Metformin selectively targets redox control of complex I energy transduction

Different effects of metformin and phenformin on hypoxia-induced Ca2+ fluxes in cultured primary neurons

Recent evidence suggests that metformin and phenformin may exert beneficial effects against neuronal injury in the ischemic brain, however, the difference of action between these two drugs and the molecular mechanism of such protection is not clear. In this study, we investigated whether mild hypoxia-affected neurons exhibit changes in cytosolic calcium handling and whether metformin and phenformin exert any effect on calcium homeostasis in hypoxia-affected neurons. Cultured primary rat cortical cells were stained with calcium sensitive dye Oregon Green 488 BAPTA-1 AM and spontaneous calcium dependent changes of fluorescence were recorded. Using obtained fluorescence traces we estimated changes in relative amplitude of recorded spontaneous signals, changes in frequency of spontaneous activity, and changes in decay of fluorescence traces. We found that hypoxia caused reduction of the relative signal amplitude, increased the spontaneous activity, and slowed the decay of calcium concentration. After pre-treatment of cells with 0.1-0.5 mM metformin, the relative signal amplitude increased and the frequency of spontaneous signals decreased in hypoxia-affected neurons. However, pre-treatment with 1-25 µM phenformin neither increased the relative signal amplitude nor reduced the frequency of spontaneous signals. The decay of fluorescence traces became faster after application of metformin or phenformin comparing to neurons under hypoxic conditions. These results suggest different action of metformin and phenformin in improvement of Ca²⁺ homeostasis in hypoxia-affected neurons, which may have different effects on neuronal survival and functions after hypoxia/ischemia.

Metformin: still the sweet spot for CV protection in diabetes?

Metformin remains the first-line drug treatment for type 2 diabetes (T2D) in most guidelines not only because it achieves significant reduction in HbA1c but also because of a wealth of clinical experience regarding its safety and observational data that has shown that metformin use is associated with lower mortality rates when compared to sulphonylureas or insulin. Recently other diabetes drugs, particularly SGLT2 inhibitors (SGLT2i) and GLP1 receptor agonists (GLP1RA), have attracted considerable attention for their cardioprotective benefits reported in cardiovascular outcome trials (CVOTs). Randomised control trials on these newer drugs are on a larger scale but have shorter follow-up than UKPDS, the main study supporting metformin use. In a recent change to the European Society of Cardiology guidelines, metformin was replaced by SGLT2i and GLP1RA as first-line for T2D with atherosclerotic cardiovascular disease, whereas American Diabetes Association and UK-wide guidelines maintain metformin as first choice drug pharmacotherapy for all T2D. A definitive evidence-base for prioritisation of these drugs is currently missing because there are no head-to-head clinical trial data. Without such trials being forthcoming, innovative, pragmatic and low-cost 'real-world' trial approaches based on electronic health records may need to be harnessed to determine the correct priority, combinations of drugs and/or identify-specific patient populations most likely to benefit from each one.

Role of metformin in various pathologies: state-of-the-art microcapsules for improving its pharmacokinetics

Metformin was originally derived from a botanical ancestry and became the most prescribed, first-line therapy for Type 2 diabetes in most countries. In the last century, metformin was discovered twice for its antiglycemic properties in addition to its antimalarial and anti-influenza effects. Metformin exhibits flip-flop pharmacokinetics with limited oral bioavailability. This review outlines metformin pharmacokinetics, pharmacodynamics and recent advances in polymeric particulate delivery systems as a potential tool to target metformin delivery to specific tissues/organs. This interesting biguanide is being rediscovered this century for multiple clinical indications as anticancer, anti-aging, anti-inflammatory, anti-Alzheimer's and much more. Microparticulate delivery systems of metformin may improve its oral bioavailability and optimize the therapeutic goals expected.

Differential effects of metformin on reductive activity and energy production in pituitary tumor cells compared to myogenic precursors

PURPOSE

Given the multiple targets of metformin within cells, the mechanism by which it may exert a growth-inhibitory action on pituitary tumor cells in vitro remains to be explored. Previous research stressed metformin-induced changes in the activity of signaling pathways regulating cell growth and cell death. In this work, we investigated the effects of metformin on cell viability markers related to cell metabolic activity in rat pituitary tumor cells versus rat myogenic precursors as a model of normal proliferating somatic cells.

METHODS

We designed our experiments in order to use the MTT reduction as a marker of cellular reductive activity and the total cellular ATP levels as a marker of energy supply during short incubations with different metabolic substrates (sodium pyruvate, D-glucose, L-glutamine, sodium citrate). Then, we extended the analysis to extracellular glucose consumption, extracellular medium acidification and pyruvate dehydrogenase (PDH) complex activity.

RESULTS

Metformin was found to be effective in both cell types at the same concentrations, although the outcome of the treatment was quite the opposite. Unexpectedly, metformin increased the viability of subconfluent rat myoblasts. Rat pituitary tumor cells and myoblasts differed in the utilization of distinct metabolic substrates and the PDH complex activity. Metformin actions on reductive activity and ATP production were substrate-dependent.

CONCLUSIONS

Overall, this work points out that metformin actions at the cellular level depend on metabolic features and metabolic requirements of cells. The pyruvate metabolic branch point is most likely to play a main role in the variability of cell response to metformin.

Brain energy rescue: an emerging therapeutic concept for neurodegenerative disorders of ageing

The brain requires a continuous supply of energy in the form of ATP, most of which is produced from glucose by oxidative phosphorylation in mitochondria, complemented by aerobic glycolysis in the cytoplasm. When glucose levels are limited, ketone bodies generated in the liver and lactate derived from exercising skeletal muscle can also become important energy substrates for the brain. In neurodegenerative disorders of ageing, brain glucose metabolism deteriorates in a progressive, region-specific and disease-specific manner - a problem that is best characterized in Alzheimer disease, where it begins presymptomatically. This Review discusses the status and prospects of therapeutic strategies for countering neurodegenerative disorders of ageing by improving, preserving or rescuing brain energetics. The approaches described include restoring oxidative phosphorylation and glycolysis, increasing insulin sensitivity, correcting mitochondrial dysfunction, ketone-based interventions, acting via hormones that modulate cerebral energetics, RNA therapeutics and complementary multimodal lifestyle changes.

Effect of long-term moderate-exercise combined with metformin-treatment on antioxidant enzymes activity and expression in the gastrocnemius of old female Wistar rats

Oxidative stress is known to be involved in the etiology of sarcopenia, a progressive loss of muscle mass and force related to elderly incapacity. A successful intervention to prevent this condition has been exercise-based therapy. Metformin (MTF), an anti-diabetic drug with pleiotropic effects, is known to retain redox homeostasis. However, the combined use of MTF with exercise has shown controversial experimental results. Our research group has shown that MTF-treatment does not limit the benefits provided by exercise, probably by inducing a hormetic response. Hence, our aim was to evaluate the effect of exercise in combination with MTF-treatment on the redox state of old female Wistar rats. Animals were divided into six groups; three groups preformed exercise on a treadmill for 5 days/week for 20 months and the other three were sedentary. Also, two groups of each, exercised and sedentary animals were treated with MTF for 6 or 12 months correspondingly, beside the untreated groups. Rats were euthanized at 24 months. Muscular functionality was analyzed as the relation between the lean mass free of bone with respect to the grip strength. Superoxide dismutase, catalase, and glutathione peroxidase content, enzymatic activity and redox state were determined in the gastrocnemius muscle. Our results showed that the exercised group treated with MTF for 12 months presented higher GSH/GSSG rate and high antioxidant scavenging power in contrast to the MTF-treatment for 6 months, where the beneficial effect was less noticeable.

Changes in peripheral mitochondrial DNA copy number in metformin-treated women with polycystic ovary syndrome: a longitudinal study

BACKGROUND

Patients with polycystic ovarian syndrome (PCOS) are associated with known alterations in mitochondria DNA copy number (mtDNA-CN). The aim of this study is to study the change in mtDNA-CN in patients with PCOS who were treated with metformin.

