Mitochondria-derived ROS activate AMP-activated protein kinase (AMPK) indirectly

Salidroside pretreatment alleviates ferroptosis induced by myocardial ischemia/reperfusion through mitochondrial superoxide-dependent AMPKα2 activation

BACKGROUND

Ferroptosis, a form of regulated cell death (RCD) that relies on excessive reactive oxygen species (ROS) generation, Fe2+accumulation, abnormal lipid metabolism and is involved in various organ ischemia/reperfusion (I/R) injury, expecially in myocardium. Mitochondria are the powerhouses of eukaryotic cells and essential in regulating multiple RCD. However, the links between mitochondria and ferroptosis are still poorly understood. Salidroside (Sal), a natural phenylpropanoid glycoside isolated from Rhodiola rosea, has mult-bioactivities. However, the effects and mechanism in alleviating ferroptosis caused by myocardial I/R injury remains unclear.

PURPOSE

This study aimed to investigate whether pretreated with Sal could protect the myocardium against I/R damage and the underlying mechanisms. In particular, the relationship between Sal pretreatment, AMPKα2 activity, mitochondria and ROS generation was explored.

STUDY DESIGN AND METHODS

Firstly, A/R or I/R injury models were employed in H9c2 cells and Sprague-Dawley rats. And then the anti-ferroptotic effects and mechanism of Sal pretreatment was detected using multi-relevant indexes in H9c2 cells. Further, how does Sal pretreatment in AMPKα2 phosphorylation was explored. Finally, these results were validated by I/R injury in rats.

RESULTS

Similar to Ferrostatin-1 (a ferroptosis inhibitor) and MitoTEMPO, a mitochondrial free radical scavenger, Sal pretreatment effectively alleviated Fe2+ accumulation, redox disequilibrium and maintained mitochondrial energy production and function in I/R-induced myocardial injury, as demonstrated using multifunctional, enzymatic, and morphological indices. However, these effects were abolished by downregulation of AMPKα2 using an adenovirus, both in vivo and in vitro. Moreover, the results also provided a non-canonical mechanism that, under mild mitochondrial ROS generation, Sal pretreatment upregulated and phosphorylated AMPKα2, which enhanced mitochondrial complex I activity to activate innate adaptive responses and increase cellular tolerance to A/R injury.

CONCLUSION

Overall, our work highlighted mitochondria are of great impotance in myocardial I/R-induced ferroptosis and demonstrated that Sal pretreatment activated AMPKα2 against I/R injury, indicating that Sal could become a candidate phytochemical for the treatment of myocardial I/R injury.

Potential role of molecular hydrogen therapy on oxidative stress and redox signaling in chronic kidney disease

Oxidative stress plays a key role in chronic kidney disease (CKD) development and progression, inducing kidney cell damage, inflammation, and fibrosis. However, effective therapeutic interventions to slow down CKD advancement are currently lacking. The multifaceted pharmacological effects of molecular hydrogen (H2) have made it a promising therapeutic avenue. H2 is capable of capturing harmful •OH and ONOO- while maintaining the crucial reactive oxygen species (ROS) involved in cellular signaling. The NRF2-KEAP1 system, which manages cell redox balance, could be used to treat CKD. H2 activates this pathway, fortifying antioxidant defenses and scavenging ROS to counteract oxidative stress. H2 can improve NRF2 signaling by using the Wnt/β-catenin pathway and indirectly activate NRF2-KEAP1 in mitochondria. Additionally, H2 modulates NF-κB activity by regulating cellular redox status, inhibiting MAPK pathways, and maintaining Trx levels. Treatment with H2 also attenuates HIF signaling by neutralizing ROS while indirectly bolstering HIF-1α function. Furthermore, H2 affects FOXO factors and enhances the activity of antioxidant enzymes. Despite the encouraging results of bench studies, clinical trials are still limited and require further investigation. The focus of this review is on hydrogen's role in treating renal diseases, with a specific focus on oxidative stress and redox signaling regulation, and it discusses its potential clinical applications.

Elevating the significance of legume intake: A novel strategy to counter aging-related mitochondrial dysfunction and physical decline

Mitochondrial dysfunction increasingly becomes a target for promoting healthy aging and longevity. The dysfunction of mitochondria with age ultimately leads to a decline in physical functions. Among them, biogenesis dysfunction and the imbalances in the metabolism of reactive oxygen species and mitochondria as signaling organelles in the aging process have aroused our attention. Dietary intervention in mitochondrial dysfunction and physical decline during aging processes is essential, and greater attention should be directed toward healthful legume intake. Legumes are constantly under investigation for their nutritional and bioactive properties, and their consumption may yield antiaging and mitochondria-protecting benefits. This review summarizes mitochondrial dysfunction with age, discusses the benefits of legumes on mitochondrial function, and introduces the potential role of legumes in managing aging-related physical decline. Additionally, it reveals the benefits of legume intake for the elderly and offers a viable approach to developing legume-based functional food.

Emerging mechanisms in the redox regulation of mitochondrial cytochrome c oxidase assembly and function

In eukaryotic cells, mitochondria perform cellular respiration through a series of redox reactions ultimately reducing molecular oxygen to water. The system responsible for this process is the respiratory chain or electron transport system (ETS) composed of complexes I-IV. Due to its function, the ETS is the main source of reactive oxygen species (ROS), generating them on both sides of the mitochondrial inner membrane, i.e. the intermembrane space (IMS) and the matrix. A correct balance between ROS generation and scavenging is important for keeping the cellular redox homeostasis and other important aspects of cellular physiology. However, ROS generated in the mitochondria are important signaling molecules regulating mitochondrial biogenesis and function. The IMS contains a large number of redox sensing proteins, containing specific Cys-rich domains, that are involved in ETS complex biogenesis. The large majority of these proteins function as cytochrome c oxidase (COX) assembly factors, mainly for the handling of copper ions necessary for the formation of the redox reactive catalytic centers. A particular case of ROS-regulated COX assembly factor is COA8, whose intramitochondrial levels are increased by oxidative stress, promoting COX assembly and/or protecting the enzyme from oxidative damage. In this review, we will discuss the current knowledge concerning the role played by ROS in regulating mitochondrial activity and biogenesis, focusing on the COX enzyme and with a special emphasis on the functional role exerted by the redox sensitive Cys residues contained in the COX assembly factors.

Hypoxia, hypoxia-inducible factors and inflammatory bowel diseases

Adequate oxygen supply is essential for maintaining the body's normal physiological function. In chronic inflammatory conditions such as inflammatory bowel disease (IBD), insufficient oxygen reaching the intestine triggers the regulatory system in response to environmental changes. However, the pathogenesis of IBD is still under investigation. Recent research has highlighted the significant role of hypoxia in IBD, particularly the involvement of hypoxia-inducible factors (HIF) and their regulatory mechanisms, making them promising therapeutic targets for IBD. This review will delve into the role of hypoxia, HIF, and the associated hypoxia-inflammatory microenvironment in the context of IBD. Potential interventions for addressing these challenging gastrointestinal inflammatory diseases will also be discussed within this framework.

Reactive oxygen species generation required for autophagy induction during butyrate- or propionate-induced release of damage-associated molecular patterns from dying gingival epithelial Ca9-22 cells

PURPOSE

Bacterial cells in mature dental plaque produce a high concentration of short-chain fatty acids (SCFAs) such as butyrate and propionate. SCFA-treatment on human gingival epithelial Ca9-22 cells induced cell death. However, the exact mechanism underlying cell death remains unclear. In this study, the relationship between reactive oxygen species (ROS) and autophagy induction during SCFA-induced cell death was examined.

METHODS

Human gingival epithelial Ca9-22 cells were treated with butyrate or propionate to induce cell death and the number of dead cells were measured using SYTOX-green dye. A siRNA for ATG5 and N-acetylcysteine (NAC) were used for autophagy reduction and ROS-scavenging, respectively. Release of damage-associated molecular patterns (DAMPs) such as Sin3A-associated protein 130 (SAP130) and high-mobility group box 1 (HMGB1) were detected using western blot.

RESULTS

Reducing autophagy significantly suppressed SCFA-induced Ca9-22 cell death. ROS generation was observed upon SCFA treatment, and scavenging ROS with NAC decreased cell death. NAC also reduced the SCFA-induced increase in microtubule-associated protein 1 light chain 3B (LC3B)-I and LC3B-II, and mitigated the release of DAMPs.

CONCLUSION

The findings suggest that ROS generation is necessary for autophagy, which is required for SCFA-induced cell death and accompanying DAMP release.

