we observed that AMPK responds to shear stress in a subcellular location-dependent manner in breast cancer cells (MDA-MB-231). While normal epithelial cells (MCF-10A) also similarly responded to shear stress, they are less sensitive to shear stress compared to MDA-MB-231 cells. Inhibition of FAK and Src significantly decreased the basal activity level of AMPK at all five subcellular locations in MDA-MB-231 cells and selectively blocked shear stress-induced AMPK activation. Moreover, testing with cytoskeletal drugs revealed that myosin II might be the critical mediator of shear stress-induced AMPK activation in MDA-MB-231 cells. These findings suggest that breast cancer cells and normal epithelial cells may have different mechanosensitivity in AMPK signaling and that FAK and Src as well as the myosin II-dependent signaling pathway are involved in subcellular AMPK mechanotransduction in breast cancer cells.

Transcriptional and post-translational activation of AMPKα by oxidative, heat, and cold stresses in the red flour beetle, Tribolium castaneum

The AMP-activated protein kinase (AMPK) has important roles in the regulation of energy metabolism, and AMPK activity and its regulation have been the focus of relevant investigations. However, functional characterization of AMPK is still limited in insects. In this study, the full-length cDNA coding AMPKα (TcAMPKα) was isolated from the red flour beetle, Tribolium castaneum. The TcAMPKα gene contains an ORF of 1581 bp encoding a protein of 526 amino acid residues, which shared conserved domain structure with Drosophila melanogaster and mammalian orthologs. Exposure of female adults to oxidative, heat, and cold stresses caused an increase in TcAMPKα mRNA expression levels and phosphorylation of Thr-173 in the activation loop. The RNAi-mediated knockdown of TcAMPKα resulted in the increased sensitivity of T. castaneum to oxidative, heat, and cold stresses. These results suggest that stress signals regulate TcAMPKα activity, and TcAMPKα plays an important role in enabling protective mechanisms and processes that confer resistance to environmental stress.

Sirtuin4 suppresses the anti-neuroinflammatory activity of infiltrating regulatory T cells in the traumatically injured spinal cord

The neuroinflammation following traumatic spinal cord injury (SCI) is a critical process that impacts both the injury and the recovery of spinal cord parenchyma. Infiltrating regulatory T (Treg) cells are potent anti-inflammatory cells that restrain post-SCI neuroinflammation. To understand the molecular mechanisms underlying the activity of infiltrating Treg cells, we used a mouse spinal cord compression injury model to analyze the role of Sirtuins (SIRTs) in the modulation of infiltrating Treg cell functions. We found that the expressions of SIRT4 and SIRT6 were up-regulated in infiltrating Treg cells. Using lentivirus-mediated gene expression or RNA interference, we revealed that SIRT4 substantially inhibited the expression of Foxp3, interleukin-10, and transforming growth factor-β in Treg cells, whereas SIRT6 had little effect on Treg cells. Consistently, SIRT4 overexpression weakened the suppressive effect of Treg cells on lipopolysaccharide-stimulated spinal cord CD11b⁺ myeloid cells. Knock-down of SIRT4 enhanced the anti-inflammatory activity of infiltrating Treg cells in the parenchyma of injured spinal cords. Additionally, SIRT4 overexpression blocked in vitro Treg cell generation from conventional T cells. Furthermore, SIRT4 down-regulated 5' AMP-activated protein kinase (AMPK) signaling in Treg cells, whereas the AMPK agonist AICAR restored the expression of Foxp3 and interleukin-10 in SIRT4-overexpressing Treg cells. In conclusion, our research unveils a new mechanism by which the post-SCI neuroinflammation is regulated.

Heat Shock Factor 1 Is a Direct Antagonist of AMP-Activated Protein Kinase

Through transcriptional control of the evolutionarily conserved heat shock, or proteotoxic stress, response, heat shock factor 1 (HSF1) preserves proteomic stability. Here, we show that HSF1, a physiological substrate for AMP-activated protein kinase (AMPK), constitutively suppresses this central metabolic sensor. By physically evoking conformational switching of AMPK, HSF1 impairs AMP binding to the γ subunits and enhances the PP2A-mediated de-phosphorylation, but it impedes the LKB1-mediated phosphorylation of Thr172, and retards ATP binding to the catalytic α subunits. These immediate and manifold regulations empower HSF1 to both repress AMPK under basal conditions and restrain its activation by diverse stimuli, thereby promoting lipogenesis, cholesterol synthesis, and protein cholesteroylation. In vivo, HSF1 antagonizes AMPK to control body fat mass and drive the lipogenic phenotype and growth of melanomas independently of its intrinsic transcriptional action. Thus, the physical AMPK-HSF1 interaction epitomizes a reciprocal kinase-substrate regulation whereby lipid metabolism and proteomic stability intertwine.