METHODS

This is a prospective cohort of patients with PCOS, who received metformin for one year. From 2009 to 2015, 88 women diagnosed with PCOS, based on the Rotterdam criteria, were enrolled. Serial measurements of mtDNA-CN, 8-hydroxydeoxyguanosine (8-OHdG), anthropometric, metabolic, endocrine, and inflammatory markers were obtained before and after 3, 6, and 12 months of treatment.

RESULTS

A significant decrease in mtDNA-CN was seen over the course of one year. Other markers, including 8-OHdG, testosterone, free androgen index, blood pressure and liver enzymes, also decreased in the same interval. On regression analysis, there was a significant association between the change in mtDNA-CN and serum total testosterone, and no association between mtDNA-CN and metabolic factors.

CONCLUSIONS

Treatment with metformin is associated with a time-dependent decrease in mtDNA-CN in patients with PCOS who are treated over the course of one year. This may signify a reduction in mitochondria dysfunction. The change in mtDNA-CN corresponds to a similar change in serum total testosterone, and suggests a possible relationship between mtDNA-CN and testosterone.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT00172523 . Registered September 15, 2005.

Bcl-2-associated athanogene 5 overexpression attenuates catecholamine-induced vascular endothelial cell apoptosis

Bcl-2 associated athanogene 5 (Bag5) is a novel endoplasmic reticulum (ER) regulator. However, its role in catecholamine-induced endothelial cells damage has not been fully understood. In our study, catecholamine was used to mimic hypertension-related endothelial cell damage. Then, western blots, enzyme-linked immunosorbent assay, immunofluorescence, quantitative polymerase chain reaction and pathway analysis were conducted to analyze the role of Bag5 in endothelial cell damage in response to catecholamine. Our results indicated that the endothelial cell viability was impaired by catecholamine. Interestingly, Bag5 overexpression significantly reversed endothelial cell viability. Mechanistically, Bag5 overexpression inhibited ER stress, attenuated oxidative stress and repressed inflammation in catecholamine-treated endothelial cells. These beneficial effects finally contributed to endothelial cell survival under catecholamine treatment. Pathway analysis demonstrated that Bag5 was under the control of the mitogen-activated protein kinase (MAPK)-extracellular-signal-regulated kinase (ERK) signaling pathway. Reactivation of the MAPK-ERK pathway could upregulate Bag5 expression and thus promote endothelial cell survival through inhibiting oxidative stress, ER stress, and inflammation. Altogether, our results illustrate that Bag5 overexpression sustains endothelial cell survival in response to catecholamine treatment. This finding identifies Bag5 downregulation and the inactivated MAPK-ERK pathway as potential mechanisms underlying catecholamine-induced endothelial cell damage.

Metformin protects against mouse oocyte apoptosis defects induced by arecoline

OBJECTIVES

Arecoline is the main bioactive substance extracted from Areca catechu L, which has cell, neural and genetic toxicity. The function of arecoline in reproductive system has not been well explored.

MATERIALS AND METHODS

To investigate the toxic effects of arecoline on oocyte development, immunofluorescence staining, qPCR, Western blotting, sperm binding assays and in vitro fertilization were performed to evaluate oocyte meiosis competence and embryo development.

RESULTS

Our data revealed that arecoline exposure disrupts actin filament dynamics, spindle assembly and kinetochore-microtubule attachment stability in mouse oocytes, leading to aneuploidy and oocyte meiosis arrest. In addition, arecoline treatment disturbs the distribution of mitochondria, reduces ATP production and increases the level of oxidative stress, which ultimately induces oocyte apoptosis. Supplementation with metformin, a medicine for type 2 diabetes in the clinic, partially alleviates these damages.

CONCLUSIONS

Metformin has a protective effect on arecoline-induced mouse oocytes apoptosis.

Hypoxia: Turning vessels into vassals of cancer immunotolerance

Hypoxia is a universal feature of solid cancers caused by a mismatch between cellular oxygen supply and consumption. To meet the increased demand for oxygen, hypoxic cancer cells (CCs) induce a multifaceted process known as angiogenesis, wherein new vessels are formed by the sprouting of pre-existing ones. In addition to providing oxygen for growth and an exit route for dissemination, angiogenic vessels and factors are co-opted by CCs to enable the generation of an immunotolerant, hypoxic tumor microenvironment, leading to therapeutic failure and mortality. In this review, we discuss how hypoxia-inducible factors (HIFs), the mechanistic target of rapamycin (mTOR), and the unfolded protein response (UPR) control angiogenic factors serving both vascular and immunomodulatory functions in the tumor microenvironment. Possible therapeutic strategies, wherein targeting oxygen sensing might enhance anti-angiogenic and immunologically-mediated anti-cancer responses, are suggested.

Novel potential of metformin on valproic acid-induced autism spectrum disorder in rats: involvement of antioxidant defence system

Prenatal exposure to valproic acid (VPA) has been shown to increase the risk of autism in children. This study examined the effect of metformin on VPA-induced autism spectrum disorders in rats. Pregnant albino rats administered VPA (500 mg/kg, i.p.) or normal saline (10 mL/kg, i.p.; vehicle-control) on gestational day 12.5. The pups were given metformin (5, 50 or 500 mg/kg, p.o.) or vehicle (10 mL/kg, p.o.) daily from postnatal day (PND) 21-50. Social behaviour, spatial learning/reference memory, repetitive behaviour and anxiety were assessed using the three-chamber social assay, Morris water maze (MWM), Y maze and elevated plus maze tests (EPM), respectively. On PND 51, the animals were euthanized and brains removed for biochemical assay. In utero VPA exposure caused significant reduction in sociability index, social novelty preference index in three-chambered apparatus and spatial learning and reference memory deficits in the MWM task as well as increase in repetitive/anxiety-like behaviour in Y maze and EPM tests, respectively, which were ameliorated by post-treatment with metformin in a dose-dependent manner. Moreover, prenatal VPA increased malondialdehyde (MDA) and nitrite levels as well as deficits in antioxidant enzymes activities in the hippocampus and prefrontal cortex (PFC) which were attenuated by metformin administration. Similarly, VPA-induced increase in acetylcholinesterase activity in the hippocampus and PFC were attenuated by postnatal treatment with metformin. Findings from this study showed that postnatal administration of metformin prevented valproic acid-induced autistic-like behaviour. Hence, metformin could be a potential adjunct in the management of autism spectrum disorders.

AMPK and the Need to Breathe and Feed: What's the Matter with Oxygen?

We live and to do so we must breathe and eat, so are we a combination of what we eat and breathe? Here, we will consider this question, and the role in this respect of the AMP-activated protein kinase (AMPK). Emerging evidence suggests that AMPK facilitates central and peripheral reflexes that coordinate breathing and oxygen supply, and contributes to the central regulation of feeding and food choice. We propose, therefore, that oxygen supply to the body is aligned with not only the quantity we eat, but also nutrient-based diet selection, and that the cell-specific expression pattern of AMPK subunit isoforms is critical to appropriate system alignment in this respect. Currently available information on how oxygen supply may be aligned with feeding and food choice, or vice versa, through our motivation to breathe and select particular nutrients is sparse, fragmented and lacks any integrated understanding. By addressing this, we aim to provide the foundations for a clinical perspective that reveals untapped potential, by highlighting how aberrant cell-specific changes in the expression of AMPK subunit isoforms could give rise, in part, to known associations between metabolic disease, such as obesity and type 2 diabetes, sleep-disordered breathing, pulmonary hypertension and acute respiratory distress syndrome.