Redox Regulation of Brain Selective Kinases BRSK1/2: Implications for Dynamic Control of the Eukaryotic AMPK family through Cys-based mechanisms

In eukaryotes, protein kinase signaling is regulated by a diverse array of post-translational modifications (PTMs), including phosphorylation of Ser/Thr residues and oxidation of cysteine (Cys) residues. While regulation by activation segment phosphorylation of Ser/Thr residues is well understood, relatively little is known about how oxidation of cysteine residues modulate catalysis. In this study, we investigate redox regulation of the AMPK-related Brain-selective kinases (BRSK) 1 and 2, and detail how broad catalytic activity is directly regulated through reversible oxidation and reduction of evolutionarily conserved Cys residues within the catalytic domain. We show that redox-dependent control of BRSKs is a dynamic and multilayered process involving oxidative modifications of several Cys residues, including the formation of intramolecular disulfide bonds involving a pair of Cys residues near the catalytic HRD motif and a highly conserved T-Loop Cys with a BRSK-specific Cys within an unusual CPE motif at the end of the activation segment. Consistently, mutation of the CPE-Cys increases catalytic activity in vitro and drives phosphorylation of the BRSK substrate Tau in cells. Molecular modeling and molecular dynamics simulations indicate that oxidation of the CPE-Cys destabilizes a conserved salt bridge network critical for allosteric activation. The occurrence of spatially proximal Cys amino acids in diverse Ser/Thr protein kinase families suggests that disulfide mediated control of catalytic activity may be a prevalent mechanism for regulation within the broader AMPK family.

Targeting autophagy with natural products as a potential therapeutic approach for diabetic microangiopathy

As the quality of life improves, the incidence of diabetes mellitus and its microvascular complications (DMC) continues to increase, posing a threat to people's health and wellbeing. Given the limitations of existing treatment, there is an urgent need for novel approaches to prevent and treat DMC. Autophagy, a pivotal mechanism governing metabolic regulation in organisms, facilitates the removal of dysfunctional proteins and organelles, thereby sustaining cellular homeostasis and energy generation. Anomalous states in pancreatic β-cells, podocytes, Müller cells, cardiomyocytes, and Schwann cells in DMC are closely linked to autophagic dysregulation. Natural products have the property of being multi-targeted and can affect autophagy and hence DMC progression in terms of nutrient perception, oxidative stress, endoplasmic reticulum stress, inflammation, and apoptosis. This review consolidates recent advancements in understanding DMC pathogenesis via autophagy and proposes novel perspectives on treating DMC by either stimulating or inhibiting autophagy using natural products.

AMPK-SP1-Guided Dynein Expression Represents a New Energy-Responsive Mechanism and Therapeutic Target for Diabetic Nephropathy

Key Points

AMP kinase senses diabetic stresses in podocytes, subsequently upregulates specificity protein 1–mediated dynein expression and promotes podocyte injury. Pharmaceutical restoration of dynein expression by targeting specificity protein 1 represents an innovative therapeutic strategy for diabetic nephropathy.

Background

Diabetic nephropathy (DN) is a major complication of diabetes. Injury to podocytes, epithelial cells that form the molecular sieve of a kidney, is a preclinical feature of DN. Protein trafficking mediated by dynein, a motor protein complex, is a newly recognized pathophysiology of diabetic podocytopathy and is believed to be derived from the hyperglycemia-induced expression of subunits crucial for the transportation activity of the dynein complex. However, the mechanism underlying this transcriptional signature remains unknown.

Methods

Through promoter analysis, we identified binding sites for transcription factor specificity protein 1 (SP1) as the most shared motif among hyperglycemia-responsive dynein genes. We demonstrated the essential role of AMP-activated protein kinase (AMPK)–regulated SP1 in the transcription of dynein subunits and dynein-mediated trafficking in diabetic podocytopathy using chromatin immunoprecipitation quantitative PCR and live cell imaging. SP1-dependent dynein-driven pathogenesis of diabetic podocytopathy was demonstrated by pharmaceutical intervention with SP1 in a mouse model of streptozotocin-induced diabetes.

Results

Hyperglycemic conditions enhance SP1 binding to dynein promoters, promoted dynein expression, and enhanced dynein-mediated mistrafficking in cultured podocytes. These changes can be rescued by chemical inhibition or genetic silencing of SP1. The direct repression of AMPK, an energy sensor, replicates hyperglycemia-induced dynein expression by activating SP1. Mithramycin inhibition of SP1-directed dynein expression in streptozotocin-induced diabetic mice protected them from developing podocytopathy and prevented DN progression.

Conclusions

Our work implicates AMPK-SP1–regulated dynein expression as an early mechanism that translates energy disturbances in diabetes into podocyte dysfunction. Pharmaceutical restoration of dynein expression by targeting SP1 offers a new therapeutic strategy to prevent DN.

Hydrogen ameliorates endotoxin-induced acute lung injury through AMPK-mediated bidirectional regulation of Caspase3

Septic lung injury is characterized by uncontrollable inflammatory infiltrations and acute onset bilateral hypoxemia. Evidence has emerged of the beneficial effect of hydrogen in acute lung injury (ALI), but the underlying mechanism is unclear. In this research, the recovery action of hydrogen on lipopolysaccharide (LPS)-induced ALI in mice and A549 cells was investigated. The 7-day survival rate and body weight of mice were measured after intraperitoneal injection of LPS. Lung function was determined by a whole body plethysmography (WBP) system using the indicators respiratory rate and enhanced pause. Hematoxylin and eosin (HE) staining confirmed the signs of pulmonary edema and inflammatory ooze. Reverse transcription-polymerase chain reaction (RT-PCR) quantification was used to detect the expression of inflammatory factors. Western blotting analysis evaluated the expression levels of involved proteins in the AMP-activated protein kinase (AMPK) pathway. The experimental results confirmed that hydrogen provided an essential solution to the dissipative effects of LPS on survival rate, weight loss and lung function. The LPS-stimulated inflammatory factors, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were also suppressed by hydrogen in A549 cells. Western blot analysis showed that hydrogen significantly upregulated the levels of phosphorylated AMPK (p-AMPK) and lowered the LPS-induced increased expression of dynamin-related protein 1 (Drp1) and Caspase3. These findings prove that hydrogen attenuated LPS-treated ALI by activating the AMPK pathway, supporting the feasibility of hydrogen treatment for sepsis.

Are reactive oxygen species always bad? Lessons from hypoxic ectotherms

Oxygen (O2) is required for aerobic energy metabolism but can produce reactive oxygen species (ROS), which are a wide variety of oxidant molecules with a range of biological functions from causing cell damage (oxidative distress) to cell signalling (oxidative eustress). The balance between the rate and amount of ROS generated and the capacity for scavenging systems to remove them is affected by several biological and environmental factors, including oxygen availability. Ectotherms, and in particular hypoxia-tolerant ectotherms, are hypothesized to avoid oxidative damage caused by hypoxia, although it is unclear whether this translates to an increase in ecological fitness. In this Review, we highlight the differences between oxidative distress and eustress, the current mechanistic understanding of the two and how they may affect ectothermic physiology. We discuss the evidence of occurrence of oxidative damage with hypoxia in ectotherms, and that ectotherms may avoid oxidative damage through (1) high levels of antioxidant and scavenging systems and/or (2) low(ering) levels of ROS generation. We argue that the disagreements in the literature as to how hypoxia affects antioxidant enzyme activity and the variable metabolism of ectotherms makes the latter strategy more amenable to ectotherm physiology. Finally, we argue that observed changes in ROS production and oxidative status with hypoxia may be a signalling mechanism and an adaptive strategy for ectotherms encountering hypoxia.

Novel naphthoquinone-1H-1,2,3-triazole hybrids: Design, synthesis and evaluation as inductors of ROS-mediated apoptosis in the MCF-7 cells

The search for novel anticancer drugs is essential to expand treatment options, overcome drug resistance, reduce toxicity, promote innovation, and tackle the economic impact. The importance of these studies lies in their contribution to advancing cancer research and enhancing patient outcomes in the battle against cancer. Here, we developed new asymmetric hybrids containing two different naphthoquinones linked by a 1,2,3-1H-triazole nucleus, which are potential new drugs for cancer treatment. The antitumor activity of the novel compounds was tested using the breast cancer cell lines MCF-7 and MDA-MB-231, using the non-cancer cell line MCF10A as control. Our results showed that two out of twenty-two substances tested presented potential antitumor activity against the breast cancer cell lines. These potential drugs, named here 12g and 12h were effective in reducing cell viability and promoting cell death of the tumor cell lines, exhibiting minimal effects on the control cell line. The mechanism of action of the novel drugs was assessed revealing that both drugs increased reactive oxygen species production with consequent activation of the AMPK pathway. Therefore, we concluded that 12g and 12h are novel AMPK activators presenting selective antitumor effects.

