A wave of reactive oxygen species (ROS)-induced ROS release in a sea of excitable mitochondria

The Dose Rate of Corpuscular Ionizing Radiation Strongly Influences the Severity of DNA Damage, Cell Cycle Progression and Cellular Senescence in Human Epidermoid Carcinoma Cells

Modern radiotherapy utilizes a broad range of sources of ionizing radiation, both low-dose-rate (LDR) and high-dose-rate (HDR). However, the mechanisms underlying specific dose-rate effects remain unclear, especially for corpuscular radiation. To address this issue, we have irradiated human epidermoid carcinoma A431 cells under LDR and HDR regimes. Reducing the dose rate has lower lethality at equal doses with HDR irradiation. The half-lethal dose after HDR irradiation was three times less than after LDR irradiation. The study of mechanisms showed that under HDR irradiation, the radiation-induced halt of mitosis with the accompanying emergence of giant cells was recorded. No such changes were recorded after LDR irradiation. The level of DNA damage is significantly greater after HDR irradiation, which may be the main reason for the different mechanisms of action of HDR and LDR irradiations. Comparing the mechanisms of cell response to LDR and HDR irradiations may shed light on the mechanisms of tumor cell response to ionizing radiation and answer the question of whether different dose rates within the same dose range can cause different clinical effects.

Mitochondrial transfer in the progression and treatment of cardiac disease

Mitochondria are the primary site for energy production and play a crucial role in supporting normal physiological functions of the human body. In cardiomyocytes (CMs), mitochondria can occupy up to 30 % of the cell volume, providing sufficient energy for CMs contraction and relaxation. However, some pathological conditions such as ischemia, hypoxia, infection, and the side effect of drugs, can cause mitochondrial dysfunction in CMs, leading to various myocardial injury-related diseases including myocardial infarction (MI), myocardial hypertrophy, and heart failure. Self-control of mitochondria quality and conversion of metabolism pathway in energy production can serve as the self-rescue measure to avoid autologous mitochondrial damage. Particularly, mitochondrial transfer from the neighboring or extraneous cells enables to mitigate mitochondrial dysfunction and restore their biological functions in CMs. Here, we described the homeostatic control strategies and related mechanisms of mitochondria in injured CMs, including autologous mitochondrial quality control, mitochondrial energy conversion, and especially the exogenetic mitochondrial donation. Additionally, this review emphasizes on the therapeutic effects and potential application of utilizing mitochondrial transfer in reducing myocardial injury. We hope that this review can provide theoretical clues for the developing of advanced therapeutics to treat cardiac diseases.

The role of mitochondria in iron overload-induced damage

Iron overload is a pathological condition characterized by the abnormal accumulation of iron within the body, which may result from excessive iron intake, disorders of iron metabolism, or specific disease states. This condition can lead to significant health complications and may pose life-threatening risks. The excessive accumulation of iron can induce cellular stress, adversely affecting the structure and function of mitochondria, thereby compromising overall organ function. Given the critical role of mitochondria in cellular metabolism and homeostasis, it is imperative to investigate how mitochondrial dysfunction induced by iron overload contributes to disease progression, as well as to explore mitochondrial-related pathways as potential therapeutic targets for various iron overload disorders. This review examines the mechanisms by which mitochondria are implicated in iron overload-induced damage, including increased oxidative stress, mitochondrial DNA damage, and disruptions in energy metabolism. Additionally, it addresses the relationship between these processes and various forms of programmed cell death, as well as alterations in mitochondrial dynamics. Furthermore, the review discusses strategies aimed at alleviating and mitigating the complications associated with iron overload in patients by targeting mitochondrial pathways.

Fusion-fission-mitophagy cycling and metabolic reprogramming coordinate nerve growth factor (NGF)-dependent neuronal differentiation

Neuronal differentiation is regulated by nerve growth factor (NGF) and other neurotrophins. We explored the impact of NGF on mitochondrial dynamics and metabolism through time-lapse imaging, metabolomics profiling, and computer modeling studies. We show that NGF may direct differentiation by stimulating fission, thereby causing selective mitochondrial network fragmentation and mitophagy, ultimately leading to increased mitochondrial quality and respiration. Then, we reconstructed the dynamic fusion-fission-mitophagy cycling of mitochondria in a computer model, integrating these processes into a single network mechanism. Both the computational model and the simulations are able to reproduce the proposed mechanism in terms of mitochondrial dynamics, levels of reactive oxygen species (ROS), mitophagy, and mitochondrial quality, thus providing a computational tool for the interpretation of the experimental data and for future studies aiming to detail further the action of NGF on mitochondrial processes. We also show that changes in these mitochondrial processes are intertwined with a metabolic function of NGF in differentiation: NGF directs a profound metabolic rearrangement involving glycolysis, TCA cycle, and the pentose phosphate pathway, altering the redox balance. This metabolic rewiring may ensure: (a) supply of both energy and building blocks for the anabolic processes needed for morphological reorganization, as well as (b) redox homeostasis.

Human beta defensin-2 loaded PLGA nanoparticles impregnated in collagen-chitosan composite scaffold for the management of diabetic wounds

Diabetic wound (DW) is the most devastating complication resulting in significant mortality and morbidity in diabetic patients. The standard treatment of DW care fails to address the prerequisites of treating DW owing to its multifactorial pathophysiology. Henceforth, developing a single treatment strategy to handle all the loopholes may effectively manage DW. The objective of the current study was to formulate Human beta defensin-2 (HBD-2) loaded Poly (lactic-co-glycolic acid) (PLGA) nanoparticle impregnated in collagen/chitosan (COL-CS) composite scaffolds for the accelerated healing of DW. Upon investigation, the developed biodegradable crosslinked scaffold possesses low matrix degradation, optimum porosity, and sustained drug release than the non-crosslinked scaffold. In vitro studies revealed that the HBD-2 COL-CS scaffold was biocompatible and accelerated cell migration and angiogenesis. The HBD-2 COL-CS scaffold showed significant antimicrobial activity in S. aureus, E. coli, and P. aeruginosa. The in vivo studies revealed that the HBD-2 COL-CS treated group accelerated healing compared to those in COL-CS and control groups. The ELISA results indicated a significant decrease in MMP-9, TNF-α, MPO, NAG, and NO with an increase in IL-10 in HBD-2 COL-CS treated group. The accelerated healing in HBD-2 COL-CS treated group might be due to the synergistic effects of PLGA (collagen synthesis and deposition and positive angiogenic effect), HBD-2 (anti-inflammatory, antibacterial, positive angiogenic effect, cell proliferation, and migration), COL (established wound healer and stabilizer) and CS (antibacterial, controlled drug release).

High Concentration Hydrogen Mitigates Sepsis-Induced Acute Lung Injury in Mice by Alleviating Mitochondrial Fission and Dysfunction

Background: Multiple organ failure (MOF) is the main cause of early death in septic shock. Lungs are among the organs that are affected in MOF, resulting in acute lung injury. A large number of inflammatory factors and stress injury in sepsis can lead to alterations in mitochondrial dynamics. Numerous studies have confirmed that hydrogen can alleviate sepsis in the animal model. The purpose of this experiment was to explore the therapeutic effect of high concentration (67%) hydrogen on acute lung injury in septic mice and its mechanism. Methods: The moderate and severe septic models were prepared by cecal ligation and puncture. Hydrogen with different concentrations was inhaled for one hour at 1 h and 6 h after the corresponding surgery. The arterial blood gas of mice during hydrogen inhalation was monitored in real time, and the 7-day survival rate of mice with sepsis was recorded. The pathological changes of lung tissues and functions of livers and kidneys were measured. The changes of oxidation products, antioxidant enzymes and pro-inflammatory cytokines in lungs and serums were detected. Mitochondrial function was measured. Results: The inhalation of 2% or 67% hydrogen improves the 7-day survival rate and reduces acute lung injury as well as liver and kidney injury in sepsis. The therapeutic effect of 67% hydrogen inhalation on sepsis was related to increasing antioxidant enzyme activity, reducing oxidation products and pro-inflammatory cytokines in lungs and serums. Compared with the Sham group, mitochondrial dysfunction was alleviated in hydrogen groups. Conclusions: Hydrogen inhalation by high or low concentration can both significantly improve sepsis; however, a high concentration demonstrates a better protective effect. High concentration hydrogen inhalation can significantly improve the mitochondrial dynamic balance and reduce the lung injury in septic mice.

