The multiple functions of cytochrome c and their regulation in life and death decisions of the mammalian cell: From respiration to apoptosis

Covalent Modification by Glyoxals Converts Cytochrome c Into its Apoptotically Competent State

The effects of glycation by glyoxal (Gly) and methylglyoxal (MGly) on the early and late conformational alterations in Cytochrome c (Cyt c) were studied. Spectroscopic measurements revealed that Cyt c undergo certain conformational alterations and exposure of heme upon overnight incubation with Gly and MGly. These were followed by the reduction of heme centre and activation of its peroxidase-like, which is crucial for initiation of the intrinsic apoptotic pathway. An extended incubation resulted in appearance of AGE-like fluorescence, with significant alterations in secondary structural compositions. However, no amyloidogenic conversions were observed as suggested by TEM analyses. The study provides an insight to the role of glycating agents, elevated under oxidative stress in inducing Cyt c release and apoptosis.

Heat stress, a serious threat to reproductive function in animals and humans

Global warming represents a major stressful environmental condition that compromises the reproductive efficiency of animals and humans via a rise of body temperature above its physiological homeothermic point (heat stress [HS]). The injuries caused by HS on reproductive function involves both male and female components, fertilization mechanisms as well as the early and late stages of embryo-fetal development. This occurrence causes great economic damage in livestock, and, in wild animals creates selective pressure towards the advantages of better-adapted genotypes to the detriment of others. Humans undergo several types of stress, including heat, and these represent putative causes of ongoing progressive decay in procreation; an increasing number of remedies in the form of antioxidant preparations are now being proposed to counteract the effects of stress. This review aims to describe the results of the most recent studies that aimed to highlight these effects and to draw information on the mechanisms acting as the basis of this problem from a comparative analysis.

Strangers in strange lands: mitochondrial proteins found at extra-mitochondrial locations

The mitochondrial proteome is estimated to contain ∼1100 proteins, the vast majority of which are nuclear-encoded, with only 13 proteins encoded by the mitochondrial genome. The import of these nuclear-encoded proteins into mitochondria was widely believed to be unidirectional, but recent discoveries have revealed that many these ‘mitochondrial’ proteins are exported, and have extra-mitochondrial activities divergent from their mitochondrial function. Surprisingly, three of the exported proteins discovered thus far are mitochondrially encoded and have significantly different extra-mitochondrial roles than those performed within the mitochondrion. In this review, we will detail the wide variety of proteins once thought to only reside within mitochondria, but now known to ‘emigrate’ from mitochondria in order to attain ‘dual citizenship’, present both within mitochondria and elsewhere.

Normothermic Machine Perfusion Protects Against Liver Ischemia-Reperfusion Injury During Reduced-Size Liver Transplantation in Pigs

Background

Normothermic machine perfusion (NMP) preservation is superior to cold preservation during reduced-size liver transplantation (RSLT) in pigs. However, the mechanism of this protective effect has not been explained. We aimed to compare the effects of NMP preservation with that of cold preservation (CS) in protecting against ischemia-reperfusion injury (IRI) during RSLT in pigs.

Material/Methods

Twenty-four healthy Bama miniature pigs were randomized into 2 groups: 1) the NMP group in which donor livers harvested without warm ischemia time and cardiac activity were connected to the NMP system to reduce liver size under normothermic conditions, and 2) the CS group in which donor livers harvested without warm ischemia time and cardiac activity were perfused using the University of Wisconsin (UW) solution and then preserved in the 0–4°C UW solution to reduce liver size under cold conditions. Livers were then transplanted without veno-venous bypass. Amounts of bile secretion for the NMP groups were recorded hourly. The serological indices were measured. Expressions of cytochrome C, caspase 3, and NF-κB p65 in liver tissue were observed.

Results

The levels of bile secretions were gradually diminished from 16.50±2.66 mL/h before splitting to 6.35±1.24 mL/h after splitting. With the exception of TNF-α on postoperative day 2, overall, levels of TNF-α, IL-1, IL-6, and MDA were significantly lower in the NMP group versus CS group for all 5 days postoperatively. Finally, cytochrome C, caspase 3, and NF-κB p65 expressions were all significantly suppressed in the NMP group as compared with the CS group.

Conclusions

MP preservation is superior to cold preservation in protecting against liver IRI during RSLT in pigs.

The Role of Mitochondrial Damage-Associated Molecular Patterns in Chronic Neuroinflammation

Mitochondrial dysfunction has been established as a common feature of neurodegenerative disorders that contributes to disease pathology by causing impaired cellular energy production. Mitochondrial molecules released into the extracellular space following neuronal damage or death may also play a role in these diseases by acting as signaling molecules called damage-associated molecular patterns (DAMPs). Mitochondrial DAMPs have been shown to initiate proinflammatory immune responses from nonneuronal glial cells, including microglia and astrocytes; thereby, they have the potential to contribute to the chronic neuroinflammation present in these disorders accelerating the degeneration of neurons. In this review, we highlight the mitochondrial DAMPs cytochrome c (CytC), mitochondrial transcription factor A (TFAM), and cardiolipin and explore their potential role in the central nervous system disorders including Alzheimer's disease and Parkinson's disease, which are characterized by neurodegeneration and chronic neuroinflammation.

Using redox-sensitive mitochondrial cytochrome Raman bands for label-free detection of mitochondrial dysfunction

We present a label-free imaging technique that detects mitochondrial activities with a sub-cellular spatial resolution.

Mitochondrial quality control as a key determinant of cell survival

Mitochondria are the energy producing dynamic double-membraned organelles essential for cellular and organismal survival. A multitude of intra- and extra-cellular signals involved in the regulation of energy metabolism and cell fate determination converge on mitochondria to promote or prevent cell survival by modulating mitochondrial function and structure. Mitochondrial fitness is maintained by mitophagy, a pathway of selective degradation of dysfunctional organelles. Mitophagy impairment and altered clearance results in increased levels of dysfunctional and structurally aberrant mitochondria, changes in energy production, loss of responsiveness to intra- and extra-cellular signals and ultimately cell death. The decline of mitochondrial function and homeostasis with age is reported to be central to age-related pathologies. Here we discuss the molecular mechanisms controlling mitochondrial dynamics, mitophagy and cell death signalling and how their perturbation may contribute to ageing and age-related illness.