NOX4 alleviates breast cancer cell aggressiveness by co-ordinating mitochondrial turnover through PGC1α/Drp1 axis

Triple Negative Breast Cancer (TNBC) is a highly aggressive form of breast cancer, with few treatment options. This study investigates the complex molecular mechanism by which NADPH oxidase 4 (NOX4), a major ROS producer in mitochondria, affects the aggressiveness of luminal and triple-negative breast cancer cells (TNBCs). We found that NOX4 expression was differentially regulated in luminal and TNBC cells, with a positive correlation to their epithelial characteristics. Time dependent analysis revealed that TNBCs exhibits higher steady-state ROS levels than luminal cells, but NOX4 silencing increased ROS levels in luminal breast cancer cells and enhanced their ability to migrate and invade. In contrast, NOX4 over expression in TNBCs had the opposite effect. The mouse tail-vein experiment showed that the group injected with NOX4 silenced luminal cells had a higher number of lung metastases compared to the control group. Mechanistically, NOX4 enhanced PGC1α dependent mitochondrial biogenesis and attenuated Drp1-mediated mitochondrial fission in luminal breast cancer cells, leading to an increased mitochondrial mass and elongated mitochondrial morphology. Interestingly, NOX4 silencing increased mitochondrial ROS (mtROS) levels without affecting mitochondrial (Δψm) and cellular integrity. Inhibition of Drp1-dependent fission with Mdivi1 reversed the effect of NOX4-dependent mitochondrial biogenesis, dynamics, and migration of breast cancer cells. Our findings suggest that NOX4 expression diminishes from luminal to a triple negative state, accompanied by elevated ROS levels, which may modulate mitochondrial turnover to attain an aggressive phenotype. The study provides potential insights for targeted therapies for TNBCs.

Mitochondrial involvement in sarcopenia

Sarcopenia lowers the quality-of-life for millions of people across the world, as accelerated loss of skeletal muscle mass and function contributes to both age- and disease-related frailty. Physical activity remains the only proven therapy for sarcopenia to date, but alternatives are much sought after to manage this progressive muscle disorder in individuals who are unable to exercise. Mitochondria have been widely implicated in the etiology of sarcopenia and are increasingly suggested as attractive therapeutic targets to help restore the perturbed balance between protein synthesis and breakdown that underpins skeletal muscle atrophy. Reviewing current literature, we note that mitochondrial bioenergetic changes in sarcopenia are generally interpreted as intrinsic dysfunction that renders muscle cells incapable of making sufficient ATP to fuel protein synthesis. Based on the reported mitochondrial effects of therapeutic interventions, however, we argue that the observed bioenergetic changes may instead reflect an adaptation to pathologically decreased energy expenditure in sarcopenic muscle. Discrimination between these mechanistic possibilities will be crucial for improving the management of sarcopenia.

The skin photoprotective effect of trilinolein: Induction of cellular autophagy via the AMPK-mTOR signaling pathway

Trilinolein (TL) is an active substance contained in traditional Chinese herbs; modern studies have shown that trilinolein has anti-inflammatory and antioxidant effects on the body. This study delves into the photoprotective effect of trilinolein on UVB-irradiated Human Skin Fibroblast (HSF) cells and the underlying mechanisms. Our findings reveal that trilinolein had a photoprotective effect on HSF cells: trilinolein enhanced cellular autophagy, restored UVB-inhibited cell proliferative viability, and curbing UVB-induced reactive oxygen species (ROS) and apoptosis. Intriguingly, after inhibition of TL-induced autophagy via wortmannin, diminished trilinolein's photoprotective effects. Meanwhile, trilinolein was shown to modulate the AMPK-mTOR signaling pathway, thus enhance cellular autophagy in HSF cells, and this tendency was suppressed after the administration of compound C (AMPK inhibitor). In a mouse model of skin photodamage, trilinolein significantly mitigated photodamage extent through morphological and histopathological analyses. This study illuminates trilinolein could inhibit the photodamaging effects of UVB irradiation by regulating cellular autophagy through the AMPK-mTOR signaling pathway, suggesting its promising application in combating UV-induced skin disorders.

Combined inhibition of pyruvate dehydrogenase kinase 1 and hexokinase 2 induces apoptsis in non-small cell lung cancer cell models

Many cancer cells exhibit enhanced glycolysis, which is seen as one of the hallmark metabolic alterations, known as Warburg effect. Substantial evidence shows that upregulated glycolytic enzymes are often linked to malignant growth. Using glycolytic inhibitors for anticancer treatment has become appealing in recent years for therapeutic intervention in cancers with highly glycolytic characteristic, including non-small cell lung cancer (NSCLC). In this work, we studied the anticancer effects and the underlying mechanisms of combination of benzerazide hydrocholoride (Benz), a hexokinase 2 (HK2) inhibitor and 64, a pyruvate dehydrogenase kinase 1 (PDK1) inhibitor, in several NSCLC cell lines. We found that combination of Benz and 64 exhibited strong synergistic anticancer effects in NCI-H1975, HCC827, NCI-H1299 and SK-LU-1 cell lines. With this combination treatment, we observed changes of certain mechanistic determinants associated with metabolic stress caused by glycolysis restriction, such as mitochondrial membrane potential depolarization, overproduction of reactive oxygen species [1], activation of AMPK and down-regulation of mTOR, which contributed to enhanced apoptosis. Moreover, Benz and 64 together significantly suppressed the tumor growth in HCC827 cell mouse xenograft model. Taken together, our study may suggest that combined inhibition of HK2 and PDK1 using Benz and 64 could be a viable anticancer strategy for NSCLC.

From workout to molecular switches: How does skeletal muscle produce, sense, and transduce subcellular redox signals?

Skeletal muscle is crucial for maintaining human health and overall quality of life. Acute exercise introduces a multifaceted intracellular stress, with numerous post-translational modifications believed to underpin the health benefits of sustained exercise training. Reactive oxygen species (ROS) are posited to serve as second messengers, triggering cytoprotective adaptations such as the upregulation of enzymatic scavenger systems. However, a significant knowledge gap exists between the generation of oxidants in muscle and the exact mechanisms driving muscle adaptations. This review delves into the current research on subcellular redox biochemistry and its role in the physiological adaptations to exercise. We propose that the subcellular regulation of specific redox modifications is key to ensuring specificity in the intracellular response.

CLPX regulates mitochondrial fatty acid β-oxidation in liver cells

Mitochondrial fatty acid oxidation (β-oxidation) is an essential metabolic process for energy production in eukaryotic cells, but the regulatory mechanisms of this pathway are largely unknown. In the present study, we found that several enzymes involved in β-oxidation are associated with CLPX, the AAA+ unfoldase that is a component of the mitochondrial matrix protease ClpXP. The suppression of CLPX expression increased β-oxidation activity in the HepG2 cell line and in primary human hepatocytes without glucagon treatment. However, the protein levels of enzymes involved in β-oxidation did not significantly increase in CLPX-deleted HepG2 cells (CLPX-KO cells). Coimmunoprecipitation experiments revealed that the protein level in the immunoprecipitates of each antibody changed after the treatment of WT cells with glucagon, and a part of these changes was also observed in the comparison of WT and CLPX-KO cells without glucagon treatment. Although the exogenous expression of WT or ATP-hydrolysis mutant CLPX suppressed β-oxidation activity in CLPX-KO cells, glucagon treatment induced β-oxidation activity only in CLPX-KO cells expressing WT CLPX. These results suggest that the dissociation of CLPX from its target proteins is essential for the induction of β-oxidation in HepG2 cells. Moreover, specific phosphorylation of AMP-activated protein kinase and a decrease in the expression of acetyl-CoA carboxylase 2 were observed in CLPX-KO cells, suggesting that CLPX might participate in the regulation of the cytosolic signaling pathway for β-oxidation. The mechanism for AMP-activated protein kinase phosphorylation remains elusive; however, our results uncovered the hitherto unknown role of CLPX in mitochondrial β-oxidation in human liver cells.

Hypoxanthine phosphoribosyl transferase 1 metabolizes temozolomide to activate AMPK for driving chemoresistance of glioblastomas

Temozolomide (TMZ) is a standard treatment for glioblastoma (GBM) patients. However, TMZ has moderate therapeutic effects due to chemoresistance of GBM cells through less clarified mechanisms. Here, we demonstrate that TMZ-derived 5-aminoimidazole-4-carboxamide (AICA) is converted to AICA ribosyl-5-phosphate (AICAR) in GBM cells. This conversion is catalyzed by hypoxanthine phosphoribosyl transferase 1 (HPRT1), which is highly expressed in human GBMs. As the bona fide activator of AMP-activated protein kinase (AMPK), TMZ-derived AICAR activates AMPK to phosphorylate threonine 52 (T52) of RRM1, the catalytic subunit of ribonucleotide reductase (RNR), leading to RNR activation and increased production of dNTPs to fuel the repairment of TMZ-induced-DNA damage. RRM1 T52A expression, genetic interruption of HPRT1-mediated AICAR production, or administration of 6-mercaptopurine (6-MP), a clinically approved inhibitor of HPRT1, blocks TMZ-induced AMPK activation and sensitizes brain tumor cells to TMZ treatment in mice. In addition, HPRT1 expression levels are positively correlated with poor prognosis in GBM patients who received TMZ treatment. These results uncover a critical bifunctional role of TMZ in GBM treatment that leads to chemoresistance. Our findings underscore the potential of combined administration of clinically available 6-MP to overcome TMZ chemoresistance and improve GBM treatment.

