Evolutionary biology: essence of mitochondria

A highly specific and ultrasensitive near-infrared fluorescent probe for imaging basal hypochlorite in the mitochondria of living cells

The development of highly specific and ultrasensitive fluorescent probes for tracking basal mitochondrial hypochlorite is very important to unravel its diverse cellular functions in the mitochondria of living cells. In this paper, we have developed a water-soluble, mitochondria-targeted near-infrared fluorescent probe NB-OCl for selectively measuring OCl^- in the presence of higher concentration (500 μM) other biologically important substances. Surprisingly, the obtained results demonstrated that probe NB-OCl could sensitively determine OCl^- in the range of 0-200 pM with the detection limit of 10.8 pM. To the best of our knowledge, NB-OCl is the first fluorescent probe for the specific determination of OCl^- at the picomolar level. Moreover, probe NB-OCl exhibits a fast response for OCl^- (< 5 s), which would be in favor of tracking the highly reactive and short-lived OCl^- in the living systems. The preeminent recognition properties of probe NB-OCl enable its applications in the monitoring of basal OCl^- and the fluctuations of endogenous/exogenous OCl^- levels in the mitochondria of living cells.

A tumor-targeting probe based on a mitophagy process for live imaging

A pH sensitive probe was designed for mitochondria and autolysosomes monitoring in cell level and tumor targeting imaging.

A self-assessed photosensitizer: inducing and dual-modal phosphorescence imaging of mitochondria oxidative stress

Mitochondria-targeted Ir(iii)–nitroxide conjugates act as self-assessed PDT agents by simultaneously inducing and dual-modal phosphorescence imaging of mitochondrial oxidative stress.

Neuroprotective effects of allicin on ischemia-reperfusion brain injury

BACKGROUND

Ischemia-reperfusion brain injury (IRBI) is an important cause for mortality and morbidity. Studies on humans and animals showed that oxidative stress (OS) plays a crucial role in ischemic stroke with or without reperfusion. Allicin is reported to be able to attenuate OS and has neuroprotective effects on rabbits' ischemia-reperfusion spinal cord injury.

AIM

To explore whether Allicin pretreatment has neuroprotective effects on IRBI in mice.

METHODS AND RESULTS

Transient middle cerebral artery occlusion (MCAO) was conducted to induce IRBI in mice. The mice were pretreated with either Allicin (MCAOA) or normal saline in the same volume (MCAONS). Sham-operated groups [Allicin group (SOA) and normal saline group (SONS)] were also set. Blood pressure and cerebral blood flow measurements revealed comparable hemodynamics. Via brain MRI and neuronal nuclear antigen (NeuN) immune-histochemical staining, MCAOA mice had a significantly reduced stroke size than MCAONS mice (P < 0.05, n = 15). Allicin pretreatment could attenuate the OS, the activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, inflammation, dysfunction of mitochondrial respiratory chain, and apoptosis (all P < 0.05, n = 15). Furthermore, Allicin also increased the activities of endogenous antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPX), and glutathione S-transferase (GST), and promoted the angiogenesis in the peri-infarct zone (all P < 0.05, n = 15).

CONCLUSION

We showed that Allicin could protect mice from IRBI through a series of mechanisms. Allicin represents a new therapeutic direction of IRBI.

Caveolin-1 controls mitochondrial function through regulation of m-AAA mitochondrial protease

Mitochondrial proteases ensure mitochondrial integrity and function after oxidative stress by providing mitochondrial protein quality control. However, the molecular mechanisms that regulate this basic biological function in eukaryotic cells remain largely unknown. Caveolin-1 is a scaffolding protein involved in signal transduction. We find that AFG3L2, a m-AAA type of mitochondrial protease, is a novel caveolin-1-interacting protein in vitro. We show that oxidative stress promotes the translocation of both caveolin-1 and AFG3L2 to mitochondria, enhances the interaction of caveolin-1 with AFG3L2 in mitochondria and stimulates mitochondrial protease activity in wild-type fibroblasts. Localization of AFG3L2 to mitochondria after oxidative stress is inhibited in fibroblasts lacking caveolin-1, which results in impaired mitochondrial protein quality control, an oxidative phosphorylation to aerobic glycolysis switch and reduced ATP production. Mechanistically, we demonstrate that a lack of caveolin-1 does not alter either mitochondrial number or morphology but leads to the cytoplasmic and proteasome-dependent degradation of complexes I, III, IV and V upon oxidant stimulation. Restoration of mitochondrial respiratory chain complexes in caveolin-1 null fibroblasts reverts the enhanced glycolysis observed in these cells. Expression of a mutant form of AFG3L2, which has reduced affinity for caveolin-1, fails to localize to mitochondria and promotes degradation of complex IV after oxidative stress. Thus, caveolin-1 maintains mitochondrial integrity and function when cells are challenged with free radicals by promoting the mitochondrial localization of m-AAA protease and its quality control functions.

