Characterizations of mitochondrial uncoupling induced by chemical mitochondrial uncouplers in cardiomyocytes

Linking triphenylphosphonium cation to a bicyclic hydroquinone improves their antiplatelet effect via the regulation of mitochondrial function

Platelets are the critical target for preventing and treating pathological thrombus formation. However, despite current antiplatelet therapy, cardiovascular mortality remains high, and cardiovascular events continue in prescribed patients. In this study, first results were obtained with ortho-carbonyl hydroquinones as antiplatelet agents; we found that linking triphenylphosphonium cation to a bicyclic ortho-carbonyl hydroquinone moiety by a short alkyl chain significantly improved their antiplatelet effect by affecting the mitochondrial functioning. The mechanism of action involves uncoupling OXPHOS, which leads to an increase in mitochondrial ROS production and a decrease in the mitochondrial membrane potential and OCR. This alteration disrupts the energy production by mitochondrial function necessary for the platelet activation process. These effects are responsive to the complete structure of the compounds and not to isolated parts of the compounds tested. The results obtained in this research can be used as the basis for developing new antiplatelet agents that target mitochondria.

Molecular mechanisms of aging and anti-aging strategies

Aging is a complex and multifaceted process involving a variety of interrelated molecular mechanisms and cellular systems. Phenotypically, the biological aging process is accompanied by a gradual loss of cellular function and the systemic deterioration of multiple tissues, resulting in susceptibility to aging-related diseases. Emerging evidence suggests that aging is closely associated with telomere attrition, DNA damage, mitochondrial dysfunction, loss of nicotinamide adenine dinucleotide levels, impaired macro-autophagy, stem cell exhaustion, inflammation, loss of protein balance, deregulated nutrient sensing, altered intercellular communication, and dysbiosis. These age-related changes may be alleviated by intervention strategies, such as calorie restriction, improved sleep quality, enhanced physical activity, and targeted longevity genes. In this review, we summarise the key historical progress in the exploration of important causes of aging and anti-aging strategies in recent decades, which provides a basis for further understanding of the reversibility of aging phenotypes, the application prospect of synthetic biotechnology in anti-aging therapy is also prospected.

Mitochondrial Dysfunction: A Roadmap for Understanding and Tackling Cardiovascular Aging

Cardiovascular aging is a progressive remodeling process constituting a variety of cellular and molecular alterations that are closely linked to mitochondrial dysfunction. Therefore, gaining a deeper understanding of the changes in mitochondrial function during cardiovascular aging is crucial for preventing cardiovascular diseases. Cardiac aging is accompanied by fibrosis, cardiomyocyte hypertrophy, metabolic changes, and infiltration of immune cells, collectively contributing to the overall remodeling of the heart. Similarly, during vascular aging, there is a profound remodeling of blood vessel structure. These remodeling present damage to endothelial cells, increased vascular stiffness, impaired formation of new blood vessels (angiogenesis), the development of arteriosclerosis, and chronic vascular inflammation. This review underscores the role of mitochondrial dysfunction in cardiac aging, exploring its impact on fibrosis and myocardial alterations, metabolic remodeling, immune response remodeling, as well as in vascular aging in the heart. Additionally, we emphasize the significance of mitochondria-targeted therapies in preventing cardiovascular diseases in the elderly.

ROS-Suppression Nanoplatform Combined Activation of STAT3/Bcl-2 Pathway for Preventing Myocardial Infarction in Mice

Myocardial infarction (MI) is the leading cause of death worldwide. The most effective way to treat myocardial infarction is to rescue ischemic cardiomyocytes. After an ischemic event, the overproduction of reactive oxygen species (ROS) is a key driver of myocardial injury. The produced ROS affects mitochondrial function and induces apoptosis in cardiomyocytes. This was accomplished by constructing platelet-membrane-encapsulated ROS-responsive drug-releasing nanoparticles (PMN@NIC-MalNPs) to deliver malonate and niclosamide (NIC). The results revealed that PMN@NIC-MalNPs degraded and released malonate and niclosamide in a high-level ROS microenvironment, effectively reducing the oxidative stress and apoptosis rate. By enhancing basal mitochondrial oxygen consumption rate (OCR), adenosine triphosphate (ATP) production, and spare respiratory capacity (SRC) in vitro, reduced the oxidative stress levels and restored mitochondrial function. In vivo studies revealed that the PMN@NIC-MalNPs improved cardiac dysfunction, inhibited succinate dehydrogenase (SDH) activity, increased ATP production, and reduced the myocardial infarct size in myocardial infarction model mice. Further, transcriptome analysis and Western blot revealed that PMN@NIC-MalNPs prevented apoptosis by activating the expressions of the signal transducer and activator of transcription 3 (STAT3) and Bcl-2, and inhibiting the expression of Bax. Thus, this study provides a novel therapeutic solution for treating myocardial infarction and predicting the viability of an antioxidant and antiapoptotic therapeutic solution in the treatment of myocardial injury.

Sorafenib extends the lifespan of C. elegans through mitochondrial uncoupling mechanism

Sorafenib is a targeted anticancer drug in clinic. Low-dose sorafenib has been reported to activate AMPK through inducing mitochondrial uncoupling without detectable toxicities. AMPK activation has been the approach for extending lifespan, therefore, we investigated the effect of sorafenib on lifespan and physical activity of C. elegans and the underlying mechanisms. In the present study, we found that the effect of sorafenib on C. elegans lifespan was typically hermetic. Sorafenib treatment at higher concentrations (100 μM) was toxic but at lower concentrations (1, 2.5, 5 μM) was beneficial to C. elegans. Sorafenib (1 μM) treatment for whole-life period extended C. elegans lifespan and improved C. elegans physical activity as manifested by increasing pharyngeal pumping and body movement, preserving intestinal barrier integrity, muscle fibers organization and mitochondrial morphology. In addition, sorafenib (1 μM) treatment enhanced C. elegans stress resistance. Sorafenib activated AMPK through inducing mitochondrial uncoupling in C. elegans. Sorafenib treatment activated DAF-16, SKN-1, and increased SOD-3, HSP-16.2, GST-4 expression in C. elegans. Sorafenib treatment induced AMPK-dependent autophagy in C. elegans. We conclude that low-dose sorafenib protects C. elegans against aging through activating AMPK/DAF-16 dependent anti-oxidant pathways and stimulating autophagy responses. Low-dose sorafenib could be a strategy for treating aging and aging-related diseases.

