Mitochondrial Oxygen Species Research Articles

Effects of glyphosate herbicide ingestion on kidney function in rats on a balanced diet.

Glyphosate is the most widely used herbicide worldwide and in Brazil. There is currently increasing concern about the effects of glyphosate on human health. The Brazilian Institute for Consumer Protection showed data on the presence of glyphosate in some of Brazil's most consumed ultra-processed products. Currently, regulations on the upper limit for these residues in ultra-processed foods have yet to be established by the National Health Surveillance, and ultra-processed food consumption is independently associated with an increased risk of incident chronic kidney disease. Since an unbalanced diet can interfere with kidney function, this study aims to investigate the effect of daily intake of 5 mg/kg bw glyphosate in conjunction with a balanced diet and the possible impact on renal function in rats. Kidney function, kidney weight, markers of renal injury, and oxidative stress were evaluated. There was a decrease in kidney weight. The main histopathological alterations in renal tissues were vacuolation in the initial stage and upregulation of the kidney injury marker KIM-1. Renal injury is associated with increased production of reactive oxygen species in mitochondria. This study showed changes in the kidney of rats exposed to a balanced diet with glyphosate, suggesting a potential risk to human kidney. Presumably, ultra-processed food that contain glyphosate can potentiate this risk. The relevance of these results lies in drawing attention to the need to regulate glyphosate concentration in ultra-processed foods in the future.

The Role of Doxorubicin in the Formation of Cardiotoxicity – Generally Accepted Statement. Part I. Prevalence and Mechanisms of Formation (Review)

Introduction. Long-term use of anthracyclines during cancer chemotherapy has been associated with the development of potentially life-threatening cardiotoxicity. Despite researches ongoing since the middle of the last century, approaches to the choice of therapy remain limited.Text. Doxorubicin currently is the most widely used chemotherapy. The leading side effect mechanism of the drug is the formation of reactive oxygen species in mitochondria with the mediated development of oxidative stress, which contributes to myocardial damage. However, despite the huge number of scientific papers devoted to various aspects of doxorubicin cardiotoxicity, its prevention and treatment, this issue requires detailed investigation in order to develop more advanced methods for early diagnosis and timely cardioprotective therapy.Conclusion. The current review discusses the pathogenetic mechanisms of cardiotoxicity associated with the use of doxorubicin chemotherapy. The pathogenesis of the cardiomyocytes death mechanism will provide an opportunity to develop new diagnostic and therapeutic approaches in the clinical practice.

Etanercept’s Protective Effect Against Lung Inflammation Caused by Polymicrobial Sepsis Induced by CLP in Male Rats

Inflammation and oxidative stress are critical factors leading to sepsis-induced severe lung injury (ALI). This study investigates the regulatory effects of Etanercept (ENT) in an animal model of sepsis-induced ALI. We established a cecal ligation and puncture (CLP) model for ALI in adult rats under anesthesia. Sepsis amplifies pathological lung tissue damage, lung endothelial permeability, serum inflammatory factor production, and the number of inflammatory cells in bronchoalveolar lavage fluid. Furthermore, it enhances the expression of phosphorylated NF-\(\kappa\)B p65, reduces lung superoxide dismutase due to CLP, and elevates lung malondialdehyde levels due to LPS-induced inflammatory factor production. This cascade of events exacerbates the expression of several genes, including TNF-\(\alpha\) and cytokines. LPS-induced inflammatory factor production also enhances the formation of reactive oxygen species in mitochondria. In summary, our current research provides evidence that ENT acts as a novel regulator of inflammation in sepsis-induced ALI in rats. The control of oxidative stress and the modulation of the inflammatory response are two key underlying mechanisms for the effects of ENT.

