Phloretin ameliorates arsenic trioxide induced mitochondrial dysfunction in H9c2 cardiomyoblasts mediated via alterations in membrane permeability and ETC complexes

Arsenic-induced mice model of Parkinson's disease: Revealing the neurotoxicity of arsenic through mitochondrial complexes inhibition and dopaminergic neurodegeneration in the substantia nigra region of brain

The role of environmental contaminants in causing Parkinson's disease (PD) is well known, with rotenone and paraquat being the notable neurotoxins. Traces of the metalloid arsenic are frequently found in drinking water which is considered a threat to the brain's health. Pre-clinical and epidemiological studies have associated arsenic with PD whereby behavioral and neurochemical alterations were observed. However, the impact of arsenic toxicity on the dopaminergic neurons of substantia nigra (SN), the hallmark region which degenerates in PD, has not been shown yet. In the present study, administration of 20 mg/kg b.w., arsenic for 28 days caused significant loss of dopaminergic neurons and their terminals respectively in the SN and striatum regions of mice brain. Moreover, the arsenic-fed rodents exhibited depleted striatal dopamine, prolonged latency to move and correct posture, and reduced exploratory behavior and neurological severity. Further, mitochondrial complexes II and IV were found to be inhibited in the SN, cortex, striatum, and hippocampus of arsenic-fed mice. Additionally, inflammatory marker glial fibrillary acidic protein (GFAP) and neuronal nitric oxide synthase (nNOS) expressed in glial cells and neurons respectively were enhanced in the nigrostriatal pathway of arsenic-fed animals. The present study for the first time reports that arsenic causes Parkinsonism by degenerating nigrostriatal dopaminergic neurons through mitochondrial complex inhibition and inflammatory stress. The study further puts forward validatory evidence for the potential of arsenic in causing PD and the reliability of the arsenic-induced PD model for exploring the disease pathogenesis and treatment.

Arsenic induced cardiotoxicity: An approach for molecular markers, epigenetic predictors and targets

Arsenic, a ubiquitous environmental toxicant, has been acknowledged as a significant issue for public health due to its widespread pollution of drinking water and food supplies. The present review aimed to study the toxicity associated with the cardiac system. Prolonged exposure to arsenic has been associated with several harmful health outcomes, especially cardiotoxicity. Arsenic-induced cardiotoxicity encompasses a range of cardiovascular abnormalities, including cardiac arrhythmias, ischemic heart disease, and cardiomyopathy. To tackle this toxicity, understanding the molecular markers, epigenetic predictors, and targets involved in arsenic-induced cardiotoxicity is essential for creating preventative and therapeutic approaches. For preventive measures against this heavy metal poisoning of groundwater, it is crucial to regularly monitor water quality, re-evaluate scientific findings, and educate the public about the possible risks. This review thoroughly summarised what is currently known in this field, highlighting the key molecular markers, epigenetic modifications, and potential therapeutic targets associated with arsenic-induced cardiotoxicity.

Phloretin prolongs lifespan of Caenorhabditis elegans via inhibition of NDUFS1 and NDUFS6 at mitochondrial complex Ⅰ

Phloretin has been widely perceived as an antioxidant. However, the bioavailability of phloretin in vivo is generally far too low to elicit a direct antioxidant effect by scavenging reactive oxygen species (ROS). Here we showed that administration of phloretin of apple polyphenols extended lifespan of Caenorhabditis elegans and promoted fitness. Specially phloretin enhanced the survival rates of nematodes under oxidants in an inverted U-shaped dose-response manner. The lifespan-extending effects of phloretin were mediated by ROS via mitochondrial complex I inhibition. The increase of ROS stimulated p38 MAPK/PMK-1 as well as transcription factors of NRF2/SKN-1 and FOXO/DAF-16. Consistent with the involvement of NRF2/SKN-1 and FOXO/DAF-16 in lifespan-extending effects, activities of superoxide dismutase (SOD) and catalase (CAT) were enhanced by phloretin. The exogenous application of antioxidants butylated hydroxyanisole and N-acetylcysteine abolished the increase of ROS, the enhancement of SOD and CAT activities, and the lifespan extending effects of phloretin. Meanwhile, with the inhibition of mitochondrial complex I, ATP was instantly decreased. Both energy sensors of AMPK/AAK-2 and SIRT1/SIR-2.1 were involved in the lifespan extension by phloretin. Transcriptomic, real-time qPCR and molecular docking analyses demonstrated that the binding of phloretin at complex I located at NDUFS1/NUO-5, NDUFS2/GAS-1, and NDUFS6/NDUF-6. The molecular dynamic simulation and binding free energy calculations showed that phloretin had high binding affinities towards NDUFS1 (-7.21 kcal/mol) and NDUFS6 (-7.02 kcal/mol). Collectively, our findings suggested phloretin had effects of life expectancy enhancement and fitness promotion via redox regulations in vivo. NDUFS1/NUO-5 and NDUFS6/NDUF-6 might be new targets in the lifespan and wellness regulations.

Implications of deltamethrin on hematology, cardiac pathology, and gene expression in Nile tilapia (Oreochromis niloticus) and its possible amelioration with Shatavari (Asparagus racemosus)

Deltamethrin (DM) is one of the extensively used pyrethroids for controlling ectoparasites. Unfortunately, DM is highly toxic to fish as it primarily targets the sodium channels of the plasma membrane thereby affecting their cardiac and nervous systems. The present study investigated the protective efficacy of Shatavari (Asparagus racemosus) against DM-induced cardiotoxicity in Nile tilapia (Oreochromis niloticus). The fish were segregated into nine groups having 36 fish/group maintained in triplicates exposed to DM (1 µg/L) and fed with a diet containing three different concentrations (10 g, 20 g, and 30 g/kg feed) of aqueous extract of A. racemosus (ARE) for 21 days. DM caused significant alterations in the blood and serum parameters, and expression of cardiac and apoptotic genes compared to the control group. The ARE cotreatment significantly reduced the increase in serum transaminases, creatine kinase, and lactate dehydrogenase levels induced by DM. ARE facilitated the regain of electrolyte (sodium, potassium, chloride) homeostasis and antioxidants such as catalase, superoxide dismutase, glutathione peroxidase, and glutathione in DM-exposed fish. The cardiac histology exhibited loose separation of the cardiomyocytes and myofibrillar loss in the DM group which was ameliorated in the DM-ARE cotreatment group. Significant modulations were observed in the expression of cardiac-specific genes (gata4, myh6, tnT, cox1) and apoptosis signaling genes and proteins (HSP70, bax, bcl-2, caspase3), in the cotreatment group compared to the DM-exposed group. The current study suggests that ARE possesses potential cardioprotective properties that are effective in mitigating the toxic effects induced by DM via ameliorating oxidative stress, electrolyte imbalance, and apoptosis in tilapia.