The homozygous variant c.797G>A/p.(Cys266Tyr) in PISD is associated with a Spondyloepimetaphyseal dysplasia with large epiphyses and disturbed mitochondrial function

Spondyloepimetaphyseal dysplasias (SEMD) are a group of genetically heterogeneous skeletal disorders characterized by abnormal vertebral bodies and epimetaphyseal abnormalities. We investigated two families with a new SEMD type with one proband each. They showed mild facial dysmorphism, flat vertebral bodies (platyspondyly), large epiphyses, metaphyseal dysplasia, and hallux valgus as common clinical features. By trio-exome sequencing, the homozygous missense variant c.797G>A/p.(Cys266Tyr) in PISD was found in both affected individuals. Based on exome data analyses for homozygous regions, the two patients shared a single homozygous block on chromosome 22 including PISD, indicating their remote consanguinity. PISD encodes phosphatidylserine (PS) decarboxylase that is localized in the inner mitochondrial membrane and catalyzes the decarboxylation of PS to phosphatidylethanolamine (PE) in mammalian cells. PE occurs at high abundance in mitochondrial membranes. Patient-derived fibroblasts showed fragmented mitochondrial morphology. Treatment of patient cells with MG-132 or staurosporine to induce activation of the intrinsic apoptosis pathway revealed significantly decreased cell viability with increased caspase-3 and caspase-7 activation. Remarkably, ethanolamine (Etn) supplementation largely restored cell viability and enhanced apoptosis in MG-132-stressed patient cells. Our data demonstrate that the biallelic hypomorphic PISD variant p.(Cys266Tyr) is associated with a novel SEMD form, which may be treatable with Etn administration.

Mitochondrial dysfunction is a key determinant of the rare disease lymphangioleiomyomatosis and provides a novel therapeutic target

Lymphangioleiomyomatosis (LAM) is a rare and progressive systemic disease affecting mainly young women of childbearing age. A deterioration in lung function is driven by neoplastic growth of atypical smooth muscle-like LAM cells in the pulmonary interstitial space that leads to cystic lung destruction and spontaneous pneumothoraces. Therapeutic options for preventing disease progression are limited and often end with lung transplantation temporarily delaying an inevitable decline. To identify new therapeutic strategies for this crippling orphan disease, we have performed array based and metabolic molecular analysis on patient-derived cell lines. Our results point to the conclusion that mitochondrial biogenesis and mitochondrial dysfunction in LAM cells provide a novel target for treatment.

Cytochrome c autocatalyzed carbonylation in the presence of hydrogen peroxide and cardiolipins

Cytochrome c (cyt c) is a small hemoprotein involved in electron shuttling in the mitochondrial respiratory chain and is now also recognized as an important mediator of apoptotic cell death. Its role in inducing programmed cell death is closely associated with the formation of a complex with the mitochondrion-specific phospholipid cardiolipin (CL), leading to a gain of peroxidase activity. However, the molecular mechanisms behind this gain and eventual cyt c autoinactivation via its release from mitochondrial membranes remain largely unknown. Here, we examined the kinetics of the H₂O₂-mediated peroxidase activity of cyt c both in the presence and absence of tetraoleoyl cardiolipin (TOCL)- and tetralinoleoyl cardiolipin (TLCL)-containing liposomes to evaluate the role of cyt c-CL complex formation in the induction and stimulation of cyt c peroxidase activity. Moreover, we examined peroxide-mediated cyt c heme degradation to gain insights into the mechanisms by which cyt c self-limits its peroxidase activity. Bottom-up proteomics revealed >50 oxidative modifications on cyt c upon peroxide reduction. Of note, one of these by-products was the Tyr-based "cofactor" trihydroxyphenylalanine quinone (TPQ) capable of inducing deamination of Lys ϵ-amino groups and formation of the carbonylated product aminoadipic semialdehyde. In view of these results, we propose that autoinduced carbonylation, and thus removal of a positive charge in Lys, abrogates binding of cyt c to negatively charged CL. The proposed mechanism may be responsible for release of cyt c from mitochondrial membranes and ensuing inactivation of its peroxidase activity.

Does Oxidation of Mitochondrial Cardiolipin Trigger a Chain of Antiapoptotic Reactions?

Oxidative stress causes selective oxidation of cardiolipin (CL), a four-tail lipid specific for the inner mitochondrial membrane. Interaction with oxidized CL transforms cytochrome c into peroxidase capable of oxidizing even more CL molecules. Ultimately, this chain of events leads to the pore formation in the outer mitochondrial membrane and release of mitochondrial proteins, including cytochrome c, into the cytoplasm. In the cytoplasm, cytochrome c promotes apoptosome assembly that triggers apoptosis (programmed cell death). Because of this amplification cascade, even an occasional oxidation of a single CL molecule by endogenously formed reactive oxygen species (ROS) might cause cell death, unless the same CL oxidation triggers a separate chain of antiapoptotic reactions that would prevent the CL-mediated apoptotic cascade. Here, we argue that the key function of CL in mitochondria and other coupling membranes is to prevent proton leak along the interface of interacting membrane proteins. Therefore, CL oxidation should increase proton permeability through the CL-rich clusters of membrane proteins (CL islands) and cause a drop in the mitochondrial membrane potential (MMP). On one hand, the MMP drop should hinder ROS generation and further CL oxidation in the entire mitochondrion. On the other hand, it is known to cause rapid fission of the mitochondrial network and formation of many small mitochondria, only some of which would contain oxidized CL islands. The fission of mitochondrial network would hinder apoptosome formation by preventing cytochrome c release from healthy mitochondria, so that slowly working protein quality control mechanisms would have enough time to eliminate mitochondria with the oxidized CL. Because of these two oppositely directed regulatory pathways, both triggered by CL oxidation, the fate of the cell appears to be determined by the balance between the CL-mediated proapoptotic and antiapoptotic reactions. Since this balance depends on the extent of CL oxidation, mitochondria-targeted antioxidants might be able to ensure cell survival in many pathologies by preventing CL oxidation.