The Metformin Mechanism on Gluconeogenesis and AMPK Activation: The Metabolite Perspective

Metformin therapy lowers blood glucose in type 2 diabetes by targeting various pathways including hepatic gluconeogenesis. Despite widespread clinical use of metformin the molecular mechanisms by which it inhibits gluconeogenesis either acutely through allosteric and covalent mechanisms or chronically through changes in gene expression remain debated. Proposed mechanisms include: inhibition of Complex 1; activation of AMPK; and mechanisms independent of both Complex 1 inhibition and AMPK. The activation of AMPK by metformin could be consequent to Complex 1 inhibition and raised AMP through the canonical adenine nucleotide pathway or alternatively by activation of the lysosomal AMPK pool by other mechanisms involving the aldolase substrate fructose 1,6-bisphosphate or perturbations in the lysosomal membrane. Here we review current interpretations of the effects of metformin on hepatic intermediates of the gluconeogenic and glycolytic pathway and the candidate mechanistic links to regulation of gluconeogenesis. In conditions of either glucose excess or gluconeogenic substrate excess, metformin lowers hexose monophosphates by mechanisms that are independent of AMPK-activation and most likely mediated by allosteric activation of phosphofructokinase-1 and/or inhibition of fructose bisphosphatase-1. The metabolite changes caused by metformin may also have a prominent role in counteracting G6pc gene regulation in conditions of compromised intracellular homeostasis.

Exendin-4 attenuates inflammation-mediated endothelial cell apoptosis in varicose veins through inhibiting the MAPK-JNK signaling pathway

Context: Inflammation response has been found to be associated with endothelial cell death in the progression of varicose veins. Exendin-4 is able to reduce inflammation and thus attenuate cell apoptosis.Aim: The aim of our study is to explore the influence of Exendin-4 on LPS-treated endothelial cells.Methods: Cells were treated with LPS. Exendin-4 was added into the medium of cells. Western blots, qPCR, and ELISA were used to analyze the role of Exendin-4 in LPS-mediated cell death.Results: We found that LPS treatment caused significantly cell death. Whereas this trend could be attenuated by Exendin-4. After treatment with Exendin-4, inflammation factors upregulation and oxidative stress activation were significantly repressed, an effect that was followed by a drop in the levels of glucose production and lactic acid generation. At the molecular levels, Exendin-4 treatment inhibited the activity of MAPK-JNK signaling pathway in the presence of LPS treatment.Conclusions: LPS causes cell apoptosis through inducing inflammation response, oxidative stress and energy stress. Exendin-4 treatment enhances cell survival, reduces inflammation, and improves energy stress through inhibiting the MAPK-JNK signaling pathway.

Mitochondrial Complex I Inhibition by Metformin: Drug-Exercise Interactions

Metformin has antidiabetic, anticancer, and prolongevity effects, but seems to interfere with aerobic training mitochondrial adaptations. The primary mechanism of action has been suggested to be the inhibition of mitochondrial complex I. Recent papers (Wang et al. and Cameron et al.), however, provide evidence to deny the hypothesis of a direct action of metformin on complex I.

Proline biosynthesis is a vent for TGFβ-induced mitochondrial redox stress

The production and secretion of matrix proteins upon stimulation of fibroblasts by transforming growth factor-beta (TGFβ) play a critical role in wound healing. How TGFβ supports the bioenergetic cost of matrix protein synthesis is not fully understood. Here, we show that TGFβ promotes protein translation at least in part by increasing the mitochondrial oxidation of glucose and glutamine carbons to support the bioenergetic demand of translation. Surprisingly, we found that in addition to stimulating the entry of glucose and glutamine carbon into the TCA cycle, TGFβ induced the biosynthesis of proline from glutamine in a Smad4-dependent fashion. Metabolic manipulations that increased mitochondrial redox generation promoted proline biosynthesis, while reducing mitochondrial redox potential and/or ATP synthesis impaired proline biosynthesis. Thus, proline biosynthesis acts as a redox vent, preventing the TGFβ-induced increase in mitochondrial glucose and glutamine catabolism from generating damaging reactive oxygen species (ROS) when TCA cycle activity exceeds the ability of oxidative phosphorylation to convert mitochondrial redox potential into ATP. In turn, the enhanced synthesis of proline supports TGFβ-induced production of matrix proteins.

Cerebral ischemia-reperfusion is modulated by macrophage-stimulating 1 through the MAPK-ERK signaling pathway

Cerebral ischemia-reperfusion (IR) injury is associated with mitochondrial damage. Macrophage-stimulating 1 (MST1) reportedly stimulates mitochondrial apoptosis by suppressing BCL-2. We investigated whether MST1 promotes the progression of cerebral IR injury by inducing mitochondrial dysfunction in vivo and in vitro. Western blot analysis, quantitative polymerase chain reaction, immunofluorescence, and mitochondrial function assays were conducted in cells from wild-type and Mst1-knockout mice subjected to cerebral IR injury. MST1 expression in wild-type glial cells increased following cerebral IR injury. Cerebral IR injury reduced the mitochondrial membrane potential and mitochondrial metabolism in glial cells, while it enhanced mitochondrial reactive oxygen species generation and mitochondrial calcium levels in these cells. The deletion of Mst1 attenuated cerebral IR injury by improving mitochondrial function and reducing mitochondrial damage. The mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathway was suppressed in wild-type glial cell upon cerebral IR injury but was reactivated in Mst1-knockout glial cell. Accordingly, blocking the MAPK/ERK pathway abolished the beneficial effects of Mst1 deletion during cerebral IR injury by inducing mitochondrial damage in glial cells. Our results suggest that cerebral IR injury is associated with MST1 upregulation in the brain, while the genetic ablation of Mst1 can attenuate mitochondrial damage and sustain brain function following cerebral IR injury.

Pak2 inhibition promotes resveratrol-mediated glioblastoma A172 cell apoptosis via modulating the AMPK-YAP signaling pathway

As a polyphenolic compound, resveratrol (Res) is widely present in a variety of plants. Previous studies have shown that Res can inhibit various tumors. However, its role in c remains largely unexplored. In the present study, we first demonstrated that Res inhibited cell viability and induced apoptosis of glioblastoma A172 cell. Further experiments showed that Res induced mitochondrial dysfunction and activated the activity of caspase-9. Functional studies have found that Res treatment is associated with an increase in the expression of Pak2. Interestingly, inhibition of Pak2 could further augment the proapoptotic effect of Res. Mechanistically, Pak2 inhibition induced reactive oxygen species overproduction, mitochondria-JNK pathway activation, and AMPK-YAP axis suppression. However, overexpression of YAP could abolish the anticancer effects of Res and Pak2 inhibition, suggesting a necessary role played by the AMPK-YAP pathway in regulating cancer-suppressive actions of Res and Pak2 inhibition. Altogether, our results indicated that Res in combination with Pak2 inhibition could further enhance the anticancer property of Res and this effect is mediated via the AMPK-YAP pathway.

Liraglutide reduces hyperglycemia-induced cardiomyocyte death through activating glucagon-like peptide 1 receptor and targeting AMPK pathway

Objective: Hyperglycemia-mediated cardiomyocyte damage is associated with inflammation and AMPK inactivation.Aim: The aim of our study is to explore the protective effects exerted by liraglutide on AMPK pathway and glucagon-like peptide 1 receptor in diabetic cardiomyopathy.Methods: Cardiomyocytes were treated with high-glucose stress and cardiomyocyte viability was determined via (3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide assay. Besides, LDH release, immunofluorescence, and qPCR were used to verify the influence of liraglutide on hyperglycemia-treated cardiomyocytes.Results: Hyperglycemia treatment caused inflammation response and oxidative stress were significantly elevated in cardiomyocytes. This alteration could be reversed by liraglutide. Besides, cell viability was reduced whereas apoptosis was increased after exposure to high glucose treatment. However, liraglutide treatment could attenuate apoptosis and reverse cell viability in cardiomyocyte. Further, we found that AMPK pathway was also activated and glucagon-like peptide 1 receptor expression was increased in response to liraglutide treatment.Conclusions: Liraglutide could attenuate hyperglycemia-mediated cardiomyocyte damage through reversing AMPK pathway and upregulating glucagon-like peptide 1 receptor.