Thinned young apple powder prevents obesity-induced neuronal apoptosis via improving mitochondrial function of cerebral cortex in mice

Mitochondrial dysfunction is one of the triggers for obesity-induced neuron apoptosis. Thinned young apple is getting more attention on account of the extensive biological activities because of rich polyphenols and polysaccharides. However, the neuroprotective effect of thinned young apple powder (YAP) is still unclear. The aim of the present study was to investigate the preventive effect of YAP on obesity-induced neuronal apoptosis. C57BL/6J male mice were divided into 5 groups, control (CON), high fat diet (HFD), HFD + orlistat (ORL), HFD + low-dose young apple powder (LYAP) and HFD + high-dose young apple powder (HYAP) groups and intervened for 12 weeks. It was found that the YAP effectively reduced body weight gain. Importantly, the levels of pro-apoptosis protein were lower in LYAP and HYAP groups than the HFD group, such as Bak/Bcl2 and cleaved caspase3/caspase3. Pathway analysis based on untargeted metabolomics suggested that YAP alleviated obesity-induced neuronal apoptosis by three main metabolic pathway including arginine metabolism, citrate cycle (TCA cycle) and glutathione metabolism. Meanwhile, YAP improved the protein expression of mitochondrial respiratory chain complex, maintained the homeostasis of TCA cycle intermediates, protected the balance of mitochondrial dynamics and alleviated lipid accumulation. In addition, the levels of several antioxidants in cerebral cortex were higher in HYAP group than the HFD group like superoxide dismutase (SOD) and catalase (CAT). In summary, YAP supplementation suppressed neuronal apoptosis in the cerebral cortex of HFD-induced obesity mice by improving mitochondrial function and inhibiting oxidative stress.

Mitochondrial Dysfunction in Cardiac Diseases and Therapeutic Strategies

Mitochondria are the main site of intracellular synthesis of ATP, which provides energy for various physiological activities of the cell. Cardiomyocytes have a high density of mitochondria and mitochondrial damage is present in a variety of cardiovascular diseases. In this paper, we describe mitochondrial damage in mitochondrial cardiomyopathy, congenital heart disease, coronary heart disease, myocardial ischemia-reperfusion injury, heart failure, and drug-induced cardiotoxicity, in the context of the key roles of mitochondria in cardiac development and homeostasis. Finally, we discuss the main current therapeutic strategies aimed at alleviating mitochondrial impairment-related cardiac dysfunction, including pharmacological strategies, gene therapy, mitochondrial replacement therapy, and mitochondrial transplantation. It is hoped that this will provide new ideas for the treatment of cardiovascular diseases.

Potential of natural products in combination with arsenic trioxide: Investigating cardioprotective effects and mechanisms

Over the past few decades, clinical trials conducted worldwide have demonstrated the efficacy of arsenic trioxide (ATO) in the treatment of relapsed acute promyelocytic leukemia (APL). Currently, ATO has become the frontline treatments for patients with APL. However, its therapeutic applicability is severely constrained by ATO-induced cardiac side effects. Any cardioprotective agents that can ameliorate the cardiac side effects and allow exploiting the full therapeutic potential of ATO, undoubtedly gain significant attention. The knowledge and use of natural products for evidence-based therapy have grown rapidly in recent years. Here we discussed the potential mechanism of ATO-induced cardiac side effects and reviewed the studies on cardiac side effects as well as the research history of ATO in the treatment of APL. Then, We summarized the protective effects and underlying mechanisms of natural products in the treatment of ATO-induced cardiac side effects. Based on the efficacy and safety of the natural product, it has a promising future in the development of cardioprotective agents against ATO-induced cardiac side effects.

Phloroglucinol Inhibits Oxidative-Stress-Induced Cytotoxicity in C2C12 Murine Myoblasts through Nrf-2-Mediated Activation of HO-1

Phloroglucinol is a class of polyphenolic compounds containing aromatic phenyl rings and is known to have various pharmacological activities. Recently, we reported that this compound isolated from Ecklonia cava, a brown alga belonging to the family Laminariaceae, has potent antioxidant activity in human dermal keratinocytes. In this study, we evaluated whether phloroglucinol could protect against hydrogen peroxide (H2O2)-induced oxidative damage in murine-derived C2C12 myoblasts. Our results revealed that phloroglucinol suppressed H2O2-induced cytotoxicity and DNA damage while blocking the production of reactive oxygen species. We also found that phloroglucinol protected cells from the induction of apoptosis associated with mitochondrial impairment caused by H2O2 treatment. Furthermore, phloroglucinol enhanced the phosphorylation of nuclear factor-erythroid-2 related factor 2 (Nrf2) as well as the expression and activity of heme oxygenase-1 (HO-1). However, such anti-apoptotic and cytoprotective effects of phloroglucinol were greatly abolished by the HO-1 inhibitor, suggesting that phloroglucinol could increase the Nrf2-mediated activity of HO-1 to protect C2C12 myoblasts from oxidative stress. Taken together, our results indicate that phloroglucinol has a strong antioxidant activity as an Nrf2 activator and may have therapeutic benefits for oxidative-stress-mediated muscle disease.

Investigating the effect of myricetin against arsenic-induced cardiac toxicity in rats

Arsenic intoxication is a serious health hazard worldwide. Its toxicity is associated with several disorders and health problems in humans. Recent studies revealed that myricetin has various biological effects, including anti-oxidation. The aim of this study is to investigate the protective effect of myricetin against arsenic-induced cardiotoxicity in rats. Rats were randomized to one of the following groups: control, myricetin (2 mg/kg), arsenic (5 mg/kg), myricetin (1 mg/kg) + arsenic, and myricetin (2 mg/kg) + arsenic. Myricetin was given intraperitoneally 30 min before arsenic administration (5 mg/kg for 10 days). After treatments, the activity of lactate dehydrogenase (LDH) and the levels of aspartate aminotransferase (AST), creatine kinase myocardial band (CK-MB), lipid peroxidation (LPO), total antioxidant capacity (TAC), and total thiol molecules (TTM) were determined in serum samples and cardiac tissues. Also, histological changes in cardiac tissue were evaluated. Myricetin pretreatment inhibited arsenic-induced increase in LDH, AST, CK-MB, and LPO levels. Pretreatment with myricetin also enhanced the decreased TAC and TTM levels. In addition, myricetin improved histopathological alterations in arsenic-treated rats. In conclusion, the results of the present study demonstrated that treatment with myricetin prevented arsenic-induced cardiac toxicity at least in part by decreasing oxidative stress and restoring the antioxidant system.