High-throughput m6A-seq reveals RNA m6A methylation patterns in the chloroplast and mitochondria transcriptomes of Arabidopsis thaliana

This study is the first to comprehensively characterize m6A patterns in the Arabidopsis chloroplast and mitochondria transcriptomes based on our open accessible data deposited in NCBI's Gene Expression Omnibus with GEO Series accession number of GSE72706. Over 86% of the transcripts were methylated by m6A in the two organelles. Over 550 and 350 m6A sites were mapped, with ~5.6 to ~5.8 and ~4.6 to ~4.9 m6A sites per transcript, to the chloroplast and mitochondria genome, respectively. The overall m6A methylation extent in the two organelles was greatly higher than that in the nucleus. The m6A motif sequences in the transcriptome of two organelles were similar to the nuclear motifs, suggesting that selection of the m6A motifs for RNA methylation was conserved between the nucleus and organelle transcriptomes. The m6A patterns of rRNAs and tRNAs in the organelle were similar to those in the nucleus. However, the m6A patterns in coding RNAs were distinct between the nucleus and the organelle, suggesting that that regulation of the m6A methylation patterns may be different between the nuclei and the organelles. The extensively methylated transcripts in the two organelles were mainly associated with rRNA, ribosomal proteins, photosystem reaction proteins, tRNA, NADH dehydrogenase and redox. On average, 64% and 79% of the transcripts in the two organelles showed differential m6A methylation across three organs of the leaves, flowers and roots. The m6A methylation extent in the chloroplast was higher than that in the mitochondria. This study provides deep insights into the m6A methylation topology and differentiation in the plant organelle transcriptomes.

The complete mitochondrial genome of Engyodontium album and comparative analyses with Ascomycota mitogenomes

Engyodontium album is a widespread pathogen that causes different kinds of dermatoses and respiratory tract diseases in humans and animals. In spite of its perniciousness, the basic genetic and molecular background of this species remains poorly understood. In this study, the mitochondrial genome sequence of E. album was determined using a high-throughput sequencing platform. The circular mitogenome was found to be 28,081 nucleotides in length and comprised of 17 protein-coding genes, 24 tRNA genes, and 2 rRNA genes. The nucleotide composition of the genome was A+T-biased (74.13%). Group-II introns were found in the nad1, nad5, and cob genes. The most frequently used codon of protein-coding genes was UAU. Isoleucine was identified as the most common amino acid, while proline was the least common amino acid in protein-coding genes. The gene-arrangement order is nearly the same when compared with other Ascomycota mitogenomes. Phylogenetic relationships based on the shared protein-coding genes revealed that E. album is closely related to the Cordycipitaceae family, with a high-confidence support value (100%). The availability of the mitogenome of E. album will shed light on the molecular systematic and genetic differentiation of this species.

Effects of ethanol extract of Bombax ceiba leaves and its main constituent mangiferin on diabetic nephropathy in mice

The present study was designed to explore the mechanism by which ethanol extract of Bombax ceiba leaves (BCE) and its main constituent mangiferin (MGF) affect diabetic nephropathy by combating oxidative stress. Oral administration of BCE and MGF to normal and streptozotocin (STZ)-induced diabetic mice were carried out. Fasting blood glucose, 24-h urinary albumin, serum creatinine, and blood urea nitrogen were tested, histopathology, and immunohistochemical analysis of kidney tissues were performed. Moreover, mesangial cells were treated with BCE and MGF for 48 h with or without 25 mmol·L^-1 of glucose. Immunofluorescence, Western blot and apoptosis analyses were used to investigate their regulation of oxidative stress and mitochondrial function. BCE and MGF ameliorated biochemical parameters and restored STZ-induced renal injury in the model mice. In vitro study showed that high glucose stimulation increased oxidative stress and cell apoptosis in mesangial cells. BCE and MGF limited mitochondrial membrane potential (Δψm) collapse by inhibiting Nox4, mitochondrially bound hexokinase II dissociation, and subsequent ROS production, which effectively reduced oxidative stress, cleaved caspase-3 expression and cell apoptosis. Our work indicated that BCE and MGF had protective effects on diabetic caused kidney injury and prevented oxidative stress in mesangial cells by regulation of hexokinase II binding and Nox4 oxidase signaling.

A Model of Exposure to Extreme Environmental Heat Uncovers the Human Transcriptome to Heat Stress

The molecular mechanisms by which individuals subjected to environmental heat stress either recover or develop heat-related complications are not well understood. We analysed the changes in blood mononuclear gene expression patterns in human volunteers exposed to extreme heat in a sauna (temperature of 75.7 ± 0.86 °C). Our analysis reveals that expression changes occur rapidly with no significant increase in core temperature and continue to amplify one hour after the end of heat stress. The reprogramed transcriptome was predominantly inhibitory, as more than two-thirds of the expressed genes were suppressed. The differentially expressed genes encoded proteins that function in stress-associated pathways; including proteostasis, energy metabolism, cell growth and proliferation, and cell death, and survival. The transcriptome also included mitochondrial dysfunction, altered protein synthesis, and reduced expression of genes -related to immune function. The findings reveal the human transcriptomic response to heat and highlight changes that might underlie the health outcomes observed during heat waves.