Metabolic reprogramming: A novel therapeutic target in diabetic kidney disease

Diabetic kidney disease (DKD) is one of the most common microvascular complications of diabetes mellitus. However, the pathological mechanisms contributing to DKD are multifactorial and poorly understood. Diabetes is characterized by metabolic disorders that can bring about a series of changes in energy metabolism. As the most energy-consuming organs secondary only to the heart, the kidneys must maintain energy homeostasis. Aberrations in energy metabolism can lead to cellular dysfunction or even death. Metabolic reprogramming, a shift from mitochondrial oxidative phosphorylation to glycolysis and its side branches, is thought to play a critical role in the development and progression of DKD. This review focuses on the current knowledge about metabolic reprogramming and the role it plays in DKD development. The underlying etiologies, pathological damages in the involved cells, and potential molecular regulators of metabolic alterations are also discussed. Understanding the role of metabolic reprogramming in DKD may provide novel therapeutic approaches to delay its progression to end-stage renal disease.

Mitochondrial bioenergetics and redox dysfunction in nephrotoxicity induced by pyrethroid permethrin are ameliorated by flavonoid-rich fraction

The present study was designed to evaluate in vitro and in vivo the potential anti-inflammatory and nephroprotective potential of ethyl acetate fraction extracted from Fumaria officinalis (EAF) against permethrin (PER). Male wistar rats were treated daily by gavage during 7 days as follows: group C: negative control rats received 2 mL/kg bw of corn oil, group EAF: positive control rats received EAF at a dose of 200 mg/kg bw dissolved in water, group PER: rats received PER at a dose of 34.05 mg/kg bw and group (PER + EAF): rats received PER (34.05 mg/kg bw) and EAF (200 mg/kg bw). In vitro study showed the ability of EAF to inhibit protein denaturation and heat-induced hemolysis confirming its anti-inflammatory activity. In vivo, PER treatment decreased calcium (Ca) and phosphorus (P) levels and increased lactate dehydrogenase (LDH) activity in plasma. It induced oxidative stress objectified by an increase in the lipid peroxidation and protein oxidation and a perturbation of antioxidant system in kidney and mitochondria. The activities of NADH-ubiquinone reductase, ubiquinol-cytochrome C reductase and cytochrome C oxidase activities were reduced. These alterations were confirmed by histopathological studies. Co-treatment with EAF improved the antioxidant status and mitochondrial bioenergetics. The nephroprotective effects of EAF could be attributed to its modulation of detoxification enzymes and/or free radical scavenging actions.

Cold Atmospheric Plasma Apoptotic and Oxidative Effects on MCF7 and HCC1806 Human Breast Cancer Cells

Breast cancer (BC) is a malignant neoplasia with the highest incidence and mortality rates in women worldwide. Currently, therapies include surgery, radiotherapy, and chemotherapy, including targeted therapies in some cases. However, treatments are often associated with serious adverse effects. Looking for new options in BC treatment, we evaluated the therapeutic potential of cold atmospheric plasma (CAP) in two cell lines (MCF7 and HCC1806) with distinct histological features. Apoptosis seemed to be the most prevalent type of death, as corroborated by several biochemical features, including phosphatidylserine exposure, the disruption of mitochondrial membrane potential, an increase in BAX/BCL2 ratio and procaspase 3 loss. Moreover, the accumulation of cells in the G2/M phase of the cell cycle points to the loss of replication ability and decreased survival. Despite reported toxic concentrations of peroxides in culture media exposed to plasma, intracellular peroxide concentration was overall decreased accompanying a reduction in GSH levels shortly after plasma exposure in both cell lines. In HCC1806, elevated nitric oxide (NO) concentration accompanied by reduced superoxide levels suggests that these cells are capable of converting plasma-derived nitrites into NO that competes with superoxide dismutase (SOD) for superoxide to form peroxinitrite. The concomitant inhibition of the antioxidative activity of cells during CAP treatment, particularly the inhibition of cytochrome c oxidase with sodium azide, synergistically increased plasma toxicity. Thus, this in vitro research enlightens the therapeutic potential of CAP in the treatment of breast cancer, elucidating its possible mechanisms of action.

Plasma activated media and direct exposition can selectively ablate retinoblastoma cells

A new therapy based on atmospheric plasma, the fourth state of matter, has raised the medical community's attention by circumventing many undesirable effects of old anticancer treatments. This work aimed to evaluate the effect, selectivity, and mechanisms of action of cold atmospheric plasma (CAP) in human retinoblastoma cells. An electronic device was designed to generate CAP in the open air, 2 mm above seeded cell cultures. Three approaches were performed: direct use of CAP, plasma-activated media (PAM), and conditioned media (CM). Timely-resolved output voltage measurement, emission spectroscopy, and quantification of reactive species (RS) of PAM were performed. To evaluate cytotoxicity and selectivity, similarly treated Y79, fibroblasts HFF1, and retinal RPE-D407 cells were assessed. After 60 s of direct CAP treatment, the metabolic activity of retinoblastoma cells decreased more than 50%, mainly due to apoptosis, while HFF1 and RPE-D407 remained viable. Similar results were obtained with indirect treatment (PAM and CM). Cell survival was reduced, and cells accumulated in S and G2/M phases; however, no DNA strand breaks were detected. Regarding RS, plasma increased extracellular and intracellular concentrations of peroxides and nitric oxide, despite glutathione activation and lack of success in reverting cytotoxicity with some RS inhibitors. RS increase comes in two timely distant waves, the first one originating from the plasma itself with secondary solubilization and passive diffusion, the second wave deriving from the mitochondrion. The addition of low doses of carboplatin to CAP-treated cells resulted in a significant increase in cytotoxicity compared with either regimen alone. Additionally, maximal antiangiogenic effects were obtained with 60 s of plasma exposure. Direct and indirect treatment with CAP might be a selective therapy with the potential to target tumour cells and supporting the microenvironment.

Protective effects and mechanism of action of ruscogenin in a mouse model of ovalbumin-induced asthma

OBJECTIVE

Ruscogenin is a natural product exhibiting anti-inflammatory, antioxidant, and anti-apoptotic effects; however, its effectiveness for asthma management has not yet been reported. The aim of this study was to explore the role of ruscogenin in airway inflammation and apoptosis in asthma.

METHODS

In vivo, female 6- to 8-week-old CL57 mice were sensitized to ovalbumin and challenged intranasally for 7 days. One group was gavaged with ruscogenin before ovalbumin challenge. At the end of the challenge period, airway hyperresponsiveness and airway inflammation were evaluated. Enzyme-linked immunosorbent assay was used to estimate the oxidative stress levels. A terminal deoxynucleotidyl transferase dUDP nick-end labeling assay was used to determine the extent of apoptosis. Immunohistochemistry and western blotting were performed to examine VDAC1 expression. In vitro, human bronchial epithelial (HBE) cells were treated with H₂O₂, ruscogenin, or disulfonate salt, and flow cytometry was used to calculate the apoptosis ratio and detect mitochondrial calcium levels.

RESULTS

In vivo, ruscogenin improved airway hyperresponsiveness and airway inflammation, while reducing oxidative stress, the apoptosis ratio and VDAC1 expression in asthmatic lungs. In vitro, ruscogenin attenuated apoptosis in HBE cells by decreasing the levels of VDAC1 expression and mitochondrial calcium.

CONCLUSION

Ruscogenin reduced oxidative stress and apoptosis in the airway epithelium by inhibiting VDAC1 expression and mitochondrial handling of calcium.

Coordinated Contribution of NADPH Oxidase- and Mitochondria-Derived Reactive Oxygen Species in Metabolic Syndrome and Its Implication in Renal Dysfunction

Metabolic syndrome (MetS), a complex of interrelated risk factors for cardiovascular disease and diabetes, is comprised of central obesity (increased waist circumference), hyperglycemia, dyslipidemia (high triglyceride blood levels, low high-density lipoprotein blood levels), and increased blood pressure. Oxidative stress, caused by the imbalance between pro-oxidant and endogenous antioxidant systems, is the primary pathological basis of MetS. The major sources of reactive oxygen species (ROS) associated with MetS are nicotinamide-adenine dinucleotide phosphate (NADPH) oxidases and mitochondria. In this review, we summarize the current knowledge regarding the generation of ROS from NADPH oxidases and mitochondria, discuss the NADPH oxidase- and mitochondria-derived ROS signaling and pathophysiological effects, and the interplay between these two major sources of ROS, which leads to chronic inflammation, adipocyte proliferation, insulin resistance, and other metabolic abnormalities. The mechanisms linking MetS and chronic kidney disease are not well known. The role of NADPH oxidases and mitochondria in renal injury in the setting of MetS, particularly the influence of the pyruvate dehydrogenase complex in oxidative stress, inflammation, and subsequent renal injury, is highlighted. Understanding the molecular mechanism(s) underlying MetS may lead to novel therapeutic approaches by targeting the pyruvate dehydrogenase complex in MetS and prevent its sequelae of chronic cardiovascular and renal diseases.