The Molecular Pharmacology of Phloretin: Anti-Inflammatory Mechanisms of Action

The isolation of phlorizin from the bark of an apple tree in 1835 led to a flurry of research on its inhibitory effect on glucose transporters in the intestine and kidney. Using phlorizin as a prototype drug, antidiabetic agents with more selective inhibitory activity towards glucose transport at the kidney have subsequently been developed. In contrast, its hydrolysis product in the body, phloretin, which is also found in the apple plant, has weak antidiabetic properties. Phloretin, however, displays a range of pharmacological effects including antibacterial, anticancer, and cellular and organ protective properties both in vitro and in vivo. In this communication, the molecular basis of its anti-inflammatory mechanisms that attribute to its pharmacological effects is scrutinised. These include inhibiting the signalling pathways of inflammatory mediators' expression that support its suppressive effect in immune cells overactivation, obesity-induced inflammation, arthritis, endothelial, myocardial, hepatic, renal and lung injury, and inflammation in the gut, skin, and nervous system, among others.

Assessing Drug-Induced Mitochondrial Toxicity in Cardiomyocytes: Implications for Preclinical Cardiac Safety Evaluation

Drug-induced cardiotoxicity not only leads to the attrition of drugs during development, but also contributes to the high morbidity and mortality rates of cardiovascular diseases. Comprehensive testing for proarrhythmic risks of drugs has been applied in preclinical cardiac safety assessment for over 15 years. However, other mechanisms of cardiac toxicity have not received such attention. Of them, mitochondrial impairment is a common form of cardiotoxicity and is known to account for over half of cardiovascular adverse-event-related black box warnings imposed by the U.S. Food and Drug Administration. Although it has been studied in great depth, mitochondrial toxicity assessment has not yet been incorporated into routine safety tests for cardiotoxicity at the preclinical stage. This review discusses the main characteristics of mitochondria in cardiomyocytes, drug-induced mitochondrial toxicities, and high-throughput screening strategies for cardiomyocytes, as well as their proposed integration into preclinical safety pharmacology. We emphasize the advantages of using adult human primary cardiomyocytes for the evaluation of mitochondrial morphology and function, and the need for a novel cardiac safety testing platform integrating mitochondrial toxicity and proarrhythmic risk assessments in cardiac safety evaluation.

Exploring the role of senescence inducers and senotherapeutics as targets for anticancer natural products

During the last few decades, cancer has remained one of the deadliest diseases that endanger human health, emphasizing urgent drug discovery. Cellular senescence has gained a great deal of attention in recent years because of its link to the development of cancer therapy. Senescent cells are incapable of proliferating due to irreversibly inhibited the initiation of the cell cycle pathways. However, senescent cells aggregate in tissues and produce a pro-inflammatory secretome called senescence-associated secretory phenotype (SASP) that can cause serious harmful effects if not managed properly. There is mounting evidence that senescent cells lead to various phases of tumorigenesis in various anatomical sites, owing mostly to the paracrine activities of the SASP. Therefore, a new treatment field called senotherapeutics has been established. Senotherapeutics are newly developed anticancer agents that have been demonstrated to inhibit cancer effectively. In light of recent findings, several promising natural products have been identified as senescence inducers and senotherapeutics, including, miliusanes, epigallocatechin gallate, phloretin, silybin, resveratrol, genistein, sulforaphane, quercetin, allicin, fisetin, piperlongumine, berberine, triptolide, tocotrienols and curcumin analogs. Several of them have already been validated through preclinical trials and exert an enormous potential for clinical trials. This review article focuses on and summarises the latest advances on cellular senescence and its potential as a target for cancer treatment and highlights the well-known natural products as senotherapeutics for cancer treatment.

Arsenic trioxide-induced cardiotoxicity triggers ferroptosis in cardiomyoblast cells

Arsenic trioxide (ATO) has been found to be effective in acute promyelocytic leukemia. However, ATO-induced severe cardiotoxicity limits its clinical application. To date, the mechanisms of ATO-induced cardiotoxicity remain unclear. It is hypothesized that ferroptosis may trigger ATO-induced cardiotoxicity; however, this has not yet been investigated. To clarify this hypothesis, rat cardiomyocyte H9c2 cells were treated with ATO with or without ferrostain-1 (Fer-1). The results indicated that ATO exposure induced H9c2 cell death and apoptosis, and the ferroptosis inhibitor Fer-1, administered for 24 h before ATO exposure, suppressed ATO-induced cell death, and apoptosis, as determined by Annexin V-APC/7-AAD apoptosis assay. Furthermore, Fer-1 displayed a cardioprotective effect through inhibiting the ATO-induced production of intracellular reactive oxygen species, improving the ATO-induced loss of the mitochondrial membrane potential, alleviating hyperactive endoplasmic reticulum stress, and alleviating the ATO-induced impairment in autophagy in H9c2 cells. Overall, the cardioprotective effect of Fer-1 against ATO-induced cell injury implies that ATO may trigger ferroptosis to induce cardiotoxicity. These findings lay the foundation for exploring the potential value of ferroptosis inhibitors against ATO-induced cardiotoxicity in the future.

Arsenic-fluoride co-exposure induced endoplasmic reticulum stress resulting in apoptosis in rat heart and H9c2 cells

Exposure to arsenic (As) or fluoride (F) has been shown to cause cardiovascular disease (CVDs). However, evidence about the effects of co-exposure to As and F on myocardium and their mechanisms remain scarce. Our aim was to fill the gap by establishing rat and H9c2 cell exposure models. We determined the effects of As and/or F exposure on the survival rate, apoptosis rate, morphology and ultrastructure of H9c2 cells; in addition, we tested the related genes and proteins of endoplasmic reticulum stress (ERS) and apoptosis in H9c2 cells and rat heart tissues. The results showed that As and/or F exposure induced early apoptosis of H9c2 cells and caused endoplasmic reticulum expansion. Additionally, the mRNA and protein expression levels of GRP78, PERK and CHOP in H9c2 cells were higher in the exposure groups than in the control group, and could be inhibited by 4-PBA. Furthermore, we found that As and/or F exposure increased the expression level of GRP78 in rat heart tissues, but interestingly, the expression level of CHOP protein was increased in the F and As groups, while significantly decreased in the co-exposure group. Overall, our results suggested that ERS-induced apoptosis was involved in the damage of myocardium by As and/or F exposure. In addition, factorial analysis results showed that As and F mainly play antagonistic roles in inducing myocardial injury, initiating ERS and apoptosis after exposure.