Dual-target drugs against Leishmania donovani for potential novel therapeutics

Antioxidant defense mechanisms are important for a parasite to overcome oxidative stress and survive within host macrophage cells. Mitochondrial iron superoxide dismutase A (FeSODA) and trypanothione reductase (TR) are critical enzymes in the antioxidant defense mechanism of Leishmania donovani. FeSODA is responsible for neutralizing reactive oxygen species in mitochondria, while TR is responsible for reducing trypanothione, the molecules that help the parasite fight oxidative stress in Leishmania. In this study, we used multitarget ligands to inhibit both the FeSODA and TR enzymes. We combined structure-based drug design using virtual screening approach to find inhibitors against both the targets. The ZINC15 database of biogenic compounds was utilized to extract drugs-like molecules against leishmaniasis. The compounds were screened by standard precision (SP) and extra precision (XP) docking methods. Two compounds, ZINC000008876351 and ZINC000253403245, were selected based on molecular docking based on the binding affinity for both the targets. The screened molecules ZINC000008876351 and ZINC000253403245 showed strong hydrogen bonding with the target proteins according to the Molecular mechanics with generalised Born and surface area solvation (MM-GBSA) techniques. These two compounds were also experimentally investigated on promastigotes stage of L. donovani. Under in vitro condition, the compounds show inhibitory effects on L. donovani promastigotes with IC50 values of 24.82 ± 0.61 µM for ZINC000008876351 and 7.52 ± 0.17 µM for ZINC000253403245. Thus, the screened compounds seem to have good potential as therapeutic candidates for leishmaniasis.

Age-associated sex difference in the expression of mitochondria-based redox sensitive proteins and effect of pioglitazone in nonhuman primate brain

BackgroundParaoxonase 2 (PON2) and neuronal uncoupling proteins (UCP4 and UCP5) possess antioxidant, anti-apoptotic activities and minimize accumulation of reactive oxygen species in mitochondria. While age and sex are risk factors for several disorders that are linked with oxidative stress, no study has explored the age- and sex-dependent expression of PON2 isoforms, UCP4 and UCP5 in primate brain or identified a drug to activate UCP4 and UCP5 in vivo. Preclinical studies suggest that the peroxisome proliferator-activated receptor gamma agonist, pioglitazone (PIO), can be neuroprotective, although the mechanism responsible is unclear. Our previous studies demonstrated that pioglitazone activates PON2 in primate brain and we hypothesized that pioglitazone also induces UCP4/5. This study was designed to elucidate the age- and sex-dependent expression of PON2 isoforms, UCP4 and UCP5, in addition to examining the impact of systemic PIO treatment on UCP4 and UCP5 expression in primate brain.MethodsWestern blot technique was used to determine the age- and sex-dependent expression of UCP4 and UCP5 in substantia nigra and striatum of African green monkeys. In addition, we tested the impact of daily oral pioglitazone (5 mg/kg/day) or vehicle for 1 or 3 weeks on expression of UCP4 and UCP5 in substantia nigra and striatum in adult male monkeys. PIO levels in plasma and cerebrospinal fluid (CSF) were determined using LC–MS.ResultsWe found no sex-based difference in the expression of PON2 isoforms, UCP4 and UCP5 in striatum and substantia nigra of young monkeys. However, we discovered that adult female monkeys exhibit greater expression of PON2 isoforms than males in substantia nigra and striatum. Our data also revealed that adult male monkeys exhibit greater expression of UCP4 and UCP5 than females in substantia nigra but not in striatum. PIO increased UCP4 and UCP5 expression in substantia nigra and striatum at 1 week, but after 3 weeks of treatment this activation had subsided.ConclusionsOur findings demonstrate a sex-, age- and region-dependent profile to the expression of PON2, UCP4 and UCP5. These data establish a biochemical link between PPARγ, PON2, UCP4 and UCP5 in primate brain and demonstrate that PON2, UCP4 and UCP5 can be pharmacologically stimulated in vivo, revealing a novel mechanism for observed pioglitazone-induced neuroprotection. We anticipate that these outcomes will contribute to the development of novel neuroprotective treatments for Parkinson’s disease and other CNS disorders.

Powerful Synergy of Traditional Chinese Medicine and Aggregation-Induced Emission-Active Photosensitizer in Photodynamic Therapy.

Breast cancer (BC) remains a significant global health challenge for women despite advancements in early detection and treatment. Isoliquiritigenin (ISL), a compound derived from traditional Chinese medicine, has shown potential as an anti-BC therapy, but its low bioavailability and poor water solubility restrict its effectiveness. In this study, we created theranostic nanoparticles consisting of ISL and a near-infrared (NIR) photosensitizer, TBPI, which displays aggregation-induced emission (AIE), with the goal of providing combined chemo- and photodynamic therapies (PDT) for BC. Initially, we designed an asymmetric organic molecule, TBPI, featuring a rotorlike triphenylamine as the donor and 1-methylpyridinium iodide as the acceptor, which led to the production of reactive oxygen species in mitochondria. We then combined TBPI with ISL and encapsulated them in DSPE-PEG-RGD nanoparticles to produce IT-PEG-RGD nanoparticles, which showed high affinity for BC, better intersystem crossing (ISC) efficiency, and Förster resonance energy transfer (FRET) between TBPI and ISL. In both 4T1 BC cell line and a 4T1 tumor-bearing BC mouse model, the IT-PEG-RGD nanoparticles demonstrated excellent drug delivery, synergistic antitumor effects, enhanced tumor-killing efficacy, and reduced drug dosage and side effects. Furthermore, we exploited the optical properties of TBPI with ISL to reveal the release process and distribution of nanoparticles in cells. This study provides a valuable basis for further exploration of IT-PEG-RGD nanoparticles and their anticancer mechanisms, highlighting the potential of theranostic nanoparticles in BC treatment.

