Resolving Contributions of Oxygen-Consuming and ROS-Generating Enzymes at the Synapse

Sevoflurane inhibited reproductive function in male mice by reducing oxidative phosphorylation through inducing iron deficiency

Sevoflurane (Sev) is one of the commonly used inhalation anesthetic chemicals in clinics. It has great impact on spermatogenesis and fertilization in male animals. The underlying mechanism remains largely unexplored. Based on our previous research, we hypothesized that Sev induced iron metabolism disturbance in the testis and epididymis and inhibited the spermatogenesis. In this study, two-month-old C57BL/6 male mice were treated with 3% Sev for 6 h, and their fertility (including sperm concentration, sperm mobility, and the number of offspring) was evaluated. Mice testis, epididymis, and sperm were harvested and subjected to Western blot analysis and immunofluorescence analysis. Iron levels were reflected by the gene expression of iron metabolism-related proteins (including ferritin, TfR1, and FpN1) and ICP-MS and Perl's iron staining. Electron transport and oxidative phosphorylation levels were measured by Oxygraph-2k and ATP contents. The activity of ribonucleotide reductase was evaluated by assay kit. DNA synthesis status in testis and/or epididymis was marked with BrdU. Cell proliferation was evaluated by double immunofluorescence staining of specific protein marker expression. Our results revealed that the mice exposed to Sev showed damaged testicular and epididymis structure and significantly reduced the sperm concentration, sperm motility, and fertility. Sev decreases the iron levels through down-regulating the expression of H-ferritin, L-ferritin, and FpN1, and up-regulating the expression of TfR1 in the testis and epididymis. Iron levels also significantly reduced in germ cells which decrease the number of germ cells, including sperm, Sertoli cells, and primary spermatocyte. Iron deficiency not only decreases electron transport, oxidative phosphorylation level, and ATP production but also suppresses the activity of ribonucleotide reductase and the expression of Ki67, DDX4, GATA1, and SCP3, indicating that Sev affects the spermatogenesis and development. Meanwhile, Sev impaired the blood-testis barrier by decreasing the ZO1 expression in the testis and epididymis. The damage effect induced by Sev can be significantly ameliorated by iron supplementation. In conclusion, our study illustrates a new mechanism by which Sev inhibits spermatogenesis and fertility through an oxidative phosphorylation pathway due to iron deficiency of epididymis and testis or sperm. Furthermore, the damaging effects could be ameliorated by iron supplementation.

Effect of Dl-3-n-butylphthalide on mitochondrial Cox7c in models of cerebral ischemia/reperfusion injury

Several studies have demonstrated the protective effect of dl-3-n-Butylphthalide (NBP) against cerebral ischemia, which may be related to the attenuation of mitochondrial dysfunction. However, the specific mechanism and targets of NBP in cerebral ischemia/reperfusion remains unclear. In this study, we used a chemical proteomics approach to search for targets of NBP and identified cytochrome C oxidase 7c (Cox7c) as a key interacting target of NBP. Our findings indicated that NBP inhibits mitochondrial apoptosis and reactive oxygen species (ROS) release and increases ATP production through upregulation of Cox7c. Subsequently, mitochondrial respiratory capacity was improved and the HIF-1α/VEGF pathway was upregulated, which contributed to the maintenance of mitochondrial membrane potential and blood brain barrier integrity and promoting angiogenesis. Therefore, our findings provided a novel insight into the mechanisms underlying the neuroprotective effects of NBP, and also proposed for the first time that Cox7c exerts a critical role by protecting mitochondrial function.

Novel mechanisms in alcohol neurodevelopmental disorders via BRCA1 depletion and BRCA1-dependent NADPH oxidase regulation

The breast cancer 1 protein (BRCA1) facilitates DNA repair, preventing embryolethality and protecting the fetus from reactive oxygen species (ROS)-induced developmental disorders mediated by oxidatively damaged DNA. Alcohol (ethanol, EtOH) exposure during pregnancy causes fetal alcohol spectrum disorders (FASD), characterized by aberrant behaviour and enhanced ROS formation and proteasomal protein degradation. Herein, ROS-producing NADPH oxidase (NOX) activity was higher in Brca1 +/- vs. +/+ fetal and adult brains, and further enhanced by a single EtOH exposure. EtOH also enhanced catalase and proteasomal activities, while conversely reducing BRCA1 protein levels without affecting Brca1 gene expression. EtOH-initiated adaptive postnatal freezing behaviour was lost in Brca1 +/- progeny. Pretreatment with the free radical spin trap and ROS inhibitor phenylbutylnitrone blocked all EtOH effects, suggesting ROS-dependent mechanisms. This is the first in vivo evidence of NOX regulation by BRCA1, and of EtOH-induced, ROS-mediated depletion of BRCA1, revealing novel mechanisms of BRCA1 protection in FASD.