Redox Activity of Flavonoids: Impact on Human Health, Therapeutics, and Chemical Safety

The cost-effectiveness of presently used therapies is a problem in overall redox-based management, which is posing a significant financial burden on communities across the world. As a result, sophisticated treatment models that provide notions of predictive diagnoses followed by targeted preventive therapies adapted to individual patient profiles are gaining global acclaim as being beneficial to patients, the healthcare sector, and society as a whole. In this context, natural flavonoids were considered due to their multifaceted antioxidant, anti-inflammatory, and anticancer effects as well as their low toxicity and ease of availability. The aim of this review is to focus on the capacity of flavonoids to modulate the responsiveness of various diseases and ailments associated with redox toxicity. The review will also focus on the flavonoids' pathway-based redox activity and the advancement of redox-based therapies as well as flavonoids' antioxidant characteristics and their influence on human health, therapeutics, and chemical safety. Research findings indicated that flavonoids significantly exhibit various redox-based therapeutic responses against several diseases such as inflammatory, neurodegenerative, cardiovascular, and hepatic diseases and various types of cancer by activating the Nrf2/Keap1 transcription system, suppressing the nuclear factor κB (NF-κB)/IκB kinase inflammatory pathway, abrogating the function of the Hsp90/Hsf1 complex, inhibiting the PTEN/PI3K/Akt pathway, and preventing mitochondrial dysfunction. Some flavonoids, especially genistein, apigenin, amentoflavone, baicalein, quercetin, licochalcone A, and biochanin A, play a potential role in redox regulation. Conclusions of this review on the antioxidant aspects of flavonoids highlight the medicinal and folk values of these compounds against oxidative stress and various diseases and ailments. In short, treatment with flavonoids could be a novel therapeutic invention in clinical trials, as we hope.

Phloretin Alleviates Arsenic Trioxide-Induced Apoptosis of H9c2 Cardiomyoblasts via Downregulation in Ca2+/Calcineurin/NFATc Pathway and Inflammatory Cytokine Release

Arsenic trioxide (ATO) is among the first-line chemotherapeutic drugs for treating acute promyelocytic leukemia patients, but its clinical use is hampered due to cardiotoxicity. The present investigation unveils the mechanism underlying ATO-induced oxidative stress that promotes calcineurin (a ubiquitous Ca²⁺/calmodulin-dependent serine/threonine phosphatase expressed only during sustained Ca²⁺ elevation) expression, inflammatory cytokine release and apoptosis in H9c2 cardiomyoblasts, and its possible modulation with phloretin (PHL, an antioxidant polyphenol present in apple peel). ATO caused Ca²⁺ overload resulting in elevated expression of calcineurin and its downstream transcriptional effector NFATc causing the release of cytokines such as IL-2, IL-6, MCP-1, IFN-γ, and TNF-α in H9c2 cardiomyoblast. There was a visible increase in the nuclear fraction of NF-κB and ROS-mediated apoptotic cell death. The expression levels of cardiac-specific genes (troponin, desmin, and caveolin-3) and genes of the apoptotic signaling pathway (BCL-2, BAX, IGF1, AKT, ERK1, -2, RAF1, and JNK) in response to ATO and PHL were studied. The putative binding mode and the potential ligand-target interactions of PHL with calcineurin using docking software (Autodock and iGEMDOCKv2) showed the high binding affinity of PHL to calcineurin. PHL co-treatment significantly reduced Ca²⁺ influx and normalized the expression of calcineurin, NFATc, NF-κB, and other cytokines. PHL co-treatment resulted in activation of BCL-2, IGF1, AKT, RAF1, ERK1, and ERK2 and inhibition of BAX and JNK. Overall, these results revealed that PHL has a protective effect against ATO-induced apoptosis and we propose calcineurin as a druggable target for the interaction of PHL in ATO cardiotoxicity in H9c2 cells.

Investigation of the ameliorative effects of baicalin against arsenic trioxide-induced cardiac toxicity in mice

Baicalin (BA), a kind of flavonoids compound, comes from Scutellaria baicalensis Georgi (a kind of perennial herb) and has beneficial effects on the cardiovascular system through anti-oxidant, anti-inflammation, and anti-apoptosis actions. However, the therapeutic effects and latent mechanisms of BA on arsenic trioxide (ATO)-induced cardiac toxicity has not been reported. The present research was performed to explore the effects and mechanisms of BA on ATO-induced heart toxicity. Male Kunming mice were treated with ATO (7.5 mg/kg) to induce cardiac toxicity. After the mice received ATO, BA (50 and 100 mg/kg) was administered for estimating its cardioprotective effects. Statistical data demonstrated that BA treatment alleviated electrocardiogram abnormalities and pathological injury caused by ATO. BA could also lead to recovery of CK and LDH activities to normal range and cause a decrease in MDA levels and ROS generation, augmentation of SOD, CAT, and GSH activities. We also found that BA caused a reduction in the expression of proinflammatory cytokines, such as TNF-α and IL-6. Moreover, BA attenuated ATO-induced apoptosis by promoting the expression of Bcl-2 and suppressing the expression of Bax and caspase-3. TUNEL test result demonstrated BA caused impediment of ATO-induced apoptosis. Furthermore, BA treatment suppressed the high expression of TLR4, NF-κB and P-NF-κB caused by ATO. In conclusion, these results indicate that BA may alleviate ATO-induced cardiac toxicity by restraining oxidative stress, apoptosis, and inflammation, and its mechanism would be associated with the inhibition of the TLR4/NF-κB signaling pathway.

Therapeutic effects of biochanin A, phloretin, and epigallocatechin-3-gallate in reducing oxidative stress in arsenic-intoxicated mice

One of the most common toxicant prevailing in our environment is the arsenic. The present study is an attempt to investigate the effects of some of the common flavonoids, such as biochanin A (BCA), phloretin, and epigallocatechin-3-gallate (EGCG), on arsenic toxicity in the Swiss albino mice. For this purpose, mice were orally treated with sodium meta-arsenite (20 mg/kg bw/day), along with co-administration of BCA (50 mg/kg bw/day), phloretin (50 mg/kg bw/day), and EGCG (40 mg/kg bw/day) for the 2-week duration. All the mice were euthanized at the end of the treatment period, and the observations were made in the following parameters. Arsenic reduced the sperm motility as compared with the control (p < 0.05) and was restored back to the normal status with the flavonoids treatment significantly (p < 0.05). The arsenic concentrations in the kidney and liver tissues were found significantly reduced with all the flavonoids co-treatment (p < 0.001). There was a reduction in the levels of superoxide dismutase (SOD), reduced glutathione (GSH), and glutathione S-transferase (GST) antioxidant markers, with the increased lipid peroxidation (LPO), protein carbonyl content (PCC), and catalase (CAT) levels in the arsenic-intoxicated mice performed in the different tissues. The biochemical homeostasis alterations were well correlated with the estimations of cholinesterase enzyme levels in the brain tissues (p < 0.05) along with DNA damage analysis (Comet) carried out in the blood cells (p < 0.05). These above results are well corroborated with the histopathological findings performed in the brain tissue, along with the increased upregulation seen in the Nrf2 signalling, with all the flavonoid co-treatment carried in the kidney tissue. The administration of BCA, phloretin, and EGCG, in a major way, reversed the alterations in the abovementioned parameters in the arsenic-intoxicated mice. Our findings revealed the beneficial effects of the flavonoids against the arsenic-induced toxicity, due to their ability to enhance the intracellular antioxidant response system by modulating the Nrf2 signaling pathway.