Severe COVID-19 Infection Associated with Endothelial Dysfunction Induces Multiple Organ Dysfunction: A Review of Therapeutic Interventions

Since December 2019, the SARS-CoV-2 (COVID-19) pandemic has transfixed the medical world. COVID-19 symptoms vary from mild to severe and underlying chronic conditions such as pulmonary/cardiovascular disease and diabetes induce excessive inflammatory responses to COVID-19 and these underlying chronic diseases are mediated by endothelial dysfunction. Acute respiratory distress syndrome (ARDS) is the most common cause of death in COVID-19 patients, but coagulation induced by excessive inflammation, thrombosis, and disseminated intravascular coagulation (DIC) also induce death by multiple-organ dysfunction syndrome. These associations imply that maintaining endothelial integrity is crucial for favorable prognoses with COVID-19 and therapeutic intervention to support this may be beneficial. Here, we summarize the extent of heart injuries, ischemic stroke and hemorrhage, acute kidney injury, and liver injury caused by immune-mediated endothelial dysfunction that result in the phenomenon of multi-organ dysfunction seen in COVID-19 patients. Moreover, the potential therapeutic effect of angiotensin receptor blockers and angiotensin-converting enzyme inhibitors that improve endothelial dysfunction as well as the bradykinin storm are discussed.

Radiation-Induced Bystander Effect: Loss of Radioprotective Capacity of Rosmarinic Acid In Vivo and In Vitro

In radiation oncology, the modulation of the bystander effect is a target both for the destruction of tumor cells and to protect healthy cells. With this objective, we determine whether the radioprotective capacity of rosmarinic acid (RA) can affect the intensity of these effects. Genoprotective capacity was obtained by determining the micronuclei frequencies in in vivo and in vitro assays and the cell survival was determined by the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay) (MTT) assay in three cell lines (PNT2, TRAMPC1 and B16F10), both in direct exposure to X-rays and after the production of radiation-induced bystander effect. The administration of RA in irradiated cells produced a decrease in the frequency of micronuclei both in vivo and in vitro, and an increase in cell survival, as expression of its radioprotective effect (p < 0.001) attributable to its ability to scavenge radio-induced free radicals (ROS). However, RA does not achieve any modification in the animals receiving serum or in the cultures treated with the irradiated medium, which expresses an absence of radioprotective capacity. The results suggest that ROS participates in the formation of signals in directly irradiated cells, but only certain subtypes of ROS, the cytotoxic products of lipid peroxidation, participate in the creation of lesions in recipient cells.

Engineering of stepwise-targeting chitosan oligosaccharide conjugate for the treatment of acute kidney injury

Acute kidney injury (AKI) is a common and serious clinical syndrome of acute renal dysfunction in a short period. One of therapeutic interventions for AKI is to reduce ROS massively generated in the mitochondria and then ameliorate cell damage and apoptosis induced by oxidative stress. In this study, stepwise-targeting chitosan oligosaccharide, triphenyl phosphine-low molecular weight chitosan-curcumin (TPP-LMWC-CUR, TLC), was constructed for sepsis-induced AKI via removing excessive ROS in renal tubular epithelial cells. Benefiting from good water solubility and low molecular weight, TLC was rapidly and preferentially distributed in the renal tissues and then specifically internalized by tubular epithelium cells via interaction between Megalin receptor and LMWC. The intracellular TLC could further delivery CUR to mitochondria due to high buffering capacity of LMWC and delocalized positive charges of TPP. Both in vitro and in vivo pharmacodynamic results demonstrated the enhanced therapeutic effect of TLC in the treatment of AKI.

HIF-1α inhibits mitochondria-mediated apoptosis and improves the survival of human adipose-derived stem cells in ischemic microenvironments

BACKGROUND

Human adipose mesenchymal stem cells (hADSCs) show poor survival after transplantation, limiting their clinical application. Tissue regeneration resulting from stem cell treatment may be caused by attenuation of hypoxia-inducible factor-1α (HIF-1α). In this study, we constructed hADSCs stably expressing HIF-1α and investigated the potential effects of HIF-1α expression in the ischemic microenvironment on mitochondrial apoptosis and survival of hADSCs, and studied the mechanisms involved.

METHOD

Apoptosis was induced by an ischemic microenvironment in vitro. ADSCs with stable HIF-1α expression were established. Cell survival and apoptosis were observed by CCK-8 assay, western blotting, flow cytometry, and fluorescence staining. ADSCs were subcutaneously transplanted into nude mice in the location where a hypoxia ischemic microenvironment was simulated in vivo. After 1, 3, and 7 d, mitochondrial apoptotic proteins were evaluated by immunohistochemistry and immunofluorescence staining.

RESULTS

Exogenous HIF-1α downregulated mitochondrial reactive oxygen species, cytochrome c, caspase-9, and caspase-3, but inhibited mitochondrial membrane potential depolarization and increased the Bcl-2/bax ratio. HIF-1α prevented apoptosis and promoted vascular endothelial growth factor (VEGF) secretion as demonstrated by enzyme-linked immunosorbent assay (ELISA), terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining, and flow cytometry analysis. HIF-1α enhanced the survival of transplanted ADSCs in nude mice.

CONCLUSION

We have shown that through inhibition of the mitochondria-mediated apoptotic pathway and promotion of VEGF secretion in hADSCs in an ischemic microenvironment, HIF-1α may potentially be applied in clinical therapy and as an alternative strategy for improving hADSC therapy.

Nobiletin Regulates ROS/ADMA/DDAHII/eNOS/NO Pathway and Alleviates Vascular Endothelium Injury by Iron Overload

Iron overload is harmful to health and associates with intracellular excessive reactive oxygen species (ROS) generation. Nobiletin (Nob) is known to be antioxidant and anti-inflammatory. However, whether Nob can protect endothelial cells against iron overload has not been studied, and the specific mechanism has not yet been elucidated. In this study, we have identified the protective effects of Nob, and its underlying molecular mechanism in human umbilical vein endothelial cells (HUVECs) suffered from iron overload via ROS/ADMA/DDAHII/eNOS/NO pathway. We found that compared with 50 μM iron dextran treatment, co-treatment with 20 μM Nob increased cell viability and decreased lactate dehydrogenase activity. Besides, Nob could upregulate DDAHII expression and activity, promote eNOS phosphorylation to produce more NO, reduce ADMA content, and therefore increase superoxide dismutase, catalase, and glutathione peroxidase activities, and decrease malondialdehyde level and ROS generation. Nob also inhibited mitochondrial permeability transition pore (mPTP) openness and cleaved caspase-3 expression, and decreased apoptosis induced by iron overload. These results were consistent when Nob was replaced by the positive control reagents L-arginine (a competitive substrate of ADMA), cyclosporin A (an mPTP closing agent), or edaravone (a free radical scavenger). The addition of pAD/DDAHII-shRNA adenovirus reversed the above effects of Nob. These data suggested that the protective mechanism of Nob was to inhibit ROS burst, upregulate DDAHII expression and activity, promote eNOS phosphorylation, produce NO, reduce ADMA content, and ultimately alleviate iron overload damage in vascular endothelium.

A Red Fluorescent Protein-Based Probe for Detection of Intracellular Reactive Sulfane Sulfur

Reactive sulfane sulfur, including persulfide and polysulfide, is a type of regular cellular component, playing an antioxidant role. Its function may be organelle-dependent; however, the shortage of probes for detecting organellar reactive sulfane sulfur has hindered further investigation. Herein, we reported a red fluorescent protein (mCherry)-based probe for specifically detecting intracellular reactive sulfane sulfur. By mutating two amino acid residues of mCherry (A150 and S151) to cysteine residues, we constructed a mCherry mutant, which reacted with reactive sulfane sulfur to form an intramolecular –S_n– bond (n ≥ 3). The bond largely decreased the intensity of 610 nm emission (excitation at 587 nm) and slightly increased the intensity of 466 nm emission (excitation at 406 nm). The 466/610 nm emission ratio was used to indicate the relative abundance of reactive sulfane sulfur. We then expressed this mutant in the cytoplasm and mitochondria of Saccharomyces cerevisiae. The 466/610 nm emission ratio revealed that mitochondria had a higher level of reactive sulfane sulfur than cytoplasm. Thus, the mCherry mutant can be used as a specific probe for detecting reactive sulfane sulfur in vivo.