A systematic review and meta-analysis of the SIRT1 response to exercise

Sirtuin 1 (SIRT1) is a key physiological regulator of metabolism and a target of therapeutic interventions for cardiometabolic and ageing-related disorders. Determining the factors and possible mechanisms of acute and adaptive SIRT1 response to exercise is essential for optimising exercise interventions aligned to the prevention and onset of disease. Exercise-induced SIRT1 upregulation has been reported in animals, but, to date, data in humans have been inconsistent. This exploratory systematic review and meta-analysis aims to assess various exercise interventions measuring SIRT1 in healthy participants. A total of 34 studies were included in the meta-analysis (13 single bout exercise, 21 training interventions). Studies were grouped according to tissue sample type (blood, muscle), biomarkers (gene expression, protein content, enzyme level, enzyme activity), and exercise protocols. A single bout of high-intensity or fasted exercise per se increases skeletal muscle SIRT1 gene expression as measured by qPCR or RT-PCR, while repeated resistance training alone increases blood SIRT1 levels measured by ELISA. A limited number of studies also show a propensity for an increase in muscle SIRT1 activity as measured by fluorometric or sirtuin activity assay. In conclusion, exercise acutely upregulates muscle SIRT1 gene expression and chronically increases SIRT1 blood enzyme levels.

Targeting redox regulation and autophagy systems in cancer stem cells

Cancer is a dysregulated cellular level pathological condition that results in tumor formation followed by metastasis. In the heterogeneous tumor architecture, cancer stem cells (CSCs) are essential to push forward the progression of tumors due to their strong pro-tumor properties such as stemness, self-renewal, plasticity, metastasis, and being poorly responsive to radiotherapy and chemotherapeutic agents. Cancer stem cells have the ability to withstand various stress pressures by modulating transcriptional and translational mechanisms, and adaptable metabolic changes. Owing to CSCs heterogeneity and plasticity, these cells display varied metabolic and redox profiles across different types of cancers. It has been established that there is a disparity in the levels of Reactive Oxygen Species (ROS) generated in CSCs vs Non-CSC and these differential levels are detected across different tumors. CSCs have unique metabolic demands and are known to change plasticity during metastasis by passing through the interchangeable epithelial and mesenchymal-like phenotypes. During the metastatic process, tumor cells undergo epithelial to mesenchymal transition (EMT) thus attaining invasive properties while leaving the primary tumor site, similarly during the course of circulation and extravasation at a distant organ, these cells regain their epithelial characteristics through Mesenchymal to Epithelial Transition (MET) to initiate micrometastasis. It has been evidenced that levels of Reactive Oxygen Species (ROS) and associated metabolic activities vary between the epithelial and mesenchymal states of CSCs. Similarly, the levels of oxidative and metabolic states were observed to get altered in CSCs post-drug treatments. As oxidative and metabolic changes guide the onset of autophagy in cells, its role in self-renewal, quiescence, proliferation and response to drug treatment is well established. This review will highlight the molecular mechanisms useful for expanding therapeutic strategies based on modulating redox regulation and autophagy activation to targets. Specifically, we will account for the mounting data that focus on the role of ROS generated by different metabolic pathways and autophagy regulation in eradicating stem-like cells hereafter referred to as cancer stem cells (CSCs).

Research progress of AMP-activated protein kinase and cardiac aging

The process of aging is marked by a gradual deterioration in the physiological functions and functional reserves of various tissues and organs, leading to an increased susceptibility to diseases and even death. Aging manifests in a tissue- and organ-specific manner, and is characterized by varying rates and direct and indirect interactions among different tissues and organs. Cardiovascular disease (CVD) is the leading cause of death globally, with older adults (aged >70 years) accounting for approximately two-thirds of CVD-related deaths. The prevalence of CVD increases exponentially with an individual's age. Aging is a critical independent risk factor for the development of CVD. AMP-activated protein kinase (AMPK) activation exerts cardioprotective effects in the heart and restores cellular metabolic functions by modulating gene expression and regulating protein levels through its interaction with multiple target proteins. Additionally, AMPK enhances mitochondrial function and cellular energy status by facilitating the utilization of energy substrates. This review focuses on the role of AMPK in the process of cardiac aging and maintaining normal metabolic levels and redox homeostasis in the heart, particularly in the presence of oxidative stress and the invasion of inflammatory factors.

Cellular heterogeneity and plasticity during NAFLD progression

Nonalcoholic fatty liver disease (NAFLD) is a progressive liver disease that can progress to nonalcoholic steatohepatitis (NASH), NASH-related cirrhosis, and hepatocellular carcinoma (HCC). NAFLD ranges from simple steatosis (or nonalcoholic fatty liver [NAFL]) to NASH as a progressive form of NAFL, which is characterized by steatosis, lobular inflammation, and hepatocellular ballooning with or without fibrosis. Because of the complex pathophysiological mechanism and the heterogeneity of NAFLD, including its wide spectrum of clinical and histological characteristics, no specific therapeutic drugs have been approved for NAFLD. The heterogeneity of NAFLD is closely associated with cellular plasticity, which describes the ability of cells to acquire new identities or change their phenotypes in response to environmental stimuli. The liver consists of parenchymal cells including hepatocytes and cholangiocytes and nonparenchymal cells including Kupffer cells, hepatic stellate cells, and endothelial cells, all of which have specialized functions. This heterogeneous cell population has cellular plasticity to adapt to environmental changes. During NAFLD progression, these cells can exert diverse and complex responses at multiple levels following exposure to a variety of stimuli, including fatty acids, inflammation, and oxidative stress. Therefore, this review provides insights into NAFLD heterogeneity by addressing the cellular plasticity and metabolic adaptation of hepatocytes, cholangiocytes, hepatic stellate cells, and Kupffer cells during NAFLD progression.

Sexual Dimorphism in Cardiometabolic Diseases: The Role of AMPK

Cardiovascular diseases (CVDs) are the leading cause of mortality and disability among both males and females. The risk of cardiovascular diseases is heightened by the presence of a risk factor cluster of metabolic syndrome, covering obesity and obesity-related cardiometabolic risk factors such as hypertension, glucose, and lipid metabolism dysregulation primarily. Sex hormones contribute to metabolic regulation and make women and men susceptible to obesity development in a different manner, which necessitates sex-specific management. Identifying crucial factors that protect the cardiovascular system is essential to enhance primary and secondary prevention of cardiovascular diseases and should be explicitly studied from the perspective of sex differences. It seems that AMP-dependent protein kinase (AMPK) may be such a factor since it has the protective role of AMPK in the cardiovascular system, has anti-diabetic properties, and is regulated by sex hormones. Those findings highlight the potential cardiometabolic benefits of AMPK, making it an essential factor to consider. Here, we review information about the cross-talk between AMPK and sex hormones as a critical point in cardiometabolic disease development and progression and a target for therapeutic intervention in human disease.

Lower dose of metformin combined with artesunate induced autophagy-dependent apoptosis of glioblastoma by activating ROS-AMPK-mTOR axis

Glioblastoma multiform (GBM), one of the most common, aggressive primary brain tumours, demonstrates resistance to radiotherapy and chemotherapy after surgical resection and treatment failure. Metformin (MET) has been shown to suppress the proliferative capacity and invasion ability of GBM cells by activating AMPK and inhibiting mTOR, but the effective dose exceeded the maximum tolerated dose. Artesunate (ART) can exert certain anti-tumour effects by activating the AMPK-mTOR axis and inducing autophagy in tumour cells. Therefore, this study investigated the effects of MET combined with ART combination therapy on autophagy and apoptosis in GBM cells. MET combined with ART treatment effectively suppressed the viability, mono-cloning ability, migration and invasion capacities, as well as metastatic ability of GBM cells. The underlying mechanism involved modulation of the ROS-AMPK-mTOR axis, which was confirmed using 3-methyladenine and rapamycin to inhibit or promote the effects of MET combined with ART, respectively. The study findings suggest that MET used in combination with ART can induce autophagy-dependent apoptosis in GBM cells by activating the ROS-AMPK-mTOR pathway, providing a potential new treatment for GBM.