Risk Compounds, Preclinical Toxicity Evaluation, and Potential Mechanisms of Chinese Materia Medica-Induced Cardiotoxicity

Chinese materia medica (CMM) has been applied for the prevention and treatment of diseases for thousands of years. However, arrhythmia, myocardial ischemia, heart failure, and other cardiac adverse reactions during CMM application were gradually reported. CMM-induced cardiotoxicity has aroused widespread attention. Our review aimed to summarize the risk compounds, preclinical toxicity evaluation, and potential mechanisms of CMM-induced cardiotoxicity. All relevant articles published on the PubMed, Embase, and China National Knowledge Infrastructure (CNKI) databases for the latest twenty years were searched and manually extracted. The risk substances of CMM-induced cardiotoxicity are relatively complex. A single CMM usually contains various risk compounds, and the same risk substance may exist in various CMM. The active and risk substances in CMM may be transformed into each other under different conditions, such as drug dosage, medication methods, and body status. Generally, the risk compounds of CMM-induced cardiotoxicity can be classified into alkaloids, terpenoids, steroids, heavy metals, organic acids, toxic proteins, and peptides. Traditional evaluation methods of chemical drug-induced cardiotoxicity primarily include cardiac function monitoring, endomyocardial biopsy, myocardial zymogram, and biomarker determination. In the preclinical stage, CMM-induced cardiotoxicity should be systematically evaluated at the overall, tissue, cellular, and molecular levels, including cardiac function, histopathology, cytology, myocardial zymogram, and biomarkers. Thanks to the development of systematic biology, the higher specificity and sensitivity of biomarkers, such as genes, proteins, and metabolic small molecules, are gradually applied for evaluating CMM-induced cardiotoxicity. Previous studies on the mechanisms of CMM-induced cardiotoxicity focused on a single drug, monomer or components of CMM. The interaction among ion homeostasis (sodium, potassium, and calcium ions), oxidative damage, mitochondrial injury, apoptosis and autophagy, and metabolic disturbance is involved in CMM-induced cardiotoxicity. Clarification on the risk compounds, preclinical toxicity evaluation, and potential mechanisms of CMM-induced cardiotoxicity must be beneficial to guide new CMM development and post-marketed CMM reevaluation.

Arsenal of Phytochemicals to Combat Against Arsenic-Induced Mitochondrial Stress and Cancer

Significance: Phytochemicals are important dietary constituents with antioxidant properties. They affect various signaling pathways involved in the overall maintenance of interior milieu of the cell. Arsenic, an environmental toxicant, is well known for its deleterious consequences, such as various diseases, including cancers in humans. Mitochondria are the cell's powerhouse that fuel all metabolic energy requirements. Dysfunctional mitochondria due to stressors may lead to abnormal functioning of the organelle, hampering the crucial cellular cross talks and ultimately leading to cancer. Application of phytochemicals against arsenic-induced mitochondrial disorders may be a preventive measure to counteract the ruinous impacts of the metalloid. Recent Advances: In recent years, extensive research on the role of mitochondria in cancer gives a better understanding of the areas the organelle covers in maintaining a healthy cell or in inducing carcinogenicity. Detailed knowledge of the mitochondrial governances would enable researchers to administer numerous phytochemicals to ameliorate altered oxidative phosphorylation, mitochondrial membrane potential (MMP), mitochondrial oxidative stress, unfolded protein response, glycolysis, or even apoptosis. Critical Issues: In this review, we have addressed how various phytochemicals belonging to diverse classes combat against arsenic-induced mitochondrial oxidative stress, depletion of MMP, cell cycle abrogation, apoptosis, glycolytic damages, oncogenic regulations, chaperones, mitochondrial complexes, and mitochondrial membrane pore formation in both in vitro and in vivo models. Future Directions: Insightful application of mitoprotective phytochemicals against arsenic-induced mitochondrial oxidative stress and carcinogenesis may guide researchers to develop preclinical chemopreventive agents to fight arsenic toxicity in humans.

C2C12 Mouse Myoblasts Damage Induced by Oxidative Stress Is Alleviated by the Antioxidant Capacity of the Active Substance Phloretin

A new direction for the treatment of skeletal myopathies, which are mainly caused by abnormal mitochondrial metabolism, is the application of drugs and active substances to relieve oxidative stress in mitochondria. Phloretin, a dihydrochalcone active substance widely present in succulent fruits, has attracted attention for its strong antioxidant activity. This study aimed to investigate the potential antioxidant effects of phloretin and its potential mechanism of action in C2C12 mouse myoblasts. Under oxidative stress caused by 500 μmol/L H₂O₂, the addition of 10 μmol/L phloretin ameliorated the high level of reactive oxygen species, increased CuZn/Mn-dependent superoxide dismutase activities, and restored the loss of mitochondrial membrane potential. Additionally, apoptosis, necrocytosis, and the inhibition of cell proliferation caused by H₂O₂ stimulation were alleviated by phloretin. Moreover, phloretin significantly increased the expression of cyclin D1 and alleviated the stagnation trend of the G1 phase of cell proliferation caused by H₂O₂. Furthermore, the addition of phloretin simultaneously significantly increased the protein and mRNA expression of heme oxygenase-1 (HO-1) and alleviated the inhibitory phosphorylation of p-nuclear factor erythroid 2-related factor 2 (Nrf2), p-AMP-activated protein kinase (AMPK), and p-liver kinase B1 (LKB1) induced by H₂O₂. Moreover, the expression of nuclear Nrf2 was higher with phloretin treatment than without phloretin treatment. Overall, phloretin alleviated the proliferation inhibition and apoptosis induced by H₂O₂ and exerted antioxidant effects via the LKB1/AMPK/Nrf2/HO-1 pathway in C2C12 cells. These results provide insight for the application of phloretin to alleviate oxidative damage to muscle.