7,8,3'-Trihydroxyflavone prevents doxorubicin-induced cardiotoxicity and mitochondrial dysfunction via activating Akt signaling pathway in H9c2 cells

Clinical application of the widely used chemotherapeutic agent, doxorubicin (DOX), is limited by its cardiotoxicity. Mitochondrial dysfunction has been revealed as a crucial factor in DOX-induced cardiotoxicity. 7,8,3'-Trihydroxyflavone (THF) is a mimetic brain-derived neurotrophic factor with neuroprotective effects. However, the potential effects of THF on DOX-induced cardiomyocyte damage and mitochondrial disorders remain unclear. H9c2 cardiomyoblasts were exposed to DOX and/or THF at different concentrations. Cardiomyocyte injury was evaluated using lactate dehydrogenase (LDH) assay and Live/Dead cytotoxicity kit. Meanwhile, mitochondrial membrane potential (MMP), morphology, mitochondrial reactive oxygen species (mito-ROS) production, and the oxygen consumption rate of cardiomyocytes were measured. The protein levels of key mitochondria-related factors such as adenosine monophosphate-activated protein kinase (AMPK), mitofusin 2 (Mfn2), dynamin-related protein 1 (Drp1), and optic atrophy protein 1 (OPA1) were examined. We found that THF reduced LDH content and death ratio of DOX-treated cardiomyocytes in a concentration-dependent manner, while increasing MMP without significantly affecting the routine and maximum capacity of mitochondrial respiration. Mechanistically, THF increased the activity of Akt and protein levels of Mfn2 and heme oxygenase 1 (HO-1). Moreover, inhibition of Akt reversed the protective role of THF, increased mito-ROS levels, and repressed Mfn2 and HO-1 expression. Therefore, we conclude, THF relieves DOX-induced cardiotoxicity and improves mitochondrial function by activating Akt-mediated Mfn2 and HO-1 pathways. This finding provides promising therapeutic insights for DOX-induced cardiac dysfunction.

Noncoupled Mitochondrial Respiration as Therapeutic Approach for the Treatment of Metabolic Diseases: Focus on Transgenic Animal Models

Mitochondrial dysfunction contributes to numerous chronic diseases, and mitochondria are targets for various toxins and xenobiotics. Therefore, the development of drugs or therapeutic strategies targeting mitochondria is an important task in modern medicine. It is well known that the primary, although not the sole, function of mitochondria is ATP generation, which is achieved by coupled respiration. However, a high membrane potential can lead to uncontrolled reactive oxygen species (ROS) production and associated dysfunction. For over 50 years, scientists have been studying various synthetic uncouplers, and for more than 30 years, uncoupling proteins that are responsible for uncoupled respiration in mitochondria. Additionally, the proteins of the mitochondrial alternative respiratory pathway exist in plant mitochondria, allowing noncoupled respiration, in which electron flow is not associated with membrane potential formation. Over the past two decades, advances in genetic engineering have facilitated the creation of various cellular and animal models that simulate the effects of uncoupled and noncoupled respiration in different tissues under various disease conditions. In this review, we summarize and discuss the findings obtained from these transgenic models. We focus on the advantages and limitations of transgenic organisms, the observed physiological and biochemical changes, and the therapeutic potential of uncoupled and noncoupled respiration.

SOX4 as a potential therapeutic target for pathological cardiac hypertrophy

Pathological cardiac hypertrophy can lead to heart failure, making its prevention crucial. SOX4, a SOX transcription factor, regulates tissue growth and development, although its role in pathological cardiac hypertrophy is unclear. We found that the SOX4 expression was elevated in hypertrophic hearts and angiotensin II (Ang II)-treated neonatal rat cardiomyocytes (NRCMs), and knocking down the SOX4 expression in NRCMs and mouse hearts significantly reduced the hypertrophic response. Mechanistically, SOX4 can bind to the SIRT3 promoter, inhibit SIRT3 transcription and expression, and thus affect downstream MnSOD acetylation levels, leading to abnormal increases in ROS and oxidative stress levels and promoting the occurrence of cardiac hypertrophy. In conclusion, this study identified a new role for SOX4 in regulating cardiac hypertrophy, and decreasing SOX4 expression may be a potential treatment for pathological cardiac hypertrophy.

BAM15 as a mitochondrial uncoupler: a promising therapeutic agent for diverse diseases

Subcellular organelles dysfunction is implicated in various diseases, including metabolic diseases, neurodegenerative diseases, cancer, and cardiovascular diseases. BAM15, a selective mitochondrial uncoupler, has emerged as a promising therapeutic agent due to its ability to enhance mitochondrial respiration and metabolic flexibility. By disrupting the coupling between electron transport and ATP synthesis, BAM15 dissipates the proton gradient, leading to increased mitochondrial respiration and energy expenditure. This review provides a comprehensive overview of BAM15, including its mechanism of action and potential therapeutic applications in diverse disease contexts. BAM15 has shown promise in obesity by increasing energy expenditure and reducing fat accumulation. In diabetes, it improves glycemic control and reverses insulin resistance. Additionally, BAM15 has potential in non-alcoholic fatty liver disease, sepsis, and cardiovascular diseases by mitigating oxidative stress, modulating inflammatory responses, and promoting cardioprotection. The safety profile of BAM15 is encouraging, with minimal adverse effects and remarkable tolerability. However, challenges such as its high lipophilicity and the need for alternative delivery methods need to be addressed. Further research is necessary to fully understand the therapeutic potential of BAM15 and optimize its application in clinical settings.