Energetic Stress-Induced Metabolic Regulation by Extracellular Vesicles

Recent studies have demonstrated that extracellular vesicles (EVs) serve powerful and complex functions in metabolic regulation and metabolic-associated disease, although this field of research is still in its infancy. EVs are released into the extracellular space from all cells and carry a wide range of cargo including miRNAs, mRNA, DNA, proteins, and metabolites that have robust signaling effects in receiving cells. EV production is stimulated by all major stress pathways and, as such, has a role in both restoring homeostasis during stress and perpetuating disease. In metabolic regulation, the dominant stress signal is a lack of energy due to either nutrient deficits or damaged mitochondria from nutrient excess. This stress signal is termed "energetic stress," which triggers a robust and evolutionarily conserved response that engages major cellular stress pathways, the ER unfolded protein response, the hypoxia response, the antioxidant response, and autophagy. This article proposes the model that energetic stress is the dominant stimulator of EV release with a focus on metabolically important cells such as hepatocytes, adipocytes, myocytes, and pancreatic β-cells. Furthermore, this article will discuss how the cargo in stress-stimulated EVs regulates metabolism in receiving cells in both beneficial and detrimental ways. © 2023 American Physiological Society. Compr Physiol 13:5051-5068, 2023.

The bridge between cell survival and cell death: reactive oxygen species-mediated cellular stress

As a requirement of aerobic metabolism, regulation of redox homeostasis is indispensable for the continuity of living homeostasis and life. Since the stability of the redox state is necessary for the maintenance of the biological functions of the cells, the balance between the pro-oxidants, especially ROS and the antioxidant capacity is kept in balance in the cells through antioxidant defense systems. The pleiotropic transcription factor, Nrf2, is the master regulator of the antioxidant defense system. Disruption of redox homeostasis leads to oxidative and reductive stress, bringing about multiple pathophysiological conditions. Oxidative stress characterized by high ROS levels causes oxidative damage to biomolecules and cell death, while reductive stress characterized by low ROS levels disrupt physiological cell functions. The fact that ROS, which were initially attributed as harmful products of aerobic metabolism, at the same time function as signal molecules at non-toxic levels and play a role in the adaptive response called mithormesis points out that ROS have a dose-dependent effect on cell fate determination. See also Figure 1(Fig. 1).

Anti-Neuroinflammatory Effects of the Human Milk Oligosaccharide, 2'-Fucosyllactose, Exerted via Modulation of M2 Microglial Activation in a Mouse Model of Ischemia-Reperfusion Injury

Cerebral ischemic stroke is one of the leading causes of death and disability worldwide. 2'-fucosyllactose (2'-FL), a human milk oligosaccharide, exerts anti-inflammatory effects and plays a protective role in arterial thrombosis; however, its role in ischemic stroke remains unclear. This study aimed to investigate the neuroprotective effects of 2'-FL and its potential mechanisms in a mouse model of ischemic stroke. Neurological score and behavior tests revealed that 2'-FL promoted the recovery of neurological deficits and motor function in middle cerebral artery occlusion (MCAO) mice, and that 2'FL led to a reduction in the size of cerebral infarct. Biochemical studies showed that administration of 2'-FL led to a reduction of reactive oxygen species (ROS)-related products in the brain of MCAO mice. 2'-FL upregulated IL-10 and downregulated TNF-α level. In addition, 2'-FL enhanced M2-type microglial polarization and upregulated CD206 expression at 7 days after MCAO. At 3 days after MCAO, 2'-FL increased IL-4 levels and activated STAT6. Our data show that 2'-FL reduced the neurological symptoms of ischemic stroke and ROS accumulation in the brain through IL-4/STAT6-dependent M2-type microglial polarization in MCAO mice. These results demonstrate that 2'-FL is a potentially effective therapeutic agent for ischemic stroke.

Targeting Oxidative Stress with Polyphenols to Fight Liver Diseases

Reactive oxygen species (ROS) are important second messengers in many metabolic processes and signaling pathways. Disruption of the balance between ROS generation and antioxidant defenses results in the overproduction of ROS and subsequent oxidative damage to biomolecules and cellular components that disturb cellular function. Oxidative stress contributes to the initiation and progression of many liver pathologies such as ischemia-reperfusion injury (LIRI), non-alcoholic fatty liver disease (NAFLD), and hepatocellular carcinoma (HCC). Therefore, controlling ROS production is an attractive therapeutic strategy in relation to their treatment. In recent years, increasing evidence has supported the therapeutic effects of polyphenols on liver injury via the regulation of ROS levels. In the current review, we summarize the effects of polyphenols, such as quercetin, resveratrol, and curcumin, on oxidative damage during conditions that induce liver injury, such as LIRI, NAFLD, and HCC.

Neurotrophic effects of intermittent fasting, calorie restriction and exercise: a review and annotated bibliography

In the last decades, important progress has been achieved in the understanding of the neurotrophic effects of intermittent fasting (IF), calorie restriction (CR) and exercise. Improved neuroprotection, synaptic plasticity and adult neurogenesis (NSPAN) are essential examples of these neurotrophic effects. The importance in this respect of the metabolic switch from glucose to ketone bodies as cellular fuel has been highlighted. More recently, calorie restriction mimetics (CRMs; resveratrol and other polyphenols in particular) have been investigated thoroughly in relation to NSPAN. In the narrative review sections of this manuscript, recent findings on these essential functions are synthesized and the most important molecules involved are presented. The most researched signaling pathways (PI3K, Akt, mTOR, AMPK, GSK3β, ULK, MAPK, PGC-1α, NF-κB, sirtuins, Notch, Sonic hedgehog and Wnt) and processes (e.g., anti-inflammation, autophagy, apoptosis) that support or thwart neuroprotection, synaptic plasticity and neurogenesis are then briefly presented. This provides an accessible entry point to the literature. In the annotated bibliography section of this contribution, brief summaries are provided of about 30 literature reviews relating to the neurotrophic effects of interest in relation to IF, CR, CRMs and exercise. Most of the selected reviews address these essential functions from the perspective of healthier aging (sometimes discussing epigenetic factors) and the reduction of the risk for neurodegenerative diseases (Alzheimer's disease, Huntington's disease, Parkinson's disease) and depression or the improvement of cognitive function.

AMP-activated protein kinase: An energy sensor and survival mechanism in the reinstatement of metabolic homeostasis

Cells are programmed to favorably respond towards the nutrient availability by adapting their metabolism to meet energy demands. AMP-activated protein kinase (AMPK) is a highly conserved serine/threonine energy-sensing kinase. It gets activated upon a decrease in the cellular energy status as reflected by an increased AMP/ATP ratio, ADP, and also during the conditions of glucose starvation without change in the adenine nucelotide ratio. AMPK functions as a centralized regulator of metabolism, acting at cellular and physiological levels to circumvent the metabolic stress by restoring energy balance. This review intricately highlights the integrated signaling pathways by which AMPK gets activated allosterically or by multiple non-canonical upstream kinases. AMPK activates the ATP generating processes (e.g., fatty acid oxidation) and inhibits the ATP consuming processes that are non-critical for survival (e.g., cell proliferation, protein and triglyceride synthesis). An integrated signaling network with AMPK as the central effector regulates all the aspects of enhanced stress resistance, qualified cellular housekeeping, and energy metabolic homeostasis. Importantly, the AMPK mediated amelioration of cellular stress and inflammatory responses are mediated by stimulation of transcription factors such as Nrf2, SIRT1, FoxO and inhibition of NF-κB serving as main downstream effectors. Moreover, many lines of evidence have demonstrated that AMPK controls autophagy through mTOR and ULK1 signaling to fine-tune the metabolic pathways in response to different cellular signals. This review also highlights the critical involvement of AMPK in promoting mitochondrial health, and homeostasis, including mitophagy. Loss of AMPK or ULK1 activity leads to aberrant accumulation of autophagy-related proteins and defective mitophagy thus, connecting cellular energy sensing to autophagy and mitophagy.

Tubulin Post-Translational Modifications: The Elusive Roles of Acetylation

Microtubules (MTs), dynamic polymers of α/β-tubulin heterodimers found in all eukaryotes, are involved in cytoplasm spatial organization, intracellular transport, cell polarity, migration and division, and in cilia biology. MTs functional diversity depends on the differential expression of distinct tubulin isotypes and is amplified by a vast number of different post-translational modifications (PTMs). The addition/removal of PTMs to α- or β-tubulins is catalyzed by specific enzymes and allows combinatory patterns largely enriching the distinct biochemical and biophysical properties of MTs, creating a code read by distinct proteins, including microtubule-associated proteins (MAPs), which allow cellular responses. This review is focused on tubulin-acetylation, whose cellular roles continue to generate debate. We travel through the experimental data pointing to α-tubulin Lys40 acetylation role as being a MT stabilizer and a typical PTM of long lived MTs, to the most recent data, suggesting that Lys40 acetylation enhances MT flexibility and alters the mechanical properties of MTs, preventing MTs from mechanical aging characterized by structural damage. Additionally, we discuss the regulation of tubulin acetyltransferases/desacetylases and their impacts on cell physiology. Finally, we analyze how changes in MT acetylation levels have been found to be a general response to stress and how they are associated with several human pathologies.