Mechanisms underlying the protective effect of tannic acid against arsenic trioxide‑induced cardiotoxicity in rats: Potential involvement of mitochondrial apoptosis

Arsenic trioxide (ATO) is a frontline chemotherapy drug used in the therapy of acute promyelocytic leukemia. However, the clinical use of ATO is hindered by its cardiotoxicity. The present study aimed to observe the potential effects and underlying mechanisms of tannic acid (TA) against ATO-induced cardiotoxicity. Male rats were intraperitoneally injected with ATO (5 mg/kg/day) to induce cardiotoxicity. TA (20 and 40 mg/kg/day) was administered to evaluate its cardioprotective efficacy against ATO-induced heart injury in rats. Administration of ATO resulted in pathological damage in the heart and increased oxidative stress as well as levels of serum cardiac biomarkers creatine kinase and lactate dehydrogenase and the inflammatory marker NF-κB (p65). Conversely, TA markedly reversed this phenomenon. Additionally, TA treatment caused a notable decrease in the expression levels of cleaved caspase-3/caspase-3, Bax, p53 and Bad, while increasing Bcl-2 expression levels. Notably, the application of TA decreased the expression levels of cytochrome c, second mitochondria-derived activator of caspases and high-temperature requirement A2, which are apoptosis mitochondrial-associated proteins. The present findings indicated that TA protected against ATO-induced cardiotoxicity, which may be associated with oxidative stress, inflammation and mitochondrial apoptosis.

Molecular Mechanisms of Cardiomyocyte Death in Drug-Induced Cardiotoxicity

Homeostatic regulation of cardiomyocytes plays a crucial role in maintaining the normal physiological activity of cardiac tissue. Severe cardiotoxicity results in cardiac diseases including but not limited to arrhythmia, myocardial infarction and myocardial hypertrophy. Drug-induced cardiotoxicity limits or forbids further use of the implicated drugs. Such drugs that are currently available in the clinic include anti-tumor drugs (doxorubicin, cisplatin, trastuzumab, etc.), antidiabetic drugs (rosiglitazone and pioglitazone), and an antiviral drug (zidovudine). This review focused on cardiomyocyte death forms and related mechanisms underlying clinical drug-induced cardiotoxicity, including apoptosis, autophagy, necrosis, necroptosis, pryoptosis, and ferroptosis. The key proteins involved in cardiomyocyte death signaling were discussed and evaluated, aiming to provide a theoretical basis and target for the prevention and treatment of drug-induced cardiotoxicity in the clinical practice.

An Overview on Arsenic Trioxide-Induced Cardiotoxicity

Arsenic trioxide (ATO) is among the first-line chemotherapeutic drugs used in oncological practice. It has shown substantial efficacy in treating patients with relapsed or refractory acute promyelocytic leukaemia. The clinical use of ATO is hampered due to cardiotoxicity and hence many patients are precluded from receiving this highly effective treatment. An alternative to this would be to use any drug that can ameliorate the cardiotoxic effects and allow exploiting the full therapeutic potential of ATO, with considerable impact on cancer therapy. Generation of reactive oxygen species is involved in a wide range of human diseases, including cancer, cardiovascular, pulmonary and neurological disorders. Hence, agents with the ability to protect against these reactive species may be therapeutically useful. The present review focuses on the beneficial as well as harmful effects of arsenic and ATO, the mechanisms underlying ATO toxicity and the possible ways that can be adopted to circumvent ATO-induced toxicity.

Dissecting the molecular pathophysiology of drug-induced liver injury

Drug-induced liver injury (DILI) has become a major topic in the field of Hepatology and Gastroenterology. DILI can be clinically divided into three phenotypes: hepatocytic, cholestatic and mixed. Although the clinical manifestations of DILI are variable and the pathogenesis complicated, recent insights using improved preclinical models, have allowed a better understanding of the mechanisms that trigger liver damage. In this review, we will discuss the pathophysiological mechanisms underlying DILI. The toxicity of the drug eventually induces hepatocellular damage through multiple molecular pathways, including direct hepatic toxicity and innate and adaptive immune responses. Drugs or their metabolites, such as the common analgesic, acetaminophen, can cause direct hepatic toxicity through accumulation of reactive oxygen species and mitochondrial dysfunction. The innate and adaptive immune responses play also a very important role in the occurrence of idiosyncratic DILI. Furthermore, we examine common forms of hepatocyte death and their association with the activation of specific signaling pathways.

Inducers of Senescence, Toxic Compounds, and Senolytics: The Multiple Faces of Nrf2-Activating Phytochemicals in Cancer Adjuvant Therapy

The reactivation of senescence in cancer and the subsequent clearance of senescent cells are suggested as therapeutic intervention in the eradication of cancer. Several natural compounds that activate Nrf2 (nuclear factor erythroid-derived 2-related factor 2) pathway, which is involved in complex cytoprotective responses, have been paradoxically shown to induce cell death or senescence in cancer. Promoting the cytoprotective Nrf2 pathway may be desirable for chemoprevention, but it might be detrimental in later stages and advanced cancers. However, senolytic activity shown by some Nrf2-activating compounds could be used to target senescent cancer cells (particularly in aged immune-depressed organisms) that escape immunosurveillance. We herein describe in vitro and in vivo effects of fifteen Nrf2-interacting natural compounds (tocotrienols, curcumin, epigallocatechin gallate, quercetin, genistein, resveratrol, silybin, phenethyl isothiocyanate, sulforaphane, triptolide, allicin, berberine, piperlongumine, fisetin, and phloretin) on cellular senescence and discuss their use in adjuvant cancer therapy. In light of available literature, it can be concluded that the meaning and the potential of adjuvant therapy with natural compounds in humans remain unclear, also taking into account the existence of few clinical trials mostly characterized by uncertain results. Further studies are needed to investigate the therapeutic potential of those compounds that display senolytic activity.

Phloretin Prevents Diabetic Cardiomyopathy by Dissociating Keap1/Nrf2 Complex and Inhibiting Oxidative Stress

Hyperglycemia induces chronic inflammation and oxidative stress in cardiomyocyte, which are the main pathological changes of diabetic cardiomyopathy (DCM). Treatment aimed at these processes may be beneficial in DCM. Phloretin (PHL), a promising natural product, has many pharmacological activities, such as anti-inflammatory, anticancer, and anti-oxidative function. The aim of this study was to investigate whether PHL could ameliorate the high glucose-mediated oxidation, hypertrophy, and fibrosis in H9c2 cells and attenuate the inflammation- and oxidation-mediated cardiac injury. In this study, PHL induced significantly inhibitory effect on the expression of pro-inflammatory, hypertrophy, pro-oxidant, and fibrosis cytokines in high glucose-stimulated cardiac H9c2 cells. Furthermore, PHL decreased the levels of serum lactate dehydrogenase, aspartate aminotransferase, and creatine kinase-MB, and attenuated the progress in the fibrosis, oxidative stress, and pathological parameters via Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor E2-related factor 2 (Nrf2) pathway in diabetic mice. In additional, molecular modeling and immunoblotting results confirmed that PHL might obstruct the interaction between Nrf2 and Keap1 through direct binding Keap1, and promoting Nrf2 expression. These results provided evidence that PHL could suppress high glucose-induced cardiomyocyte oxidation and fibrosis injury, and that targeting Keap1/Nrf2 may provide a novel therapeutic strategy for human DCM in the future.