How treatments with endocrine and metabolic drugs influence pituitary cell function

A variety of endocrine and metabolic signals regulate pituitary cell function acting through the hypothalamus-pituitary neuroendocrine axes or directly at the pituitary level. The underlying intracellular transduction mechanisms in pituitary cells are still debated. AMP-activated protein kinase (AMPK) functions as a cellular sensor of low energy stores in all mammalian cells and promotes adaptive changes in response to calorie restriction. It is also regarded as a target for therapy of proliferative disorders. Various hormones and drugs can promote tissue-specific activation or inhibition of AMPK by enhancing or inhibiting AMPK phosphorylation, respectively. This review explores the preclinical studies published in the last decade that investigate the role of AMP-activated protein kinase in the intracellular transduction pathways downstream of endocrine and metabolic signals or drugs affecting pituitary cell function, and its role as a target for drug therapy of pituitary proliferative disorders. The effects of the hypoglycemic agent metformin, which is an indirect AMPK activator, are discussed. The multiple effects of metformin on cell metabolism and cell signalling and ultimately on cell function may be either dependent or independent of AMPK. The in vitro effects of metformin may also help highlighting differences in metabolic requirements between pituitary adenomatous cells and normal cells.

Combination of melatonin and irisin ameliorates lipopolysaccharide-induced cardiac dysfunction through suppressing the Mst1-JNK pathways

Despite significant advances in therapies in past decades, the mortality rate of septic cardiomyopathy remains high. The aim of this study is to explore the therapeutic effects of combined treatment using melatonin and irisin in a mouse model of lipopolysaccharide (LPS)-mediated septic cardiomyopathy. Our data found that melatonin and irisin could further attenuate LPS-induced myocardial depression. Molecular investigation illustrated that melatonin and irisin cotreatment sustained cardiomyocyte viability and improved mitochondrial function under LPS stress. Pathway analysis demonstrated that macrophage-stimulating 1 (Mst1), which was significantly activated by LPS, was drastically inhibited by melatonin/irisin cotreatment. Mechanically, Mst1 activated c-Jun N-terminal kinase (JNK) pathway and the latter induced oxidative stress, adenosine triphosphate metabolism disorder, mitochondrial membrane potential reduction, and cardiomyocyte death activation. Melatonin and irisin cotreatment effectively inhibited the Mst1-JNK pathway and, thus, promoted cardiomyocyte survival and mitochondrial homeostasis. Interestingly, Mst1 overexpression abolished the beneficial effects of melatonin and irisin in vivo and in vitro. Altogether, our results confirmed that melatonin and irisin combination treatment could protect heart against sepsis-induced myocardial depression via modulating the Mst1-JNK pathways.

Metformin lowers glucose 6-phosphate in hepatocytes by activation of glycolysis downstream of glucose phosphorylation

The chronic effects of metformin on liver gluconeogenesis involve repression of the G6pc gene, which is regulated by the carbohydrate-response element-binding protein through raised cellular intermediates of glucose metabolism. In this study we determined the candidate mechanisms by which metformin lowers glucose 6-phosphate (G6P) in mouse and rat hepatocytes challenged with high glucose or gluconeogenic precursors. Cell metformin loads in the therapeutic range lowered cell G6P but not ATP and decreased G6pc mRNA at high glucose. The G6P lowering by metformin was mimicked by a complex 1 inhibitor (rotenone) and an uncoupler (dinitrophenol) and by overexpression of mGPDH, which lowers glycerol 3-phosphate and G6P and also mimics the G6pc repression by metformin. In contrast, direct allosteric activators of AMPK (A-769662, 991, and C-13) had opposite effects from metformin on glycolysis, gluconeogenesis, and cell G6P. The G6P lowering by metformin, which also occurs in hepatocytes from AMPK knockout mice, is best explained by allosteric regulation of phosphofructokinase-1 and/or fructose bisphosphatase-1, as supported by increased metabolism of [3-³H]glucose relative to [2-³H]glucose; by an increase in the lactate m2/m1 isotopolog ratio from [1,2-¹³C₂]glucose; by lowering of glycerol 3-phosphate an allosteric inhibitor of phosphofructokinase-1; and by marked G6P elevation by selective inhibition of phosphofructokinase-1; but not by a more reduced cytoplasmic NADH/NAD redox state. We conclude that therapeutically relevant doses of metformin lower G6P in hepatocytes challenged with high glucose by stimulation of glycolysis by an AMP-activated protein kinase-independent mechanism through changes in allosteric effectors of phosphofructokinase-1 and fructose bisphosphatase-1, including AMP, P_i, and glycerol 3-phosphate.

Synthesis, biological evaluation and anti-proliferative mechanism of fluorine-containing proguanil derivatives

Proguanil, a member of biguanide family, has excellent anti-proliferative activities. Fluorine-containing compounds have been demonstrated to have super biological activities including enhanced binding interactions, metabolic stability, and reduced toxicity. In this study, based on the intermediate derivatization methods, we synthesized 13 new fluorine-containing proguanil derivatives, and found that 7a,7d and 8e had much lower IC₅₀ than proguanil in 5 human cancerous cell lines. The results of clonogenic and scratch wound healing assays revealed that the inhibitory effects of derivatives 7a,7d and 8e on proliferation and migration of human cancer cell lines were much better than proguanil as well. Mechanistic study based on representative derivative 7a indicated that this compound up-regulates AMPK signal pathway and downregulates mTOR/4EBP1/p70S6K. In conclusion, these new fluorine-containing derivatives show potential for the development of cancer chemotherapeutic drugs.

Control of Inflammation by Calorie Restriction Mimetics: On the Crossroad of Autophagy and Mitochondria

Mitochondrial metabolism and autophagy are two of the most metabolically active cellular processes, playing a crucial role in regulating organism longevity. In fact, both mitochondrial dysfunction or autophagy decline compromise cellular homeostasis and induce inflammation. Calorie restriction (CR) is the oldest strategy known to promote healthspan, and a plethora of CR mimetics have been used to emulate its beneficial effects. Herein, we discuss how CR and CR mimetics, by modulating mitochondrial metabolism or autophagic flux, prevent inflammatory processes, protect the intestinal barrier function, and dampen both inflammaging and neuroinflammation. We outline the effects of some compounds classically known as modulators of autophagy and mitochondrial function, such as NAD⁺ precursors, metformin, spermidine, rapamycin, and resveratrol, on the control of the inflammatory cascade and how these anti-inflammatory properties could be involved in their ability to increase resilience to age-associated diseases.

Yes-associated protein reduces neuroinflammation through upregulation of Sirt3 and inhibition of JNK signaling pathway

Objective: Neuroinflammation is linked to a series of neurodegenerative diseases through the unknown mechanisms.Aim: The aim of this study was to investigate the role of Yes-associated protein (Yap) in the regulation of neuroinflammation.Methods: BV-2 neuroglia cells were treated with TNFα in vitro. Then, western blots, qPCR, immunofluorescence, and ELISA were used to verify the influence of Yap in BV-2 cells neuroinflammation response.Results: After exposure to TNFα, viability of BV-2 cells decreased whereas apoptosis index was increased. Of note, Yap expression in BV-2 cells was significantly reduced, when compared to the normal cells. Interestingly, adenovirus-induced Yap overexpression was capable to reverse cell viability and thus reduce apoptotic index in TNFα-treated BV-2 cells. Molecular investigation demonstrated that Yap overexpression was linked to Sirt3 upregulation. Increased Sirt3 reduced endoplasmic reticulum (ER) stress, attenuated mitochondrial damage, and blocked JNK pro-apoptotic pathway. Interestingly, loss of Sirt3 abolished the protective effects induced by Yap overexpression in TNFα-treated BV-2 cells.Conclusions: Altogether, our results demonstrated that neuroinflammation could be caused by Yap downregulation, possible driven through Sirt3 inhibition and JNK activation. However, overexpression of Yap could protect BV-2 cells against TNFα-mediated apoptosis through modulating Sirt3-JNK signaling pathways.