Lipophilic methylene violet analogues as modulators of mitochondrial function and dysfunction

In an effort to identify methylene blue analogues having improved antioxidant activity, a series of new methylene violet analogues have been designed and synthesized. The analogues were prepared following a synthetic route that is more efficient than the previously reported methods, both in terms of yield and purity of the final products. The route involves the Smiles rearrangement as one of the crucial steps. Smiles rearrangement of suitably substituted diphenyl sulfide intermediates afforded the corresponding phenothiazine analogues in high yields, which were subsequently converted to the final products. The methylene violet analogues were evaluated for their ability to preserve mitochondrial function in Friedreich's ataxia (FRDA) lymphocytes. The analogues were shown to be efficient ROS scavengers, and able to protect cultured FRDA lymphocytes from oxidative stress resulting from inhibition of complex I. The analogues also preserved mitochondrial membrane potential and augmented ATP production. The analogues were found to be better antioxidants than the parent compounds methylene blue and methylene violet.

Mitochondria in chronic obstructive pulmonary disease and lung cancer: where are we now?

Recent advances in mitochondrial biogenesis have provided the emerging recognition that mitochondria do much more than 'simply providing energy for cellular function'. Currently, a constantly improving understanding of the mitochondrial structure and function has been providing valuable insights into the contribution of defects in mitochondrial metabolism to various human diseases, including chronic obstructive pulmonary disease and lung cancer. The growing interest in mitochondria research led to development of new biomedical fields in the two main smoking-related lung diseases. However, there is considerable paucity in our understanding of mechanisms by which mitochondrial dynamics regulate lung diseases. In this review, we will discuss our current knowledge on the role of mitochondrial dysfunction in the pathogenesis of chronic obstructive pulmonary disease and non-small-cell lung cancer.

Identification of Symmetrical RNA Editing Events in the Mitochondria of Salvia miltiorrhiza by Strand-specific RNA Sequencing

Salvia miltiorrhiza is one of the most widely-used medicinal plants. Here, we systematically analyzed the RNA editing events in its mitochondria. We developed a pipeline using REDItools to predict RNA editing events from stand-specific RNA-Seq data. The predictions were validated using reverse transcription, RT-PCR amplification and Sanger sequencing experiments. Putative sequences motifs were characterized. Comparative analyses were carried out between S. miltiorrhiza, Arabidopsis thaliana and Oryza sativa. We discovered 1123 editing sites, including 225 “C to U” sites in the protein-coding regions. Fourteen of sixteen (87.5%) sites were validated. Three putative DNA motifs were identified around the predicted sites. The nucleotides on both strands at 115 of the 225 sites had undergone RNA editing, which we called symmetrical RNA editing (SRE). Four of six these SRE sites (66.7%) were experimentally confirmed. Re-examination of strand-specific RNA-Seq data from A. thaliana and O. sativa identified 327 and 369 SRE sites respectively. 78, 20 and 13 SRE sites were found to be conserved among A. thaliana, O. sativa and S. miltiorrhiza respectively. This study provides a comprehensive picture of RNA editing events in the mitochondrial genome of S. miltiorrhiza. We identified SREs for the first time, which may represent a universal phenomenon.

MitoQ regulates autophagy by inducing a pseudo-mitochondrial membrane potential

During the process of oxidative phosphorylation, protons are pumped into the mitochondrial intermembrane space to establish a mitochondrial membrane potential (MMP). The electrochemical gradient generated allows protons to return to the matrix through the ATP synthase complex and generates ATP in the process. MitoQ is a lipophilic cationic drug that is adsorbed to the inner mitochondrial membrane; however, the cationic moiety of MitoQ remains in the intermembrane space. We found that the positive charges in MitoQ inhibited the activity of respiratory chain complexes I, III, and IV, reduced proton production, and decreased oxygen consumption. Therefore, a pseudo-MMP (PMMP) was formed via maintenance of exogenous positive charges. Proton backflow was severely impaired, leading to a decrease in ATP production and an increase in AMP production. Excess AMP activates AMP kinase, which inhibits the MTOR (mechanistic target of rapamycin) pathway and induces macroautophagy/autophagy. Therefore, we conclude that MitoQ increases PMMP via proton displacement with exogenous positive charges. In addition, PMMP triggered autophagy in hepatocellular carcinoma HepG2 cells via modification of mitochondrial bioenergetics pathways.