Hydrogen peroxide diffusion and scavenging shapes mitochondrial network instability and failure by sensitizing ROS-induced ROS release

The mitochondrial network of cardiac cells is finely tuned for ATP delivery to sites of energy demand; however, emergent phenomena, such as mitochondrial transmembrane potential oscillations or propagating waves of depolarization have been observed under metabolic stress. While regenerative signaling by reactive oxygen species (ROS)-induced ROS release (RIRR) has been suggested as a potential trigger, it is unknown how it could lead to widespread responses. Here, we present a novel computational model of RIRR transmission that explains the mechanisms of this phenomenon. The results reveal that superoxide mediates neighbor-neighbor activation of energy-dissipating ion channels, while hydrogen peroxide distributes oxidative stress to sensitize the network to mitochondrial criticality. The findings demonstrate the feasibility of RIRR as a synchronizing factor across the dimensions of the adult heart cell and illustrate how a cascade of failures at the organellar level can scale to impact cell and organ level functions of the heart.

Novel Dual-Fluorescent Mitophagy Reporter Reveals a Reduced Mitophagy Flux in Type 1 Diabetic Mouse Heart

CONTEXT

Patients with diabetes are susceptible to heart failure. Defective mitochondria can cause cardiac damage. Mitochondrial autophagy or mitophagy is a quality control mechanism that eliminates dysfunctional mitochondria through lysosome degradation. Mitophagy is essential for maintaining a pool of healthy mitochondria for normal cardiac function. However, the effect of diabetes on the functional status of cardiac mitophagy remains unclear.

OBJECTIVE

To determine and compare cardiac mitophagy flux between diabetic and nondiabetic mice.

METHODS

Using a novel dual fluorescent mitophagy reporter termed mt-Rosella, we labeled and traced mitochondrial fragments that are sequestered by the autophagosome and delivered to and degraded in the lysosome.

RESULTS

Mitophagic activity was reduced in high-glucose-treated cardiomyocytes and in the heart tissue of type 1 diabetic mice.

CONCLUSIONS

Mitophagy was impaired in the heart of diabetic mice, suggesting that restoring or accelerating mitophagy flux may be a useful strategy to reduce cardiac injury caused by diabetes.

In vivo assessment of reactive oxygen species production and oxidative stress effects induced by chronic exposure to gamma radiation in Caenorhabditis elegans

In the current study, effects of chronic exposure to ionizing gamma radiation were assessed in the radioresistant nematode Caenorhabditis elegans in order to understand whether antioxidant defences (AODs) could ameliorate radical formation, or if increased ROS levels would cause oxidative damage. This analysis was accompanied by phenotypical as well as molecular investigations, via assessment of reproductive capacity, somatic growth and RNA-seq analysis. The use of a fluorescent reporter strain (sod1::gfp) and two ratiometric biosensors (HyPer and Grx1-roGFP2) demonstrated increased ROS production (H₂O₂) and activation of AODs (SOD1 and Grx) in vivo. The data showed that at dose-rates ≤10 mGy h^-1 defence mechanisms were able to prevent the manifestation of oxidative stress. In contrast, at dose-rates ≥40 mGy h^-1 the continuous formation of radicals caused a redox shift, which lead to oxidative stress transcriptomic responses, including changes in mitochondrial functions, protein degradation, lipid metabolism and collagen synthesis. Moreover, genotoxic effects were among the most over-represented functions affected by chronic gamma irradiation, as indicated by differential regulation of genes involved in DNA damage, DNA repair, cell-cycle checkpoints, chromosome segregation and chromatin remodelling. Ultimately, the exposure to gamma radiation caused reprotoxic effects, with >20% reduction in the number of offspring per adult hermaphrodite at dose-rates ≥40 mGy h^-1, accompanied by the down-regulation of more than 300 genes related to reproductive system, apoptosis, meiotic functions and gamete development and fertilization.

Clinico-pathological significance of Drp1 dysregulation and its correlation to apoptosis in oral cancer patients

Dysregulation in mitochondrial dynamics has been associated with several diseases including cancer. Present study assessed the alteration in mitochondrial fission protein (Drp1) in oral epithelial cells collected from clinically confirmed pre-cancer and cancer patients and further correlates it with the cellular apoptosis signaling. Results indicate the ROS accumulation in OSCC patients is accompanied by several changes including increase in mitochondrial mass, expression of mitochondrial fission protein (Drp1) and alteration in apoptotic signaling. The positive co-relation has been observed between the expressions of anti-apoptotic Bcl-2proteinswith mitochondrial fission protein Drp1. Higher mitochondrial fission in oral cancer cells was also correlated with the increased expression of cell cycle marker CyclinD1 indicating highly proliferative stage of oral cancer cells. The clinical correlation can be extended to develop biomarker for diagram and program in oral cancer management.

Doxorubicin Induces Endotheliotoxicity and Mitochondrial Dysfunction via ROS/eNOS/NO Pathway

Background: Doxorubicin (Dox) can induce endotheliotoxicity and damage the vascular endothelium (VE). The most principle mechanism might be excess reactive oxygen species (ROS) generation. Nevertheless, the characteristics of ROS generation, downstream mechanisms, and target organelles in Dox-induced endotheliotoxicity have yet to be elucidated.

Methods and Results: In order to explore the related problems, the VE injury models were established in mice and human umbilical vein endothelial cells (HUVECs) by Dox-induced endotheliotoxicity. Results showed that the activities of lactate dehydrogenase (LDH) and creatine kinase of mice’s serum increased after injected Dox. The thoracic aortic strips’ endothelium-dependent dilation was significantly impaired, seen noticeable inflammatory changes, and brown TUNEL-positive staining in microscopy. After Dox-treated, HUVECs viability lowered, LDH and caspase-3 activities, and apoptotic cells increased. Both intracellular/mitochondrial ROS generation significantly increased, and intracellular ROS generation lagged behind mitochondria. HUVECs treated with Dox plus ciclosporin A (CsA) could basically terminate ROS burst, but plus edaravone (Eda) could only delay or inhibit, but could not completely cancel ROS burst. Meanwhile, the expression of endothelial nitric oxide synthase (eNOS) decreased, especially phosphorylation of eNOS significantly. Then nitric oxide content decreased, the mitochondrial function was impaired, mitochondrial membrane potential (MMP) impeded, mitochondrial swelled, mitochondrial permeability transition pore (mPTP) was opened, and cytochrome C was released from mitochondria into the cytosol.

Conclusion: Dox produces excess ROS in the mitochondria, thereby weakens the MMP, opens mPTP, activates the ROS-induced ROS release mechanism, induces ROS burst, and leads to mitochondrial dysfunction, which in turn damages VE. Therefore, interrupting any step of the cycles, as mentioned above can end the related vicious cycle and prevent the occurrence and development of injury.

Redox Signaling from Mitochondria: Signal Propagation and Its Targets

Progress in mass spectroscopy of posttranslational oxidative modifications has enabled researchers to experimentally verify the concept of redox signaling. We focus here on redox signaling originating from mitochondria under physiological situations, discussing mechanisms of transient redox burst in mitochondria, as well as the possible ways to transfer such redox signals to specific extramitochondrial targets. A role of peroxiredoxins is described which enables redox relay to other targets. Examples of mitochondrial redox signaling are discussed: initiation of hypoxia-inducible factor (HIF) responses; retrograde redox signaling to PGC1α during exercise in skeletal muscle; redox signaling in innate immune cells; redox stimulation of insulin secretion, and other physiological situations.