BDNF mimetic 7,8-dihydroxyflavone rescues rotenone-induced cytotoxicity in cardiomyocytes by ameliorating mitochondrial dysfunction

The relationship between mitochondrial dysfunction and cardiovascular disease pathogenesis is well recognized. 7,8-Dihydroxyflavone (7,8-DHF), a mimetic of brain-derived neurotrophic factor, inhibits mitochondrial impairments and improves cardiac function. However, the regulatory role of 7,8-DHF in the mitochondrial function of cardiomyocytes is not fully understood. To investigate the potential mito-protective effects of 7,8-DHF in cardiomyocytes, we treated H9c2 or HL-1 cells with the mitochondrial respiratory complex I inhibitor rotenone (Rot) as an in vitro model of mitochondrial dysfunction. We found that 7,8-DHF effectively eliminated various concentrations of Rot-induced cell death and reduced lactate dehydrogenase release. 7,8-DHF significantly improved mitochondrial membrane potential and inhibited mitochondrial reactive oxygen species. Moreover, 7,8-DHF decreased routine and leak respiration, restored protein levels of mitochondrial complex I-IV, and increased ATP production in Rot-treated H9c2 cells. The protective role of 7,8-DHF in Rot-induced damage was validated in HL-1 cells. Nuclear phosphorylation protein expression of signal transducer and activator of transcription 3 (STAT3) was significantly increased by 7,8-DHF. The present study suggests that 7,8-DHF rescues Rot-induced cytotoxicity by inhibiting mitochondrial dysfunction and promoting nuclear translocation of p-STAT3 in cardiomyocytes, thus nominating 7,8-DHF as a new pharmacological candidate agent against mitochondrial dysfunction in cardiac diseases.

Repurposing nitazoxanide as a novel anti-atherosclerotic drug based on mitochondrial uncoupling mechanisms

BACKGROUND AND PURPOSE

The anthelmintic drug nitazoxanide has a mitochondrial uncoupling effect. Mitochondrial uncouplers have been proven to inhibit smooth muscle cell proliferation and migration, inhibit NLRP3 inflammasome activation of macrophages and improve dyslipidaemia. Therefore, we aimed to demonstrate that nitazoxanide would protect against atherosclerosis.

EXPERIMENTAL APPROACH

The mitochondrial oxygen consumption of cells was measured by using the high-resolution respirometry system, Oxygraph-2K. The proliferation and migration of A10 cells were measured by using Edu immunofluorescence staining, wound-induced migration and the Boyden chamber assay. Protein levels were measured by using the western blot technique. ApoE (-/-) mice were fed with a Western diet to establish an atherosclerotic model in vivo.

KEY RESULTS

The in vitro experiments showed that nitazoxanide and tizoxanide had a mitochondrial uncoupling effect and activated cellular AMPK. Nitazoxanide and tizoxanide inhibited serum- and PDGF-induced proliferation and migration of A10 cells. Nitazoxanide and tizoxanide inhibited NLRP3 inflammasome activation in RAW264.7 macrophages, the mechanism by which involved the AMPK/IκBα/NF-κB pathway. Nitazoxanide and tizoxanide also induced autophagy in A10 cells and RAW264.7 macrophages. The in vivo experiments demonstrated that oral administration of nitazoxanide reduced the increase in serum IL-1β and IL-6 levels and suppressed atherosclerosis in Western diet-fed ApoE (-/-) mice.

CONCLUSION AND IMPLICATIONS

Nitazoxanide inhibits the formation of atherosclerotic plaques in ApoE (-/-) mice fed on a Western diet. In view of nitazoxanide being an antiprotozoal drug already approved by the FDA, we propose it as a novel anti-atherosclerotic drug with clinical translational potential.

Paeonol protects against doxorubicin-induced cardiotoxicity by promoting Mfn2-mediated mitochondrial fusion through activating the PKCε-Stat3 pathway

INTRODUCTION

The anti-cancer medication doxorubicin (Dox) is largely restricted in clinical usage due to its significant cardiotoxicity. The only medication approved by the FDA for Dox-induced cardiotoxicity is dexrazoxane, while it may reduce the sensitivity of cancer cells to chemotherapy and is restricted for use. There is an urgent need for the development of safe and effective medicines to alleviate Dox-induced cardiotoxicity.

OBJECTIVES

The objective of this study was to determine whether Paeonol (Pae) has the ability to protect against Dox-induced cardiotoxicity and if so, what are the underlying mechanisms involved.

METHODS

Sprague-Dawley rats and primary cardiomyocytes were used to create Dox-induced cardiotoxicity models. Pae's effects on myocardial damage, mitochondrial function, mitochondrial dynamics and signaling pathways were studied using a range of experimental methods.

RESULTS

Pae enhanced Mfn2-mediated mitochondrial fusion, restored mitochondrial function and cardiac performance both in vivo and in vitro under the Dox conditions. The protective properties of Pae were blunted when Mfn2 was knocked down or knocked out in Dox-induced cardiomyocytes and hearts respectively. Mechanistically, Pae promoted Mfn2-mediated mitochondria fusion by activating the transcription factor Stat3, which bound to the Mfn2 promoter in a direct manner and up-regulated its transcriptional expression. Furthermore, molecular docking, surface plasmon resonance and co-immunoprecipitation studies showed that Pae's direct target was PKCε, which interacted with Stat3 and enabled its phosphorylation and activation. Pae-induced Stat3 phosphorylation and Mfn2-mediated mitochondrial fusion were inhibited when PKCε was knocked down. Furthermore, Pae did not interfere with Dox's antitumor efficacy in several tumor cells.