The clinical potential of thiol redox proteomics

Introduction: Protein thiols are susceptible to oxidation in health and disease. Redox proteomics methods facilitate the identification, quantification, and rationalization of oxidation processes including those involving protein thiols. These residues are crucial to understanding redox homeostasis underpinning normal cell functioning and regulation as well as novel biomarkers of pathology and promising novel drug targets.Areas covered: This article reviews redox proteomic approaches to study of protein thiols in some important human pathologies and assesses the clinical potential of individual Cys residues as novel biomarkers for disease detection and as targets for novel treatments.Expert commentary: Although protein thiols are not as routinely used as redox biomarkers as some other lesions such as carbonylation, there has been growing recent interest in their potential. Driven largely by developments in high-resolution mass spectrometry it is possible now to identify proteins that are redox modified at thiol groups or that interact with regulatory oxidoreductases. Thiols that are specifically susceptible to modification by reactive oxygen species can be routinely identified now and quantitative MS can be used to quantify the proportion of a protein that is redox modified.

Pharmacology of metformin - An update

Despite being a successful diabetes type 2 drug for more than a half-century in Europe, the mode of action of metformin is still debated. It is the purpose of this review to inform the reader about most recent findings for metformin with respect to its antidiabetic activity as well as proposed benefits beyond glucose control in humans. Clinical evidence now suggests that most of metformin benefits originate from its actions in the gut, involving hormone signaling by glucagon-like peptide 1 and peptide YY. Growth differentiation factor 15, also mainly produced in the gut, was first identified as a biomarker for metformin use but is now suggested to play a significant role in e.g. weight loss of prediabetics. The pharmacokinetics of the drug in humans as basis for pharmacodynamics, resulting in high tissue levels of the intestinal wall, including the colon, proven by biopsies, is presented. A critical survey of metformin actions on mitochondria, increasing the AMP/ATP ratio but also acting as a mild uncoupler, and of postulated new cellular targets (lysosomes) is included.

MKP1 reduces neuroinflammation via inhibiting endoplasmic reticulum stress and mitochondrial dysfunction

MAP kinase phosphatase 1 (MKP1) has been identified as an antiapoptotic protein via sustaining mitochondrial function. However, the role of MKP1 in neuroinflammation has not been fully understood. The aim of this study is to figure out the influence of MKP1 in lipopolysaccharide (LPS)-treated microglia BV-2 cells and investigate whether MKP1 reduces BV-2 cell death via modulating endoplasmic reticulum (ER) stress and mitochondrial dysfunction. The results of this study demonstrated that MKP1 was rapidly downregulated after exposure to LPS. However, the transfection of MKP1 adenovirus could reverse cell viability and attenuate LPS-mediated BV-2 cell apoptosis. Mechanistically, MKP1 overexpression alleviated ER stress and corrected LPS-induced calcium overloading. Besides, MKP1 adenovirus transfection also reversed mitochondrial bioenergetics, maintained mitochondrial membrane potential, and blocked mitochondria-initiated apoptosis signals. Furthermore, we found that MKP1 overexpression is associated with inactivation of mitogen-activated protein kinase-c-Jun N-terminal kinase (MAPK-JNK) pathway. Interestingly, the activation of MAPK-JNK pathway could abolish the protective effects of MKP1 on BV-2 cells survival and mitochondrial function in the presence of LPS. Altogether, our results identified MKP1 as a primary defender of neuroinflammation via modulating ER stress and mitochondrial function in a manner dependent on MAPK-JNK pathway. These findings may open a new window for the treatment of neuroinflammation in the clinical setting.

Therapeutic effects of bone mesenchymal stem cells on oral and maxillofacial defects: a novel signaling pathway involving miR-31/CXCR4/Akt axis

Context: Although bone mesenchymal stem cells (BMSCs) have been used for the treatment of oral and maxillofacial defects, the survival rate and limited proliferation reduces the therapeutic efficiency of BMSC.Objective: The aim of our study is to explore the role of miR-31 in regulating survival, proliferation, and migration of BMSC in vitro.Materials and methods: LPS was used in vitro to induce BMSC damage and then miR-31 was used to incubate with BMSC. Subsequently, BMSC proliferation, survival, and migration were determined via ELISA, qPCR, western blots, and immunofluorescence.Results: The expression of miR-31 was downregulated in response to LPS stress. Interestingly, supplementation of miR-31 could reverse the survival, proliferation and migration of BMSC under LPS. Mechanically, miR-31 treatment inhibited the activation of caspase, and thus promoted BMSC survival. Besides, miR-31 upregulated the genes related to cell proliferation, an effect that was followed by an increase in the levels of migratory factors. Further, we found that miR-31 treatment activated the CXCR4/Akt pathway and blockade of CXCR4/Akt could abolish the beneficial effects of miR-31 on BMSC proliferation, survival, and migration.Conclusions: miR-31 could increase the therapeutic efficiency of BMSC via the CXCR4/Akt pathway.

Melatonin attenuates ER stress and mitochondrial damage in septic cardiomyopathy: A new mechanism involving BAP31 upregulation and MAPK-ERK pathway

Septic cardiomyopathy is associated with mitochondrial damage and endoplasmic reticulum (ER) dysfunction. However, the upstream mediator of mitochondrial injury and ER stress has not been identified and thus little drug is available to treat septic cardiomyopathy. Here, we explored the role of B-cell receptor-associated protein 31 (BAP31) in septic cardiomyopathy and figure out whether melatonin could attenuate sepsis-mediated myocardial depression via modulating BAP31. Lipopolysaccharide (LPS) was used to establish the septic cardiomyopathy model. Pathway analysis was performed via western blot, quantitative polymerase chain reaction and immunofluorescence. Mitochondrial function and ER stress were detected via enzyme-linked immunosorbent assay, western blot, and immunofluorescence. After exposure to LPS, cardiac function was reduced due to excessive inflammation response and extensive cardiomyocyte death. Mechanistically, melatonin treatment could dose-dependently improve cardiomyocyte viability via preserving mitochondrial function and reducing ER stress. Further, we found that BAP31 transcription was repressed by LPS whereas melatonin could restore BAP31 expression; this effect was dependent on the MAPK-ERK pathway. Inhibition of the ERK pathway and/or knockdown of BAP31 could attenuate the beneficial effects of melatonin on mitochondrial function and ER homeostasis under LPS stress. Altogether, our results indicate that ERK-BAP31 pathway could be used as a critical mediator for mitochondrial function and ER homeostasis in sepsis-related myocardial injury. Melatonin could stabilize BAP31 via the ERK pathway and thus contribute to the preservation of cardiac function in septic cardiomyopathy.

Metformin therapy in patients with diabetes mellitus is associated with a reduced risk of vasculopathy and cardiovascular mortality after heart transplantation

Background

Cardiac allograft vasculopathy (CAV) is a major cause of morbidity and mortality following heart transplantation (HT). Reduced cardiovascular mortality and morbidity have been reported in non-HT patients treated with metformin. Given the high prevalence of type 2 diabetes mellitus (T2DM) in HT patients, we investigated the association between metformin therapy and cardiovascular outcomes after HT.

Methods

The study population comprised 103 DM patients who had undergone HT between 1994 and 2018 and were prospectively followed-up. We excluded from the study patients with type 1 diabetes mellitus. Fifty-five HT patients (53%) in the cohort were treated with metformin. Clinical data were recorded on prospectively designed forms. The primary outcomes included CAV, survival, and the combined end-point of CAV or cardiovascular mortality.