Targeting mitochondria as a potential therapeutic strategy against chemoresistance in cancer

The importance of mitochondria is not only limited to energy generation but also in several physical and chemical processes critical for cell survival. Mitochondria play an essential role in cellular apoptosis, calcium ion transport and cellular metabolism. Mutation in the nuclear and mitochondrial genes, altered oncogenes/tumor suppressor genes, and deregulated signalling for cell viability are major reasons for cancer progression and chemoresistance. The development of drug resistance in cancer patients is a major challenge in cancer treatment as the resistant cells are often more aggressive. The drug resistant cells of numerous cancer types exhibit the deregulation of mitochondrial function. The increased biogenesis of mitochondria and its dynamic alteration contribute to developing resistance. Further, a small subpopulation of cancer stem cells in the heterogeneous tumor is primarily responsible for chemoresistance and has an attribute of mitochondrial dysfunction. This review highlights the critical role of mitochondrial dysfunction in chemoresistance in cancer cells through the processes of apoptosis, autophagy/mitophagy, and cancer stemness. Mitochondria-targeted therapeutic strategies might help reduce cancer progression and chemoresistance induced by various cancer drugs.

Antioxidants and Oxidants in Boar Spermatozoa and Their Surrounding Environment Are Associated with AMPK Activation during Liquid Storage

Activation of the AMP-activated protein kinase (AMPK) has been demonstrated to be beneficial for boar sperm quality and functionality, while the underlying mechanism of AMPK activation of boar spermatozoa remains obscure. This study aimed to explore the effect of antioxidants and oxidants in boar spermatozoa and their surrounding fluid (SF) on the activation of AMPK during the liquid storage. Ejaculates from Duroc boars, routinely used for semen production, were collected and diluted to a final concentration of 25 × 106/mL. In experiment 1, twenty-five semen samples from eighteen boars were stored at 17 °C for 7 days. In experiment 2, three pooled semen samples created from nine ejaculates of nine boars were used, and each sample was treated with 0, 0.1, 0.2, and 0.4 μM/L H2O2 and stored at 17 °C for 3 h. Sperm quality and functionality, antioxidants and oxidants in boar spermatozoa and SF, the intracellular AMP/ATP ratio, and the expression levels of the phosphorylated AMPK (Thr172) were determined. Sperm quality significantly decreased with storage time in terms of viability (p < 0.05). Antioxidant and oxidant levels were markedly affected with storage time, with a decline in the SF total antioxidant capacity (TAC) (p < 0.05), SF malondialdehyde (MDA) (p < 0.05), and the sperm’s total oxidant status (TOS), as well as a fluctuation in sperm superoxidase dismutase-like (SOD-like) activity (p < 0.05). The intracellular AMP/ATP ratio increased (p < 0.05) on day 4 and subsequently decreased to its lowest value on days 6 and 7 (p < 0.05). The phosphorylated AMPK levels increased from day 2 to day 7 (p < 0.05). Correlation analyses indicate that sperm quality during liquid storage was correlated to antioxidants and oxidants in spermatozoa and SF (p < 0.05), which were correlated to the phosphorylation of sperm AMPK (p < 0.05). Treatment with H2O2 induced damages in sperm quality (p < 0.05), a decline in antioxidant levels (SF TAC, p < 0.05; sperm SOD-like activity, p < 0.01), an increase in oxidant levels (SF MDA, p < 0.05; intracellular ROS production, p < 0.05), a higher AMP/ATP ratio (p < 0.05), and phosphorylated AMPK levels (p < 0.05) in comparison with the control. The results suggest that antioxidants and oxidants in boar spermatozoa and SF are involved in AMPK activation during liquid storage.

Anticancer Activity and Molecular Mechanisms of an Ursodeoxycholic Acid Methyl Ester-Dihydroartemisinin Hybrid via a Triazole Linkage in Hepatocellular Carcinoma Cells

Hepatocellular carcinoma is the third most common cause of cancer-related death according to the International Agency for Research on Cancer. Dihydroartemisinin (DHA), an antimalarial drug, has been reported to exhibit anticancer activity but with a short half-life. We synthesized a series of bile acid-dihydroartemisinin hybrids to improve its stability and anticancer activity and demonstrated that an ursodeoxycholic-DHA (UDC-DHA) hybrid was 10-fold more potent than DHA against HepG2 hepatocellular carcinoma cells. The objectives of this study were to evaluate the anticancer activity and investigate the molecular mechanisms of UDCMe-Z-DHA, a hybrid of ursodeoxycholic acid methyl ester and DHA via a triazole linkage. We found that UDCMe-Z-DHA was even more potent than UDC-DHA in HepG2 cells with IC₅₀ of 1 μM. Time course experiments and stability in medium determined by cell viability assay as well as HPLC-MS/MS analysis revealed that UDCMe-Z-DHA was more stable than DHA, which in part accounted for the increased anticancer activity. Mechanistic studies revealed that UDCMe-Z-DHA caused G0/G1 arrest and induced reactive oxygen species (ROS), mitochondrial membrane potential loss and autophagy, which may in turn lead to apoptosis. Compared to DHA, UDCMe-Z-DHA displayed much lower cytotoxicity toward normal cells. Thus, UDCMe-Z-DHA may be a potential drug candidate for hepatocellular carcinoma.

Malignant growth of arsenic-transformed cells depends on activated Akt induced by reactive oxygen species

Arsenic is an identified carcinogen for humans.In this study, chronic exposure of human hepatocyte L-02 to low-doses of inorganic arsenic caused cell malignant proliferation. Meanwhile, compared with normal L-02 cells, arsenic-transformed malignant cells, L-02-As displayed more ROS and significantly higher Cyclin D1 expression as well as aerobic glycolysis. Moreover, Akt activation is followed by the upregulation of Cyclin D1 and HK2 expression in L-02-As cells, since inhibition of Akt activity by Ly294002 attenuated the colony formation in soft agar and decreased the levels of Cyclin D1 and HK2. In addition, scavenging of ROS by NAC resulted in a decreased expression of phospho-Akt, HK2 and Cyclin D1, and attenuates the ability of anchorage-independent growth ofL-02-As cells, suggested that ROS mediated the Akt activation in L-02-As cells. In summary, our results demonstrated that ROS contributes to the malignant phenotype of arsenic-transformed human hepatocyte L-02-As via the activation of Akt pathway.

Differential expression of glucose metabolism-related genes and AMP-activated protein kinases in crop tissue of male and female pigeons (Columba livia domestica) during the incubation and chick-rearing periods

The objective of this study was to explore the carbohydrate contents of crop milk, insulin and glucose concentrations in serum and the expression patterns of AMP-activated protein kinases (AMPKs) and genes related to glucose metabolism in pigeon crops during the breeding period. Crop milk was collected from squabs of rearing Day 1 (R1) to R6. Contents of total sugar and reducing sugar increased to the maximum levels at R6 (p < 0.05). Forty-two pairs of adult pigeons were allotted to seven groups by different breeding stages, and their crops and serum were sampled. No significant differences were found in either insulin or glucose levels in serum. The glucose transporter 2 gene level was the greatest at R15 in females, whereas it was at R7 in males. However, sodium-dependent glucose transporters 1 expression in both sexes decreased from incubation Day 17 (I17) to R7. In females, glucokinase expression peaked at R1, and at R1 and R7 in males. Pyruvate kinase mRNA levels peaked at R7 in females and at R15 males. The mRNA abundance of fructose-1,6-bisphosphatase 1 in both sexes and glucose-6-phosphatase in females decreased after I10. While phosphoenolpyruvate carboxykinase 1 expression decreased after I17 (p < 0.05). Protein levels of AMPKα in crops were minimized at R1 (p < 0.05). In females, expression of AMPKα1 and AMPKα2 was inhibited at I17 and R1 (p < 0.05). In males, AMPKα1 expression was decreased at R7 (p < 0.05) and AMPKα2 was reduced at I10 and R1. pAMPK expression was the lowest at I17 in females, and it was at R7 and R25 in males. Conclusively, glycolysis in pigeon crops was enhanced during chick-rearing, while gluconeogenesis was significantly inhibited. The stability of the insulin level suggests that it was probably not involved in the regulation of glucose metabolism in crop tissues.