CONCLUSION

Pae protects the heart against Dox-induced damage by stimulating mitochondrial fusion via the PKCε-Stat3-Mfn2 pathway, indicating that Pae might be a promising therapeutic therapy for Dox-induced cardiotoxicity while maintaining Dox's anticancer activity.

Niclosamide Is a Much More Potent Toxicant of Mitochondrial Respiration than TFM in the Invasive Sea Lamprey (Petromyzon marinus)

Invasive sea lampreys in the Laurentian Great Lakes are controlled by applying TFM (3-trifluoromethyl-4-nitrophenol) and niclosamide to streams infested with their larvae. Both agents uncouple oxidative phosphorylation in the mitochondria, but TFM specifically targets lampreys, which have a lower capacity to detoxify the lampricide. Niclosamide lacks specificity and is more potent than TFM. However, its greater potency is poorly understood. We tested the hypothesis that niclosamide is a stronger uncoupler of mitochondrial oxidative phosphorylation than TFM by measuring oxygen consumption rates in isolated liver mitochondria exposed to physiologically relevant concentrations of TFM, niclosamide, or their mixture (100 TFM:1 niclosamide) at environmentally relevant temperatures (7, 13, and 25 °C). Niclosamide increased State 4 respiration and decreased the respiratory control ratio (RCR) at much lower concentrations than TFM. Calculations of the relative EC₅₀ values, the amount of TFM or niclosamide required to decrease the RCR by 50%, indicated that niclosamide was 40-60 times more potent than TFM. Warmer temperature did not appear to decrease the sensitivity of mitochondria to niclosamide or TFM, as observed in the intact sea lamprey exposed to TFM in warmer waters. We conclude that the extreme sensitivity of mitochondria to niclosamide contributes to its greater in vivo toxicity in the whole animal.

Anthelmintics nitazoxanide protects against experimental hyperlipidemia and hepatic steatosis in hamsters and mice

Lipid metabolism disorders contribute to hyperlipidemia and hepatic steatosis. It is ideal to develop drugs simultaneous improving both hyperlipidemia and hepatic steatosis. Nitazoxanide is an FDA-approved oral antiprotozoal drug with excellent pharmacokinetic and safety profile. We found that nitazoxanide and its metabolite tizoxanide induced mild mitochondrial uncoupling and subsequently activated AMPK in HepG2 cells. Gavage administration of nitazoxanide inhibited high-fat diet (HFD)-induced increases of liver weight, blood and liver lipids, and ameliorated HFD-induced renal lipid accumulation in hamsters. Nitazoxanide significantly improved HFD-induced histopathologic changes of hamster livers. In the hamsters with pre-existing hyperlipidemia and hepatic steatosis, nitazoxanide also showed therapeutic effect. Gavage administration of nitazoxanide improved HFD-induced hepatic steatosis in C57BL/6J mice and western diet (WD)-induced hepatic steatosis in Apoe ^-/- mice. The present study suggests that repurposing nitazoxanide as a drug for hyperlipidemia and hepatic steatosis treatment is promising.

Fifty Years of Research on Protonophores: Mitochondrial Uncoupling As a Basis for Therapeutic Action

Protonophores are compounds capable of electrogenic transport of protons across membranes. Protonophores have been intensively studied over the past 50 years owing to their ability to uncouple oxidation and phosphorylation in mitochondria and chloroplasts. The action mechanism of classical uncouplers, such as DNP and CCCP, in mitochondria is believed to be related to their protonophoric activity; i.e., their ability to transfer protons across the lipid part of the mitochondrial membrane. Given the recently revealed deviations in the correlation between the protonophoric activity of some uncouplers and their ability to stimulate mitochondrial respiration, this review addresses the involvement of some proteins of the inner mitochondrial membrane, such as the ATP/ADP antiporter, dicarboxylate carrier, and ATPase, in the uncoupling process. However, these deviations do not contradict the Mitchell theory but point to a more complex nature of the interaction of DNP, CCCP, and other uncouplers with mitochondrial membranes. Therefore, a detailed investigation of the action mechanism of uncouplers is required for a more successful pharmacological use, including their antibacterial, antiviral, anticancer, as well as cardio-, neuro-, and nephroprotective effects.

Anthelmintic niclosamide attenuates pressure-overload induced heart failure in mice

The heart is a high energy demand organ and enhancing mitochondrial function is proposed as the next-generation therapeutics for heart failure. Our previous study found that anthelmintic drug niclosamide enhanced mitochondrial respiration and increased adenosine triphosphate (ATP) production in cardiomyocytes, therefore, this study aimed to determine the effect of niclosamide on heart failure in mice and the potential molecular mechanisms. The heart failure model was induced by transverse aortic constriction (TAC) in mice. Oral administration of niclosamide improved TAC-induced cardiac hypertrophy, cardiac fibrosis, and cardiac dysfunction in mice. Oral administration of niclosamide reduced TAC-induced increase of serum IL-6 in heart failure mice. In vitro, niclosamide within 0.1 μM increased mitochondrial respiration and ATP production in mice heart tissues. At the concentrations more than 0.1 μM, niclosamide reduced the increased interleukin- 6 (IL-6) mRNA expression in lipopolysaccharide (LPS)-stimulated RAW264.7 and THP-1 derived macrophages. In cultured primary cardiomyocytes and cardiac fibroblasts, niclosamide (more than 0.1 μM) suppressed IL-6- and phenylephrine-induced cardiomyocyte hypertrophy, and inhibited collagen secretion from cardiac fibroblasts. In conclusion, niclosamide attenuates heart failure in mice and the underlying mechanisms include enhancing mitochondrial respiration of cardiomyocytes, inhibiting collagen secretion from cardiac fibroblasts, and reducing the elevated serum inflammatory mediator IL-6. The present study suggests that niclosamide might be therapeutic for heart failure.