Influence of substituent heteroatoms on the cytoprotective properties of pyrimidinol antioxidants

Recently, we described the optimization of novel pyrimidinol-based antioxidants as potential therapeutic molecules for targeting mitochondrial diseases. That study focused on improving the potency and metabolic stability of pyrimidinol antioxidants. This led us to consider the possibility of altering the positions of the exocyclic alkoxy and alkylamino substituents on the pyrimidinol scaffold. Twelve new analogues were prepared and their biological activities were investigated. The metabolic stability of the prepared regioisomers was also assessed in vitro using bovine liver microsomes. Unexpectedly, the 2-alkoxy-4-alkylamino substituted pyrimidinol antioxidants were found to have properties in protecting mitochondrial function superior to the isomeric 4-alkoxy-2-alkylamino substituted pyrimidinols evaluated in all earlier studies. This observation suggests a possible mode of action involving the intermediacy of an ortho-iminoquinone, a species not previously associated with mitochondrial respiratory chain function.

Two-photon photodynamic ablation of tumor cells by mitochondria-targeted iridium(iii) complexes in aggregate states

Two iridium(iii) complexes with a rotary phenyl substituent ligand were used as mitochondria-targeted photosensitizers for two-photon photodynamic therapy in aggregate states.

Mitochondrial Ubiquitin Ligase in Cardiovascular Disorders

Mitochondrial dynamics play a critical role in cellular responses and physiological process. However, their dysregulation leads to a functional degradation, which results in a diverse array of common disorders, including cardiovascular disease. In this background, the mitochondrial ubiquitin ligase has been attracting substantial research interest in recent years. Mitochondrial ubiquitin ligase is localized in the mitochondrial outer membrane, where it plays an essential role in the regulation of mitochondrial dynamics and apoptosis. In this chapter, we provide a comprehensive overview of the functions of mitochondrial ubiquitin ligases identified hitherto, with a special focus on cardiovascular disorders.

Development of a viscosity sensitive fluorescent probe for real-time monitoring of mitochondria viscosity

Through rational design, two new mitochondria-targeted fluorescent viscosity probes were developed, which exhibited favorable properties such as large turn on fluorescence signal, good selectivity, low cytotoxicity, and high colocation coefficient (>0.90).

Effect of oxidative phosphorylation signaling pathway on silkworm midgut following exposure to phoxim

Organophosphate pesticides are applied widely in the world for agricultural purposes, and their exposures often resulted in non-cocooning of Bombyx mori in China. Silkworm midgut is the major organ for digestion and nutrient absorption, importantly it is also a barrier against foreign substances and chemical pesticides. The purpose of this study was to determine the mechanism of oxidative injury in silkworm midgut with phoxim induction. The results showed that the transcription level of oxidative phosphorylation signaling pathway genes of midgut under phoxim stress. Digital gene expression (DGE) analysis revealed that 24 electron transport chain (ETC)-related genes were upregulated. Quantitative real time polymerase chain reaction results indicated that the ETC the genes encoding NADH-CoQ1, Succinic-Q, cyt c reductase-S, cyt c oxidase-S, cytochrome c oxidase polypeptide IV, ATP synthase, and vacuolar H+ ATP synthase were all significantly up-regulated by 1.50-, 1.31-, 1.42-, 1.44-, 1.70-, 2.03- and 1.43-fold, respectively. Phoxim induction enhanced the activity of ETC complex in mitochondria, and induced the accumulation of ROS in midgut. These results indicated that trace phoxim enhanced respiration in midgut, and the imbalance between the activity changes of ETC may led to reactive oxygen species accumulation. The ETC of mitochondria may be potential biomarkers of midgut toxicity in B. mori caused by phoxim exposure. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 167-175, 2017.

Nuclear but not mitochondrial-encoded oxidative phosphorylation genes are altered in aging, mild cognitive impairment, and Alzheimer's disease

INTRODUCTION

We have comprehensively described the expression profiles of mitochondrial DNA and nuclear DNA genes that encode subunits of the respiratory oxidative phosphorylation (OXPHOS) complexes (I-V) in the hippocampus from young controls, age matched, mild cognitively impaired (MCI), and Alzheimer's disease (AD) subjects.

METHODS

Hippocampal tissues from 44 non-AD controls (NC), 10 amnestic MCI, and 18 AD cases were analyzed on Affymetrix Hg-U133 plus 2.0 arrays.

RESULTS

The microarray data revealed significant down regulation in OXPHOS genes in AD, particularly those encoded in the nucleus. In contrast, there was up regulation of the same gene(s) in MCI subjects compared to AD and ND cases. No significant differences were observed in mtDNA genes identified in the array between AD, ND, and MCI subjects except one mt-ND6.

DISCUSSION

Our findings suggest that restoration of the expression of nuclear-encoded OXPHOS genes in aging could be a viable strategy for blunting AD progression.