The CRISPR-cas system promotes antimicrobial resistance in Campylobacter jejuni

AIM

The purpose of current study is to find out relationship between cas9 gene and antimicrobial resistance in Campylobacter jejuni NCTC11168.

MATERIALS & METHODS

The involvement of the cas9 gene in antimicrobial resistance of C. jejuni was determined by assessment of minimum inhibitory concentration, clustered regularly interspaced short palindromic repeats (CRISPR)-cas gene expression in standard strains, in vitro resistance development and transcriptome analysis of a cas9 deletion mutant and wild strains.

RESULTS

Increased expression of CRISPR-related genes was observed in standard strains. We also observed that Δcas9 mutant strain is more sensitive to antibiotics than its wild strain. Transcriptome analysis revealed that cas9 gene regulate several genes to promote antimicrobial resistance in C. jejuni.

CONCLUSION

CRISPR-cas system plays role in the enhancement of antimicrobial resistance in C. jejuni.

Neuroprotective Effects of Purple Sweet Potato Balinese Cultivar in Wistar Rats With Ischemic Stroke

BACKGROUND:

Purple sweet potato (Ipomoea Batatas L.) is one of the sources for anthocyanin, which promotes the health through antioxidant, anti-inflammatory, anti-cancer, neuroprotection, and anti-apoptosis activities. Oxidative stress has been shown to be the cause of apoptosis in ischemic stroke.

AIM:

The objective of this research was to delineate the pleiotropic effects of anthocyanin for neuroprotection during an acute stroke event.

METHODS:

Anthocyanin was extracted from Balinese cultivar of purple sweet potato and subsequently administered to rat models of induced ischemic stroke (labelled as treatment group), as well as a placebo (labelled as a control group). Several parameters were in turn evaluated, i.e. the activities of anti-apoptotic (Bcl-2) as well as pro-apoptotic (cytochrome c, caspase-3) molecules, and apoptosis rate. Bcl-2 levels were determined using the histochemical method, cytochrome c and caspase-3 via ELISA method, while apoptosis rate was measured by TdT-medicated Dutp-Nick End Labeling (TUNEL) assay.

RESULTS:

Bcl-2 expression demonstrated significantly higher Bcl-2 expression in the treatment compared with control group (median 31.2 vs. 1.1; p = 0.001). Accordingly, pro-apoptotic cytochrome c and caspase-3 levels were also found significantly lower in the treatment as opposed to control group (mean 4.17 vs. 8.06; p = 0.001; mean 3.81 vs. 8.02; p = 0.001). Ultimately, apoptosis rate was found markedly lower among treatment than control groups (mean 3.81 vs. control 21.97; p = 0.003).

CONCLUSION:

The results of this study indicated a significant neuroprotective effect of anthocyanin derived from Balinese cultivar of PSP. Anthocyanin was able to increase and reduce anti-apoptotic and pro-apoptotic protein levels, respectively, resulting in lesser cellular apoptotic rate when compared with placebo. The potential mechanism was thought mainly due to its anti-oxidant properties.

High-pressure carbon dioxide pneumoperitoneum induces oxidative stress and mitochondria-associated apoptotic pathway in rabbit kidneys with severe hydronephrosis

The primary aim of the present study was to investigate the potential effect of high‑pressure carbon dioxide (CO2) pneumoperitoneum on kidneys with severe hydronephrosis and to investigate the possible underlying mechanism. A total of 18 rabbits underwent a surgical procedure inducing severe hydronephrosis. Rabbits were then divided at random into three groups (n=6 each) and subjected to intraabdominal pressure of 0, 8 or 18 mmHg, respectively. CO2 inflation lasted for 90 min in the pneumoperitoneum groups. Oxidative stress was assessed by measurements of reactive oxygen species (ROS). Activation of apoptosis was analyzed by western blot analysis of B‑cell lymphoma 2 (Bcl‑2), Bcl‑2‑associated x protein (Bax), cytochrome c (Cyt c), caspase‑3 and caspase‑9 levels. In addition, TUNEL assay, hematoxylin and eosin (H&E) staining, measurement of mitochondrial membrane potential (MMP) and detection of changes to kidney ultramicrostructure were performed. In the 0 and 8 mmHg groups, all results were normal and similar. However, in the 18 mmHg group, the kidneys suffered oxidative damage and mitochondrial injuries, and increased ROS levels, lower MMP and mitochondrial vacuolization were observed. Furthermore, the mitochondrial/caspase‑dependent pathway of apoptosis was activated, as indicated by the apoptotic index, and the expression levels and translocation of Bax, Bcl‑2, Cyt c, caspase‑3 and caspase‑9. Therefore, it is concluded that high‑pressure CO2 pneumoperitoneum induces oxidative damage and apoptosis in rabbit kidneys with severe hydronephrosis, which is associated with the mitochondrial apoptotic pathway.

Monitoring alkaline transitions of yeast iso-1 cytochrome c at natural isotopic abundance using trimethyllysine as a native NMR probe

Spectral overlap makes it difficult to use NMR for mapping the conformational profile of heterogeneous conformational ensembles of macromolecules. Here, we apply a 1H-14N HSQC experiment to monitor the alkaline conformational transitions of yeast iso-1 cytochrome c (ycyt c) at natural isotopic abundance. Trimethylated Lys72 of ycyt c is selectively detected by a 1H-14N HSQC experiment, and used as a probe to trace conformational transitions of ycyt c under alkaline conditions. It was found that at least four different conformers of ycyt c coexisted under alkaline conditions. Besides the native structure, Lys73 or Lys79 coordinated conformers and a partially unfolded state with exposed heme were observed. These results indicate that the method is powerful at simplifying spectra of a trimethylated protein, which makes it possible to study complex conformational transitions of naturally extracted or chemically modified trimethylated protein at natural isotopic abundance.

