Apoptosis-Inducing Factor (AIF) in Physiology and Disease: The Tale of a Repented Natural Born Killer

Nobiletin Exhibits Neuroprotective Effects against Mitochondrial Complex I Inhibition via Regulating Apoptotic Signaling

Nobiletin, a polymethoxylated flavonoid found in citrus, has been studied because of its modulatory functions in cellular signaling cascades, and effects to prevent mitochondrial calcium overload and neuronal cell death. Particularly, we previously reported that nobiletin induced changes in the mitochondrial membrane potential through K⁺ channel regulation, suggesting that nobiletin might exert neuroprotective effects via regulating mitochondrial functions associated with the electron transport chain (ETC) system. This study investigated whether nobiletin regulated mitochondrial dysfunction mediated by ETC system downregulation by inhibiting complex I (CI) and complex III (CIII) in pure mitochondria and the cortical neurons of rats. The results showed that nobiletin significantly reduced mitochondrial reactive oxygen species (ROS) production, inhibited apoptotic signaling, enhanced ATP production and then restored neuronal viability under conditions of CI inhibition, but not CIII inhibition. These effects were attributed to the downregulation of translocation of apoptosis-induced factor (AIF), and the upregulation of CI activity and the expression of antioxidant enzymes such as Nrf2 and HO-1. Together with our previous study, these results indicate that the neuroprotective effects of nobiletin under mitochondrial dysfunction may be associated with its function to activate antioxidant signaling cascades. Our findings suggest the possibility that nobiletin has therapeutic potential in treating oxidative neurological and neurodegenerative diseases mediated by mitochondrial dysfunction.

TEGDMA (Triethylene Glycol Dimethacrylate) Induces Both Caspase-Dependent and Caspase-Independent Apoptotic Pathways in Pulp Cells

Monomers leached from resin-based composites (RBCs) may reach intrapulpal concentrations of the millimolar (mM) range, which could contribute to inflammation. The aim of this investigation was to assess the cytotoxicity of triethylene glycol dimethacrylate (TEGDMA) monomers on pulp cells as well as to identify molecular mechanisms leading to apoptosis. Pulp cells were harvested from molars extracted for orthodontic reasons and cultured through an explant method. To assess cytotoxicity, cells underwent a 5-day exposure to 0.75, 1.5, and 3 mM TEGDMA and were subject to cell counting and WST-1 staining. Based on the findings, cells were subsequently exposed to 0.1, 0.2, 0.75, 1.5, and 3 mM TEGDMA for 24 h to uncover the details of apoptosis. Changes in the production or cleavage of the apoptosis-specific proteins caspase-8, caspase-9, caspase-3, caspase-12, and Apoptosis-Inducing Factor (AIF) were measured by Western blot. The 5-day study showed concentration- and time-dependent cytotoxicity. Significant cell death was detected after 24 h with TEGDMA concentrations of 1.5 and 3 mM. One-day exposure to TEGDMA led to the activation of caspase-8, -9, -3, and -12 and an increased AIF production. Results suggest that relevant concentrations of TEGDMA monomers, leached from RBCs, induce apoptosis in pulp cells through both caspase-dependent as well as caspase-independent mechanisms. Endoplasmic reticulum stress and the activation of caspase-independent apoptotic pathways may be further mechanisms by which monomers induce apoptosis in pulp cells.

Alopecia in Harlequin mutant mice is associated with reduced AIF protein levels and expression of retroviral elements

We investigated the contribution of apoptosis-inducing factor (AIF), a key regulator of mitochondrial biogenesis, in supporting hair growth. We report that pelage abnormalities developed during hair follicle (HF) morphogenesis in Harlequin (Hq) mutant mice. Fragility of the hair cortex was associated with decreased expression of genes encoding structural hair proteins, though key transcriptional regulators of HF development were expressed at normal levels. Notably, Aifm1 (R200 del) knockin males and Aifm1(R200 del)/Hq females showed minor hair defects, despite substantially reduced AIF levels. Furthermore, we cloned the integrated ecotropic provirus of the Aifm1Hq allele. We found that its overexpression in wild-type keratinocyte cell lines led to down-regulation of HF-specific Krt84 and Krtap3-3 genes without altering Aifm1 or epidermal Krt5 expression. Together, our findings imply that pelage paucity in Hq mutant mice is mechanistically linked to severe AIF deficiency and is associated with the expression of retroviral elements that might potentially influence the transcriptional regulation of structural hair proteins.