2,3,7,8-Tetrachlorodibenzo-p-dioxin induces liver lipid metabolism disorder via the ROS/AMPK/CD36 signaling pathway

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is widely considered as the most toxic and common carcinogen in the world. Exposure to TCDD causes liver lipid metabolism disorder and steatosis. However, the molecular mechanism of TCDD-induced liver lipid accumulation is not completely clear. Here, we found that a 5 μg/kg TCDD exposure for 3 weeks induced hepatocyte lipid deposition, increased CD36 expression, and promoted AMP-activated protein kinase (AMPK) ɑ phosphorylation in the liver of C57BL/6J mice. Furthermore, sulfo-N-succinimidyl oleate, a CD36 inhibiter, blunted TCDD-induced lipid deposition in Huh7 cells, confirming the critical role of CD36 in TCDD-induced hepatic steatosis. In terms of molecular mechanisms, we found that TCDD exposure increased reactive oxygen species (ROS) levels in Huh7 cells, which activated AMPK. Moreover, the activated AMPK upregulated CD36 expression. Therefore, we can see that the increase in CD36 expression induced by TCDD was regulated by ROS/AMPK/CD36 signaling pathway. Our results help to clarify the molecular mechanism of TCDD-induced hepatic steatosis.

Rationed and satiated growth hormone transgenic Coho Salmon (Oncorhynchus kisutch) show tissue specific differences in energy stores

Growth hormone transgenic coho salmon experience increased growth rates, driven primarily through elevated feed intake and feed conversion. However, neuropeptides that signal appetite stimulation have been shown to exhibit variable responses across fed states, suggesting a more complex system mediating growth in these fish. Studies have proposed that growth hormone may have a modulatory role on the energy reserves of fish, possibly through AMP-activated protein kinase (AMPK) activation. AMPK, an energy sensor in cells, has previously been shown to be upregulated in growth hormone transgenic salmon when compared to wild type, however, whether this effect is seen across fed states is unknown. Here, we tested the hypothesis that growth hormone induces an energetic deficit in metabolic tissues, leading to constitutive AMPK activation in growth hormone transgenic salmon. This study compared AMPK activity, ATP, and glycogen, of the liver, heart, and muscle of wild-type, and growth hormone transgenic salmon either fed to satiation or a wild-type ration. The results suggest that white muscle ATP levels in growth hormone salmon are elevated in satiation and rationed conditions. In the liver, growth hormone transgenic salmon fed a rationed wild-type diet experience reductions in ATP level and glycogen. In none of the tissues examined, did AMPK activity change. Taken together, these results indicate that growth hormone transgenic salmon experience metabolic duress when not fed to satiation.

Quercetin protects mouse oocytes against chromium-induced damage in vitro and in vivo

BACKGROUND

Chromium (Cr) is a naturally-occurring element that is used in various fields of industry. Humans may be exposed to hexavalent chromium [Cr(VI)], which is one of the stable valence states of the chromium through contaminated soil, air, and water. Exposure to Cr(VI) through contaminated drinking water, soil and air causes various cancers and also fertility problems in animals and humans. Quercetin (QCT), a common flavonoid compound, has numerous biological effects as an antioxidant and free radical scavenger, but its function and mechanisms in reproductive processes in various species remain unclear. This study aims to determine the chromium effects on mice oocyte quality and the ameliorative effect of QCT in both in vitro and in vivo experimental models.

METHODS

For the in vitro experiment, oocytes were collected and divided into the control, sham, QCT-treated, Cr(VI) (potassium dichromate), and treatment [Cr(VI)+QCT] groups. Collected oocytes were cultured in maturation medium with or without 10 µM quercetin and 10 µM Cr(VI) for 14 h based on the defined experimental design. For the in vivo experiment, the mice were randomly divided into the control, sham, QCT-treated, Cr(VI), and Cr(VI) + QCT groups. Control and sham mice received regular drinking water and diet. Cr(VI) group received Cr(VI) (50 ppm in drinking water) and Cr(VI) + QCT group received 50 ppm Cr(VI) with QCT (20 mg/kg body wt, through i.p) for a period of 21 days and then oocytes were collected and cultured for 14 h for in vitro maturation. For both experiments, at the end of the culture period, we examined the ameliorative effect of QCT on oocyte maturation, spindle formation, ROS production, mitochondrial function, and apoptosis.

RESULTS

Our in vitro and in vivo results showed that Cr(VI) disrupt the oocyte maturation and spindle formation (P < 0.001). Furthermore, we found that exposure to Cr(VI) significantly increased ROS levels and decreased mitochondrial membrane potential (P < 0.001). In addition, exposure to Cr(VI) induced early apoptosis and downregulated the Bcl-2 mRNA expression and upregulated the Caspase-3 and Bax mRNAs expression (P < 0.01). Finally, quercetin significantly restored the detrimental effects of Cr(VI).

CONCLUSION

The results indicated that quercetin protects the oocytes against Cr(VI) toxicity through the suppression of oxidative stress and apoptosis. The conclusions drawn from our study's findings suggest that quercetin might be useful agent for oocyte maturation in case of possible exposure to toxic substances such as chromium.

More than Just Antioxidants: Redox-Active Components and Mechanisms Shaping Redox Signalling Network

The concept of oxidative stress as a condition underlying a multitude of human diseases has led to immense interest in the search for antioxidant-based remedies. The simple and intuitive story of "the bad" reactive oxygen species (ROS) and "the good" antioxidants quickly (and unsurprisingly) lead to the commercial success of products tagged "beneficial to health" based solely on the presence of antioxidants. The commercial success of antioxidants by far preceded the research aimed at understanding the exact redox-related mechanisms that are in control of shaping the states of health and disease. This review describes the redox network formed by the interplay of ROS with cellular molecules and the resulting regulation of processes at the genomic and proteomic levels. Key players of this network are presented, both involved in redox signalling and control of cellular metabolism linked to most, if not all, physiological processes. In particular, this review focuses on the concept of reductive stress, which still remains less well-established compared to oxidative stress.

Hepatoprotective effect of botanical drug formula on high-fat diet-induced non-alcoholic fatty liver disease by inhibiting lipogenesis and promoting anti-oxidation

With the prevalence of obesity and other components of metabolic syndrome, Non-alcoholic fatty liver disease (NAFLD) has become increasingly common. In recent years, much attention has been paid to various plant sources, hoping to find a treatment for NAFLD in plants. The Livsooth authentic herbal formula (LAH, ), a botanical drug formula combined with Puerariae lobatae radix, Lonicerae japonicae flos, Hoveniae semen, and Siraitiae fructus. This study used a network pharmacology approach to predict the potential mechanisms of LAH against NAFLD. Gene Ontology (GO) and KEGG pathway enrichment analyses have identified potential biochemical and signaling pathways. Subsequently, the potential mechanism of action of LAH on NAFLD predicted by network pharmacology analysis was validated in a high-fat diet (HFD)-induced NAFLD model in C57BL/6 mice. Our results demonstrated that LAH ameliorated hepatocyte steatosis in liver tissue by activating the AMPK pathway and decreasing serum triglycerides, low-density lipoprotein, glucose, and cholesterol. Besides, LAH increased the hepatic antioxidant enzymes activities, suggested that LAH improved oxidative stress markers in HFD induced NAFLD mice. In vitro experiments confirmed that the active component of LAH, puerarin, regulates lipid accumulation through the AMPK pathway. In conclusion, our study shows that network pharmacology predictions are consistent with experimental validation. LAH can be a candidate supplement for the prevention of NAFLD.

Effect of Empagliflozin on Thioacetamide-Induced Liver Injury in Rats: Role of AMPK/SIRT-1/HIF-1α Pathway in Halting Liver Fibrosis

Hepatic fibrosis causes severe morbidity and death. No viable treatment can repair fibrosis and protect the liver until now. We intended to discover the empagliflozin's (EMPA) hepatoprotective efficacy in thioacetamide (TAA)-induced hepatotoxicity by targeting AMPK/SIRT-1 activity and reducing HIF-1α. Rats were treated orally with EMPA (3 or 6 mg/kg) with TAA (100 mg/kg, IP) thrice weekly for 6 weeks. EMPA in both doses retracted the serum GGT, ALT, AST, ammonia, triglycerides, total cholesterol, and increased serum albumin. At the same time, EMPA (3 or 6 mg/kg) replenished the hepatic content of GSH, ATP, AMP, AMPK, or SIRT-1 and mitigated the hepatic content of MDA, TNF-α, IL-6, NF-κB, or HIF-1α in a dose-dependent manner. Likewise, hepatic photomicrograph stained with hematoxylin and eosin or Masson trichrome stain of EMPA (3 or 6 mg/kg) revealed marked regression of the hepatotoxic effect of TAA with minimal injury. Similarly, in rats given EMPA (3 or 6 mg/kg), the immunohistochemically of hepatic photomicrograph revealed minimal stain of either α-SMA or caspase-3 compared to the TAA group. Therefore, we concluded that EMPA possessed an antifibrotic effect by targeting AMPK/SIRT-1 activity and inhibiting HIF-1α. The present study provided new insight into a novel treatment of liver fibrosis.