The significance of oxidative stress in the pathophysiology of Long COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)

Long COVID is now well accepted as an ongoing post-viral syndrome resulting from infection of a single virus, the pandemic SARS-CoV-2. It mirrors the post-viral fatigue syndrome, Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome, a global debilitating illness arising mainly from sporadic geographically-specific viral outbreaks, and from community endemic infections, but also from other stressors. Core symptoms of both syndromes are post-exertional malaise (a worsening of symptoms following mental or physical activity), pervasive fatigue, cognitive dysfunction (brain fog), and sleep disturbance. Long COVID patients frequently also suffer from shortness of breath, relating to the lung involvement of the SARS-CoV-2 virus. There is no universally accepted pathophysiology, or recognized biomarkers yet for Long COVID or indeed for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. Clinical case definitions with very similar characteristics for each have been defined. Chronic inflammation, immune dysfunction, and disrupted energy production in the peripheral system has been confirmed in Long COVID and has been well documented in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. Neuroinflammation occurs in the brain in Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome as shown from a small number of positron emission tomography and magnetic resonance spectroscopy studies, and has now been demonstrated for Long COVID. Oxidative stress, an increase in reactive oxygen and reactive nitrogen species, and free radicals, has long been suggested as a potential cause for many of the symptoms seen in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome, resulting from both activation of the brain’s immune system and dysregulation of mitochondrial function throughout the body. The brain as a high producer of energy may be particularly susceptible to oxidative stress. It has been shown in peripheral immune cells that the balanced production of proteins involved in regulation of the reactive oxygen species in mitochondria is disturbed in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. Fluctuations in the chronic low level neuroinflammation during the ongoing course of Long COVID as well as Myalgic Encephalomyelitis/Chronic Fatigue Syndrome have been proposed to cause the characteristic severe relapses in patients. This review explores oxidative stress as a likely significant contributor to the pathophysiology of Long COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome, and the mechanisms by which oxidative stress could cause the symptoms seen in both syndromes. Treatments that could mitigate oxidative stress and thereby lessen the debilitating symptoms to improve the life of patients are discussed.

Age-related changes in the energy of human mesenchymal stem cells.

Aging is a physiological process that leads to a higher risk for the most devastating diseases. There are a number of theories of human aging proposed, and many of them are directly or indirectly linked to mitochondria. Here, we used mesenchymal stem cells (MSCs) from young and older donors to study age-related changes in mitochondrial metabolism. We have found that aging in MSCs is associated with a decrease in mitochondrial membrane potential and lower NADH levels in mitochondria. Mitochondrial DNA content is higher in aged MSCs, but the overall mitochondrial mass is decreased due to increased rates of mitophagy. Despite the higher level of ATP in aged cells, a higher rate of ATP consumption renders them more vulnerable to energy deprivation compared to younger cells. Changes in mitochondrial metabolism in aged MSCs activate the overproduction of reactive oxygen species in mitochondria which is compensated by a higher level of the endogenous antioxidant glutathione. Thus, energy metabolism and redox state are the drivers for the aging of MSCs/mesenchymal stromal cells.

Baicalein resensitizes tamoxifen-resistant breast cancer cells by reducing aerobic glycolysis and reversing mitochondrial dysfunction via inhibition of hypoxia-inducible factor-1α.