Linking 7-Nitrobenzo-2-oxa-1,3-diazole (NBD) to Triphenylphosphonium Yields Mitochondria-Targeted Protonophore and Antibacterial Agent

Appending lipophilic cations to small molecules has been widely used to produce mitochondria-targeted compounds with specific activities. In this work, we obtained a series of derivatives of the well-known fluorescent dye 7-nitrobenzo-2-oxa-1,3-diazole (NBD). According to the previous data [Denisov et al. (2014) Bioelectrochemistry, 98, 30-38], alkyl derivatives of NBD can uncouple isolated mitochondria at concentration of tens of micromoles despite a high pK_a value (~11) of the dissociating group. Here, a number of triphenylphosphonium (TPP) derivatives linked to NBD via hydrocarbon spacers of varying length (C5, C8, C10, and C12) were synthesized (mitoNBD analogues), which accumulated in the mitochondria in an energy-dependent manner. NBD-C10-TPP (C10-mitoNBD) acted as a protonophore in artificial lipid membranes (liposomes) and uncoupled isolated mitochondria at micromolar concentrations, while the derivative with a shorter linker (NBD-C5-TPP, or C5-mitoNBD) exhibited no such activities. In accordance with this data, C10-mitoNBD was significantly more efficient than C5-mitoNBD in suppressing the growth of Bacillus subtilis. C10-mitoNBD and C12-mitoNBD demonstrated the highest antibacterial activity among the investigated analogues. C10-mitoNBD also exhibited the neuroprotective effect in the rat model of traumatic brain injury.

Progress in Redirecting Antiparasitic Drugs for Cancer Treatment

Drug repurposing is a feasible strategy in developing novel medications. Regarding the cancer field, scientists are continuously making efforts to redirect conventional drugs into cancer treatment. This approach aims at exploring new applications in the existing agents. Antiparasitic medications, including artemisinin derivatives (ARTs), quinine-related compounds, niclosamide, ivermectin, albendazole derivatives, nitazoxanide and pyrimethamine, have been deeply investigated and widely applied in treating various parasitic diseases for a long time. Generally, their pharmacokinetic and pharmacodynamic properties are well understood, while the side effects are roughly acceptable. Scientists noticed that some of these agents have anticancer potentials and explored the underlying mechanisms to achieve drug repurposing. Recent studies show that these agents inhibit cancer progression via multiple interesting ways, inducing ferroptosis induction, autophagy regulation, mitochondrial disturbance, immunoregulation, and metabolic disruption. In this review, we summarize the recent advancement in uncovering antiparasitic drugs' anticancer properties from the perspective of their pharmacological targets. Instead of paying attention to the previously discovered mechanisms, we focus more on newly emerging ones that are worth noticing. While most investigations are focusing on the mechanisms of their antiparasitic effect, more in vivo exploration in clinical trials in the future is necessary. Moreover, we also paid attention to what limits the clinical application of these agents. For some of these agents like ARTs and niclosamide, drug modification, novel delivery system invention, or drug combination are strongly recommended for future exploration.

An update of the molecular mechanisms underlying doxorubicin plus trastuzumab induced cardiotoxicity

Cardiotoxicity is a major side effect of the chemotherapeutic drug doxorubicin (Dox), which is further exacerbated when it is combined with trastuzumab, a standard care approach for Human Epidermal growth factor Receptor-type 2 (HER2) positive cancer patients. However, the molecular mechanisms of the underlying cardiotoxicity of this combination are still mostly elusive. Increased oxidative stress, impaired energetic substrate uses and topoisomerase IIB inhibition are among the biological processes proposed to explain Dox-induced cardiomyocyte dysfunction. Since cardiomyocytes express HER2, trastuzumab can also damage these cells by interfering with neuroregulin-1 signaling and mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K)/Akt and focal adhesion kinase (FAK)-dependent pathways. Nevertheless, Dox and trastuzumab target other cardiac cell types, such as endothelial cells, fibroblasts, cardiac progenitor cells and leukocytes, which can contribute to the clinical cardiotoxicity observed. This review aims to summarize the current knowledge on the cardiac signaling pathways modulated by these two antineoplastic drugs highly used in the management of breast cancer, not only focusing on cardiomyocytes but also to broaden the knowledge of the potential impact on other cells found in the heart.

The potential endocrine disruption mechanism of anthelmintic drug niclosamide by activating estrogen receptors and estrogen-related receptors

Niclosamide (NIC), a helminthic drug used widely for controlling schistosomiasis, can reportedly disrupt the endocrine system. However, its underlying mechanisms are still unclear. In this study, we revealed the potential endocrine disruption mechanism of NIC by activating estrogen receptors (ERs) and estrogen-related receptors (ERRs). The binding potency of NIC with ERα, ERβ and ERRγ were determined by fluorescence competitive binding assays, which shows an IC₅₀ (the concentration of NIC needed to displace 50 % of the probe from the receptor) of 90 ± 4.1, 10 ± 1.7 nM and 0.59 ± 0.07 nM respectively. The IC₅₀ for ERRγ is the lowest one among the three detected receptors, which is three orders of magnitude lower than the known agonist GSK4716.The transcriptional activities of NIC on ERs and ERRs were detected by MVLN cells (stably transfected with ERs reporter gene) and HeLa cells (transiently transfected with ERRs reporter gene)-based luciferase reporter gene assay. The lowest observable effective concentration (LOEC) ranked as follows: ERRγ (0.5 nM) < ERRα (10 nM) < ERs (100 nM). The maximum observed induction rate for ERRγ (294 %) was higher than that for ERRα (191 %). The maximum observed induction rate of NIC for ERs was 30 % relative to 17β-estradiol. In addition, we simulated the interactions of NIC with ERs and ERRs by molecular docking. NIC could dock into the ligand binding pockets of ERs and ERRs and form hydrogen bonds with different amino acids. The binding energy ranked as follows: ERRγ (-8.90 kcal/mol) < ERβ (-7.57 kcal/mol) < ERRα (-7.15 kcal/mol) < ERα (-6.53 kcal/mol), which implied that NIC bound to ERRγ with higher binding affinity than the other receptors. Overall, we clarify that ERRγ might be the dominant target for NIC in cells rather than ERRα and ERs. We reveal potential novel mechanisms for the endocrine disruption effects of NIC by activating both ERRs and ERs at environmentally-related nanomolar levels.