Results

Kaplan–Meier survival analysis showed that the CAV rate at 20 years of follow-up was lower in DM patients treated with metformin than in those who were not (30 vs. 65%; log-rank p = 0.044). Similarly, the combined risk of CAV or cardiovascular mortality was lower in the metformin-treated patients than in those not receiving metformin (32 vs. 68%; log rank p = 0.01). Consistently, multivariate analysis adjusted for age and comorbidities showed that metformin therapy was independently associated with a significant 90% reduction (95% confidence interval 0.02–0.46, p = 0.003) in the risk for the development of CAV, and a 91% reduction (95% confidence interval 0.02–0.42; p = 0.003) in the risk for CAV or cardiovascular mortality.

Conclusions

In diabetic HT patients, metformin therapy is independently associated with a significant reduction in the long-term risk for CAV and the combined end-point of CAV or cardiovascular mortality after HT.

Metformin and Aging: A Review

Metformin is sometimes proposed to be an "anti-aging" drug, based on preclinical experiments with lower-order organisms and numerous retrospective data on beneficial health outcomes for type 2 diabetics. Large prospective, placebo-controlled trials are planned, in pilot stage or running, to find a new use (or indication) for an aging population. As one of the metformin trials has "frailty" as its endpoint, similar to a trial with a plant-derived senolytic, the latter class of novel anti-aging drugs is briefly discussed. Concerns exist not only for vitamin B12 and B6 deficiencies, but also about whether there are adverse effects of metformin on individuals who try to remain healthy by maintaining cardiovascular fitness via exercise.

Relationship Between Oxidative Stress, ER Stress, and Inflammation in Type 2 Diabetes: The Battle Continues

Type 2 diabetes (T2D) is a metabolic disorder characterized by hyperglycemia and insulin resistance in which oxidative stress is thought to be a primary cause. Considering that mitochondria are the main source of ROS, we have set out to provide a general overview on how oxidative stress is generated and related to T2D. Enhanced generation of reactive oxygen species (ROS) and oxidative stress occurs in mitochondria as a consequence of an overload of glucose and oxidative phosphorylation. Endoplasmic reticulum (ER) stress plays an important role in oxidative stress, as it is also a source of ROS. The tight interconnection between both organelles through mitochondrial-associated membranes (MAMs) means that the ROS generated in mitochondria promote ER stress. Therefore, a state of stress and mitochondrial dysfunction are consequences of this vicious cycle. The implication of mitochondria in insulin release and the exposure of pancreatic β-cells to hyperglycemia make them especially susceptible to oxidative stress and mitochondrial dysfunction. In fact, crosstalk between both mechanisms is related with alterations in glucose homeostasis and can lead to the diabetes-associated insulin-resistance status. In the present review, we discuss the current knowledge of the relationship between oxidative stress, mitochondria, ER stress, inflammation, and lipotoxicity in T2D.

Fatty Acid Metabolites Combine with Reduced β Oxidation to Activate Th17 Inflammation in Human Type 2 Diabetes

Mechanisms that regulate metabolites and downstream energy generation are key determinants of T cell cytokine production, but the processes underlying the Th17 profile that predicts the metabolic status of people with obesity are untested. Th17 function requires fatty acid uptake, and our new data show that blockade of CPT1A inhibits Th17-associated cytokine production by cells from people with type 2 diabetes (T2D). A low CACT:CPT1A ratio in immune cells from T2D subjects indicates altered mitochondrial function and coincides with the preference of these cells to generate ATP through glycolysis rather than fatty acid oxidation. However, glycolysis was not critical for Th17 cytokines. Instead, β oxidation blockade or CACT knockdown in T cells from lean subjects to mimic characteristics of T2D causes cells to utilize ¹⁶C-fatty acylcarnitine to support Th17 cytokines. These data show long-chain acylcarnitine combines with compromised β oxidation to promote disease-predictive inflammation in human T2D.

Metformin ameliorates acetaminophen-induced sub-acute toxicity via antioxidant property

Acetaminophen or N-acetyl-p-amino-phenol (APAP) is a drug which is available over-the-counter for fever and pain. Its overdosing causes oxidative stress and subsequent acute liver damage. In the present study, we scrutinized the protective effect of metformin co-treatment in APAP induced blood and liver sub-acute toxicity. This is a pre-clinical study in which male Wistar Rats (BW: 300 ± 20 g) were orally co-treated with APAP (1 g/kg/day) and metformin (300 mg/kg/day) for 28-days. Pro- and anti-oxidant markers viz reactive oxygen species, protein carbonyl, malondialdehyde (MDA), the ferric reducing ability of plasma (FRAP), plasma membrane redox system(PMRS) and reduced glutathione (GSH) were evaluated in blood. Additionally, in liver tissue, catalase (CAT), superoxide dismutase (SOD), MDA and GST level were also evaluated. Histological study and estimation of alanine aminotransferase (ALT), and aspartate aminotransferase (AST) level in serum were performed. APAP induces pro-oxidant markers as well as reduces anti-oxidant markers in blood and liver. Hepatic tissues degeneration and vacuolization of hepatocytes were evident after APAP treatment. Metformin treatment reduces pro-oxidant markers as well as increases anti-oxidant markers in both tissues. It also improves liver tissue architecture after treatment. The outcome of this study suggests that metformin has protective capability against APAP-induced blood and liver toxicity. Thus, metformin co-treatment with APAP attenuates oxidative stress and its consequences.

Mitochondrial targets of metformin-Are they physiologically relevant?

Metformin is the most widely prescribed treatment of hyperglycemia and type II diabetes since 1970s. During the last 15 years, its popularity increased due to epidemiological evidence, that metformin administration reduces incidence of cancer. However, despite the ongoing effort of many researchers, the molecular mechanisms underlying antihyperglycemic or antineoplastic action of metformin remain elusive. Most frequently, metformin is associated with modulation of mitochondrial metabolism leading to lowering of blood glucose or activation of antitumorigenic pathways. Here we review the reported effects of metformin on mitochondrial metabolism and their potential relevance as effective molecular targets with beneficial therapeutic outcome.

Long-term metformin use may improve clinical outcomes in diabetic patients with non-alcoholic steatohepatitis and bridging fibrosis or compensated cirrhosis

BACKGROUND

Metformin may protect against hepatocellular carcinoma and mortality among patients with type 2 diabetes.

AIM

To investigate whether long-term use of metformin improves survival and reduces liver-related outcomes among patients with type 2 diabetes and non-alcoholic steatohepatitis.

METHODS

A total of 191 diabetic patients with biopsy-proven non-alcoholic steatohepatitis and bridging fibrosis or compensated cirrhosis were retrospectively identified at Indiana University Medical Center between October 2004 and January 2016. Of them, 110 were users and 81 never-users of metformin. Primary outcomes were transplant-free survival, development of hepatocellular carcinoma or a first event of hepatic decompensation.

RESULTS

Cirrhosis was present in 85% of metformin users and 88% of nonusers. Metformin dose was greater than or equal to 1 g/d in 104 out of 110 users and its median duration of use was 6 (95% CI: 4.4-7.9) years. The mean follow-up was 6.92 and 6.80 years for metformin users and non-users, respectively. During follow-up, 28 patients developed hepatocellular carcinoma (metformin users: 7, nonusers: 21), and 52 died (metformin users: 7, nonusers: 24) or were transplanted (metformin users: 13, non-users: 13). Metformin use was associated with lower risk of overall mortality or transplant (HR: 0.42; 95% CI: 0.24-0.74, P = 0.003) and hepatocellular carcinoma (sHR: 0.25; 95% CI: 0.11-0.58, P = 0.001), and remained independently associated with both outcomes after propensity-score and covariate-adjusted analyses. No instances of hepatotoxicity or lactic acidosis were observed.

CONCLUSION

Our study demonstrated an association between long-term metformin use and reduced the risk of all-cause mortality/transplant and hepatocellular carcinoma in diabetics with non-alcoholic steatohepatitis and advanced fibrosis.