Sleep/wake calcium dynamics, respiratory function, and ROS production in cardiac mitochondria

Introduction

Incidents of myocardial infarction and sudden cardiac arrest vary with time of the day, but the mechanism for this effect is not clear. We hypothesized that diurnal changes in the ability of cardiac mitochondria to control calcium homeostasis dictate vulnerability to cardiovascular events.

Objectives

Here we investigate mitochondrial calcium dynamics, respiratory function, and reactive oxygen species (ROS) production in mouse heart during different phases of wake versus sleep periods.

Methods

We assessed time-of-the-day dependence of calcium retention capacity of isolated heart mitochondria from young male C57BL6 mice. Rhythmicity of mitochondrial-dependent oxygen consumption, ROS production and transmembrane potential in homogenates were explored using the Oroboros O2k Station equipped with a fluorescence detection module. Changes in expression of essential clock and calcium dynamics genes/proteins were also determined at sleep versus wake time points.

Results

Our results demonstrate that cardiac mitochondria exhibit higher calcium retention capacity and higher rates of calcium uptake during sleep period. This was associated with higher expression of clock gene Bmal1, lower expression of per2, greater expression of MICU1 gene (mitochondrial calcium uptake 1), and lower expression of the mitochondrial transition pore regulator gene cyclophilin D. Protein levels of mitochondrial calcium uniporter (MCU), MICU2, and sodium/calcium exchanger (NCLX) were also higher at sleep onset relative to wake period. While complex I and II-dependent oxygen utilization and transmembrane potential of cardiac mitochondria were lower during sleep, ROS production was increased presumably due to mitochondrial calcium sequestration.

Conclusions

Taken together, our results indicate that retaining mitochondrial calcium in the heart during sleep dissipates membrane potential, slows respiratory activities, and increases ROS levels, which may contribute to increased vulnerability to cardiac stress during sleep-wake transition. This pronounced daily oscillations in mitochondrial functions pertaining to stress vulnerability may at least in part explain diurnal prevalence of cardiac pathologies.

Autism spectrum disorder (ASD)-associated mitochondrial deficits are revealed in children's platelets but unimproved by hyperbaric oxygen therapy

Mitochondrial and immune dysfunctions are often implicated in the aetiology of autism spectrum disorder (ASD). Here, we studied for the first time the relationship between ASD severity measures and mitochondrial respiratory rates in freshly isolated platelets as well as the activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) in isolated neutrophils. We also verified the impact of hyperbaric oxygen therapy (HBOT) on mitochondrial and immune functions as well as on ASD severity measures. Blood samples were collected from three age-matched male groups (Control (Norm-N), autistic (Aut-N), and autistic + HBOT (Aut-H); N = 10 per group). Using high resolution respirometry, we found that routine basal respiration, complex I- and complex I + II-dependent oxidative phosphorylation rate were significantly impaired in Aut-N platelets. Similarly, deficits in immune response of neutrophils were evidenced through lower rates of oxygen consumption and reactive oxygen species (ROS) production by phagocytic NOX. ASD-related behavioural outcomes were found to moderately correlate with platelets' mitochondrial bioenergetic parameters as well as with NOX-mediated activity in neutrophils. HBOT was not able to improve mitochondrial dysfunctions or to counteract ASD-related behavioral deficits. Although HBOT improved one measure of the immune response; namely, NOX-mediated superoxide burst, this was not associated with significant changes in trends of recurrent infections between groups. Taken together, our data suggest that ASD-associated mitochondria and immune deficits are detectable in platelets and neutrophils. We also found no evidence that HBOT confers any significant improvement of ASD-associated physiological or behavioural phenotypes.

Role of vinpocetine in ischemic stroke and poststroke outcomes: A critical review

Vinpocetine (VPN) is a synthetic ethyl-ester derivative of the alkaloid apovincamine from Vinca minor leaves. VPN is a selective inhibitor of phosphodiesterase type 1 (PDE1) that has potential neurological effects through inhibition of voltage-gated sodium channel and reduction of neuronal calcium influx. VPN has noteworthy antioxidant, anti-inflammatory, and anti-apoptotic effects with inhibitory effect on glial and astrocyte cells during and following ischemic stroke (IS). VPN is effective as adjuvant therapy in the management of epilepsy; it reduces seizure frequency by 50% in a dose of 2 mg/kg/day. VPN improves psychomotor performances through modulation of brain monoamine pathway mainly on dopamine and serotonin, which play an integral role in attenuation of depressive symptoms. VPN recover cognitive functions and spatial memory through inhibition of hippocampal and cortical PDE1 with augmentation of cyclic adenosin monophosphate and cyclic guanosin monophosphate ratio, enhancement of cholinergic neurotransmission, and inhibition of neuronal inflammatory mediators. Therefore, VPN is an effective agent in the management of IS and plays an integral role in the prevention and attenuation of poststroke epilepsy, depression, and cognitive deficit through direct cAMP/cGMP-dependent pathway or indirectly through anti-inflammatory and antioxidant effects.