A Spatiotemporal Ventricular Myocyte Model Incorporating Mitochondrial Calcium Cycling

Intracellular calcium (Ca2+) cycling dynamics in cardiac myocytes are spatiotemporally generated by stochastic events arising from a spatially distributed network of coupled Ca2+ release units that interact with an intertwined mitochondrial network. In this study, we developed a spatiotemporal ventricular myocyte model that integrates mitochondria-related Ca2+ cycling components into our previously developed ventricular myocyte model consisting of a three-dimensional Ca2+ release unit network. Mathematical formulations of mitochondrial membrane potential, mitochondrial Ca2+ cycling, mitochondrial permeability transition pore stochastic opening and closing, intracellular reactive oxygen species signaling, and oxidized Ca2+/calmodulin-dependent protein kinase II signaling were incorporated into the model. We then used the model to simulate the effects of mitochondrial depolarization on mitochondrial Ca2+ cycling, Ca2+ spark frequency, and Ca2+ amplitude, which agree well with experimental data. We also simulated the effects of the strength of mitochondrial Ca2+ uniporters and their spatial localization on intracellular Ca2+ cycling properties, which substantially affected diastolic and systolic Ca2+ levels in the mitochondria but exhibited only a small effect on sarcoplasmic reticulum and cytosolic Ca2+ levels under normal conditions. We show that mitochondrial depolarization can cause Ca2+ waves and Ca2+ alternans, which agrees with previous experimental observations. We propose that this new, to our knowledge, spatiotemporal ventricular myocyte model, incorporating properties of mitochondrial Ca2+ cycling and reactive-oxygen-species-dependent signaling, will be useful for investigating the effects of mitochondria on intracellular Ca2+ cycling and action potential dynamics in ventricular myocytes.

Tetramethylpyrazine Attenuates the Endotheliotoxicity and the Mitochondrial Dysfunction by Doxorubicin via 14-3-3γ/Bcl-2

Doxorubicin (Dox) with cardiotoxicity and endotheliotoxicity limits its clinical application for cancer. The toxicitic mechanism involves excess ROS generation. 14-3-3s have the protective effects on various injured tissues and cells. Tetramethylpyrazine (TMP) is an alkaloid extracted from the rhizome of Ligusticum wallichii and has multiple bioactivities. We hypothesize that TMP has the protective effects on vascular endothelium by upregulating 14-3-3γ. To test the hypothesis, Dox-induced endotheliotoxicity was used to establish vascular endothelium injury models in mice and human umbilical vein endothelial cells. The effects of TMP were assessed by determining thoracic aortic strips' endothelium-dependent dilation (EDD), as well as LDH, CK, caspase-3, SOD, CAT, GSH-Px activities and MDA level in serum, apoptotic rate, and histopathological changes of vascular tissue (in vivo). Also, cell viability, LDH and caspase-3 activities, ROS generation, levels of NAD⁺/NADH and GSH/GSSG, MMP, mPTP opening, and apoptotic rate were evaluated (in vitro). The expression of 14-3-3γ and Bcl-2, as well as phosphorylation of Bad (S112), were determined by Western blot. Our results showed that Dox-induced injury to vascular endothelium was decreased by TMP via upregulating 14-3-3γ expression in total protein and Bcl-2 expression in mitochondria, activating Bad (S112) phosphorylation, maintaining EDD, reducing LDH, CK, and caspase-3 activities, thereby causing a reduction in apoptotic rate, and histopathological changes of vascular endothelium (in vivo). Furthermore, TMP increased cell viability and MMP levels, maintained NAD⁺/NADH, GSH/GSSG balance, decreased LDH and caspase-3 activities, ROS generation, mPTP opening, and apoptotic rate (in vitro). However, the protective effects to vascular endothelium of TMP were significantly canceled by pAD/14-3-3γ-shRNA, an adenovirus that caused knockdown 14-3-3γ expression, or ABT-737, a specific Bcl-2 inhibitor. In conclusion, this study is the first to demonstrate that TMP protects the vascular endothelium against Dox-induced injury via upregulating 14-3-3γ expression, promoting translocation of Bcl-2 to the mitochondria, closing mPTP, maintaining MMP, inhibiting RIRR mechanism, suppressing oxidative stress, improving mitochondrial function, and alleviating Dox-induced endotheliotoxicity.

Iron Overload Damages the Endothelial Mitochondria via the ROS/ADMA/DDAHII/eNOS/NO Pathway

It has been recognized that iron overload may harm the body's health. Vascular endothelial cells (VECs) are one of the main targets of iron overload injury, and the mechanism involved was thought to be related to the excessive generation of reactive oxygen species (ROS). However, the subcellular and temporal characteristics of ROS generation, potential downstream mechanisms, and target organelles in VECs injured by iron overload have not been expounded yet. In this study, we elucidated the abovementioned issues through both in vivo and in vitro experiments. Mice were fed pellet diets that were supplemented with iron for 4 consecutive months. Results showed that the thoracic aortic strips' endothelium-dependent dilation was significantly impaired and associated with inflammatory changes, noticeable under brown TUNEL-positive staining in microscopy analysis. In addition, the serum content of asymmetric dimethylarginine (ADMA) increased, whereas nitric oxide (NO) levels decreased. Furthermore, the dimethylarginine dimethylaminohydrolase II (DDAHII) expression and activity, as well as the phosphorylation of endothelial nitric oxide synthase (eNOS) in aortic tissue, were inhibited. Human umbilical vein endothelial cells were treated with 50 μM iron dextran for 48 hours, after which the cell viability, NO content, DDAHII expression and activity, and phosphorylation of eNOS decreased and lactate dehydrogenase and caspase-3 activity, ADMA content, and apoptotic cells significantly increased. After the addition of L-arginine (L-Arg) or pAD/DDAHII, the abovementioned changes were reversed. By dynamically detecting the changes of ROS generation in the cytoplasm and mitochondria and interfering with different aspects of signaling pathways, we have confirmed for the first time that excessive ROS originates from the cytoplasm and activates the ROS-induced ROS release (RIRR) mechanism, leading to mitochondrial dysfunction. Together, our data suggested that excessive free iron ions produced excess ROS in the cytoplasm. Thus, excess ROS create one vicious circle by activating the ADMA/eNOS/DDAHII/NO pathway and another vicious circle by activation of the RIRR mechanism, which, when combined, induce a ROS burst, resulting in mitochondrial dysfunction and damaged VECs.

The Role of Mitochondria in the Mechanisms of Cardiac Ischemia-Reperfusion Injury

Mitochondria play a critical role in maintaining cellular function by ATP production. They are also a source of reactive oxygen species (ROS) and proapoptotic factors. The role of mitochondria has been established in many aspects of cell physiology/pathophysiology, including cell signaling. Mitochondria may deteriorate under various pathological conditions, including ischemia-reperfusion (IR) injury. Mitochondrial injury can be one of the main causes for cardiac and other tissue injuries by energy stress and overproduction of toxic reactive oxygen species, leading to oxidative stress, elevated calcium and apoptotic and necrotic cell death. However, the interplay among these processes in normal and pathological conditions is still poorly understood. Mitochondria play a critical role in cardiac IR injury, where they are directly involved in several pathophysiological mechanisms. We also discuss the role of mitochondria in the context of mitochondrial dynamics, specializations and heterogeneity. Also, we wanted to stress the existence of morphologically and functionally different mitochondrial subpopulations in the heart that may have different sensitivities to diseases and IR injury. Therefore, various cardioprotective interventions that modulate mitochondrial stability, dynamics and turnover, including various pharmacologic agents, specific mitochondrial antioxidants and uncouplers, and ischemic preconditioning can be considered as the main strategies to protect mitochondrial and cardiovascular function and thus enhance longevity.

Nutritional preconditioning induced by astragaloside Ⅳ on isolated hearts and cardiomyocytes against myocardial ischemia injury via improving Bcl-2-mediated mitochondrial function

Ischemic preconditioning and pharmacological preconditioning are common strategies to prevent lethal myocardial injury, especially nutritional preconditioning (NPC). In this study, we investigated the effects of astragaloside IV (Ast), as an NPC agent, on myocardium suffered anoxia/reoxygenation (A/R) injury. Rats received 5 mg/kg Ast daily for 3 weeks by intragastric administration. Then, hearts were harvested and underwent A/R treatment using a Langendorff apparatus. Ast- pretreatment significantly promoted functional recovery of the myocardium, reduced infarct size, and oxidative stress, and decreased the apoptotic index. Similar findings were demonstrated in H9c2 cardiomyocytes that were pretreated with Ast for 24 h. Moreover, Ast-pretreatment significantly upregulated Bcl-2 expression, especially in mitochondria. The effects of Ast treatment against A/R injury were also reflected by increased antioxidant potential, inhibited reactive oxygen species (ROS) burst, increased oxygen consumption rate, maintained mitochondrial membrane potential (MMP), inhibited mitochondrial permeability transition pore (mPTP) opening, and prevented apoptosis. Selective inhibition of Bcl-2 by ABT-737 decreased myocardial injury protection of Ast. Ast-pretreatment resulted in NPC- related effects against A/R, and mitochondria may be the target of a cascade of events elicited by upregulating Bcl-2 expression, promoting translocation of Bcl-2 into mitochondria, maintaining MMP, inhibiting ROS bursts, thereby leading to recovery of mitochondrial respiration, preventing mPTP opening, decreasing cytochrome C release, preventing apoptosis, and ultimately alleviating myocardial injury.