Long non-coding RNA MALAT1 plays a protective role in bronchopulmonary dysplasia via the inhibition of apoptosis and interaction with the Keap1/Nrf2 signal pathway

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a common respiratory disease in premature infants and is characterized by alveolar and pulmonary vascular dysplasia. Long-term oxygen exposure can cause BPD in preterm infants. Numerous studies have shown that long non-coding ribonucleic acid (lncRNA) is involved in the process of biological metabolism; however, its role in the development of BPD is unclear. Apoptosis-induced factor (AIF) is a key component involved in apoptosis. The Kelch-like ECH-associated protein 1/nuclear factor erythroid-2-related factor 2 (Keap1/Nrf2) signaling pathway is a body-derived antioxidant signaling pathway.

METHODS

In this study, the relative expression of metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), AIF, Keap1, and Nrf2 was detected by real-time polymerase chain reaction (PCR). Also, the apoptosis of A549 cells was detected by flow cytometry.

RESULTS

The results showed that, compared to the control group, the expression of MALAT1 increased significantly, and AIF decreased substantially in BPD premature infants. In the A549 hyperoxic lung injury model, compared with the air group, the expression of MALAT1 in the hyperoxia group decreased markedly, while the expression of Keap1 and Nrf2 increased considerably. Furthermore, compared with the control plasmid transfection air group (NC group), the expression of Keap1 and Nrf2 increased significantly in the small interfering RNA (siRNA) group.

CONCLUSIONS

These results indicate that MALAT1 can play a protective role in BPD via the reduction of apoptosis and anti-oxidation, offering clinicians a new way to prevent and treat BPD.

Role of apoptosis-inducing factor in perinatal hypoxic-ischemic brain injury

Perinatal complications, such as asphyxia, can cause brain injuries that are often associated with subsequent neurological deficits, such as cerebral palsy or mental retardation. The mechanisms of perinatal brain injury are not fully understood, but mitochondria play a prominent role not only due to their central function in metabolism but also because many proteins with apoptosis-related functions are located in the mitochondrion. Among these proteins, apoptosis-inducing factor has already been shown to be an important factor involved in neuronal cell death upon hypoxia-ischemia, but a better understanding of the mechanisms behind these processes is required for the development of more effective treatments during the early stages of perinatal brain injury. In this review, we focus on the molecular mechanisms of hypoxic-ischemic encephalopathy, specifically on the importance of apoptosis-inducing factor. The relevance of apoptosis-inducing factor is based not only because it participates in the caspase-independent apoptotic pathway but also because it plays a crucial role in mitochondrial energetic functionality, especially with regard to the maintenance of electron transport during oxidative phosphorylation and in oxidative stress, acting as a free radical scavenger. We also discuss all the different apoptosis-inducing factor isoforms discovered, focusing especially on apoptosis-inducing factor 2, which is only expressed in the brain and the functions of which are starting now to be clarified. Finally, we summarized the interaction of apoptosis-inducing factor with several proteins that are crucial for both apoptosis-inducing factor functions (pro-survival and pro-apoptotic) and that are highly important in order to develop promising therapeutic targets for improving outcomes after perinatal brain injury.