Quantifying Activity for Repair of the DNA Lesion 8-Oxoguanine by Oxoguanine Glycosylase 1 (OGG1) in Mouse Adult and Fetal Brain Nuclear Extracts Using Biotin-Labeled DNA

The reactive oxygen species (ROS)-initiated DNA lesion 8-oxoguanine (8-oxoG) is commonly used as a biomarker to measure oxidative stress levels in tissue samples from animals and humans. This lesion also can play a pathogenic role in cancer, birth defects, and neurodegeneration, among other disorders. The level of 8-oxoG may be enhanced due to ROS-initiating environmental factors (e.g., drugs, gamma radiation, microbial infection) or due to a decrease in the activity of oxoguanine glycosylase 1 (OGG1), an enzyme that repairs this lesion. Measurement of the activity of OGG1 can be useful in elucidating mechanisms and complements measurements of 8-oxoG levels in tissues of interest. This protocol describes an assay for measuring the activity of 8-oxoG in mouse adult and fetal brain tissues. Briefly, a synthetic duplex containing the 8-oxoG residue in one of the nucleotides (49-mer), labeled with biotin at the 3'-end, is incubated with protein extract from the tissue of interest containing OGG1, which cleaves the 8-oxoG residue producing a cleavage product of ~27-mer. The percent cleavage quantifies the activity of OGG1 in that tissue. The biotin tag allows rapid and sensitive detection of the cleavage product via chemiluminescence, avoiding the problems of safety and short half-lives of radionuclides encountered in assays employing a radioactively-labeled substrate.

The Mitochondrial Targets of Neuroprotective Drug Vinpocetine on Primary Neuron Cultures, Brain Capillary Endothelial Cells, Synaptosomes, and Brain Mitochondria

Vinpocetine is considered as neuroprotectant drug and used for treatment of brain ischemia and cognitive deficiencies for decades. A number of enzymes, channels and receptors can bind vinpocetine, however the mechanisms of many effects' are still not clear. The present study investigated the effects of vinpocetine from the mitochondrial bioenergetic aspects. In primary brain capillary endothelial cells the purinergic receptor-stimulated mitochondrial Ca²⁺ uptake and efflux were studied. Vinpocetine exerted a partial inhibition on the mitochondrial calcium efflux. In rodent brain synaptosomes vinpocetine (30 μM) inhibited respiration in uncoupler stimulated synaptosomes and decreased H₂O₂ release from the nerve terminals in resting and in complex I inhibited conditions, respectively. In isolated rat brain mitochondria using either complex I or complex II substrates leak respiration was stimulated, but ADP-induced respiration was inhibited by vinpocetine. The stimulation of oxidation was associated with a small extent of membrane depolarization. Mitochondrial H₂O₂ production was inhibited by vinpocetine under all conditions investigated. The most pronounced effects were detected with the complex II substrate succinate. Vinpocetine also mitigated both Ca²⁺-induced mitochondrial Ca²⁺-release and Ca²⁺-induced mitochondrial swelling. It lowered the rate of mitochondrial ATP synthesis, while increasing ATPase activity. These results indicate more than a single mitochondrial target of this vinca alkaloid. The relevance of the affected mitochondrial mechanisms in the anti ischemic effect of vinpocetine is discussed.

Oxidative stress and DNA damage in the mechanism of fetal alcohol spectrum disorders