Quercetin protects cardiomyocytes against doxorubicin-induced toxicity by suppressing oxidative stress and improving mitochondrial function via 14-3-3γ

Cardiotoxicity limits the clinical applications of doxorubicin (Dox), which mechanism might be excess generation of intracellular ROS. Quercetin (Que) is a flavonoid that possesses anti-oxidative activities, exerts myocardial protection. We hypothesized that the cardioprotection against Dox injury of Que involved 14-3-3γ, and mitochondria. To investigate the hypothesis, we treated primary cardiomyocytes with Dox and determined the effects of Que pretreatment with or without 14-3-3γ knockdown. We analyzed various cellular and molecular indexes. Our data showed that Que attenuated Dox-induced toxicity in cardiomyocytes by upregulating 14-3-3γ expression. Que pretreatment increased cell viability, SOD, catalase, and GPx activities, GSH levels, MMP and the GSH/GSSG ratio; decreased LDH and caspase-3 activities, MDA and ROS levels, mPTP opening and the percentage of apoptotic cells. However, Que's cardioprotection were attenuated by knocking down 14-3-3γ expression using pAD/14-3-3γ-shRNA. In conclusion, Que protects cardiomyocytes against Dox injury by suppressing oxidative stress and improving mitochondrial function via 14-3-3γ.

Neural plasticity and adult neurogenesis: the deep biology perspective

The recognition that neurogenesis does not stop with adolescence has spun off research towards the reduction of brain disorders by enhancing brain regeneration. Adult neurogenesis is one of the tougher problems of developmental biology as it requires the generation of complex intracellular and pericellular anatomies, amidst the danger of neuroinflammation. We here review how a multitude of regulatory pathways optimized for early neurogenesis has to be revamped into a new choreography of time dependencies. Distinct pathways need to be regulated, ranging from neural growth factor induced differentiation to mitochondrial bioenergetics, reactive oxygen metabolism, and apoptosis. Requiring much Gibbs energy consumption, brain depends on aerobic energy metabolism, hence on mitochondrial activity. Mitochondrial fission and fusion, movement and perhaps even mitoptosis, thereby come into play. All these network processes are interlinked and involve a plethora of molecules. We recommend a deep thinking approach to adult neurobiology.

Curcumin attenuates doxorubicin-induced cardiotoxicity via suppressing oxidative stress and preventing mitochondrial dysfunction mediated by 14-3-3γ

Doxorubicin (Dox) induces cardiotoxicity, thereby limiting its clinical application for chemotherapy of cancer. The mechanism of cardiotoxicity includes the production of excess intracellular ROS. 14-3-3s have been found to protect the myocardium against various types of injury. Curcumin (Cur) is a polyphenolic compound that is derived from turmeric and has multiple bioactivities, including anti-oxidative and radical-scavenging activities that exert cytoprotection. We hypothesize that the cardioprotective effects of Cur are exerted by regulating 14-3-3γ. To test the hypothesis, Dox-induced cardiotoxicity was used to establish an in vivo myocardial injury model in mice (in vivo) and primary cardiomyocytes (in intro). The effects of Cur were assessed by determining the heart rate and ECG's ST segments, as well as lactate dehydrogenase (LDH) and creatine kinase (CK) activities in the serum, caspase-3 activity, apoptosis rate, and histopathological changes of the myocardium (in vivo). In addition, cell viability, LDH, SOD, CAT, GPx, and caspase-3 activities, levels of ROS, MDA, and MMP, mPTP opening, and the apoptosis rate (in vitro) were evaluated. The expression of 14-3-3γ and Bcl-2 as well as the phosphorylation levels of Bad (S112) were determined by western blot analysis. Our results showed that Dox-induced injury to the myocardium was decreased by Cur treatment via upregulating the protein expression of 14-3-3γ in total protein and Bcl-2 expression on mitochondria, activating Bad (S112) phosphorylation, reducing the heart rate and ST segment, and reducing LDH and CK activities in the serum, thereby causing a reduction in caspase-3 activity, the apoptosis rate, and histopathological changes of the myocardium (in vivo). Furthermore, Dox treatment increased cell viability and MMP levels, decreased LDH and caspase-3 activity, ROS levels, mPTP opening, and the apoptosis rate (in vitro). However, the cardioprotective effects of Cur were attenuated by pAD/14-3-3γ-shRNA, an adenovirus that caused a knock-down of intracellular 14-3-3γ expression. In conclusion, this is the first study to demonstrate that Cur protected the myocardium against Dox-induced injury via upregulating 14-3-3γ expression, thereby promoting the translocation of Bcl-2 to mitochondria, suppressing oxidative stress, and improving mitochondrial function.

The Mitochondrial Translocator Protein and the Emerging Link Between Oxidative Stress and Arrhythmias in the Diabetic Heart

The mitochondrial translocator protein (TSPO) is a key outer mitochondrial membrane protein that regulates the activity of energy-dissipating mitochondrial channels in response to oxidative stress. In this article, we provide an overview of the role of TSPO in the systematic amplification of reactive oxygen species (ROS) through an autocatalytic process known as ROS-induced ROS-release (RIRR). We describe how this TSPO-driven process destabilizes the mitochondrial membrane potential leading to electrical instability at the cellular and whole heart levels. Finally, we provide our perspective on the role of TSPO in the pathophysiology of diabetes, in general and diabetes-related arrhythmias, in particular.

Effects of low dose of aliskiren on isoproterenol-induced acute myocardial infarction in rats

This study examined the effects of aliskiren (Ali) (direct renin inhibitor) on serum cardiac enzymes (LDH and CK-MB), electrocardiography (ECG) changes, myocardial oxidative stress markers (MDA, CAT, and GSH) and the expression of Bcl2, HO-1, and Nrf2 genes in isoproterenol (ISO)-induced myocardial infarction (MI). A total of 40 male albino rats were allocated into four groups, (1) normal control (NC) group, (2) Ali group (rats received Ali at 10 mg/kg/day p.o. for 5 days), (3) ISO group (rats received ISO 150 mg/kg i.p. for two consecutive days at 24 h intervals), and (4) Ali + ISO group (rats received ISO + Ali at 10 mg/kg/day p.o. for 5 days from the 2^nd dose of ISO). ISO group showed significant rise in serum cardiac enzymes (CK-MB and LDH), myocardial damage scores, myocardial MDA, HO-1, myocardial Nrf2 expression with significant reduction in myocardial antioxidants (CAT and GSH), and Bcl2 expression compared to the normal group (p < 0.05). ECG showed ST segment elevation, prolonged QT interval and QRS complex, and increased heart rate in ISO group. Co-administration of Ali and ISO caused significant increase in cardiac enzymes and morphology with increase in MDA, serum K, and creatinine with significant decrease in Bcl2, HO-1, and Nrf2 without significant changes in ECG parameters compared to ISO group. We concluded that low dose of Ali seems to exacerbate the myocardial injury in ISO-MI, which might be due to the enhanced oxidative stress and apoptosis.