Mechanotransduction of mitochondrial AMPK and its distinct role in flow-induced breast cancer cell migration

The biophysical microenvironment of the tumor site has significant impact on breast cancer progression and metastasis. The importance of altered mechanotransduction in cancerous tissue has been documented, yet its role in the regulation of cellular metabolism and the potential link between cellular energy and cell migration remain poorly understood. In this study, we investigated the role of mechanotransduction in AMP-activated protein kinase (AMPK) activation in breast cancer cells in response to interstitial fluid flow (IFF). Additionally, we explored the involvement of AMPK in breast cancer cell migration. IFF was applied to the 3D cell-matrix construct. The subcellular signaling activity of Src, FAK, and AMPK was visualized in real-time using fluorescent resonance energy transfer (FRET). We observed that breast cancer cells (MDA-MB-231) are more sensitive to IFF than normal epithelial cells (MCF-10A). AMPK was activated at the mitochondria of MDA-MB-231 cells by IFF, but not in other subcellular compartments (i.e., cytosol, plasma membrane, and nucleus). The inhibition of FAK or Src abolished flow-induced AMPK activation in the mitochondria of MDA-MB-231 cells. We also observed that global AMPK activation reduced MDA-MB-231 cell migration. Interestingly, specific AMPK inhibition in the mitochondria reduced cell migration and blocked flow-induced cell migration. Our results suggest the linkage of FAK/Src and mitochondria-specific AMPK in mechanotransduction and the differential role of AMPK in breast cancer cell migration depending on its subcellular compartment-specific activation.

Inhibition of soluble epoxide hydrolase attenuates a high-fat diet-mediated renal injury by activating PAX2 and AMPK

A high-fat diet (HFD) causes obesity-associated morbidities involved in macroautophagy and chaperone-mediated autophagy (CMA). AMPK, the mediator of macroautophage, has been reported to be inactivated in HFD-caused renal injury. However, PAX2, the mediator for CMA, has not been reported in HFD-caused renal injury. Here we report that HFD-caused renal injury involved the inactivation of Pax2 and Ampk, and the activation of soluble epoxide hydrolase (sEH), in a murine model. Specifically, mice fed on an HFD for 2, 4, and 8 wk showed time-dependent renal injury, the significant decrease in renal Pax2 and Ampk at both mRNA and protein levels, and a significant increase in renal sEH at mRNA, protein, and molecular levels. Also, administration of an sEH inhibitor, 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl)urea, significantly attenuated the HFD-caused renal injury, decreased renal sEH consistently at mRNA and protein levels, modified the renal levels of sEH-mediated epoxyeicosatrienoic acids (EETs) and dihydroxyeicosatrienoic acids (DHETs) as expected, and increased renal Pax2 and Ampk at mRNA and/or protein levels. Furthermore, palmitic acid (PA) treatment caused significant increase in Mcp-1, and decrease in both Pax2 and Ampk in murine renal mesangial cells (mRMCs) time- and dose-dependently. Also, 14(15)-EET (a major substrate of sEH), but not its sEH-mediated metabolite 14,15-DHET, significantly reversed PA-induced increase in Mcp-1, and PA-induced decrease in Pax2 and Ampk. In addition, plasmid construction revealed that Pax2 may positively regulate Ampk transcriptionally in mRMCs. This study provides insights into and therapeutic target for the HFD-mediated renal injury.

Cellular senescence is associated with reorganization of the microtubule cytoskeleton

Senescent cells undergo structural and functional changes that affect essentially every aspect of cell physiology. To date, the impact of senescence on the cytoskeleton is poorly understood. This study evaluated the cytoskeleton in two independent cellular models of kidney epithelium senescence. Our work identified multiple senescence-related alterations that impact microtubules and filamentous actin during interphase. Both filamentous systems reorganized profoundly when cells became senescent. As such, microtubule stability increased during senescence, making these filaments more resistant to disassembly in the cold or by nocodazole. Microtubule stabilization was accompanied by enhanced α-tubulin acetylation on lysine 40 and the depletion of HDAC6, the major deacetylase for α-tubulin lysine 40. Rho-associated kinase Rock1 is an upstream regulator that modulates key properties of the cytoplasmic cytoskeleton. Our research shows that Rock1 concentrations were reduced significantly in senescent cells, and we revealed a mechanistic link between microtubule stabilization and Rock1 depletion. Thus, Rock1 overexpression partially restored the cold sensitivity of microtubules in cells undergoing senescence. Additional components relevant to microtubules were affected by senescence. Specifically, we uncovered the senescence-related loss of the microtubule nucleating protein γ-tubulin and aberrant formation of γ-tubulin foci. Concomitant with the alterations of microtubule and actin filaments, senescent cells displayed functional changes. In particular, cell migration was impaired significantly in senescent cells. Taken together, our study identified new senescence-associated deficiencies of the microtubule and actin cytoskeleton, provided insights into the underlying molecular mechanisms and demonstrated functional consequences that are important to the physiology and function of renal epithelial cells.