Proinflammation effect of Mst1 promotes BV-2 cell death via augmenting Drp1-mediated mitochondrial fragmentation and activating the JNK pathway

Inflammation has been increasingly studied as part of the pathophysiology of neurodegenerative diseases. Mammalian Ste20-like kinase 1 (Mst1), a key factor of the Hippo pathway, is connected to cell death. Unfortunately, little study has been performed to detect the impact of Mst1 in neuroninflammation. The results indicated that Mst1 expression was upregulated because of LPS treatment. However, the loss of Mst1 sustained BV-2 cell viability and promoted cell survival in the presence of LPS treatment. Molecular investigation assay demonstrated that Mst1 deletion was followed by a drop in the levels of mitochondrial fission via repressing Drp1 expression. However, Drp1 adenovirus transfection reduced the protective impacts of Mst1 knockdown on mitochondrial stress and neuronal dysfunction. Finally, our results illuminated that Mst1 affected Drp1 content and mitochondrial fission in a JNK-dependent mechanism. Reactivation of the JNK axis inhibited Mst1 knockdown-mediated neuronal protection and mitochondrial homeostasis. Altogether, our results indicated that Mst1 upregulation and the activation of JNK-Drp1-mitochondrial fission pathway could be considered as the novel mechanism regulating the progression of neuroninflammation. This finding would pave a new road for the treatment of neurodegenerative diseases via modulating the Mst1-JNK-Drp1-mitochondrial fission axis.

Caveolin-1 knockdown increases the therapeutic sensitivity of lung cancer to cisplatin-induced apoptosis by repressing Parkin-related mitophagy and activating the ROCK1 pathway

Chemotherapy is the first-line treatment option for patients with lung cancer. However, therapeutic resistance occurs through an incompletely understood mechanism. Our research wants to investigate the influence of Caveolin-1 (Cav-1) on the therapeutic sensitivity of lung cancer in vitro. Results in this study demonstrated that Cav-1 levels were markedly inhibited in A549 lung cancer cells after exposure to cisplatin. Knockdown of caveolin further enhanced cisplatin-triggered cancer death in A549 cells. The functional investigation demonstrated that Cav-1 inhibition amplified the mitochondrial stress signaling induced by cisplatin, as evidenced by the mitochondrial reactive oxygen species burst, cellular metabolic disruption, mitochondrial membrane potential reduction, and mitochondrial caspase-9-related apoptosis activation. At the molecular level, cav-1 augmented cisplatin-mediated mitochondrial damage by inhibiting Parkin-related mitochondrial autophagy. Mitophagy activation effectively attenuated the promotive impact of Cav-1 knockdown on mitochondrial damage and cell death. Furthermore, our data indicated that Cav-1 affected Parkin-related mitophagy by activating the Rho-associated coiled-coil kinase 1 (ROCK1) pathway; inhibition of the ROCK1 axis prevented cav-1 knockdown-mediated cell death and mitochondrial damage. Taken together, our results provide ample data illuminate the necessary action exerted by Cav-1 on affecting cisplatin-related therapeutic resistance. Silencing of Cav-1 inhibited Parkin-related mitophagy, thus amplifying cisplatin-mediated mitochondrial apoptotic signaling. This finding identifies the Cav-1/ROCK1/Parkin/mitophagy axis as a potential target to overcome cisplatin-related resistance in lung cancer cells.

Hippo/Mst1 overexpression induces mitochondrial death in head and neck squamous cell carcinoma via activating β-catenin/Drp1 pathway

Mammalian Ste20-like kinase 1 (Mst1) is associated with cell apoptosis. In the current study, we explored the regulatory effects of Mst1 on squamous cell carcinoma of the head and neck (SCCHN) in vitro. SCCHN Cal27 cells and Tu686 cells were transfected with adenovirus-loaded Mst1 to detect the role of Mst1 in cell viability. Then, siRNA against Drp1 was transfected into cells to evaluate the influence of mitochondrial fission in cancer survival. Our data illustrated that Mst1 overexpression promoted SCCHN Cal27 cell and Tu686 cell death via activating mitochondria-related apoptosis. Cells transfected with adenovirus-loaded Mst1 have increased expression of DRP1 and higher DRP1 promoted mitochondrial fission. Active mitochondrial fission mediated mitochondrial damage, as evidenced by increased mitochondrial oxidative stress, decreased mitochondrial energy production, and reduced mitochondrial respiratory complex function. Moreover, Mst1 overexpression triggered mitochondria-dependent cell apoptosis via DRP1-related mitochondrial fission. Further, we found that Mst1 overexpression controlled mitochondrial fission via the β-catenin/DRP1 pathways; inhibition of β-catenin and/or knockdown of DRP1 abolished the pro-apoptotic effects of Mst1 overexpression on SCCHN Cal27 cells and Tu686 cells, leading to the survival of cancer cells in vitro. In sum, our results illustrate that Mst1/β-catenin/DRP1 axis affects SCCHN Cal27 cell and Tu686 cell viability via controlling mitochondrial dynamics balance. This finding identifies Mst1 activation might be an effective therapeutic target for the treatment of SCCHN.

Inhibitory effect of melatonin on Mst1 ameliorates myocarditis through attenuating ER stress and mitochondrial dysfunction

Viral myocarditis has been found to be one of the leading causes of sudden death in young adults. However, no effective drugs have been developed to intervene the progression of myocarditis. Accordingly, the present study is carried out to explore the protective role played by melatonin in the setting of viral myocarditis with a focus on Mst1-Hippo pathway, mitochondrial dysfunction and ER stress. Cardiac function was determined via echocardiographic examination. Mitochondrial function and ER stress were detected via ELISA, western blots, and immunofluorescence. Our data demonstrated that virus injection induced cardiac dysfunction as evidenced by reduced contractile function in myocardium. Besides, LDH release assay and western blotting analysis demonstrated that cardiomyocyte death was activated by virus injection. Interestingly, melatonin treatment improved cardiac function and repressed virus-mediated cardiomyocyte apoptosis. At the molecular levels, mitochondrial dysfunction was induced by virus infection, as indicated by mitochondrial membrane potential reduction, mPTP opening rate elevation and caspase-9-related apoptosis activation. Besides, ER stress parameters were also elevated in virus-treated cardiomyocytes. Interestingly, melatonin treatment maintained mitochondrial dysfunction and repressed ER stress. To the end, we found that Mst1 was upregulated by virus infection; this effect was attenuated through supplementation with melatonin. However, Mst1 overexpression reduced the beneficial impact exerted by melatonin on cardiomyocyte viability, mitochondrial function and ER homeostasis. Our study illustrated that melatonin treatment attenuated viral myocarditis via sustaining cardiomyocyte viability, repressing mitochondrial dysfunction and inhibiting ER stress in a manner dependent on Mst1 inhibition.

Mst1 deletion reduces septic cardiomyopathy via activating Parkin-related mitophagy

Cardiomyocyte function and viability are highly modulated by mammalian Ste20-like kinase 1 (Mst1)-Hippo pathway and mitochondria. Mitophagy, a kind of mitochondrial autophagy, is a protective program to attenuate mitochondrial damage. However, the relationship between Mst1 and mitophagy in septic cardiomyopathy has not been explored. In the present study, Mst1 knockout mice were used in a lipopolysaccharide (LPS)-induced septic cardiomyopathy model. Mitophagy activity was measured via immunofluorescence, Western blotting, and enzyme-linked immunosorbent assay. Pathway blocker and small interfering RNA were used to perform the loss-of-function assay. The results demonstrated that Mst1 was rapidly increased in response to LPS stress. Knockout of Mst1 attenuated LPS-mediated inflammation damage, reduced cardiomyocyte death, and improved cardiac function. At the molecular levels, LPS treatment activated mitochondrial damage, such as mitochondrial respiratory dysfunction, mitochondrial potential reduction, mitochondrial ATP depletion, and caspase family activation. Interestingly, in response to mitochondrial damage, Mst1 deletion activated mitophagy which attenuated LPS-mediated mitochondrial damage. However, inhibition of mitophagy via inhibiting parkin mitophagy abolished the protective influences of Mst1 deletion on mitochondrial homeostasis and cardiomyocyte viability. Overall, our results demonstrated that septic cardiomyopathy is linked to Mst1 upregulation which is followed by a drop in the protective mitophagy.