Protective Effect of N-Acetylcysteine against Oxidative Stress Induced by Zearalenone via Mitochondrial Apoptosis Pathway in SIEC02 Cells

Zearalenone (ZEN), a nonsteroidal estrogen mycotoxin, is widely found in feed and foodstuffs. Intestinal cells may become the primary target of toxin attack after ingesting food containing ZEN. Porcine small intestinal epithelial (SIEC02) cells were selected to assess the effect of ZEN exposure on the intestine. Cells were exposed to ZEN (20 µg/mL) or pretreated with (81, 162, and 324 µg/mL) N-acetylcysteine (NAC) prior to ZEN treatment. Results indicated that the activities of glutathione peroxidase (Gpx) and glutathione reductase (GR) were reduced by ZEN, which induced reactive oxygen species (ROS) and malondialdehyde (MDA) production. Moreover, these activities increased apoptosis and mitochondrial membrane potential (ΔΨm), and regulated the messenger RNA (mRNA) expression of Bax, Bcl-2, caspase-3, caspase-9, and cytochrome c (cyto c). Additionally, NAC pretreatment reduced the oxidative damage and inhibited the apoptosis induced by ZEN. It can be concluded that ZEN-induced oxidative stress and damage may further induce mitochondrial apoptosis, and pretreatment of NAC can degrade this damage to some extent.

Inhibiting Succinate Dehydrogenase by Dimethyl Malonate Alleviates Brain Damage in a Rat Model of Cardiac Arrest

Brain damage is a leading cause of death in patients with cardiac arrest (CA). The accumulation of succinate during ischemia by succinate dehydrogenase (SDH) is an important mechanism of ischemia-reperfusion injury. It was unclear whether inhibiting the oxidation of accumulated succinate could also mitigate brain damage after CA. In this study, rats were subjected to a 6 min of CA, and cardiopulmonary resuscitation (CPR) was performed with administration of normal saline or dimethyl malonate (DMM, a competitive inhibitor of SDH). After the return of spontaneous circulation, neurological function of the rats was assessed by a tape removal test for 3 days. The rats were then sacrificed, and their brains were used to assess neuronal apoptosis by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Hippocampal tissues were used for Western blotting analysis and biochemical detection. In addition, hippocampal mitochondria during CA and CPR were isolated. The relative mitochondrial membrane potential (MMP) and cytochrome C in the cytosol were detected. Our results show that DMM promoted ROSC and neurological performance in rats after CA. The TUNEL assay showed that DMM reduced neuronal apoptosis. Western blotting analysis showed that DMM inhibited the activation of caspase-3 and enhanced the expression of HIF-1α. Moreover, DMM inhibited excessive hyperpolarization of MMP after CPR, and prevented the release of cytochrome C. Therefore, inhibiting SDH by DMM alleviated brain damage after CA, and the main mechanisms included inhibiting the excessive hyperpolarization of MMP, reducing the generation of mtROS and stabilizing the structure of HIF-1α.

Evaluation of renal injury caused by acute volume replacement with hydroxyethyl starch 130/0.4 or Ringer's lactate solution in pigs

This work aimed to evaluate the effects on renal tissue integrity after hydroxyethyl starch (HES) 130/0.4 and Ringer's lactate (RL) administration in pigs under general anesthesia after acute bleeding. A total of 30 mL/kg of blood were passively removed from the femoral artery in two groups of Large White pigs, under total intravenous anesthesia with propofol and remifentanil. After bleeding, Group 1 (n = 11) received RL solution (25 mL/kg) and Group 2 (n = 11) received HES 130/0.4 solution (20 mL/kg). Additionally, Group 3 (n = 6) was not submitted to bleeding or volume replacement. Pigs were euthanized and kidneys were processed for histopathological and immunohistochemical analyses. Minimal to moderate glomerular, tubular, and interstitial changes, as well as papillary necrosis, were observed in all experimental groups. Pre-apoptosis and apoptosis indicators were higher in pigs that received HES 130/0.4, indicating a higher renal insult. Both HES 130/0.4 and RL administration may cause renal injury, although renal injury may be more significant in pigs receiving HES 13/0.4. Results also suggest that total intravenous anesthesia with propofol and remifentanil may cause renal injury, and this effect can be dose related.

The K79G Mutation Reshapes the Heme Crevice and Alters Redox Properties of Cytochrome c

The two roles of cytochrome c (cyt c), in oxidative phosphorylation and apoptosis, critically depend on redox properties of its heme iron center. The K79G mutant has served as a parent protein for a series of mutants of yeast iso-1 cyt c. The mutation preserves the Met80 coordination to the heme iron, as found in WT* (K72A/C102S), and many spectroscopic properties of K79G and WT* are indistinguishable. The K79G mutation does not alter the global stability, fold, rate of Met80 dissociation, or thermodynamics of the alkaline transition (p K_a) of the protein. However, the reduction potential of the heme iron decreases; further, the p K_H of the trigger group and the rate of the Met-to-Lys ligand exchange associated with the alkaline transition decrease, suggesting changes in the environment of the heme. The rates of electron self-exchange and bimolecular electron transfer (ET) with positively charged inorganic complexes increase, as does the intrinsic peroxidase activity. Analysis of the reaction rates suggests that there is increased accessibility of the heme edge in K79G and supports the importance of the Lys79 site for bimolecular ET reactions of cyt c, including those with some of its native redox partners. Structural modeling rationalizes the observed effects to arise from changes in the volume of the heme pocket and solvent accessibility of the heme group. Kinetic and structural analyses of WT* characterize the properties of the heme crevice of this commonly employed reference variant. This study highlights the important role of Lys79 for defining functional redox properties of cyt c.

Mitochondrial bioenergetics and cardiolipin alterations in myocardial ischemia-reperfusion injury: implications for pharmacological cardioprotection

Mitochondrial dysfunction plays a central role in myocardial ischemia-reperfusion (I/R) injury. Increased reactive oxygen species production, impaired electron transport chain activity, aberrant mitochondrial dynamics, Ca²⁺ overload, and opening of the mitochondrial permeability transition pore have been proposed as major contributory factors to mitochondrial dysfunction during myocardial I/R injury. Cardiolipin (CL), a mitochondria-specific phospholipid, plays a pivotal role in multiple mitochondrial bioenergetic processes, including respiration and energy conversion, in mitochondrial morphology and dynamics as well as in several steps of the apoptotic process. Changes in CL levels, species composition, and degree of oxidation may have deleterious consequences for mitochondrial function with important implications in a variety of pathophysiological conditions, including myocardial I/R injury. In this review, we focus on the role played by CL alterations in mitochondrial dysfunction in myocardial I/R injury. Pharmacological strategies to prevent myocardial injury during I/R targeting mitochondrial CL are also examined.