ROS-induced ROS release in plant and animal cells

Reactive oxygen species (ROS) play a key signaling role in plant and animal cells. Among the many cellular mechanisms used to generate and transduce ROS signals, ROS-induced ROS release (RIRR) is emerging as an important pathway involved in different human pathologies and plant responses to environmental stress. RIRR is a process in which one cellular compartment or organelle generates or releases ROS, triggering the enhanced production or release of ROS by another compartment or organelle. It was initially described in animal cells and proposed to mediate mitochondria-to-mitochondria communication, but later expanded to include communication between mitochondria and plasma membrane-localized NADPH oxidases. In plants a process of RIRR was demonstrated to mediate long distance rapid systemic signaling in response to biotic and abiotic stress. This process is thought to involve the enhanced production of ROS by one cell that triggers the enhanced production of ROS by a neighboring cell in a process that propagates the enhanced "ROS production state" all the way from one part of the plant to another. In contrast to the intracellular nature of the RIRR process of animal cells, the plant RIRR process is therefore primarily studied at the cell-to-cell communication level. Studies on intracellular (organelle-to-organelle, or organelle-to-NADPH oxidase) RIRR pathways are very scarce in plants, whereas studies on cell-to-cell RIRR are very scarce in animals. Here we will attempt to highlight what is known in both systems and what each system can learn from the other.

Tetramethylpyrazine attenuates lipopolysaccharide-induced cardiomyocyte injury via improving mitochondrial function mediated by 14-3-3γ

Lipopolysaccharide (LPS) is one of the many reasons that can cause myocardial injury. Our previous works have demonstrated that 14-3-3γ could protect myocardium against LPS-induced injury. Tetramethylpyrazine (TMP), an alkaloid found in Chinese herbs, exerts myocardial protection in many ways with multiple targets. We hypothesized that the cardioprotection of TMP against LPS-induced injury is attributed to upregulation of 14-3-3γ and improvement of mitochondrial function. To test the hypothesis, we investigated the effects of TMP on LPS-induced injury to cardiomyocytes by determining cell viability, LDH and caspase-3 activities, reactive oxygen species and MMP levels, mPTP openness, and apoptosis rate. The expression of 14-3-3γ and Bcl-2, and the phosphorylation of Bad (S112) were examined by Western blot. LPS-induced injury to cardiomyocytes was attenuated by TMP via upregulating expression of 14-3-3γ, and Bcl-2 on mitochondria, activating Bad (S112) phosphorylation, increasing cell viability and MMP levels, decreasing LDH and caspase-3 activity, reactive oxygen species generation, mPTP opening and apoptosis rate. However, the cardioprotection of TMP was attenuated by pAD/14-3-3γ-shRNA, an adenovirus that knocked down intracellular 14-3-3γ expression. In conclusion, the cardioprotection of TMP against LPS-induced injury was through up-regulating the expression of 14-3-3γ, promoting the translocation of Bcl-2 to mitochondria, and improving the function of mitochondria.

Potential relationship between the biological effects of low-dose irradiation and mitochondrial ROS production

Exposure to ionizing radiation (IR) induces various types of DNA damage, of which DNA double-strand breaks are the most severe, leading to genomic instability, tumorigenesis, and cell death. Hence, cells have developed DNA damage responses and repair mechanisms. IR also causes the accumulation of endogenous reactive oxidative species (ROS) in the irradiated cells. Upon exposure to low-dose irradiation, the IR-induced biological effects mediated by ROS were relatively more significant than those mediated by DNA damage. Accumulating evidence suggests that such increase in endogenous ROS is related with mitochondria change in irradiated cells. Thus, in this review we focused on the mechanism of mitochondrial ROS production and its relationship to the biological effects of IR. Exposure of mammalian cells to IR stimulates an increase in the production of endogenous ROS by mitochondria, which potentially leads to mitochondrial dysfunction. Since the remains of damaged mitochondria could generate or leak more ROS inside the cell, the damaged mitochondria are removed by mitophagy. The disruption of this pathway, involved in maintaining mitochondrial integrity, could lead to several disorders (such as neurodegeneration) and aging. Thus, further investigation needs to be performed in order to understand the relationship between the biological effects of low-dose IR and mitochondrial integrity.

Indolylmaleimide Derivative IM-17 Shows Cardioprotective Effects in Ischemia-Reperfusion Injury

We previously developed IM-54 as a novel type of inhibitor of hydrogen-peroxide-induced necrotic cell death. Here, we examined its cell death inhibition profile. IM-54 was found to selectively inhibit oxidative stress-induced necrosis, but it did not inhibit apoptosis induced by various anticancer drugs or Fas ligand, or necroptosis. IM-17, an IM derivative having improved water-solubility and metabolic stability, was developed and confirmed to retain necrosis-inhibitory activity. IM-17 showed cardioprotective effects in an isolated rat heart model and an in vivo arrhythmia model, suggesting that IM derivatives may have therapeutic potential.

Apoptosis induction in K562 human myelogenous leukaemia cells is connected to the modulation of Wnt/β-catenin signalling by BHX, a novel pyrazoline derivative

OBJECTIVES

The goal of this study was to explore the effects of BHX on human chronic myeloid leukaemia (CML) cells and to elucidate the underlying molecular mechanism.

MATERIALS AND METHODS

CML cell line K562 cells were treated with BHX. The effects of BHX on cell proliferation, apoptosis and cell cycle were detected. Subsequently, the caspase, ATP activity, Ca²⁺ , ROS and mitochondrial membrane potential (MMP) levels treated with various concentrations of BHX were analysed. The variation of relevant proteins and genes was detected. Further, toxicity of BHX on peripheral blood cells, bone marrow-nucleated cells (BMNC) and organ index were investigated on mice.

RESULTS

Results showed that BHX suppressed K562 cell proliferation in a dose-dependent manner and induced apoptosis and G0/G1 phase arrest. BHX induced mitochondria-mediated apoptosis, which was associated with downregulation of MMP, activation of caspase-3 and caspase-9, generation of intracellular ROS and elevation of Ca²⁺ in K562 cells. In treated cells, ATP levels were decreased, expression of total β-catenin, phosphorylated β-catenin and β-catenin in the nucleus was decreased, and expression of cell cycle-related proteins was decreased. Further analysis revealed that BHX lowered the transcriptional level of β-catenin. Lastly, BHX treatment significantly reduced the number of white blood cells, but had no effect on BMNC and organ index.

CONCLUSIONS

These findings provide further insight into the potential use of BHX as an anti-cancer agent against human leukaemia.

Dual action of vitamin C in iron supplement therapeutics for iron deficiency anemia: prevention of liver damage induced by iron overload

Vitamin C, an excellent reducing agent, aids in increasing absorbable ferrous iron in iron deficiency anemia.

Melatonin-mediated upregulation of Sirt3 attenuates sodium fluoride-induced hepatotoxicity by activating the MT1-PI3K/AKT-PGC-1α signaling pathway

Mitochondrial reactive oxygen species (ROS) production has been implicated in the pathogenesis of fluoride toxicity in liver. Melatonin, an indolamine synthesized in the pineal gland, was previously shown to protect against sodium fluoride (NaF)-induced hepatotoxicity. This study investigated the protective effects of melatonin pretreatment on NaF-induced hepatotoxicity and elucidates the potential mechanism of melatonin-mediated protection. Reducing mitochondrial ROS by melatonin substantially attenuated NaF-induced NADPH oxidase 4 (Nox4) upregulation and cytotoxicity in L-02 cells. Melatonin exerted its hepatoprotective effects by upregulating Sirtuin 3 (Sirt3) expression level and its activity. Melatonin increased the activity of manganese superoxide dismutase (SOD2) by promoting Sirt3-mediated deacetylation and promoted SOD2 expression through Sirt3-regulated DNA-binding activity of forkhead box O3 (FoxO3a), thus inhibiting the production of mitochondrial ROS induced by NaF. Notably, increased peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α) by melatonin activated the Sirt3 expression, which was regulated by an estrogen-related receptor (ERR) binding element (ERRE) mapped to Sirt3 promoter region. Analysis of the cell signaling pathway profiling systems and specific pathway inhibition indicated that melatonin enhances PGC-1α expression by activating the PI3K/AKT signaling pathway. Importantly, inhibition of melatonin receptor (MT)-1 blocked the melatonin-activated PI3K/AKT-PGC-1α-Sirt3 signaling. Mechanistic study revealed that the protective effects of melatonin were associated with down-regulation of JNK1/2 phosphorylation. Our findings provided a theoretical basis that melatonin mitigated NaF-induced hepatotoxicity, which, in part, was mediated through the activation of the Sirt3 pathway.