Acute high-intensity aerobic exercise increases gene expression of calcium-related proteins and activates endoplasmic reticulum stress responses in diabetic hearts

Regular aerobic exercise training has a wide range of beneficial cardiac effects, but recent data also show that acute very strenuous aerobic exercise may impose a transient cardiac exhaustion. The aim of this study was to assess the response to acute high-intensity aerobic exercise on properties of mitochondrial respiration, cardiomyocyte contractile function, Ca2+ handling and transcriptional changes for key proteins facilitating Ca2+ handling and endoplasmic reticulum (ER) stress responses in type 2 diabetic mice. Diabetic mice were assigned to either sedentary control or an acute bout of exercise, consisting of a 10×4 minutes high-intensity interval treadmill run. Mitochondrial respiration, contractile and Ca2+ handling properties of cardiomyocytes were analysed 1 hour after completion of exercise. Gene expression levels of key Ca2+ handling and ER stress response proteins were measured in cardiac tissue samples harvested 1 hour and 24 hours after exercise. We found no significant changes in mitochondrial respiration, cardiomyocyte contractile function or Ca2+ handling 1 hour after the acute exercise. However, gene expression of Atp2a2, Slc8a1 and Ryr2, encoding proteins involved in cardiomyocyte Ca2+ handling, were all significantly upregulated 24 hours after the acute exercise bout. Acute exercise also altered gene expression of several key proteins in ER stress response and unfolded protein response, including Grp94, total Xbp1, Gadd34, and Atf6. The present results show that despite no significant alterations in functional properties of cardiomyocyte function, Ca2+ handling or mitochondrial respiration following one bout of high intensity aerobic exercise training, the expression of genes involved in Ca2+ handling and key components in ER stress and the unfolded protein response were changed. These transcriptional changes may constitute important steps in initiating adaptive remodelling to exercise training in type 2 diabetes.

Chemical mitochondrial uncouplers share common inhibitory effect on NLRP3 inflammasome activation through inhibiting NFκB nuclear translocation

Activation of NLRP3 inflammasome is implicated in varieties of pathologies, the aim of the present study is to characterize the effect and mechanism of mitochondrial uncouplers on NLRP3 inflammasome activation by using three types of uncouplers, niclosamide, CCCP and BAM15. Niclosamide, CCCP and BAM15 inhibited LPS plus ATP-induced increases of NLRP3 protein and IL-1β mRNA levels in RAW264.7 macrophages and THP-1 derived macrophages. Niclosamide, CCCP and BAM15 inhibited LPS plus ATP-induced increase of NFκB (P65) phosphorylation, and inhibited NFκB (P65) nuclear translocation in RAW264.7 macrophages. Niclosamide and BAM15 inhibited LPS-induced increase of IκBα phosphorylation in RAW264.7 macrophages, and the inhibitory effect was dependent on increased intracellular [Ca²⁺]_i; however, CCCP showed no significant effect on IκBα phosphorylation in RAW264.7 macrophages stimulated with LPS. In conclusion, chemical mitochondrial uncouplers niclosamide, CCCP and BAM15 share common inhibitory effect on NLRP3 inflammasome activation through inhibiting NFκB nuclear translocation.

Moderate Hydrogen Peroxide Postconditioning Ameliorates Ischemia/Reperfusion Injury in Cardiomyocytes via STAT3-Induced Calcium, ROS, and ATP Homeostasis

INTRODUCTION

Moderate hydrogen peroxide postconditioning (H2O2PoC) activates signal transducer and activator of transcription 3 (STAT3) to alleviate mitochondrial calcium overload during cardiac ischemia/reperfusion (I/R). However, the initial time window of STAT3-induced calcium hemostasis, the production of reactive oxygen species (ROS) and adenosine triphosphate (ATP) in H2O2PoC, and its regulated mechanism remain unknown. This study aimed to investigate H2O2PoC-induced homeostasis of calcium, ROS and ATP, and the role of STAT3 in the regulation.

METHODS

Isolated rat cardiomyocytes were exposed to H2O2PoC and Janus kinase 2 (JAK2)/STAT3 inhibitor AG490 during I/R. Ca2+ transients, cell contraction, intracellular calcium concentration, ROS production, ATP contents, phosphorylation of STAT3, gene and protein expression of manganese superoxide dismutase (MnSOD), metallothionein 1 (MT1) and metallothionein 2 (MT2), as well as activities of mitochondrial complex I and complex II were detected.

RESULTS

Moderate H2O2PoC improved post-ischemic Ca2+ transients and cell contraction recovery as well as alleviated cytosolic and mitochondrial calcium overload, which were abrogated by AG490 in rat cardiomyocytes. Moderate H2O2PoC increased ROS production and rate of ROS production at early reperfusion in rat I/R cardiomyocytes, and this phenomenon was also abrogated by AG490. Notably, the expression of phosphorylated nuclear STAT3; gene and protein expression of MnSOD, MT1, and MT2; and activities of mitochondrial complex I and complex II were upregulated by moderate H2O2PoC but downregulated by AG490.