Relating the multi-functionality of cytochrome c to membrane binding and structural conversion

Cytochrome c is known as an electron-carrying protein in the respiratory chain of mitochondria. Over the last 20 years, however, alternative functions of this very versatile protein have become the focus of research interests. Upon binding to anionic lipids such as cardiolipin, the protein acquires peroxidase activity. Multiple lines of evidence suggest that this requires a conformational change of the protein which involves partial unfolding of its tertiary structure. This review summarizes the current state of knowledge of how cytochrome c interacts with cardiolipin-containing surfaces and how this affects its structure and function. In this context, we delineate partially conflicting results regarding the affinity of cytochrome c binding to cardiolipin-containing liposomes of different size and its influence on the structure of the protein and the morphology of the membrane.

Vitamin D Receptor Is Necessary for Mitochondrial Function and Cell Health

Vitamin D receptor (VDR) mediates many genomic and non-genomic effects of vitamin D. Recently, the mitochondrial effects of vitamin D have been characterized in many cell types. In this article, we investigated the importance of VDR not only in mitochondrial activity and integrity but also in cell health. The silencing of the receptor in different healthy, non-transformed, and cancer cells initially decreased cell growth and modulated the cell cycle. We demonstrated that, in silenced cells, the increased respiratory activity was associated with elevated reactive oxygen species (ROS) production. In the long run, the absence of the receptor caused impairment of mitochondrial integrity and, finally, cell death. Our data reveal that VDR plays a central role in protecting cells from excessive respiration and production of ROS that leads to cell damage. Because we confirmed our observations in different models of both normal and cancer cells, we conclude that VDR is essential for the health of human tissues.

The transcriptional regulator CCCTC-binding factor limits oxidative stress in endothelial cells

The CCCTC-binding factor (CTCF) is a versatile transcriptional regulator required for embryogenesis, but its function in vascular development or in diseases with a vascular component is poorly understood. Here, we found that endothelial Ctcf is essential for mouse vascular development and limits accumulation of reactive oxygen species (ROS). Conditional knockout of Ctcf in endothelial progenitors and their descendants affected embryonic growth, and caused lethality at embryonic day 10.5 because of defective yolk sac and placental vascular development. Analysis of global gene expression revealed Frataxin (Fxn), the gene mutated in Friedreich's ataxia (FRDA), as the most strongly down-regulated gene in Ctcf-deficient placental endothelial cells. Moreover, in vitro reporter assays showed that Ctcf activates the Fxn promoter in endothelial cells. ROS are known to accumulate in the endothelium of FRDA patients. Importantly, Ctcf deficiency induced ROS-mediated DNA damage in endothelial cells in vitro, and in placental endothelium in vivo Taken together, our findings indicate that Ctcf promotes vascular development and limits oxidative stress in endothelial cells. These results reveal a function for Ctcf in vascular development, and suggest a potential mechanism for endothelial dysfunction in FRDA.

Raman detection and identification of normal and leukemic hematopoietic cells

The analysis of leukocytes of peripheral blood is a crucial step in hematologic exams commonly used for disease diagnosis and, typically, requires molecular labelling. In addition, only a detailed, laborious phenotypic analysis allows identifying the presence and stage of specific pathologies such as leukemia. Most of the biochemical information is lost in the routine blood tests. In the present study, we tackle 2 important issues of label-free biochemical identification and classification of leukocytes using Raman spectroscopy (RS). First, we demonstrate that leukocyte subpopulations of lymphocytes (B, T and NK cells), monocytes and granulocytes can be identified by the unsupervised statistical approach of principal component analysis and classified by linear discriminant analysis with approximately 99% of accuracy. Second, we apply the same procedure to identify and discriminate normal B cells and transformed MN60 lymphocyte leukemic cell lines. In addition, we demonstrate that RS can be efficiently used for monitoring the cell response to low-dose chemotherapy treatment, experimentally eliciting the sensitivity to a dose-dependent cell response, which is of fundamental importance to determine the efficacy of any treatment. These results largely expand established Raman-based research protocols for label-free analysis of white blood cells, leukemic cells and chemotherapy treatment follow-up.

Cytochrome b5 reductase is the component from neuronal synaptic plasma membrane vesicles that generates superoxide anion upon stimulation by cytochrome c

In this work, we measured the effect of cytochrome c on the NADH-dependent superoxide anion production by synaptic plasma membrane vesicles from rat brain. In these membranes, the cytochrome c stimulated NADH-dependent superoxide anion production was inhibited by antibodies against cytochrome b5 reductase linking the production to this enzyme. Measurement of the superoxide anion radical generated by purified recombinant soluble and membrane cytochrome b5 reductase corroborates the production of the radical by different enzyme isoforms. In the presence of cytochrome c, a burst of superoxide anion as well as the reduction of cytochrome c by cytochrome b5 reductase was measured. Complex formation between both proteins suggests that cytochrome b5 reductase is one of the major partners of cytochrome c upon its release from mitochondria to the cytosol during apoptosis. Superoxide anion production and cytochrome c reduction are the consequences of the stimulated NADH consumption by cytochrome b5 reductase upon complex formation with cytochrome c and suggest a major role of this enzyme as an anti-apoptotic protein during cell death.