Stomatin-like protein-2 relieve myocardial ischemia/reperfusion injury by adenosine 5'-monophosphate-activated protein kinase signal pathway

Previous studies have shown that stomatin-like protein-2 (SLP-2) could regulate mitochondrial biogenesis and function. The study was designed to explore the contribution of SLP-2 to the myocardial ischemia and reperfusion (I/R) injury. Anesthetized rats were treated with SLP-2 and subjected to ischemia for 30 minutes before 3 hours of reperfusion. An oxygen-glucose deprivation/reoxygenation model of I/R was established in H9C2 cells. In vivo, SLP-2 significantly improved cardiac function recovery of myocardial I/R injury rats by increasing fractional shortening and ejection fraction. SLP-2 pretreatment alleviated infarct area and myocardial apoptosis, which was paralleled by decreasing the level of cleaved caspase-3 and the ratio of Bax/Bcl-2, increasing the content of superoxide dismutase and reducing oxidative stress damage in serum. In addition, SLP-2 increased the level of ATP and stabilized mitochondrial potential (Ψm). The present in vitro study revealed that overexpression with SLP-2 reduced H9C2 cells apoptosis, accompanied by an increased level of ATP, the ratio of mitochondrial DNA/nuclear DNA, activities of complex II and V, and decreased the production of mitochondrial reactive oxygen species. Simultaneously, SLP-2 activated the adenosine 5'-monophosphate-activated protein kinase (AMPK) signaling pathway in myocardial I/R injury rats and H9C2 cells. This study revealed that SLP-2 mediates the cardioprotective effect against I/R injury by regulating AMPK signaling pathway.

Constitutive androstane receptor 1 is constitutively bound to chromatin and 'primed' for transactivation in hepatocytes

The constitutive androstane receptor (CAR) is a xenobiotic sensor expressed in hepatocytes that activates genes involved in drug metabolism, lipid homeostasis, and cell proliferation. Much progress has been made in understanding the mechanism of activation of human CAR by drugs and xenobiotics. However, many aspects of the activation pathway remain to be elucidated. In this report, we have used viral constructs to express human CAR, its splice variants, and mutant CAR forms in hepatocytes from Car-/- mice in vitro and in vivo. We demonstrate CAR expression rescued the ability of Car-/- hepatocytes to respond to a wide range of CAR activators including phenobarbital. Additionally, two major splice isoforms of human CAR, CAR2 and CAR3, were inactive with almost all the agents tested. In contrast to the current model of CAR activation, ectopic CAR1 is constitutively localized in the nucleus and is loaded onto Cyp2b10 gene in the absence of an inducing agent. In studies to elucidate the role of threonine T38 in CAR regulation, we found that the T38D mutant was inactive even in the presence of CAR activators. However, the T38A mutant was activated by CAR inducers, showing that T38 is not essential for CAR activation. Also, using the inhibitor erlotinib, we could not confirm a role for the epidermal growth factor receptor in CAR regulation. Our data suggest that CAR is constitutively bound to gene regulatory regions and is regulated by exogenous agents through a mechanism which involves protein phosphorylation in the nucleus.

Heat exposure affects jejunal tight junction remodeling independently of adenosine monophosphate-activated protein kinase in 9-day-old broiler chicks

Dysfunction of the intestinal epithelial barrier under elevated temperatures is assumed to prompt pathological conditions and to eventually impede chickens' growth, resulting in massive economic losses in broiler industries. The aims of this research were to determine the impact of acute heat stress on the intestinal tight junction network of broiler chicks (Gallus domesticus L.) and to elucidate whether adenosine monophosphate-activated protein kinase (AMPK) was involved in the integrated response of the broiler's gastrointestinal tract to heat stress. A total of 80 9-day-old Arbor Acres chicks were subjected to temperature treatment (thermoneutral versus heat stress) and AMPK inhibition treatment (5 mg/kg body weight intraperitoneal injection of compound C vs. sham treatment) for 72 h. In addition to monitoring growth performance, the mRNA and protein levels of key tight junction proteins, target components of the AMPK pathway, and biomarkers of intestinal inflammation and oxidative stress were assessed in the jejunum under both stressors at 24 and 72 h. An increase of the major tight junction proteins, claudin-1 and zonula occludens-1, was implemented in response to an exacerbated expression of the AMP-activated protein kinase. Heat stress did not affect zootechnical performance but was confirmed by an increased gene expression of heat shock proteins 70 and 90 as well as heat shock factor-1. In addition, hyperthermia induced significant effects on tight junction proteins, although it was independent of AMPK.