CONCLUSION

These findings indicated that the cardioprotection of moderate H2O2PoC against cardiac I/R could be associated with activated STAT3 at early reperfusion to maintain calcium, ROS, and ATP homeostasis in rat cardiomyocytes.

Crystalline silica particles cause rapid NLRP3-dependent mitochondrial depolarization and DNA damage in airway epithelial cells

BACKGROUND

Respirable crystalline silica causes lung carcinomas and many thousand future cancer cases are expected in e.g. Europe. Critical questions are how silica causes genotoxicity in the respiratory epithelium and if new cases can be avoided by lowered permissible exposure levels. In this study we investigate early DNA damaging effects of low doses of silica particles in respiratory epithelial cells in vitro and in vivo in an effort to understand low-dose carcinogenic effects of silica particles.

RESULTS

We find DNA damage accumulation already after 5-10 min exposure to low doses (5 μg/cm²) of silica particles (Min-U-Sil 5) in vitro. DNA damage was documented as increased levels of γH2AX, pCHK2, by Comet assay, AIM2 induction, and by increased DNA repair (non-homologous end joining) signaling. The DNA damage response (DDR) was not related to increased ROS levels, but to a NLRP3-dependent mitochondrial depolarization. Particles in contact with the plasma membrane elicited a Ser198 phosphorylation of NLRP3, co-localization of NLRP3 to mitochondria and depolarization. FCCP, a mitochondrial uncoupler, as well as overexpressed NLRP3 mimicked the silica-induced depolarization and the DNA damage response. A single inhalation of 25 μg silica particles gave a similar rapid DDR in mouse lung. Biomarkers (CC10 and GPRC5A) indicated an involvement of respiratory epithelial cells.

CONCLUSIONS

Our findings demonstrate a novel mode of action (MOA) for silica-induced DNA damage and mutagenic double strand breaks in airway epithelial cells. This MOA seems independent of particle uptake and of an involvement of macrophages. Our study might help defining models for estimating exposure levels without DNA damaging effects.

Triclosan induces ROS-dependent cell death and autophagy in A375 melanoma cells

Melanoma is a common type of cutaneous tumor, but current drug treatments do not satisfy clinical practice requirements. At present, mitochondrial uncoupling is an effective antitumor treatment. Triclosan, a common antimicrobial, also acts as a mitochondrial uncoupler. The aims of the present study were to investigate the effects of triclosan on melanoma cells and the underlying mechanisms. Mitochondrial membrane potential (MMP), mitochondrial morphology, mitochondrial reactive oxygen species (mito-ROS), intracellular superoxide anion and [Ca²⁺]_i were measured using confocal microscopy. It was found that triclosan application was associated with decreased A375 cell viability in a dose- and time-dependent manner and these effects may have cell specificity. Furthermore, triclosan induced MMP depolarization, ATP content decrease, mito-ROS and [Ca²⁺]_i level increases, excessive mitochondrial fission, AMP-activated protein kinase (AMPK) activation and STAT3 inhibition. Moreover, these aforementioned effects were reversed by acetylcysteine treatment. Triclosan acute treatment also induced mitochondrial swelling, which was reversed after AMPK-knockdown associated with [Ca²⁺]_i overload. Cell death was caused by STAT3 inhibition but not AMPK activation. Moreover, triclosan induced autophagy via the ROS/AMPK/p62/microtubule-associated protein 1A/1B-light chain 3 (LC3) signaling pathway, which may serve a role in feedback protection. Collectively, the present results suggested that triclosan increased mito-ROS production in melanoma cells, following induced cell death via the STAT3/Bcl-2 pathway and autophagy via the AMPK/p62/LC3 pathway.

Mitochondrial oxidative stress induces leaky ryanodine receptor during mechanical ventilation

RATIONALE

Ventilator-induced diaphragm dysfunction (VIDD) increases morbidity and mortality in critical care patients. Although VIDD has been associated with mitochondrial oxidative stress and calcium homeostasis impairment, the underling mechanisms are still unknown. We hypothesized that diaphragmatic mitochondrial oxidative stress causes remodeling of the ryanodine receptor (RyR1)/calcium release channel, contributing to sarcoplasmic reticulum (SR) Ca²⁺ leak, proteolysis and VIDD.

METHOD

In mice diaphragms mechanically ventilated for short (6 h) and long (12 h) period, we assessed mitochondrial ROS production, mitochondrial aconitase activity as a marker of mitochondrial oxidative stress, RyR1 remodeling and function, Ca²⁺ dependent proteolysis, TGFβ1 and STAT3 pathway, muscle fibers cross-sectional area, and diaphragm specific force production, with or without the mitochondrial targeted anti-oxidant peptide d-Arg-2', 6'-dimethyltyrosine-Lys-Phe-NH₂ (SS31).

MEASUREMENTS AND MAIN RESULTS

6 h of mechanical ventilation (MV) resulted in increased mitochondrial ROS production, reduction of mitochondrial aconitase activity, increased oxidation, S-nitrosylation, S-glutathionylation and Ser-2844 phosphorylation of RyR1, depletion of stabilizing subunit calstabin1 from RyR1, increased SR Ca²⁺ leak. Preventing mROS production by SS31 treatment does not affect the TGFβ1 and STAT3 activation, which suggests that mitochondrial oxidative stress is a downstream pathway to TGFβ1 and STAT3, early involved in VIDD. This is further supported by the fact that SS-31 rescue all the other described cellular events and diaphragm contractile dysfunction induced by MV, while SS20, an analog of SS31 lacking antioxidant properties, failed to prevent these cellular events and the contractile dysfunction. Similar results were found in ventilated for 12 h. Moreover, SS31 treatment prevented calpain1 activity and diaphragm atrophy observed after 12 h of MV. This study emphasizes that mitochondrial oxidative stress during 6 h-MV contributes to SR Ca²⁺ leak via RyR1 remodeling, and diaphragm weakness, while longer periods of MV (12 h) were also associated with increased Ca²⁺-dependent proteolysis and diaphragm atrophy.