Drug resistance is a major hurdle for the effectiveness of tamoxifen (TAM) to provide clinical benefit. Therefore, it is essential to identify a sensitizer that could be used to improve TAM efficacy in treating TAM‐resistant breast cancer. Here, we investigated the ability of baicalein to reverse TAM resistance. We found that baicalein increased the efficacy of TAM in inhibiting proliferation and inducing apoptosis of TAM‐resistant cells. It also enhanced the TAM‐induced growth reduction of resistant cells from NOD/SCID mouse mammary fat pads, without causing obvious systemic toxicity. Analyses using the CellMiner tool and the Kaplan–Meier plotter database showed that HIF‐1α expression was inversely correlated with TAM therapeutic response in NCI‐60 cancer cells and breast cancer patients. HIF‐1α expression was increased in TAM‐resistant cells due to an increase in mRNA levels and reduced ubiquitin‐mediated degradation. Baicalein reduced HIF‐1α expression by promoting its interaction with PHD2 and pVHL, thus facilitating ubiquitin ligase‐mediated proteasomal degradation and thereby suppressing the nuclear translocation, binding to the hypoxia‐response element, and transcriptional activity of HIF‐1α. As a result, baicalein downregulated aerobic glycolysis by restricting glucose uptake, lactate production, ATP generation, lactate/pyruvate ratio and expression of HIF‐1α‐targeted glycolytic genes, thereby enhancing the antiproliferative efficacy of TAM. Furthermore, baicalein interfered with HIF‐1α inhibition of mitochondrial biosynthesis, which increased mitochondrial DNA content and mitochondrial numbers, restored the generation of reactive oxygen species in mitochondria, and thus enhanced the TAM‐induced mitochondrial apoptotic pathway. The HIF‐1α stabilizer dimethyloxallyl glycine prevented the baicalein‐induced downregulation of glycolysis and mitochondrial biosynthesis and reduced the effects of baicalein on reversing TAM resistance. Our results indicate that baicalein is a promising candidate to help overcome TAM resistance by sensitizing resistant cells to TAM‐induced growth inhibition and apoptosis. The mechanism underlying the effects of baicalein consists of inhibition of HIF‐1α–mediated aerobic glycolysis and mitochondrial dysfunction.

Mitochondria and chronic effects of cancer therapeutics: The clinical implications.

One of the major mechanisms of action of chemo-radiation is to induce cellular senescence, which exerts crucial roles in age-related pathology. The concept of senescence is evolved, and the novel understanding of senescence-associated reprogramming/stemness has emerged. This new concept emphasizes senescence as not only cell cycle arrest but describes that subsets of senescent cells induced by chemotherapy can re-enter cell cycles, proliferate rapidly, and acquire "stemness" status. Cancer therapeutics, including chemo-radiation triggers toxicity effects through damaging mitochondria, primarily through the upregulation of mtROS production leading to subsequent mtDNA and telomeric DNA damage elicitng DNA damage responses (DDR). The ultimate goal of this review is to highlight the new concept of senescence-associated stemnessthat is induced by cancer treatment and its adverse effects on the vascular system. We will describe how chemo-radiation exerts toxicity effects by simultaneously producing reactive oxygen species in mitochondria and promoting DDR in the nucleus. We discuss the potential of clinical targeting poly (ADP-ribose) polymerase which might prevent downstream mitochondrial dysfunction and confer protection to cancer survivors. Overall we emphasize the importance of recognizing the consequences of cardio-toxic effects of several cancer treatments and therefore developing personalized therapeutic approaches to screen for inflammatory and cardiac testing for better patient survival.

Botch protects neurons from ischemic insult by antagonizing Notch-mediated neuroinflammation

Owing to the continued high morbidity and high mortality rate after stroke, it is important to seek treatments other than conventional thrombolysis. Notch1 up-regulation participates in inflammatory responses after cerebral ischemia-reperfusion (I/R) injury, and it has been reported that Botch binds to and blocks Notch1 maturation. In this study, we investigated the role of Botch during cerebral (I/R) injury and explored its potential mechanisms. A middle-cerebral-artery occlusion/reperfusion (MCAO/R) model was established in adult male Sprague-Dawley rats in vivo, and cultured neurons and microglia were exposed to oxygen-glucose deprivation/reoxygenation (OGD/R) to mimic I/R injury in vitro. The results showed that protein levels of Botch and the Notch1 intracellular domain (NICD) were increased after MCAO/R. Furthermore, after overexpression of Botch, the generation of the activated form of Notch1, NICD, was decreased, while Botch knockdown or mutation led to an increase in NICD generation. As a result, Botch overexpression exhibited neuroprotective effects by significantly decreasing neurobehavioral phenotypes, improving infiltration of activated microglia, ameliorating inflammatory cytokine release, and inhibiting neuronal cell death. Conversely, Botch knockdown and mutation induced opposite effects. In addition, NICD was found to translocate to the mitochondria after OGD/R in neurons and microglia, which stimulated accumulation of reactive oxygen species in mitochondria and resulted in neuronal cell death and microglial activation. Botch overexpression inhibited the generation of NICD and decreased the translocation of NICD to the mitochondria, which inhibited neuronal cell death and ameliorated neuroinflammation. In conclusion, we found that Botch exerts neuroprotective effects via antagonizing the maturation of Notch1-induced neuronal injury and neuroinflammation, which may provide insights into novel therapeutic targets for the treatment of I/R injury.