Antioxidants Protect against Arsenic Induced Mitochondrial Cardio-Toxicity

Arsenic is a potent cardiovascular toxicant associated with numerous biomarkers of cardiovascular diseases in exposed human populations. Arsenic is also a carcinogen, yet arsenic trioxide is used as a therapeutic agent in the treatment of acute promyelotic leukemia (APL). The therapeutic use of arsenic is limited due to its severe cardiovascular side effects. Many of the toxic effects of arsenic are mediated by mitochondrial dysfunction and related to arsenic's effect on oxidative stress. Therefore, we investigated the effectiveness of antioxidants against arsenic induced cardiovascular dysfunction. A growing body of evidence suggests that antioxidant phytonutrients may ameliorate the toxic effects of arsenic on mitochondria by scavenging free radicals. This review identifies 21 antioxidants that can effectively reverse mitochondrial dysfunction and oxidative stress in cardiovascular cells and tissues. In addition, we propose that antioxidants have the potential to improve the cardiovascular health of millions of people chronically exposed to elevated arsenic concentrations through contaminated water supplies or used to treat certain types of leukemias. Importantly, we identify conceptual gaps in research and development of new mito-protective antioxidants and suggest avenues for future research to improve bioavailability of antioxidants and distribution to target tissues in order reduce arsenic-induced cardiovascular toxicity in a real-world context.

Silencing a phloretin-specific glycosyltransferase perturbs both general phenylpropanoid biosynthesis and plant development

The polyphenol profile of apple (Malus × domestica) is dominated by the dihydrochalcone glycoside phloridzin, but its physiological role is yet to be elucidated. Biosynthesis of phloridzin occurs as a side branch of the main phenylpropanoid pathway, with the final step mediated by the phloretin-specific glycosyltransferase UGT88F1. Unexpectedly, given that UGTs are sometimes viewed as 'decorating enzymes', UGT88F1 knockdown lines were severely dwarfed, with greatly reduced internode lengths, narrow lanceolate leaves, and changes in leaf and fruit cellular morphology. These changes suggested that auxin transport had been altered in the knockdown lines, which was confirmed in assays showing that auxin flux from the shoot apex was increased in the transgenic lines. Metabolite analysis revealed no accumulation of the phloretin aglycone, as well as decreases in many non-target phenylpropanoid compounds. This decreased accumulation of metabolites appeared to be mediated by the repression of the phenylpropanoid pathway via a reduction in key transcript levels (e.g. phenylalanine ammonia lyase, PAL) and enzyme activities (PAL and chalcone synthase). Application of exogenous phloridzin to the UGT88F1 knockdown lines in tissue culture enhanced axial leaf growth and partially restored some aspects of 'normal' apple leaf growth. Together, our results strongly implicate dihydrochalcones as critical compounds in modulating phenylpropanoid pathway flux and establishing auxin patterning early in apple development.

Organ-specific effects of low-dose zinc pre-exposure on high-dose zinc induced mitochondrial dysfunction in large yellow croaker Pseudosciaena crocea

The study was carried out to evaluate the effects of low-dose zinc (Zn) pre-exposure on survival rate, new Zn accumulation, and mitochondrial bioenergetics in the liver and spleen of large yellow croaker exposed to high-dose Zn. To the end, fish were pre-exposed to 0 and 2 mg L^-1 Zn for 48 h and post-exposed to 0 and 12 mg L^-1 Zn for 48 h. Twelve milligrams Zn per liter exposure alone reduced survival rate, but the effect did not appear in the 2 mg L^-1 Zn pre-exposure groups. Two milligrams per liter Zn pre-exposure also ameliorated 12 mg Zn L^-1 induced new Zn accumulation, reactive oxygen species (ROS) levels, and mitochondrial swelling in the liver. However, these effects did not appear in the spleen. In the liver, 2 mg L^-1 Zn pre-exposure apparently relieved 12 mg L^-1 Zn induced down-regulation of activities of ATP synthase (F-ATPase), succinate dehydrogenase (SDH), and malate dehydrogenase (MDH). The mRNA levels of these genes remained relatively stable in fish exposed to 12 mg L^-1 Zn alone, but increased in fish exposed to 12 mg L^-1 Zn with 2 mg L^-1 Zn pre-treatment. In the spleen, 2 mg Zn L^-1 pre-exposure did not mitigate the down-regulation of mRNA levels of genes and activities of relative enzymes induced by 12 mg L^-1 Zn. In conclusion, our study demonstrated low-dose zinc pre-exposure ameliorated high-dose zinc induced mitochondrial dysfunction in the liver but not in the spleen of large yellow croaker, indicating an organ-specific effect.

Phloretin Prevents High-Fat Diet-Induced Obesity and Improves Metabolic Homeostasis

Reactive oxygen species generated as a by-product in metabolism play a central role in the development of obesity and obesity-related metabolic complications. The objective of the current study is to explore the possibility to block obesity and improve metabolic homeostasis via phloretin, a natural antioxidant product from apple tree leaves and Manchurian apricot. Both preventive and therapeutic activities of phloretin were assessed using a high-fat diet-induced obesity mouse model. Phloretin was injected intraperitoneally twice weekly into regular and obese mice fed a high-fat diet. The effects of phloretin treatment on body weight and composition, fat content in the liver, glucose and lipid metabolism, and insulin resistance were monitored and compared to the control animals. Phloretin treatment significantly blocks high-fat diet-induced weight gain but did not induce weight loss in obese animals. Phloretin improved glucose homeostasis and insulin sensitivity and alleviated hepatic lipid accumulation. RT-PCR analysis showed that phloretin treatment suppresses expression of macrophage markers (F4/80 and Cd68) and pro-inflammatory genes (Mcp-1 and Ccr2) and enhances adiponectin gene expression in white adipose tissue. In addition, phloretin treatment elevated the expression of fatty acid oxidation genes such as carnitine palmitoyltransferase 1a and 1b (Cpt1a and Cpt1b) and reduced expression of monocyte chemoattractant protein-1 (Mcp-1), de novo lipogenesis transcriptional factor peroxisome proliferator-activated receptor-γ 2 (Pparγ2), and its target monoacylglycerol O-acyltransferase (Mgat-1) genes. These results provide direct evidence to support a possible use of phloretin for mitigation of obesity and maintenance of metabolic homeostasis.