Optimization of pyrimidinol antioxidants as mitochondrial protective agents: ATP production and metabolic stability

Previously we described a novel series of pyrimidinol antioxidants and their structural optimization as potential therapeutic agents for neurodegenerative and mitochondrial disorders. Our initial lead compound was a potent antioxidant in vitro, but was subsequently found to exhibit poor stability to oxidative metabolism. The current study focused on balancing potency with metabolic stability through structural modification, and involved modifications at positions 2 and 4 of the pyrimidinol redox core, likely sites of oxidative metabolism. Eight new analogues have been prepared and their ability to suppress lipid peroxidation and reactive oxygen species (ROS), and to preserve mitochondrial membrane potential (Δψ_m) and support ATP production, has been investigated. The metabolic stability of the prepared compounds was also assessed in vitro using bovine liver microsomes to obtain preliminary insight on this class of compounds. This study revealed the complexity of balancing reasonable metabolic stability with efficient antioxidant properties. While a few analogues appear promising, especially in terms of metabolic stability, a 4-isopropoxy derivative conserved the favorable biological activity and exhibited good metabolic stability. The favorable metabolic stability conferred by the combination of the azetidine and isopropoxy moieties in analogue 6 makes this compound an excellent candidate for further evaluation.

Mitochondrial haplogroups and expression studies of commonly used human cell lines

We developed a multiplex fragment length analysis (MFLA) for clearly assigning mitochondrial haplogroups mostly endemic in Europe for future cardiac diagnostics. As a technical proof, 23 commonly used human cell lines were haplotyped as reference standards. The functional analysis on mtDNA copies per cell revealed no correlation to haplogroups but a relatively high rate of mitochondria per cell and at the same time a very low expression of all mitochondrial and some nuclear encoded mitochondrial related genes. Established MFLA is an easy to handle method for analysing European mitochondrial haplogroups to perform epidemic studies and elucidate correlations to distinct diseases.

Development and sensing applications of fluorescent motifs within the mitochondrial environment

The potential use of fluorescent molecular probes to measure ions and biomolecules has contributed incessantly to the understanding of chemical and biological systems. The approach has many advantages such as high sensitivity, simplicity and non-destructive cellular imaging that offer visible information about the targeted species. In this article, our objective is to discuss fluorescent probes that have sensing applications within the mitochondrial environment. Mitochondria are cellular organelles which are well known for their unique physiological functions and have been found to be associated with various diseases and disorders. It is therefore, important to develop new tools and tactics that can provide useful information concerning the mitochondrial environment which in turn is essential to understand its biophysical functioning and related diseases.

Dissecting tRNA-derived fragment complexities using personalized transcriptomes reveals novel fragment classes and unexpected dependencies

We analyzed transcriptomic data from 452 healthy men and women representing five different human populations and two races, and, 311 breast cancer samples from The Cancer Genome Atlas. Our studies revealed numerous constitutive, distinct fragments with overlapping sequences and quantized lengths that persist across dozens of individuals and arise from the genomic loci of all nuclear and mitochondrial human transfer RNAs (tRNAs). Surprisingly, we discovered that the tRNA fragments' length, starting and ending points, and relative abundance depend on gender, population, race and also on amino acid identity, anticodon, genomic locus, tissue, disease, and disease subtype. Moreover, the length distribution of mitochondrially-encoded tRNAs differs from that of nuclearly-encoded tRNAs, and the specifics of these distributions depend on tissue. Notably, tRNA fragments from the same anticodon do not have correlated abundances. We also report on a novel category of tRNA fragments that significantly contribute to the differences we observe across tissues, genders, populations, and races: these fragments, referred to as i-tRFs, are abundant in human tissues, wholly internal to the respective mature tRNA, and can straddle the anticodon. HITS-CLIP data analysis revealed that tRNA fragments are loaded on Argonaute in a cell-dependent manner, suggesting cell-dependent functional roles through the RNA interference pathway. We validated experimentally two i-tRF molecules: the first was found in 21 of 22 tested breast tumor and adjacent normal samples and was differentially abundant between health and disease whereas the second was found in all eight tested breast cancer cell lines.

A novel thiophene-3-carboxamide analog of annonaceous acetogenin exhibits antitumor activity via inhibition of mitochondrial complex I

Previously we synthesized JCI‐20679, a novel thiophene‐3‐carboxamide analog of annonaceous acetogenins which have shown potent antitumor activity, with no serious side effects, in mouse xenograft models. In this study, we investigated the antitumor mechanism of JCI‐20679. The growth inhibition profile (termed “fingerprint”) of this agent across a panel of 39 human cancer cell lines (termed “JFCR39”) was measured; this fingerprint was analyzed by the COMPARE algorithm utilizing the entire drug sensitivity database for the JFCR39 panel. The JCI‐20679‐specific fingerprint exhibited a high similarity to those of two antidiabetic biguanides and a natural rotenoid deguelin which were already known to be mitochondrial complex I inhibitors. In addition, the fingerprint exhibited by JCI‐20679 was not similar to that displayed by any typical anticancer drugs within the database, suggesting that it has a unique mode of action. In vitro experiments using bovine heart‐derived mitochondria showed direct inhibition of mitochondrial complex I by JCI‐20679 and associated derivatives. This inhibition of enzymatic activity positively correlated with tumor cell growth inhibition. Furthermore, a fluorescently labeled derivative of JCI‐20679 localized to the mitochondria of live cancer cells in vitro. These results suggest that JCI‐20679 can inhibit cancer cell growth by inhibiting mitochondrial complex I. Our results show that JCI‐20679 is a novel anticancer drug lead with a unique mode of action.