Defining the short-term effects of pharmacological 5'-AMP activated kinase modulators on mitochondrial polarization, morphology and heterogeneity

Background

Under aerobic growth conditions, mitochondria are the major producers of cellular ATP and crucial for the proper performance of organs and tissues. This applies especially to cells with high energy demand, such as the renal proximal tubule epithelium. Mitochondrial dysfunction contributes to the pathology of human health conditions, including various kidney diseases. The improvement of mitochondrial function ameliorates some of these pathologies. This can potentially be achieved with pharmacological compounds. For example, long-term treatment with activators of 5'-AMP activated kinase (AMPK) enhances mitochondrial biogenesis. However, pharmacological damage control during acute cell injury requires that the short-term effects of these compounds and the impact on healthy cells are also understood. It was our objective to define the changes elicited by established modulators of AMPK activity in healthy renal proximal tubule cells.

Methods

Our work combines confocal microscopy with quantitative image analysis, 3D image reconstruction and Western blotting to provide novel insights into the biology of mitochondria. Specifically, we evaluated the effects of pharmacological AMPK modulators (compound C, AICAR, phenformin, resveratrol) on mitochondrial polarization, morphology and heterogeneity. Microscopic studies generated information at the single cell and subcellular levels. Our research focused on LLC-PK1 cells that are derived from the renal proximal tubule. Mitochondrial heterogeneity was also examined in MCF7 breast cancer cells.

Results

Pharmacological agents that affect AMPK activity in renal proximal tubule cells can alter mitochondrial organization and the electrochemical potential across the inner mitochondrial membrane. These changes were compound-specific. Short-term incubation with the AMPK inhibitor compound C caused mitochondrial hyperpolarization. This was accompanied by mitochondrial fragmentation. By contrast, AMPK activators AICAR, phenformin and resveratrol had little impact. We further show that the biological properties of mitochondria are determined by their subcellular location. Mitochondria at the cell periphery displayed higher MitoTracker/Tom70 values as compared to organelles located in the vicinity of the nucleus. This was not limited to renal proximal tubule cells, but also observed in MCF7 cells. Pharmacological AMPK modulators altered these location-dependent properties in a compound-specific fashion. While the region-dependent differences were enhanced with phenformin, they were ameliorated by resveratrol.

Discussion

We evaluated the rapid changes in mitochondrial characteristics that are induced by pharmacological AMPK modulators. Our research supports the concept that pharmacological agents that target AMPK can rearrange mitochondrial networks at the single cell level. Collectively, these insights are relevant to the development of proper strategies for the short-term adjustment of mitochondrial performance.

The effects of lanthanide-doped upconverting nanoparticles on cancer cell biomarkers

Lanthanide-doped upconverting nanoparticles (Ln-UCNPs) possess optical and physicochemical properties that are promising for the design of new theranostic platforms. This applies in particular to the treatment of cancer. Towards this goal, oleate-capped-NaLuF4:Tm3+(0.5%)/Yb3+(20%)/Gd3+(30%) with an average size of 35 nm ± 2 nm were synthesized by co-precipitation. Due to their hydrophobic surface, these Ln-UCNPs produced agglomerates under cell culture conditions. To assess the cellular response to Ln-UCNPs at the molecular level, we evaluated several key aspects of tumor cell physiology. Using cancer lines of different origins, we demonstrated Ln-UCNP dependent changes of cancer cell biomarkers. Multiple cellular components that regulate tumorigenesis and cancer cell homeostasis were affected. In particular, Ln-UCNPs reduced the abundance of hsp70s, elevated DNA damage, and diminished nucleolin and B23/nucleophosmin, proteins required for the assembly of ribosomes. Treatment with Ln-UCNPs also decreased the concentration of paxillin, a focal adhesion protein that is involved in directed cell migration. Furthermore, epidermal growth factor (EGFR) levels were decreased by Ln-UCNPs for most cancer cell lines examined. Taken together, we identified several potential cancer cell targets that were affected by Ln-UCNPs. Our work thereby provides the foundation to optimize Ln-UCNPs for the targeted killing of tumor cells.