A mitochondria-targetable two-photon fluorescent probe with a far-red to near-infrared emission for sensing hypochlorite in biosystems

Hypochlorite (ClO−), one of reactive oxygen species (ROS), is closely related with many physiological and pathological processes. Especially as one of cellular reactive oxygen species in mitochondria, ClO− can induce mitochondrial permeability, which leads to apoptosis. Thus, developing an effective method which is able to sense ClO− in mitochondria is important. Although fluorescent probe has become a powerful tool for imaging ClO− in mitochondria, most of them suffered from phototoxicity to biosamples, autofluorescence, and photobleaching phenomenon due to their short-wavelength excitations and emissions. Based on advantages of two-photon fluorescent probe and far-red to NIR fluorescent probe, a mitochondria-targetable two-photon fluorescent probe with a turn-on signal in far-red to NIR region, Mito-TP-ClO, was developed for ClO− in this paper. Mito-TP-ClO is consisted of a triphenylphosphonium cations as a mitochondria-targetable unit and a structure of dibenzoylhydrazine as a response unit to ClO−. Mito-TP-ClO exhibited a high sensitivity and a high selectivity to ClO−, with a linear range from 6.0 × 10−8 to 1.0 × 10−5 M and a detection limit of 2.5 × 10−8 M. Due to its large two-photon cross section (267 GM) and far-red to NIR emission, Mito-TP-ClO exhibits excellent performances including low autofluorescence, photostable fluorescence signal, and deep tissue penetration (230 μM). Moreover, Mito-TP-ClO was successfully used to detect endogenous ClO− in bacteria-infected cells and inflammatory mouse model, which confirmed that Mito-TP-ClO is a powerful tool to monitor ClO− in mitochondria and study on effects of hypochlorite on mitochondria.

The Generation of Superoxide Radicals by Cardiac Mitochondria and the Antioxidant Effect of the Water-Soluble Form of Ubiquinol-10

We have studied the effect of the water-soluble form of ubiquinol-10 (CoQ10-H2) on the processes of electron transport, oxidative phosphorylation, and the formation of reactive oxygen species in mitochondria isolated from the hearts of Wistar rats. It has been shown that preincubation of isolated mitochondria with different concentrations of ubiquinol-10 has only a minor effect on the rate of oxygen uptake and respiratory control. The interaction of ubiquinol-10 with superoxide radicals formed in complex III (bc1 segment) of cardiac mitochondria has been studied using the EPR spin trapping and EPR oximetry method. Ubiquinol-10 has been found to act as an efficient antioxidant within the physiological range of the lipid concentrations, while the magnitude and kinetic characteristics of the antiradical effect depend on the drug concentration.

Lysosomal Signaling Promotes Longevity by Adjusting Mitochondrial Activity

Lysosomes and mitochondria are both crucial cellular organelles for metabolic homeostasis and organism health. However, mechanisms linking their metabolic activities to promote organism longevity remain poorly understood. We discovered that the induction of specific lysosomal signaling mediated by a LIPL-4 lysosomal acid lipase and its lipid chaperone LBP-8 increases mitochondrial ß-oxidation to reduce lipid storage and promote longevity in Caenorhabditis elegans. We further discovered that increased mitochondrial ß-oxidation reduces mitochondrial electron transport chain complex II activity, contributing to theinduction of reactive oxygen species in mitochondria (mtROS) and the longevity effect conferred by LIPL-4-LBP-8 signaling. Moreover, by activating theJUN-1 transcription factor downstream of mtROS, the LIPL-4-LBP-8 signaling pathway induces antioxidant targets and oxidative stress tolerance. Together, these results reveal regulatory mechanisms by which lysosomal signaling triggers adjustments in mitochondrial activity and suggest the significance of these metabolic adjustments for improving metabolic fitness, redox homeostasis, and longevity.