Mitochondrial Dynamics Tracking with Two-Photon Phosphorescent Terpyridyl Iridium(III) Complexes

Mitochondrial dynamics, including fission and fusion, control the morphology and function of mitochondria, and disruption of mitochondrial dynamics leads to Parkinson's disease, Alzheimer's disease, metabolic diseases, and cancers. Currently, many types of commercial mitochondria probes are available, but high excitation energy and low photo-stability render them unsuitable for tracking mitochondrial dynamics in living cells. Therefore, mitochondrial targeting agents that exhibit superior anti-photo-bleaching ability, deep tissue penetration and intrinsically high three-dimensional resolutions are urgently needed. Two-photon-excited compounds that use low-energy near-infrared excitation lasers have emerged as non-invasive tools for cell imaging. In this work, terpyridyl cyclometalated Ir(III) complexes (Ir1-Ir3) are demonstrated as one- and two-photon phosphorescent probes for real-time imaging and tracking of mitochondrial morphology changes in living cells.

Effects of formaldehyde on mitochondrial dysfunction and apoptosis in SK-N-SH neuroblastoma cells

Methanol ingestion is neurotoxic in humans due to its metabolites, formaldehyde and formic acid. Here, we compared the cytotoxicity of methanol and its metabolites on different types of cells. While methanol and formic acid did not affect the viability of the cells, formaldehyde (200-800 μg/mL) was strongly cytotoxic in all cell types tested. We investigated the effects of formaldehyde on oxidative stress, mitochondrial respiratory functions, and apoptosis on the sensitive neuronal SK-N-SH cells. Oxidative stress was induced after 2 h of formaldehyde exposure. Formaldehyde at a concentration of 400 μg/mL for 12 h of treatment greatly reduced cellular adenosine triphosphate (ATP) levels. Confocal microscopy indicated that the mitochondrial membrane potential (MMP) was dose-dependently reduced by formaldehyde. A marked and dose-dependent inhibition of mitochondrial respiratory enzymes, viz., NADH dehydrogenase (complex I), cytochrome c oxidase (complex IV), and oxidative stress-sensitive aconitase was also detected following treatment with formaldehyde. Furthermore, formaldehyde caused a concentration-dependent increase in nuclear fragmentation and in the activities of the apoptosis-initiator caspase-9 and apoptosis-effector caspase-3/-7, indicating apoptosis progression. Our data suggests that formaldehyde exerts strong cytotoxicity, at least in part, by inducing oxidative stress, mitochondrial dysfunction, and eventually apoptosis. Changes in mitochondrial respiratory function and oxidative stress by formaldehyde may therefore be critical in methanol-induced toxicity.

A mitochondria-targeted near-infrared probe for colorimetric and ratiometric fluorescence detection of hypochlorite in living cells

A mitochondria-targeted near-infrared probe for rapid, sensitive and specific detection of hypochlorite with colorimetric and ratiometric fluorescence dual responses.

Fluorescent probes for the selective detection of chemical species inside mitochondria

This feature article systematically summarizes the development of fluorescent probes for the selective detection of chemical species inside mitochondria.

Pyruvic acid levels in serum and saliva: A new course for oral cancer screening?

OBJECTIVE

Cancerous cells show increased glycolysis rate. This will increase overall levels of pyruvate as it is one of the end products of glycolysis. The present on-going study is to estimate the levels of pyruvate in saliva and serum among healthy and oral cancer subjects.

SETTINGS AND DESIGN

Hospital-based cross-sectional comparative study.

METHODOLOGY

A total of 50 subjects among healthy and oral cancer subjects were selected based on clinical and histological criteria. Saliva and serum samples were collected and subjected to pyruvate level estimation using biochemical analysis.

STATISTICAL ANALYSIS

Descriptive analysis and Mann-Whitney test were used to find the statistical difference between the two independent groups.

RESULTS

Serum pyruvic acid levels of the healthy group were 1.09 ± 0.14 and for oral cancer, it was 2.95 ± 0.59 and salivary level were 3.49 ± 0.47 and 1.32 ± 0.10 respectively. Mann-Whitney test showed statistically significant difference in serum and salivary pyruvate level in between two groups (P < 0.000 respectively).