An apple a day to prevent cancer formation: Reducing cancer risk with flavonoids

The purpose of this review is to update and discuss key findings from in vitro and in vivo studies on apple and its biocompounds, with a special focus on its anticancer role. Several studies have proposed that apple and its extracts exhibit a variety of biological functions that may contribute to health benefits including beneficial effects against chronic heart and vascular disorders, respiratory and pulmonary dysfunction, diabetes, obesity, and cancer. In this review, we summarize the molecular mechanism(s) of various components in apple, as established in previous studies that indicated their growth-inhibitory effects in various cancer cell types. Moreover, an attempt is made to delineate the direction of future studies that could lead to the development of apple components as a potent chemo-preventive/chemotherapeutic agent against cancer.

Arsenic trioxide triggered calcium homeostasis imbalance and induced endoplasmic reticulum stress-mediated apoptosis in adult rat ventricular myocytes

Arsenic trioxide (ATO) is a potent anticancer drug agent but its clinical use is often limited by severe cardiotoxicity. However, its exact mechanism remains poorly understood. In this study, we simultaneously explored the direct effect of ATO on cardiac contraction in adult rat ventricular myocytes and its effects on Ca²⁺ transient in real time by using an IonOptix MyoCam system. The results showed that ATO increased the amplitude of sarcomere shortening, the maximal velocity of relengthening and shortening (-dL/dt_max and +dL/dt_max), time-to-90% relengthening (TR90), and time-to-peak shortening (TPS), resulting in abnormal cardiomyocyte contraction. Meanwhile, ATO markedly increased the resting Ca²⁺ ratio, amplitude/resting calcium, the maximal velocity of Ca²⁺ shortening and relaxation (+d[Ca²⁺]/dt_max and -d[Ca²⁺]/dt_max), time-to-50% peak [Ca²⁺] _i and the decay rate of [Ca²⁺] _i transients, suggesting that ATO leads to intracellular imbalance of calcium homeostasis. ATO also inhibited sarcoplasmic reticulum Ca²⁺-ATPase 2a (SERCA2a) activity in a time-dependent manner and activated the endoplasmic reticulum (ER) stress reaction. These results revealed that ATO dramatically aggravates Ca²⁺ overload and promotes ER stress, eventually causing abnormal cardiomyocyte contraction in a dose-dependent and time-dependent manner.

Role of endoplasmic reticulum stress in drug-induced toxicity

Drug‐induced toxicity is a key issue for public health because some side effects can be severe and life‐threatening. These adverse effects can also be a major concern for the pharmaceutical companies since significant toxicity can lead to the interruption of clinical trials, or the withdrawal of the incriminated drugs from the market. Recent studies suggested that endoplasmic reticulum (ER) stress could be an important event involved in drug liability, in addition to other key mechanisms such as mitochondrial dysfunction and oxidative stress. Indeed, drug‐induced ER stress could lead to several deleterious effects within cells and tissues including accumulation of lipids, cell death, cytolysis, and inflammation. After recalling important information regarding drug‐induced adverse reactions and ER stress in diverse pathophysiological situations, this review summarizes the main data pertaining to drug‐induced ER stress and its potential involvement in different adverse effects. Drugs presented in this review are for instance acetaminophen (APAP), arsenic trioxide and other anticancer drugs, diclofenac, and different antiretroviral compounds. We also included data on tunicamycin (an antibiotic not used in human medicine because of its toxicity) and thapsigargin (a toxic compound of the Mediterranean plant Thapsia garganica) since both molecules are commonly used as prototypical toxins to induce ER stress in cellular and animal models.

Phloretin-induced cytoprotective effects on mammalian cells: A mechanistic view and future directions

Phloretin (C15 H14 O5 ), a dihydrochalcone flavonoid, is mainly found in fruit, leaves, and roots of apple tree. Phloretin exerts antioxidant, anti-inflammatory, and anti-tumor activities in mammalian cells through mechanisms that have been partially elucidated throughout the years. Phloretin bioavailability is well known in humans, but still remains to be better studied in experimental animals, such as mouse and rat. The focus of the present review is to gather information regarding the mechanisms involved in the phloretin-elicited effects in different in vitro and in vivo experimental models. Several manuscripts were analyzed and data raised by authors were described and discussed here in a mechanistic manner. Comparisons between the effects elicited by phloretin and phloridzin were made whenever possible, as well as with other polyphenols, clarifying questions about the use of phloretin as a potential therapeutic agent. Toxicological aspects associated to phloretin exposure were also discussed here. Furthermore, a special section containing future directions was created as a suggestive guide towards the elucidation of phloretin-related actions in mammalian cells and tissues.

Low-Concentration Arsenic Trioxide Inhibits Skeletal Myoblast Cell Proliferation via a Reactive Oxygen Species-Independent Pathway

Myoblast proliferation and differentiation are essential for skeletal muscle regeneration. Myoblast proliferation is a critical step in the growth and maintenance of skeletal muscle. The precise action of inorganic arsenic on myoblast growth has not been investigated. Here, we investigated the in vitro effect of inorganic arsenic trioxide (As₂O₃) on the growth of C2C12 myoblasts. As₂O₃ decreased myoblast growth at submicromolar concentrations (0.25–1 μM) after 72 h of treatment. Submicromolar concentrations of As₂O₃ did not induce the myoblast apoptosis. Low-concentration As₂O₃ (0.5 and 1 μM) significantly suppressed the myoblast cell proliferative activity, which was accompanied by a small proportion of bromodeoxyuridine (BrdU) incorporation and decreased proliferating cell nuclear antigen (PCNA) protein expression. As₂O₃ (0.5 and 1 μM) increased the intracellular arsenic content but did not affect the reactive oxygen species (ROS) levels in the myoblasts. Cell cycle analysis indicated that low-concentrations of As₂O₃ inhibited cell proliferation via cell cycle arrest in the G1 and G2/M phases. As₂O₃ also decreased the protein expressions of cyclin D1, cyclin E, cyclin B1, cyclin-dependent kinase (CDK) 2, and CDK4, but did not affect the protein expressions of p21 and p27. Furthermore, As₂O₃ inhibited the phosphorylation of Akt. Insulin-like growth factor-1 significantly reversed the inhibitory effect of As₂O₃ on Akt phosphorylation and cell proliferation in the myoblasts. These results suggest that submicromolar concentrations of As₂O₃ alter cell cycle progression and reduce myoblast proliferation, at least in part, through a ROS-independent Akt inhibition pathway.