Fibroblast-Specific β-Catenin Signaling Dictates the Outcome of AKI

AKI is a devastating condition with high morbidity and mortality. The pathologic features of AKI are characterized by tubular injury, inflammation, and vascular impairment. Whether fibroblasts in the renal interstitium have a role in the pathogenesis of AKI is unknown. In this study, we investigated the role of fibroblast-specific β-catenin signaling in dictating the outcome of AKI, using conditional knockout mice in which β-catenin was specifically ablated in fibroblasts (Gli1-β-cat-/-). After ischemia-reperfusion injury (IRI), Gli1-β-cat-/- mice had lower serum creatinine levels and less morphologic injury than Gli1-β-cat+/+ littermate controls. Moreover, we detected fewer apoptotic cells, as well as decreased cytochrome C release; reduced expression of Bax, FasL, and p53; and increased phosphorylation of Akt, in the Gli1-β-cat-/- kidneys. Gli1-β-cat-/- kidneys also exhibited upregulated expression of proliferating cell nuclear antigen and Ki-67, which are markers of cell proliferation. Furthermore, Gli1-β-cat-/- kidneys displayed suppressed NF-κB signaling and cytokine expression and reduced infiltration of inflammatory cells. Notably, loss of β-catenin in fibroblasts induced renal expression of hepatocyte growth factor (HGF) and augmented the tyrosine phosphorylation of c-met receptor after IRI. In vitro, treatment with Wnt ligands or ectopic expression of active β-catenin inhibited HGF mRNA and protein expression and repressed HGF promoter activity. Collectively, these results suggest that fibroblast-specific β-catenin signaling can control tubular injury and repair in AKI by modulating HGF expression. Our studies uncover a previously unrecognized role for interstitial fibroblasts in the pathogenesis of AKI.

Cyanidin-3-o-glucoside directly binds to ERα36 and inhibits EGFR-positive triple-negative breast cancer

Anthocyanins have been shown to inhibit the growth and metastatic potential of breast cancer (BC) cells. However, the effects of individual anthocyanins on triple-negative breast cancer (TNBC) have not yet been studied. In this study, we found that cyanidin-3-o-glucoside (Cy-3-glu) preferentially promotes the apoptosis of TNBC cells, which co-express the estrogen receptor alpha 36 (ERα36) and the epidermal growth factor receptor (EGFR). We demonstrated that Cy-3-glu directly binds to the ligand-binding domain (LBD) of ERα36, inhibits EGFR/AKT signaling, and promotes EGFR degradation. We also confirmed the therapeutic efficacy of Cy-3-glu on TNBC in the xenograft mouse model. Our data indicates that Cy-3-glu could be a novel preventive/therapeutic agent against the TNBC co-expressed ERα36/EGFR.

Functionally Active Membrane Proteins Incorporated in Mesostructured Silica Films

A versatile synthetic protocol is reported that allows high concentrations of functionally active membrane proteins to be incorporated in mesostructured silica materials. Judicious selections of solvent, surfactant, silica precursor species, and synthesis conditions enable membrane proteins to be stabilized in solution and during subsequent coassembly into silica-surfactant composites with nano- and mesoscale order. This was demonstrated by using a combination of nonionic ( n-dodecyl-β-d-maltoside or Pluronic P123), lipid-like (1,2-diheptanoyl- s n-glycero-3-phosphocholine), and perfluoro-octanoate surfactants under mild acidic conditions to coassemble the light-responsive transmembrane protein proteorhodopsin at concentrations up to 15 wt % into the hydrophobic regions of worm-like mesostructured silica materials in films. Small-angle X-ray scattering, electron paramagnetic resonance spectroscopy, and transient UV-visible spectroscopy analyses established that proteorhodopsin molecules in mesostructured silica films exhibited native-like function, as well as enhanced thermal stability compared to surfactant or lipid environments. The light absorbance properties and light-activated conformational changes of proteorhodopsin guests in mesostructured silica films are consistent with those associated with the native H+-pumping mechanism of these biomolecules. The synthetic protocol is expected to be general, as demonstrated also for the incorporation of functionally active cytochrome c, a peripheral membrane protein enzyme involved in electron transport, into mesostructured silica-cationic surfactant films.

One pot environmental friendly synthesis of gold nanoparticles using Punica Granatum Juice: A novel antioxidant agent for future dermatological and cosmetic applications

HYPOTHESIS

The interesting properties of Gold Nanoparticles (AuNPs) make them attractive for different application fields such as cosmetology, medicine and clinical nanotechnologies. In this work a fast, easy and eco-friendly method for the AuNPs synthesis is proposed by using the Punica Granatum Juice (PGJ) with potential dermatological and cosmetic applications. The AuNPs antioxidant activity, due to the presence of phenols from the juice, and their use as booster for improving the Sun Protection Factor (SPF) in commercial sunscreen formulations, are thus expounded.

EXPERIMENTS

By using appropriate amounts of PGJ and HAuCl₄, under mild work conditions, AuNPs with a mean size of 100 ± 40 nm are observed and carefully characterized. Solution pH, temperature, and volume were also changed for optimizing the AuNPs formation and features. The antioxidant activity was studied, by evaluating the AuNP ability of scavenging the radical 2,2-diphenyl-1-picrylhydrazylhydrate (DPPH). This finding was confirmed performing special experiments focused on the reaction between AuNPs and H₂O₂, by using suitable probes, such as 4-thiothymidine (S⁴TdR) and Cytochrome-c (Cyt-c). The SPF value was also calculated.

FINDINGS

The synthetized AuNPs showed a surface plasmon in visible range at 577 nm and resulted stable for long time in aqueous medium, also changing the pH values in the range 2-12. The studied antioxidant activity, confirmed also by performing special experiments with suitable probes, demonstrated the high performance of AuNPs. The AuNP photostability under sun irradiation is also shown. The calculated SPF values were in the range 3-18, related to AuNPs concentration in the range 1.80 × 10^-12-1.00 × 10^-11 M. The same AuNPs concentrations were used for cellular experiments. Indeed, since the AuNPs-PGJ mediated will be potentially introduced by dermal contact, dermal fibroblasts (Human Dermal Fibroblasts, HDF) and Human Microvascular Endothelial Cells (HMVEC) were used to evaluate the possible effects of these nanoparticles as a preliminary step. The results indicated that an AuNP concentrations in the range 1.80 × 10^-12-3.60 × 10^-12 M could be adopted since they do not appeared cyctotoxic.