TRPM4 activation by chemically- and oxygen deprivation-induced ischemia and reperfusion triggers neuronal death

Cerebral ischemia-reperfusion injury triggers a deleterious process ending in neuronal death. This process has two components, a glutamate-dependent and a glutamate-independent mechanism. In the glutamate-independent mechanism, neurons undergo a slow depolarization eventually leading to neuronal death. However, little is known about the molecules that take part in this process. Here we show by using mice cortical neurons in culture and ischemia-reperfusion protocols that TRPM4 is fundamental for the glutamate-independent neuronal damage. Thus, by blocking excitotoxicity, we reveal a slow activating, glibenclamide- and 9-phenanthrol-sensitive current, which is activated within 5 min upon ischemia-reperfusion onset. TRPM4 shRNA-based silenced neurons show a reduced ischemia-reperfusion induced current and depolarization. Neurons were protected from neuronal death up to 3 hours after the ischemia-reperfusion challenge. The activation of TRPM4 during ischemia-reperfusion injury involves the increase in both, intracellular calcium and H₂O₂, which may act together to produce a sustained activation of the channel.

Two mutations in mitochondrial ATP6 gene of ATP synthase, related to human cancer, affect ROS, calcium homeostasis and mitochondrial permeability transition in yeast

The relevance of mitochondrial DNA (mtDNA) mutations in cancer process is still unknown. Since the mutagenesis of mitochondrial genome in mammals is not possible yet, we have exploited budding yeast S. cerevisiae as a model to study the effects of tumor-associated mutations in the mitochondrial MTATP6 gene, encoding subunit 6 of ATP synthase, on the energy metabolism. We previously reported that four mutations in this gene have a limited impact on the production of cellular energy. Here we show that two mutations, Atp6-P163S and Atp6-K90E (human MTATP6-P136S and MTATP6-K64E, found in prostate and thyroid cancer samples, respectively), increase sensitivity of yeast cells both to compounds inducing oxidative stress and to high concentrations of calcium ions in the medium, when Om45p, the component of porin complex in outer mitochondrial membrane (OM), was fused to GFP. In OM45-GFP background, these mutations affect the activation of yeast permeability transition pore (yPTP, also called YMUC, yeast mitochondrial unspecific channel) upon calcium induction. Moreover, we show that calcium addition to isolated mitochondria heavily induced the formation of ATP synthase dimers and oligomers, recently proposed to form the core of PTP, which was slower in the mutants. We show the genetic evidence for involvement of mitochondrial ATP synthase in calcium homeostasis and permeability transition in yeast. This paper is a first to show, although in yeast model organism, that mitochondrial ATP synthase mutations, which accumulate during carcinogenesis process, may be significant for cancer cell escape from apoptosis.

Neferine ameliorates cardiomyoblast apoptosis induced by doxorubicin: possible role in modulating NADPH oxidase/ROS-mediated NFκB redox signaling cascade

Doxorubicin (DOX) mediated cardiomyopathy is a major challenge in cancer chemotherapy. Redox-cycling of doxorubicin by flavoenzymes makes the heart more vulnerable to oxidative stress leading to cardiac dysfunction. The present study evaluates the role of neferine, a bisbenzylisoquinoline alkaloid, in curbing the molecular consequences of DOX-exposure in H9c2 cardiomyoblasts. Neferine pre-treatment increased cell viability upon DOX-exposure. DOX activates NADPH oxidase subunits, (p22phox, p47phox, gp91phox) as the primary event followed by peak in [Ca2+]i accumulation by 2 h, ROS by 3 h and activated ERK1/2 and p38 MAPKinases, time dependently along with the activation and translocation of NFκB and up-regulated COX2 and TNF-α expressions. Neferine pre-treatment modulated NADPH oxidase/ROS system, inhibited MAPKinases and NFκB activation, reduced sub G1 cell population and concomitantly increased cyclin D1 expression reducing DOX-mediated apoptosis. The study demonstrates for the first time, the molecular sequential events behind DOX toxicity and the mechanism of protection offered by neferine with specific relevance to NADPH oxidase system, MAPKinases, inflammation and apoptosis in H9c2 cells. Our data suggests the use of neferine as a new approach in pharmacological interventions against cardiovascular disorders as secondary complications.

Humanin directly protects cardiac mitochondria against dysfunction initiated by oxidative stress by decreasing complex I activity

Humanin (HN) is an endogenous peptide that exerts cytoprotection against oxidative stress and apoptosis. We recently reported that Humanin analogue (HNG) pretreatment can reduce reactive oxygen species production in the heart subjected to ischemia/reperfusion (I/R) injury via attenuating mitochondrial dysfunction. However, it is unclear if HNG has direct effects on mitochondrial function against oxidative stress. Thus, we sought to determine the effects of HNG on mitochondrial function under hydrogen peroxide (H₂O₂) induced oxidative stress in isolated cardiac mitochondria. We found that HNG has direct protective effects on cardiac mitochondrial function against H₂O₂ induced oxidative stress through decreasing complex I activity.

Mitochondrial Ca2+-activated K+ channels and their role in cell life and death pathways

Ca²⁺-activated K⁺ channels (K_Ca) are expressed at the plasma membrane and in cellular organelles. Expression of all K_Ca channel subtypes (BK, IK and SK) has been detected at the inner mitochondrial membrane of several cell types. Primary functions of these mitochondrial K_Ca channels include the regulation of mitochondrial ROS production, maintenance of the mitochondrial membrane potential and preservation of mitochondrial calcium homeostasis. These channels are therefore thought to contribute to cellular protection against oxidative stress through mitochondrial mechanisms of preconditioning. In this review, we summarize the current knowledge on mitochondrial KCa channels, and their role in mitochondrial function in relation to cell death and survival pathways. More specifically, we systematically discuss studies on the role of these mitochondrial K_Ca channels in pharmacological preconditioning, and according protective effects on ischemic insults to the brain and the heart.

Synchronism in mitochondrial ROS flashes, membrane depolarization and calcium sparks in human carcinoma cells

Mitochondria are major producers of reactive oxygen species (ROS) in many cells including cancer cells. However, complex interrelationships between mitochondrial ROS (mitoROS), mitochondrial membrane potential (ΔΨm) and Ca²⁺ are not completely understood. Using human carcinoma cells, we further highlight biphasic ROS dynamics: - gradual mitoROS increase followed by mitoROS flash. Also, we demonstrate heterogeneity in rates of mitoROS generation and flash initiation time. Comparing mitochondrial and near-extra-mitochondrial signals, we show that mechanisms of mitoROS flashes in single mitochondria, linked to mitochondrial permeability transition pore opening (ΔΨm collapse) and calcium sparks, may involve flash triggering by certain levels of external ROS released from the same mitochondria. In addition, mitochondria-mitochondria interactions can produce wave propagations of mitoROS flashes and ΔΨm collapses in cancer cells similar to phenomena of ROS-induced ROS release (RIRR). Our data suggest that in cancer cells RIRR, activation of mitoROS flashes and mitochondrial depolarization may involve participation of extramitochondrial-ROS produced either by individual mitochondria and/or by neighboring mitochondria. This could represent general mechanisms in ROS-ROS signaling with suggested role in both mitochondrial and cellular physiology and signaling.

Plin5 alleviates myocardial ischaemia/reperfusion injury by reducing oxidative stress through inhibiting the lipolysis of lipid droplets

Myocardial ischaemia-reperfusion (I/R) injury is a complex pathophysiological process. Current research has suggested that energy metabolism disorders, of which the abnormal consumption of fatty acids is closely related, compose the main pathological basis for myocardial I/R injury. Lipid droplets (LD) are critical regulators of lipid metabolism by LD-associated proteins. Among the lipid droplet proteins, the perilipin family members regulate lipolysis and lipogenesis through different mechanisms. Plin5, an important perilipin protein, promotes LD generation and lowers fatty acid oxidation, thus protecting the myocardium from lipotoxicity. This study investigated the protective effects of Plin5 in I/R myocardium. Our results indicated that Plin5 deficiency exacerbated the myocardial infarct area, aggravated left ventricular systolic dysfunction, reduced lipid storage, and elevated free fatty acids. Plin5-deficient myocardium exhibited severely damaged mitochondria, elevated reactive oxygen species (ROS) and malondialdehyde (MDA) levels, and decreased superoxide dismutase (SOD) activity. Furthermore, the decreased phosphorylation of PI3K/Akt in Plin5-null cardiomyocytes might contribute to I/R injury aggravation. In conclusion, Plin5, a new regulator of myocardial lipid metabolism, decreases free fatty acid peroxidation by inhibiting the lipolysis of intracellular lipid droplets, thus providing cardioprotection against I/R injury and shedding new light on therapeutic solutions for I/R diseases.