CONCLUSION

The present study showed noticeable variation in the level of pyruvic acid among healthy and oral cancer subjects. This generates the hypothesis that estimation of the pyruvic acid can be a new tool to screening of the cancer.

Estimation of Pyruvic acid in serum and saliva among healthy and potentially malignant disorder subjects - a stepping stone for cancer screening?

BACKGROUND

According to Warburg's effect, the rate of glycolysis increases in cancerous cells. This will increase overall levels of pyruvic acid. The present on-going study was conducted to estimate the levels of pyruvic acid in saliva and serum in normal, oral PMD subjects.

MATERIAL AND METHODS

A total of 50 subjects in healthy, PMD of the oral cavity individuals were selected based on clinical and histological criteria. Collected saliva and serum samples were subjected to pyruvic acid level estimation using biochemical analysis.

RESULTS

Of the 50 participants 25 (13: Males; 12: Females) & 25 (16: Males; 9: Females) were PMD group. Independent samples t test showed statistically significant difference in serum & salivary pyruvic acid level in between 2 groups (p < 0.001 respectively).

CONCLUSIONS

Estimation of pyruvic acid showed sequential increase in the level in PMD group compared to healthy. Hence the study results open new direction in cancer screening.

KEY WORDS

Pyruvic acid, glycolysis, warburg's effect.

Mitochondria-controlled signaling mechanisms of brain protection in hypoxia

The article is focused on the role of the cell bioenergetic apparatus, mitochondria, involved in development of immediate and delayed molecular mechanisms for adaptation to hypoxic stress in brain cortex. Hypoxia induces reprogramming of respiratory chain function and switching from oxidation of NAD-related substrates (complex I) to succinate oxidation (complex II). Transient, reversible, compensatory activation of respiratory chain complex II is a major mechanism of immediate adaptation to hypoxia necessary for (1) succinate-related energy synthesis in the conditions of oxygen deficiency and formation of urgent resistance in the body; (2) succinate-related stabilization of HIF-1α and initiation of its transcriptional activity related with formation of long-term adaptation; (3) succinate-related activation of the succinate-specific receptor, GPR91. This mechanism participates in at least four critical regulatory functions: (1) sensor function related with changes in kinetic properties of complex I and complex II in response to a gradual decrease in ambient oxygen concentration; this function is designed for selection of the most efficient pathway for energy substrate oxidation in hypoxia; (2) compensatory function focused on formation of immediate adaptive responses to hypoxia and hypoxic resistance of the body; (3) transcriptional function focused on activated synthesis of HIF-1 and the genes providing long-term adaptation to low pO2; (4) receptor function, which reflects participation of mitochondria in the intercellular signaling system via the succinate-dependent receptor, GPR91. In all cases, the desired result is achieved by activation of the succinate-dependent oxidation pathway, which allows considering succinate as a signaling molecule. Patterns of mitochondria-controlled activation of GPR-91- and HIF-1-dependent reaction were considered, and a possibility of their participation in cellular-intercellular-systemic interactions in hypoxia and adaptation was proved.

PK11195-chitosan-graft-polyethylenimine-modified SPION as a mitochondria-targeting gene carrier

Superparamagnetic iron oxide nanoparticle (SPION) holds great potential as a gene delivery system due to its unique properties, such as good biocompatibility and non-invasive targeting ability. In this study, we modified SPION with chitosan-graft-PEI (CHI-g-PEI) and PK11195, to fabricate a mitochondria-targeting gene carrier, PK-CP-SPION. PK-CP-SPION manifested prominent physicochemical properties for magnetic guided gene delivery, and it could effectively condense and protect DNA at proper weight ratios. The in vitro cytotoxicity of PK-CP-SPIONs was mild. Under an external magnetic field, the transfection efficiency of PK-CP-SPIONs was comparable to PEI 25 K with shorter transfection time. PK11195 facilitated the specific accumulation of PK-CP-SPIONs in mitochondria, leading to the leakage of cytochrome c, the dissipation of mitochondrial membrane potential and subsequently the activation of mitochondria apoptosis pathway. These results indicated that with further development, PK-CP-SPIONs could serve as a multifunctional nanoplatform for magnetic targeting gene delivery and mitochondria-targeting therapy, leading enhanced therapeutic effect towards tumor cells.

Synonymous codon usage bias in plant mitochondrial genes is associated with intron number and mirrors species evolution

Synonymous codon usage bias (SCUB) is a common event that a non-uniform usage of codons often occurs in nearly all organisms. We previously found that SCUB is correlated with both intron number and exon position in the plant nuclear genome but not in the plastid genome; SCUB in both nuclear and plastid genome can mirror the evolutionary specialization. However, how about the rules in the mitochondrial genome has not been addressed. Here, we present an analysis of SCUB in the mitochondrial genome, based on 24 plant species ranging from algae to land plants. The frequencies of NNA and NNT (A- and T-ending codons) are higher than those of NNG and NNC, with the strongest preference in bryophytes and the weakest in land plants, suggesting an association between SCUB and plant evolution. The preference for NNA and NNT is more evident in genes harboring a greater number of introns in land plants, but the bias to NNA and NNT exhibits even among exons. The pattern of SCUB in the mitochondrial genome differs in some respects to that present in both the nuclear and plastid genomes.