Interference-free surface-enhanced Raman scattering nanosensor for imaging and dynamic monitoring of reactive oxygen species in mitochondria during photothermal therapy

Highly reliable detection, imaging, and monitoring of reactive oxygen species (ROS) at subcellular organelles are critical for understanding the biological roles of ROS and learning the pathogenesis of some diseases. In this study, we presented an interference-free surface-enhanced Raman scattering (SERS)-active nanoprobe for the intracellular ROS detection. This nanoprobe was designed as an Au core-Ag shell nanoparticle (Au@Ag NPs) with a SERS reporter (4-mercaptobenzonitrile) resided in the inner of the core-shell. Intracellular ROS is able to etch the Ag shell and dramatically decreases the SERS intensity of the SERS reporters. It is worth mentioning that the Raman band of the reporter we used in this study locate in the cellular Raman-silent region (1800–2800 cm−1), which eliminates interference possibility from cellular molecules. The shell can also further protect the reporters from the interference of mediums. We detected ROS at subcellular organelle level, e.g. mitochondria, by modifying the surface of the nanoprobes with a mitochondria-targeting peptide. And for the first time, the SERS-based monitoring of ROS at mitochondria during the photothermal therapy process was validated and the profiles of the ROS distribution were disclosed by SERS mapping.

Autophagy and Energy Metabolism.

Autophagy is a lysosome-dependent catabolic process. Both extra- and intra-cellular components are engulfed in autophagic vacuoles and degraded to simple molecules, such as monosaccharides, fatty acids and amino acids. Then, these molecules can be further used to produce ATP through catabolic reactions and/or provide building blocks for the synthesis of essential proteins. Therefore, we consider autophagy a critical and fine-tuned process in maintaining energy homeostasis. The complicated relationships between autophagy and energy metabolism have raised broad interest and have been extensively studied. In this chapter, we summarize the relationships enabling autophagy to control or modulate energy metabolism and allowing metabolic pathways to regulate autophagy. Specifically, we review the correlations between autophagy and energy homeostasis in terms of oxidative phosphorylation, reactive oxygen species in mitochondria, glycolysis, metabolism of glycogen and protein, and so on. An understanding of the role of autophagy in energy homeostasis could help us better appreciate how autophagy determines cell fate under stressful conditions or pathological processes.

Simvastatin alleviates bone resorption in apical periodontitis possibly by inhibition of mitophagy-related osteoblast apoptosis.

To assess the connection between mitophagy and hypoxia-induced apoptosis in osteoblasts and whether simvastatin alleviates bone resorption in apical periodontitis through modulation of mitophagy-related apoptosis. Hypoxia-induced generation of reactive oxygen species in mitochondria and changes in mitochondrial membrane potential were evaluated, respectively, by MitoSOX and JC-1 fluorescence dye signalling. Accumulation of mitophagy markers PTEN-induced putative kinase 1 (PINK1) and Parkin in mitochondria was examined by Western blotting and immunofluorescence microscopy. Osteoblast apoptosis was assessed by Western analysis of cleaved-poly (adenosine diphosphate ribose) polymerase (PARP). In a rat model of induced apical periodontitis, the therapeutic effect of simvastatin and its action on osteoblast mitophagy and apoptosis were examined. anova, Fisher's and Student's t-test were used for data analysis. Hypoxia-induced mitochondrial dysfunction and stimulated mitophagy in osteoblasts. Hypoxia also provoked apoptosis in osteoblasts and inhibition of mitophagy decreased hypoxia-augmented apoptotic activity. Simvastatin alleviated hypoxia-induced mitochondrial dysfunction, mitophagy and apoptosis. The protective action of simvastatin against apoptosis was related to its antimitophagy activity. Experiments in the rat model of induced apical periodontitis supported the laboratory findings. Simvastatin treatment mitigated periapical bone loss and reduced the activities of apoptosis and mitophagy in regional osteoblasts. The results suggest that modulation of osteoblast mitophagy may help diminish bone loss associated with inflammation and has potential as an auxiliary therapy for apical periodontitis.

Inhibition of mitophagy decreases survival of Caenorhabditis elegans by increasing protein aggregation.