A new insight into meat toughness of callipyge lamb loins - The relevance of anti-apoptotic systems to decreased proteolysis

The objective of this study was to determine associations of small heat shock proteins (sHSPs) in tenderness development of loins from callipyge and normal genotype lambs. Loins (M. longissimus lumborum) from sixteen lambs across four genotypes were collected throughout 9 days of postmortem aging. The loins from callipyge lambs had more intact desmin and troponin T throughout aging periods, as well as less μ-calpain autolysis and more calpastatin compared to loins from other genotypes (P < 0.05). Delayed onset of apoptosis was found in the callipyge loins indicated by less cytochrome c and more inactive procaspase-3 compared to normal lamb loins (P < 0.05). Less degraded HSP27 was also consistently found in the callipyge loins compared with loins from normal lambs (P < 0.001). The results found up-regulation of anti-apoptotic activities coincided with toughness in callipyge loins, which suggest apoptosis is likely involved in postmortem proteolysis and subsequent meat tenderization.

Silicon nanoparticles coated with an epitope-imprinted polymer for fluorometric determination of cytochrome c

The authors describe a composite consisting of silicon nanoparticles that were first coated with SiO₂ and then with a molecularly imprinted polymer (SiNP@SiO₂@MIP). The MIP was generated by dual epitope imprinting such that it can recognize cytochrome c (Cyt c). The MIP on the NPs was prepared from the functional monomer zinc(II) acrylate (ZnA), the crosslinker ethylene glycol dimethacrylate and the initiator 2,2'-azoisobutyronitrile. Dual epitope templates for Cyt c included (a) a C-terminal nonapeptide (AYLKKATNE), and (b) an N-terminal nonapeptide (GDVEKGKKI). The chelation between Zn(II) of ZnA and the amino groups or hydroxy groups of the template nonapeptides warrants good recognition and capture of Cyt c. The fluorescence originating from SiNPs has excitation/emission peaks at 360/480 nm and is quenched by Cyt c in the 0.50-40.0 μM concentration range. The correlation coefficient for the calibration plot of the imprinted NPs is 0.9937. The detection limit is 0.32 ± 0.01 μM, the precisions of six replicate detections at levels of 0.5, 20 and 40 μM Cyt c are 3.2, 2.7 and 2.8%, respectively, and the imprinting factor is 2.43. Compared to single epitope template imprinting, dual epitope imprinting results in improved selectivity. The imprinted nanoparticles can discriminate Cyt c even if one amino acid is mismatched. The method was applied to the determination of Cyt c in spiked diluted human serum and gave recoveries between 94.0 and 107.5%. Graphical Abstract A fluorescent material of the architecture silicon nanoparticle@SiO₂@molecularly imprinted polymer (SiNP@SiO₂@MIP) was fabricated by dual epitope imprinting and a metal-chelating method. The chelation between Zn(II) of the functional monomer zinc(II) acrylate and the amino groups or hydroxy groups of template warrants that the material recognizes and captures cytochrome c well, and this results in fluorescence quenching.

Nuclear cytochrome c - a mitochondrial visitor regulating damaged chromatin dynamics

Over the past decade, evidence has emerged suggesting a broader role for cytochrome c (Cyt c) in programmed cell death. Recently, we demonstrated the ability of Cyt c to inhibit the nucleosome assembly activity of histone chaperones SET/template-activating factor Iβ and NAP1-related protein during DNA damage in humans and plants respectively. Here, we hypothesise a dual concentration-dependent function for nuclear Cyt c in response to DNA damage. We propose that low levels of highly cytotoxic DNA lesions - such as double-strand breaks - induce nuclear translocation of Cyt c, leading to the attenuation of nucleosome assembly and, thereby, increasing the time available for DNA repair. If DNA damage persists or is exacerbated, the nuclear Cyt c concentration would exceed a given threshold, causing the haem protein to block DNA remodelling altogether.

Differentiation and cell density upregulate cytochrome c levels in megakaryoblastic cell lines: Implications for analysis of CYCS-associated thrombocytopenia

Mutations in the cytochrome c gene (CYCS) cause autosomal dominant thrombocytopenia by an unknown mechanism. While attempting to generate megakaryoblastic cell lines exogenously expressing cytochrome c variants, we discovered that endogenous cytochrome c expression increased both upon induction of differentiation with the phorbol ester phorbol 12-myristate 13-acetate (PMA), and as cell density increased. A concomitant increase in cytochrome c oxidase subunit II in response to PMA, but not cell higher cell density, suggests upregulation of the mitochondrial respiratory chain may be a specific feature of differentiation. These results highlight the likely importance of cytochrome c in both differentiating and proliferating cells, and illustrate the unsuitability of megakaryoblastic lines for modeling CYCS-associated thrombocytopenia.

Nitric oxide mediated inhibition of antigen presentation from DCs to CD4+ T cells in cancer and measurement of STAT1 nitration

Myeloid derived suppressor cells (MDSC) produce nitric oxide (NO) and inhibit dendritic cell (DC) immune responses in cancer. DCs present cancer cell antigens to CD4⁺ T cells through Jak-STAT signal transduction. In this study, NO donors (SNAP and DETA-NONOate) inhibited DC antigen presentation. As expected, MDSC isolated from peripheral blood mononuclear cells (PBMC) from cancer patients produced high NO levels. We hypothesized that NO producing MDSC in tumor-bearing hosts would inhibit DC antigen presentation. Antigen presentation from DCs to CD4⁺ T cells (T cell receptor transgenic OT-II) was measured via a [³H]-thymidine incorporation proliferation assay. MDSC from melanoma tumor models decreased the levels of proliferation more than pancreatic cancer derived MDSC. T cell proliferation was restored when MDSC were treated with inhibitors of inducible nitric oxide synthase (L-NAME and NCX-4016). A NO donor inhibited OT II T cell receptor recognition of OT II specific tetramers, thus serving as a direct measure of NO inhibition of antigen presentation. Our group has previously demonstrated that STAT1 nitration also mediates MDSC inhibitory effects on immune cells. Therefore, a novel liquid chromatography-tandem mass spectrometry assay demonstrated that nitration of the STAT1-Tyr701 occurs in PBMC derived from both pancreatic cancer and melanoma patients.