Mitochondria-focused gene expression profile reveals common pathways and CPT1B dysregulation in both rodent stress model and human subjects with PTSD

Posttraumatic stress disorder (PTSD), a trauma-related mental disorder, is associated with mitochondrial dysfunction in the brain. However, the biologic approach to identifying the mitochondria-focused genes underlying the pathogenesis of PTSD is still in its infancy. Previous research, using a human mitochondria-focused cDNA microarray (hMitChip3) found dysregulated mitochondria-focused genes present in postmortem brains of PTSD patients, indicating that those genes might be PTSD-related biomarkers. To further test this idea, this research examines profiles of mitochondria-focused gene expression in the stressed-rodent model (inescapable tail shock in rats), which shows characteristics of PTSD-like behaviors and also in the blood of subjects with PTSD. This study found that 34 mitochondria-focused genes being upregulated in stressed-rat amygdala. Ten common pathways, including fatty acid metabolism and peroxisome proliferator-activated receptors (PPAR) pathways were dysregulated in the amygdala of the stressed rats. Carnitine palmitoyltransferase 1B (CPT1B), an enzyme in the fatty acid metabolism and PPAR pathways, was significantly over-expressed in the amygdala (P < 0.007) and in the blood (P < 0.01) of stressed rats compared with non-stressed controls. In human subjects with (n = 28) or without PTSD (n = 31), significant over-expression of CPT1B in PTSD was also observed in the two common dysregulated pathways: fatty acid metabolism (P = 0.0027, false discovery rate (FDR) = 0.043) and PPAR (P = 0.006, FDR = 0.08). Quantitative real-time polymerase chain reaction validated the microarray findings and the CPT1B result. These findings indicate that blood can be used as a specimen in the search for PTSD biomarkers in fatty acid metabolism and PPAR pathways, and, in addition, that CPT1B may contribute to the pathology of PTSD.

Genome analysis of medicinal Ganoderma spp. with plant-pathogenic and saprotrophic life-styles

Ganoderma is a fungal genus belonging to the Ganodermataceae family and Polyporales order. Plant-pathogenic species in this genus can cause severe diseases (stem, butt, and root rot) in economically important trees and perennial crops, especially in tropical countries. Ganoderma species are white rot fungi and have ecological importance in the breakdown of woody plants for nutrient mobilization. They possess effective machineries of lignocellulose-decomposing enzymes useful for bioenergy production and bioremediation. In addition, the genus contains many important species that produce pharmacologically active compounds used in health food and medicine. With the rapid adoption of next-generation DNA sequencing technologies, whole genome sequencing and systematic transcriptome analyses become affordable approaches to identify an organism's genes. In the last few years, numerous projects have been initiated to identify the genetic contents of several Ganoderma species, particularly in different strains of Ganoderma lucidum. In November 2013, eleven whole genome sequencing projects for Ganoderma species were registered in international databases, three of which were already completed with genomes being assembled to high quality. In addition to the nuclear genome, two mitochondrial genomes for Ganoderma species have also been reported. Complementing genome analysis, four transcriptome studies on various developmental stages of Ganoderma species have been performed. Information obtained from these studies has laid the foundation for the identification of genes involved in biological pathways that are critical for understanding the biology of Ganoderma, such as the mechanism of pathogenesis, the biosynthesis of active components, life cycle and cellular development, etc. With abundant genetic information becoming available, a few centralized resources have been established to disseminate the knowledge and integrate relevant data to support comparative genomic analyses of Ganoderma species. The current review carries out a detailed comparison of the nuclear genomes, mitochondrial genomes and transcriptomes from several Ganoderma species. Genes involved in biosynthetic pathways such as CYP450 genes and in cellular development such as matA and matB genes are characterized and compared in detail, as examples to demonstrate the usefulness of comparative genomic analyses for the identification of critical genes. Resources needed for future data integration and exploitation are also discussed.

Alzheimer's pathogenesis and its link to the mitochondrion

Alzheimer's disease (AD) is the most common form of dementia in the elderly. This neurodegenerative disorder is clinically characterized by impairment of cognitive functions and changes in behaviour and personality. The pathogenesis of AD is still unclear. Recent evidence supports some role of mitochondria dysfunction and oxidative stress in the development of the neurodegenerative process. In this review, we discuss the role of mitochondrial dysfunction in AD, focusing on the mechanisms that lead to mitochondrial impairment, oxidative stress, and neurodegeneration, a “vicious circle” that ends in dementia.