The different response of cardiomyocytes and cardiac fibroblasts to mitochondria inhibition and the underlying role of STAT3

Cardiomyocyte loss and cardiac fibrosis are the main characteristics of cardiac ischemia and heart failure, and mitochondrial function of cardiomyocytes is impaired in cardiac ischemia and heart failure, so the aim of this study is to identify fate variability of cardiomyocytes and cardiac fibroblasts with mitochondria inhibition and explore the underlying mechanism. The mitochondrial respiratory function was measured by using Oxygraph-2k high-resolution respirometry. The STAT3 expression and activity were evaluated by western blot. Cardiomyocytes and cardiac fibroblasts displayed different morphology. The mitochondrial respiratory function and the expressions of mitochondrial complex I, II, III, IV, and V of cardiac fibroblasts were lower than that of cardiomyocytes. Mitochondrial respiratory complex I inhibitor rotenone and H₂O₂ (100 µM, 4 h) treatment induced cell death of cardiomyocyte but not cardiac fibroblasts. The function of complex I/II was impaired in cardiomycytes but not cardiac fibroblasts stimulated with H₂O₂ (100 µM, 4 h) and in ischemic heart of mice. Rotenone and H₂O₂ (100 µM, 4 h) treatment reduced STAT3 expression and activity in cardiomyocytes but not cardiac fibroblasts. Inhibition of STAT3 impaired mitochondrial respiratory capacity and exacerbated H₂O₂-induced cell injury in cardiomycytes but not significantly in cardiac fibroblasts. In conclusion, the different susceptibility of cardiomyocytes and cardiac fibroblasts to mitochondria inhibition determines the cell fate under the same pathological stimuli and in which STAT3 plays a critical role.

Activation of cardiac TrkB receptor by its small molecular agonist 7,8-dihydroxyflavone inhibits doxorubicin-induced cardiotoxicity via enhancing mitochondrial oxidative phosphorylation

Brain-derived neurotrophic factor (BDNF)/tropomyosin-related receptor kinase B (TrkB) pathway has been revealed as a novel therapeutic target for several neurological diseases. Recently, small-molecule TrkB agonist 7,8-dihydroxyflavone (7,8-DHF) has received considerable attention as a novel potential candidate for the treatment of various BDNF-implicated human disorders. However, its roles in cardiac diseases are not fully understood. Here, the present study aimed to clarify the effects and mechanisms of 7,8-DHF on doxorubicin (Dox)-induced cardiotoxicity. Kunming mice and H9c2 cells were employed to investigate the functional role of 7,8-DHF both in vivo and in vitro. 7,8-DHF markedly increased cell viability and reduced cell death of Dox-treated cells. Meanwhile, 7,8-DHF significantly increased mitochondrial respiration, membrane potential, and optic atrophy 1 (OPA1) protein expression. 7,8-DHF improved cardiac function and attenuated cardiac injury in Dox mice model. Expression of AMP-activated protein kinase (AMPK) and signal transducers and activators of transcription 3 (STAT3) was restored by 7,8-DHF. Furthermore, the protective role of 7,8-DHF was abolished by ANA-12 (a specific antagonist of TrkB). In elucidating the molecular mechanism, the phosphorylation of Akt was significantly increased while extracellular regulated protein kinase (ERK) was decreased after 7,8-DHF treatment. The regulatory effects of 7,8-DHF on STAT3 and AMPK was reversed by Akt inhibitor. In summary, 7,8-DHF attenuated Dox-induced cardiotoxicity by activating Akt and increasing mitochondrial oxidative phosphorylation and thereby regulating STAT3, AMPK, and ERK signals. The present study enhanced current understanding of TrkB receptor in the cardiovascular system and provided a novel target for prevention and treatment of heart diseases.

FR58P1a; a new uncoupler of OXPHOS that inhibits migration in triple-negative breast cancer cells via Sirt1/AMPK/β1-integrin pathway

Highly malignant triple-negative breast cancer (TNBC) cells rely mostly on glycolysis to maintain cellular homeostasis; however, mitochondria are still required for migration and metastasis. Taking advantage of the metabolic flexibility of TNBC MDA-MB-231 cells to generate subpopulations with glycolytic or oxidative phenotypes, we screened phenolic compounds containing an ortho-carbonyl group with mitochondrial activity and identified a bromoalkyl-ester of hydroquinone named FR58P1a, as a mitochondrial metabolism-affecting compound that uncouples OXPHOS through a protonophoric mechanism. In contrast to well-known protonophore uncoupler FCCP, FR58P1a does not depolarize the plasma membrane and its effect on the mitochondrial membrane potential and bioenergetics is moderate suggesting a mild uncoupling of OXPHOS. FR58P1a activates AMPK in a Sirt1-dependent fashion. Although the activation of Sirt1/AMPK axis by FR58P1a has a cyto-protective role, selectively inhibits fibronectin-dependent adhesion and migration in TNBC cells but not in non-tumoral MCF10A cells by decreasing β1-integrin at the cell surface. Prolonged exposure to FR58P1a triggers a metabolic reprograming in TNBC cells characterized by down-regulation of OXPHOS-related genes that promote cell survival but comprise their ability to migrate. Taken together, our results show that TNBC cell migration is susceptible to mitochondrial alterations induced by small molecules as FR58P1a, which may have therapeutic implications.