Intermedin Alleviates Vascular Calcification in CKD through Sirtuin 3-Mediated Inhibition of Mitochondrial Oxidative Stress

Vascular calcification (VC) is a common pathophysiological process of chronic kidney disease (CKD). Sirtuin 3 (Sirt3), a major NAD⁺-dependent protein deacetylase predominantly in mitochondria, is involved in the pathogenesis of VC. We previously reported that intermedin (IMD) could protect against VC. In this study, we investigated whether IMD attenuates VC by Sirt3-mediated inhibition of mitochondrial oxidative stress. A rat VC with CKD model was induced by the 5/6 nephrectomy plus vitamin D₃. Vascular smooth muscle cell (VSMC) calcification was induced by CaCl₂ and β-glycerophosphate. IMD_1-53 treatment attenuated VC in vitro and in vivo, rescued the depressed mitochondrial membrane potential (MMP) level and decreased mitochondrial ROS levels in calcified VSMCs. IMD_1-53 treatment recovered the reduced protein level of Sirt3 in calcified rat aortas and VSMCs. Inhibition of VSMC calcification by IMD_1-53 disappeared when the cells were Sirt3 absent or pretreated with the Sirt3 inhibitor 3-TYP. Furthermore, 3-TYP pretreatment blocked IMD_1-53-mediated restoration of the MMP level and inhibition of mitochondrial oxidative stress in calcified VSMCs. The attenuation of VSMC calcification by IMD_1-53 through upregulation of Sirt3 might be achieved through activation of the IMD receptor and post-receptor signaling pathway AMPK, as indicated by pretreatment with an IMD receptor antagonist or AMPK inhibitor blocking the inhibition of VSMC calcification and upregulation of Sirt3 by IMD_1-53. AMPK inhibitor treatment reversed the effects of IMD_1-53 on restoring the MMP level and inhibiting mitochondrial oxidative stress in calcified VSMCs. In conclusion, IMD attenuates VC by improving mitochondrial function and inhibiting mitochondrial oxidative stress through upregulating Sirt3.

Endogenous Adenosine 5'-Monophosphate, But Not Acetylcholine or Histamine, is Associated with Asthma Control, Quality of Life, and Exacerbations

OBJECTIVE

Endogenous adenosine 5'-monophosphate (AMP), acetylcholine (ACh), and histamine (HA) are known to be important in bronchial contraction, but their clinical relevance to asthma is poorly understood. We aimed to quantify endogenous AMP, ACh, and HA in induced sputum samples and explore their relationships with asthma control and exacerbations.

METHODS

20 healthy subjects and 112 asthmatics underwent clinical assessment, sputum induction, and blood sampling. The level of asthma control was determined by the asthma control test (ACT) questionnaire. Asthma exacerbation was evaluated according to the criteria of the American Thoracic Society/European Respiratory Society. Levels of AMP, ACh, and HA in sputum were measured by liquid chromatography coupled to tandem mass spectrometry. IL-β, IL-4, IL-5, IL-6, IL-8, IL-13, IL-17A, TNF-α, IFN-γ, and macrophage-derived chemokine (MDC) were also measured.

RESULTS

Compared to healthy controls, asthmatics had higher levels of HA, lower levels of ACh, and similar levels of AMP in induced sputum samples. Compared to controlled asthma (n = 54), uncontrolled asthma (n = 58) showed higher AMP levels (P = 0.002), but similar HA and ACh levels. AMP was negatively correlated with ACT scores (r = - 0.348) and asthma quality of life questionnaire scores (r = - 0.188) and positively correlated with blood monocytes percentage (r = 0.195), sputum MDC (r = 0.214), and IL-6 levels (r = 0.196). Furthermore, AMP was associated with an increased risk of exacerbations in the preceding year.

CONCLUSION

Endogenous AMP, but not ACh or HA, was associated with asthma control, quality of life, and exacerbations in the previous year, which indicates that AMP could be a clinically useful biomarker of asthma.

Hypertension and renal disease programming: focus on the early postnatal period

The developmental origin of hypertension and renal disease is a concept highly supported by strong evidence coming from both human and animal studies. During development there are periods in which the organs are more vulnerable to stressors. Such periods of susceptibility are also called 'sensitive windows of exposure'. It was shown that as earlier an adverse event occurs; the greater are the consequences for health impairment. However, evidence show that the postnatal period is also quite important for hypertension and renal disease programming, especially in rodents because they complete nephrogenesis postnatally, and it is also important during preterm human birth. Considering that the developing kidney is vulnerable to early-life stressors, renal programming is a key element in the developmental programming of hypertension and renal disease. The purpose of this review is to highlight the great number of studies, most of them performed in animal models, showing the broad range of stressors involved in hypertension and renal disease programming, with a particular focus on the stressors that occur during the early postnatal period. These stressors mainly include undernutrition or specific nutritional deficits, chronic behavioral stress, exposure to environmental chemicals, and pharmacological treatments that affect some important factors involved in renal physiology. We also discuss the common molecular mechanisms that are activated by the mentioned stressors and that promote the appearance of these adult diseases, with a brief description on some reprogramming strategies, which is a relatively new and promising field to treat or to prevent these diseases.

Protection of zero-valent iron nanoparticles against sepsis and septic heart failure

Background

Septic heart failure accounts for high mortality rates globally. With a strong reducing capacity, zero-valent iron nanoparticles (nanoFe) have been applied in many fields. However, the precise roles and mechanisms of nanoFe in septic cardiomyopathy remain unknown.

Results

NanoFe was prepared via the liquid-phase reduction method and functionalized with the biocompatible polymer sodium carboxymethylcellulose (CMC). We then successfully constructed a mouse model of septic myocardial injury by challenging with cecal ligation and puncture (CLP). Our findings demonstrated that nanoFe has a significant protective effect on CLP-induced septic myocardial injury. This may be achieved by attenuating inflammation and oxidative stress, improving mitochondrial function, regulating endoplasmic reticulum stress, and activating the AMPK pathway. The RNA-seq results supported the role of nanoFe treatment in regulating a transcriptional profile consistent with its role in response to sepsis.

Conclusions

The results provide a theoretical basis for the application strategy and combination of nanoFe in sepsis and septic myocardial injury.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01589-1.

AMPK and NRF2: Interactive players in the same team for cellular homeostasis?

NRF2 (Nuclear factor E2 p45-related factor 2) is a stress responsive transcription factor lending cells resilience against oxidative, xenobiotic, and also nutrient or proteotoxic insults. AMPK (AMP-activated kinase), considered as prime regulator of cellular energy homeostasis, not only tunes metabolism to provide the cell at any time with sufficient ATP or building blocks, but also controls redox balance and inflammation. Due to observed overlapping cellular responses upon AMPK or NRF2 activation and common stressors impinging on both AMPK and NRF2 signaling, it is plausible to assume that AMPK and NRF2 signaling may interdepend and cooperate to readjust cellular homeostasis. After a short introduction of the two players this narrative review paints the current picture on how AMPK and NRF2 signaling might interact on the molecular level, and highlights their possible crosstalk in selected examples of pathophysiology or bioactivity of drugs and phytochemicals.

AXL Promotes Metformin-Induced Apoptosis Through Mediation of Autophagy by Activating ROS-AMPK-ULK1 Signaling in Human Esophageal Adenocarcinoma

AXL receptor tyrosine kinase promotes an invasive phenotype and chemotherapy resistance in esophageal adenocarcinoma (EAC). AXL has been implicated in the regulation of autophagy, but the underlying molecular mechanism remains poorly understood. Herein, we investigate the mechanistic role of AXL in autophagy as well as metformin-induced effects on the growth and survival of EAC. We demonstrate that AXL mediates autophagic flux through activation of AMPK-ULK1 signaling in a reactive oxygen species (ROS)-dependent mechanism by glucose starvation. AXL positively regulates basal cellular ROS levels without significantly affecting mitochondrial ROS production in EAC cells. Pharmacological inhibition of cellular ROS using Trolox abrogates glucose starvation-induced AMPK signaling and autophagy. We demonstrate that AXL expression is required for metformin-induced apoptosis in EAC cells in vitro. The apoptosis induction by metformin is markedly attenuated by inhibition of autophagy through genetic silencing of Beclin1 or ATG7 autophagy mediators, thereby confirming the requirement of intact autophagy for enhancing metformin-induced apoptosis in EAC cells. Our data indicate that metformin-induced autophagy displays a pro-apoptotic function in EAC cells. We show that the metformin-induced suppression of tumor growth in vivo is highly dependent on AXL expression in a tumor xenograft mouse model of EAC. We demonstrate that AXL promotes metformin-induced apoptosis through activation of autophagy in EAC. AXL may be a valuable biomarker to identify tumors that are sensitive to metformin. Therefore, AXL expression could inform the selection of patients for future clinical trials to evaluate the therapeutic efficacy of metformin in EAC.