Heightened Dynamics of the Oxidized Y48H Variant of Human Cytochrome c Increases Its Peroxidatic Activity

Proteins performing multiple biochemical functions are called "moonlighting proteins" or extreme multifunctional (EMF) proteins. Mitochondrial cytochrome c is an EMF protein that binds multiple partner proteins to act as a signaling molecule, transfers electrons in the respiratory chain, and acts as a peroxidase in apoptosis. Mutations in the cytochrome c gene lead to the disease thrombocytopenia, which is accompanied by enhanced apoptotic activity. The Y48H variant arises from one such mutation and is found in the 40-57 Ω-loop, the lowest-unfolding free energy substructure of the cytochrome c fold. A 1.36 Å resolution X-ray structure of the Y48H variant reveals minimal structural changes compared to the wild-type structure, with the axial Met80 ligand coordinated to the heme iron. Despite this, the intrinsic peroxidase activity is enhanced, implying that a pentacoordinate heme state is more prevalent in the Y48H variant, corroborated through determination of a Met80 "off rate" of >125 s^-1 compared to a rate of ∼6 s^-1 for the wild-type protein. Heteronuclear nuclear magnetic resonance measurements with the oxidized Y48H variant reveal heightened dynamics in the 40-57 Ω-loop and the Met80-containing 71-85 Ω-loop relative to the wild-type protein, illustrating communication between these substructures. Placed into context with the G41S cytochrome c variant, also implicated in thrombocytopenia, a dynamic picture associated with this disease relative to cytochrome c is emerging whereby increasing dynamics in substructures of the cytochrome c fold serve to facilitate an increased population of the peroxidatic pentacoordinate heme state in the following order: wild type < G41S < Y48H.

Divergent roles of three cytochrome c in CTSB-modulating coelomocyte apoptosis in Apostichopus japonicus

Cytochrome c plays crucial roles in apoptosis and the immune response. We previously demonstrated that cathepsin B from Apostichopus japonicus (AjCTSB) induces coelomocyte apoptosis. However, the mechanistic explanation and the regulation of this process have not been investigated. In the present study, we identified three cytochrome c cDNAs from A. japonicus (designated Ajcytc1, Ajcytc-1, and Ajcytc-2) using expressed sequence tag- (EST) and RACE-based approaches. The deduced amino acid sequences of the three cytochrome isoforms contained conserved CXXCH motifs, which are involved in binding heme and maintaining proteolytic activity. Time course expression analysis in vitro and in vivo revealed that the three cytochrome isoforms were induced upon pathogen challenge and LPS exposure. More importantly, AjCTSB knockdown by siRNA dramatically increased mitochondrial membrane potential (ΔΨm) in a time-dependent manner based on JC-1 fluorescent probe staining. AjCTSB knockdown also resulted in decreased expression of these three cytochromes 24 h after siAjCTSB transfection. Functional analysis using isoform-specific siRNAs revealed that Ajcytc-1, but not Ajcytc1 or Ajcytc-2, is involved in coelomocyte apoptosis. Moreover, the transcript level of Ajcaspase-3, an apoptosis executioner, was also consistently down-regulated upon silencing of Ajcytc-1 but not Ajcytc1 or Ajcytc-2. Collectively, these results indicate that Ajcytc1, Ajcytc-1, and Ajcytc-2 play distinct roles in mediating the immune response to bacteria according to AjCTSB expression. Moreover, Ajcytc-1 could be released upon dissipation of the ΔΨm, which could further trigger coelomocyte apoptosis through the activation of Ajcaspase-3.

Helix structure of the double-stranded DNA for aptameric biosensing and imaging of cytochrome c

Here, a method is introduced for construction the aptameric biosensor for biosensing detection of cytochrome C (CYC) based on chain-shape structure of aptasensor by using highly dispersed silver nanoparticles (AgNPs) on acid-oxidized carbon nanotube (CNTs) substrate. The animated capture probe (ssDNA1) and CYC-aptamer (ssDNA2) was immobilized on AgNPs/CNTs surface by covalent amide bonds formed by the carboxyl groups on the nanotubes and the amino groups on the oligonucleotides and hybridization, respectively. In this protocol, the nucleic acids at both ends of the ssDNA1 were sequenced to be complementary (tailor-made ssDNA1). The helix structure of the double-stranded DNA was fabricated by hybridizing ssDNA2 with its complementary sequence (ssDNA1). CYC-aptamer could be forced to dissociate from the sensing interface after CYC triggered structure switching of the aptamer and ssDNA1 thus tend to form a chain-shape structure through the hybridization of the complementary sequences at both its ends. The proposed assay permitted to detect CYC in the linear range of 0.01-750 nM with a very low limit of detection (LOD) (1.66 pM). In addition, the specificity of this sensing system for the detection of CYC was also demonstrated by using albumin, fructose, myoglobin, and hemoglobin.

Role of adaptor protein p66Shc in renal pathologies

p66Shc is one of the three adaptor proteins encoded by the Shc1 gene, which are expressed in many organs, including the kidney. Recent studies shed new light on several key questions concerning the signaling mechanisms mediated by p66Shc. The central goal of this review article is to summarize recent findings on p66Shc and the role it plays in kidney physiology and pathology. This article provides a review of the various mechanisms whereby p66Shc has been shown to function within the kidney through a wide range of actions. The mitochondrial and cytoplasmic signaling of p66Shc, as it relates to production of reactive oxygen species (ROS) and renal pathologies, is further discussed.

Near-complete backbone resonance assignments of acid-denatured human cytochrome c in dimethylsulfoxide: a prelude to studying interactions with phospholipids

Human cytochrome c plays a central role in the mitochondrial electron transfer chain and in the intrinsic apoptosis pathway. Through the interaction with the phospholipid cardiolipin, cytochrome c triggers release of pro-apoptotic factors, including itself, from the mitochondrion into the cytosol of cells undergoing apoptosis. The cytochrome c/cardiolipin complex has been extensively studied through various spectroscopies, most recently with high-field solution and solid-state NMR spectroscopies, but there is no agreement between the various studies on key structural features of cytochrome c in its complex with cardiolipin. In the present study, we report backbone ¹H, ¹³C, ¹⁵N resonance assignments of acid-denatured human cytochrome c in the aprotic solvent dimethylsulfoxide. These have led to the assignment of a reference 2D ¹H-¹⁵N HSQC spectrum in which out of the 99 non-proline residues 87% of the backbone amides are assigned. These assignments are being used in an interrupted H/D exchange strategy to map the binding site of cardiolipin on human cytochrome c.