Mst1 deletion reduces hyperglycemia-mediated vascular dysfunction via attenuating mitochondrial fission and modulating the JNK signaling pathway

Diabetes is a leading cause of microvascular complications, such as nephropathy and retinopathy. Recent studies have proposed that hyperglycemia-induced endothelial cell dysfunction is modulated by mitochondrial stress. Therefore, our experiment was to detect the upstream mediator of mitochondrial stress in hyperglycemia-treated endothelial cells with a focus on macrophage-stimulating 1 (Mst1) and mitochondrial fission. Our data illuminated that hyperglycemia incubation reduced cell viability, as well as increased apoptosis ratio in endothelial cell, and this alteration seemed to be associated with Mst1 upregulation. Inhibition of Mst1 via transfection of Mst1 siRNA into an endothelial cell could sustain cell viability and maintain mitochondrial function. At the molecular levels, endothelial cell death was accompanied with the activation of mitochondrial oxidative stress, mitochondrial apoptosis, and mitochondrial fission. Genetic ablation of Mst1 could reduce mitochondrial oxidative injury, block mitochondrial apoptosis, and repress mitochondrial fission. Besides, we also found Mst1 triggered mitochondrial dysfunction as well as endothelial cell damage through augmenting JNK pathway. Suppression of JNK largely ameliorated the protective actions of Mst1 silencing on hyperglycemia-treated endothelial cells and sustain mitochondrial function. The present study identifies Mst1 as a primary key mediator for hyperglycemia-induced mitochondrial damage and endothelial cell dysfunction. Increased Mst1 impairs mitochondrial function and activates endothelial cell death via opening mitochondrial death pathway through JNK.

Mitochondrial dynamics and transport in Alzheimer's disease

Mitochondrial dysfunction is now recognized as a contributing factor to the early pathology of multiple human conditions including neurodegenerative diseases. Mitochondria are signaling organelles with a multitude of functions ranging from energy production to a regulation of cellular metabolism, energy homeostasis, stress response, and cell fate. The success of these complex processes critically depends on the fidelity of mitochondrial dynamics that include the ability of mitochondria to change shape and location in the cell, which is essential for the maintenance of proper function and quality control, particularly in polarized cells such as neurons. This review highlights several aspects of alterations in mitochondrial dynamics in Alzheimer's disease, which may contribute to the etiology of this debilitating condition. We also discuss therapeutic strategies to improve mitochondrial dynamics and function that may provide an alternative approach to failed amyloid-directed interventions.

TrxR2 overexpression alleviates inflammation-mediated neuronal death via reducing the oxidative stress and activating the Akt-Parkin pathway

Neuronal death caused by inflammatory cytokine-mediated neuroinflammation is being extensively explored. Thioredoxin reductase (TrxR) 2 is a novel mediator of inflammation response. In the current study, we focus on the mechanisms of TrxR2 overexpression in inflammation-mediated neuronal death. LPS was used to induce neuroinflammation in N2a cells in vitro. Adenovirus-loaded TrxR2 was transfected into N2a cells to up-regulate TrxR2 expression. Then, cell viability was determined via MTT assay and TUNEL assay. Apoptosis was measured via western blotting and ELISA. Oxidative stress was detected via ELISA and flow cytometry. A pathway inhibitor was used to verify the role of the Akt-Parkin pathway in the LPS-mediated N2a cell death in the presence of TrxR2 overexpression. With the help of immunofluorescence assay and western blotting, we found that TrxR2 expression was significantly reduced in response to LPS treatment, and this effect was associated with N2a cell death via apoptosis. At the molecular level, TrxR2 overexpression elevated the activity of the Akt-Parkin pathway, as evidenced by the increased expression of p-Akt and Parkin. Interestingly, inhibition of the Akt-Parkin pathway abolished the regulatory effect of TrxR2 on LPS-treated N2a cells, as evidenced by the decreased cell viability and increased apoptotic ratio. Besides, TrxR2 overexpression also reduced oxidative stress, inflammation factor transcription and mitochondrial apoptosis. However, inhibition of Akt-Parkin axis abrogated the protective effects of TrxR2 on redox balance, mitochondrial performance and cell survival. LPS-mediated neuronal death was linked to a drop in TrxR2 overexpression and the inactivation of the Akt-Parkin pathway. Overexpression of TrxR2 sustained mitochondrial function, inhibited oxidative stress, repressed inflammation response, and blocked mitochondrial apoptosis, finally sending a pro-survival signal for the N2a cells in the setting of LPS-mediated inflammation environment.

Sirt3 modulate renal ischemia-reperfusion injury through enhancing mitochondrial fusion and activating the ERK-OPA1 signaling pathway

Mitochondrial fusion is linked to heart and liver ischemia-reperfusion (IR) insult. Unfortunately, there is no report to elucidate the detailed influence of mitochondrial fusion in renal IR injury. This study principally investigated the mechanism by which mitochondrial fusion protected kidney against IR injury. Our results indicated that sirtuin 3 (Sirt3) was inhibited after renal IR injury in vivo and in vitro. Overexpression of Sirt3 improved kidney function, modulated oxidative injury, repressed inflammatory damage, and reduced tubular epithelial cell apoptosis. The molecular investigation found that Sirt3 overexpression attenuated IR-induced mitochondrial damage in renal tubular epithelial cells, as evidenced by decreased reactive oxygen species production, increased antioxidants sustained mitochondrial membrane potential, and inactivated mitochondria-initiated death signaling. In addition, our information also illuminated that Sirt3 maintained mitochondrial homeostasis against IR injury by enhancing optic atrophy 1 (OPA1)-triggered fusion of mitochondrion. Inhibition of OPA1-induced fusion repressed Sirt3 overexpression-induced kidney protection, leading to mitochondrial dysfunction. Further, our study illustrated that OPA1-induced fusion could be affected through ERK; inhibition of ERK abolished the regulatory impacts of Sirt3 on OPA1 expression and mitochondrial fusion, leading to mitochondrial damage and tubular epithelial cell apoptosis. Altogether, our results suggest that renal IR injury is closely associated with Sirt3 downregulation and mitochondrial fusion inhibition. Regaining Sirt3 and/or activating mitochondrial fission by modifying the ERK-OPA1 cascade may represent new therapeutic modalities for renal IR injury.

Mst1 contributes to nasal epithelium inflammation via augmenting oxidative stress and mitochondrial dysfunction in a manner dependent on Nrf2 inhibition

Nasal epithelium inflammation plays an important role in transmitting and amplifying damage signals for the lower airway. However, the molecular basis of nasal epithelium inflammation damage has not been fully addressed. Mst1 is reported to modulate inflammation via multiple effects. Thus, the aim of our study is to understand the pathological mechanism underlying Mst1-related nasal epithelium inflammation in vitro. Our result indicated that Mst1 expression was rapidly increased in response to tumor necrosis factor-α (TNF-α) treatment in vitro and this effect was a dose-dependent manner. Interestingly, knockdown of Mst1 via transfecting small interfering RNA markedly reversed cell viability in the presence of TNF-α. Further, we found that Mst1 deficiency reduced cellular oxidative stress and attenuated mitochondrial dysfunction, as evidenced by reversed mitochondrial complex-I activity, decreased mitochondrial permeability transition pore opening rate, and stabilized mitochondrial membrane potential. Besides, we found that Nrf2 expression was increased after deletion of Mst1 whereas silencing of Nrf2 abolished the protective effects of Mst1 deletion on nasal epithelium survival and mitochondrial homeostasis. Moreover, Nrf2 overexpression also protected nasal epithelium against TNF-α-induced inflammation damage. Altogether, our data confirm that the Mst1 activation and Nrf2 downregulation seem to be the potential mechanisms responsible for the inflammation-mediated injury in nasal epithelium via mediating mitochondrial damage and cell oxidative stress.