This review covers molecular mechanisms involving oxidative stress and DNA damage that may contribute to morphological and functional developmental disorders in animal models resulting from exposure to alcohol (ethanol, EtOH) in utero or in embryo culture. Components covered include: (a) a brief overview of EtOH metabolism and embryopathic mechanisms other than oxidative stress; (b) mechanisms within the embryo and fetal brain by which EtOH increases the formation of reactive oxygen species (ROS); (c) critical embryonic/fetal antioxidative enzymes and substrates that detoxify ROS; (d) mechanisms by which ROS can alter development, including ROS-mediated signal transduction and oxidative DNA damage, the latter of which leads to pathogenic genetic (mutations) and epigenetic changes; (e) pathways of DNA repair that mitigate the pathogenic effects of DNA damage; (f) related indirect mechanisms by which EtOH enhances risk, for example by enhancing the degradation of some DNA repair proteins; and, (g) embryonic/fetal pathways like NRF2 that regulate the levels of many of the above components. Particular attention is paid to studies in which chemical and/or genetic manipulation of the above mechanisms has been shown to alter the ability of EtOH to adversely affect development. Alterations in the above components are also discussed in terms of: (a) individual embryonic and fetal determinants of risk and (b) potential risk biomarkers and mitigating strategies. FASD risk is likely increased in progeny which/who are biochemically predisposed via genetic and/or environmental mechanisms, including enhanced pathways for ROS formation and/or deficient pathways for ROS detoxification or DNA repair.

Measurement of the Oxidative DNA Lesion 8-Oxoguanine (8-oxoG) by ELISA or by High-Performance Liquid Chromatography (HPLC) with Electrochemical Detection

Reactive oxygen species (ROS) can oxidize cellular macromolecules like DNA, causing DNA damage. The most common form of DNA damage is the 8-oxoguanine (8-oxoG) lesion, typically repaired by the base excision repair (BER) pathway, which is initiated by the enzyme oxoguanine glycosylase 1 (OGG1). ROS are produced endogenously and can be enhanced by environmental factors, such as xenobiotics, radiation, and microbial pathogens. As a commonly used biomarker of oxidative damage, 8-oxoG can be measured in two different ways described herein. Commercially available ELISA kits allow for easy detection of the 8-oxoG lesion, while more difficult HPLC assays with UV and electrochemical detection allow for a more definitive identification and quantification of 8-oxoG.

A Tale of Two Concepts: Harmonizing the Free Radical and Antagonistic Pleiotropy Theories of Aging

SIGNIFICANCE

The two foremost concepts of aging are the mechanistic free radical theory (FRT) of how we age and the evolutionary antagonistic pleiotropy theory (APT) of why we age. Both date from the late 1950s. The FRT holds that reactive oxygen species (ROS) are the principal contributors to the lifelong cumulative damage suffered by cells, whereas the APT is generally understood as positing that genes that are good for young organisms can take over a population even if they are bad for the old organisms. Recent Advances: Here, we provide a common ground for the two theories by showing how aging can result from the inherent chemical reactivity of many biomolecules, not just ROS, which imposes a fundamental constraint on biological evolution. Chemically reactive metabolites spontaneously modify slowly renewable macromolecules in a continuous way over time; the resulting buildup of damage wrought by the genes coding for enzymes that generate such small molecules eventually masquerades as late-acting pleiotropic effects. In aerobic organisms, ROS are major agents of this damage but they are far from alone.

CRITICAL ISSUES

Being related to two sides of the same phenomenon, these theories should be compatible. However, the interface between them is obscured by the FRT mistaking a subset of damaging processes for the whole, and the APT mistaking a cumulative quantitative process for a qualitative switch.

FUTURE DIRECTIONS

The manifestations of ROS-mediated cumulative chemical damage at the population level may include the often-observed negative correlation between fitness and the rate of its decline with increasing age, further linking FRT and APT. Antioxid. Redox Signal. 29, 1003-1017.

Crosstalk between Rac1-mediated actin regulation and ROS production

The small RhoGTPase Rac1 is implicated in a variety of events related to actin cytoskeleton rearrangement. Remarkably, another event that is completely different from those related to actin regulation has the same relevance; the Rac1-mediated production of reactive oxygen species (ROS) through NADPH oxidases (NOX). Each outcome involves different Rac1 downstream effectors; on one hand, events related to the actin cytoskeleton require Rac1 to bind to WAVEs proteins and PAKs that ultimately promote actin branching and turnover, on the other, NOX-derived ROS production demands active Rac1 to be bound to a cytosolic activator of NOX. How Rac1-mediated signaling ends up promoting actin-related events, NOX-derived ROS, or both is poorly understood. Rac1 regulators, including scaffold proteins, are known to exert tight control over its functions. Hence, evidence of Rac1 regulatory events leading to both actin remodeling and NOX-mediated ROS generation are discussed. Moreover, cellular functions linked to physiological and pathological conditions that exhibit crosstalk between Rac1 outcomes are analyzed, while plausible roles in neuronal functions (and dysfunctions) are highlighted. Together, discussed evidence shed light on cellular mechanisms which requires Rac1 to direct either actin- and/or ROS-related events, helping to understand crucial roles of Rac1 dual functionality.