Autophagy of mitochondria, i.e., mitophagy, plays a crucial role in coping with stressors in the aging process, metabolic disturbances, and neurological disorders. Impairments of the process might consequently lead to enhanced accumulation of aged and aggregated proteins and reduced cellular integrity in response to stress. In the present study, we used the stress-sensitive mutant mev-1 of Caenorhabditis elegans to assess the effects of the knockdown of mitophagy relevant genes on survival under heat stress, the amount of autophagosomes, and on protein aggregation. RNA interference for dct-1, drp-1, eat-3, fis-1, fzo1, glb-1, pink-1, and pgam-5 all resulted in a significant reduction of survival time at 37°C. These effects were associated with a decrease in autophagosomal flux of proteins, as indicated by increased accumulation of GFP-tagged SQST-1, and a reduced amount of lysosomes demonstrating that autophagy was hampered. Moreover, the gene knockdowns led to increased levels of reactive oxygen species in mitochondria and an enhanced protein aggregation. In conclusion, our studies show that mitophagy is of central importance to keep mitochondria functional in order to prevent production of excess reactive oxygen species and protein aggregation and finally a reduction of survival under heat stress.

Signaling Mechanisms Regulating Diverse Plant Cell Responses to UVB Radiation.

UVB radiation (290-320nm) causes diverse effects in plant cells that vary with the fluence rate of exposure. High fluence rates of UVB radiation cause damage to DNA and formation of reactive oxygen species in mitochondria and chloroplasts, which lead to oxidation of membrane proteins and lipids and inhibition of cellular functions. In response to oxidative stress, mitochondrial transmembrane potential dissipates, resulting in cytochrome c release and activation of metacaspases. This leads to the apoptosis-like cell death. The signaling mechanism based on UVB DNA damage includes checkpoint activation, cell-cycle arrest, and finally programmed cell death with characteristic DNA fragmentation and morphological hallmarks typical of apoptotic cells. Recently, it was shown that among the components of this signaling mechanism the transcriptional factor SOG1 (suppressor of gamma response 1) plays a key role in regulation of programmed cell death in plants. In contrast to its damaging effects, UVB radiation at low fluence rates can act as a regulatory signal that is specifically perceived by plants to promote acclimation and survival in sunlight. The protective action of UVB is based on expression of various genes, including those encoding flavonoid synthesis enzymes that provide a UVB-absorbing sunscreen in epidermal tissues and DNA photorepair enzymes. These processes are mediated by the UVB photoreceptor UVR8, which has been recently characterized at the molecular level. Now progress is made in uncovering the UVR8-mediated signaling pathway mechanism in the context of UVB photon perception and revealing the biochemical components of the early stages of light signal transduction. In this review, attention is focused on the achievements in studying these UVB-induced signaling processes.

Electron transfer kinetics of the mitochondrial outer membrane protein mitoNEET.

Increasing evidence suggests that the mitochondrial outer membrane protein mitoNEET is a key regulator of energy metabolism, iron homeostasis, and production of reactive oxygen species in mitochondria. Previously, we reported that mitoNEET is a redox enzyme that catalyzes electron transfer from the reduced flavin mononucleotide (FMNH2) to oxygen or ubiquinone via its unique [2Fe-2S] clusters. Here, we explore the reduction and oxidation kinetics of the mitoNEET [2Fe-2S] clusters under anaerobic and aerobic conditions. We find that the mitoNEET [2Fe-2S] clusters are rapidly reduced by a catalytic amount of FMNH2 which is reduced by flavin reductase and an equivalent amount of NADH under anaerobic conditions. When the reduced mitoNEET [2Fe-2S] clusters are exposed to air, the [2Fe-2S] clusters are slowly oxidized by oxygen at a rate constant of about 6.0 M-1 s-1. Compared with oxygen, ubiquinone-2 has a much higher activity to oxidize the reduced mitoNEET [2Fe-2S] clusters at a rate constant of about 3.0 × 103 M-1 s-1 under anaerobic conditions. Under aerobic conditions, the mitoNEET [2Fe-2S] clusters can still be reduced by FMNH2 in the presence of flavin reductase and excess NADH. However, when NADH is completely consumed, the reduced mitoNEET [2Fe-2S] clusters are gradually oxidized by oxygen. Addition of ubiquinone-2 also rapidly oxidizes the pre-reduced mitoNEET [2Fe-2S] clusters and effectively prevents the FMNH2-mediated reduction of the mitoNEET [2Fe-2S] clusters under aerobic conditions. The results suggest that ubiquinone may act as an intrinsic oxidant of the reduced mitoNEET [2Fe-2S] clusters in mitochondria under aerobic and anaerobic conditions.