The 89-kDa PARP1 cleavage fragment serves as a cytoplasmic PAR carrier to induce AIF-mediated apoptosis

Poly(ADP-ribose) polymerase 1 (PARP1) is a nuclear protein that is activated by binding to DNA lesions and catalyzes poly(ADP-ribosyl)ation of nuclear acceptor proteins, including PARP1 itself, to recruit DNA repair machinery to DNA lesions. When excessive DNA damage occurs, poly(ADP-ribose) (PAR) produced by PARP1 is translocated to the cytoplasm, changing the activity and localization of cytoplasmic proteins, e.g., apoptosis-inducing factor (AIF), hexokinase, and resulting in cell death. This cascade, termed parthanatos, is a caspase-independent programmed cell death distinct from necrosis and apoptosis. In contrast, PARP1 is a substrate of activated caspases 3 and 7 in caspase-dependent apoptosis. Once cleaved, PARP1 loses its activity, thereby suppressing DNA repair. Caspase cleavage of PARP1 occurs within a nuclear localization signal near the DNA-binding domain, resulting in the formation of 24-kDa and 89-kDa fragments. In the present study, we found that caspase activation by staurosporine- and actinomycin D-induced PARP1 autopoly(ADP-ribosyl)ation and fragmentation, generating poly(ADP-ribosyl)ated 89-kDa and 24-kDa PARP1 fragments. The 89-kDa PARP1 fragments with covalently attached PAR polymers were translocated to the cytoplasm, whereas 24-kDa fragments remained associated with DNA lesions. In the cytoplasm, AIF binding to PAR attached to the 89-kDa PARP1 fragment facilitated its translocation to the nucleus. Thus, the 89-kDa PARP1 fragment is a PAR carrier to the cytoplasm, inducing AIF release from mitochondria. Elucidation of the caspase-mediated interaction between apoptosis and parthanatos pathways extend the current knowledge on mechanisms underlying programmed cell death and may lead to new therapeutic targets.

Exercise Training and Neurodegeneration in Mitochondrial Disorders: Insights From the Harlequin Mouse

Aim

Cerebellar neurodegeneration is a main phenotypic manifestation of mitochondrial disorders caused by apoptosis-inducing factor (AIF) deficiency. We assessed the effects of an exercise training intervention at the cerebellum and brain level in a mouse model (Harlequin, Hq) of AIF deficiency.

Methods

Male wild-type (WT) and Hq mice were assigned to an exercise (Ex) or control (sedentary [Sed]) group (n = 10-12/group). The intervention (aerobic and resistance exercises) was initiated upon the first symptoms of ataxia in Hq mice (∼3 months on average) and lasted 8 weeks. Histological and biochemical analyses of the cerebellum were performed at the end of the training program to assess indicators of mitochondrial deficiency, neuronal death, oxidative stress and neuroinflammation. In brain homogenates analysis of enzyme activities and levels of the oxidative phosphorylation system, oxidative stress and neuroinflammation were performed.

Results

The mean age of the mice at the end of the intervention period did not differ between groups: 5.2 ± 0.2 (WT-Sed), 5.2 ± 0.1 (WT-Ex), 5.3 ± 0.1 (Hq-Sed), and 5.3 ± 0.1 months (Hq-Ex) (p = 0.489). A significant group effect was found for most variables indicating cerebellar dysfunction in Hq mice compared with WT mice irrespective of training status. However, exercise intervention did not counteract the negative effects of the disease at the cerebellum level (i.e., no differences for Hq-Ex vs. Hq-Sed). On the contrary, in brain, the activity of complex V was higher in both Hq mice groups in comparison with WT animals (p < 0.001), and post hoc analysis also revealed differences between sedentary and trained Hq mice.

Conclusion

A combined training program initiated when neurological symptoms and neuron death are already apparent is unlikely to promote neuroprotection in the cerebellum of Hq model of mitochondrial disorders, but it induces higher complex V activity in the brain.

A Proteomics Signature of Mild Hypospadias: A Pilot Study

Background and Objective: Mild hypospadias is a birth congenital condition characterized by the relocation of the male urethral meatus from its typical anatomical position near the tip of the glans penis, to a lower ventral position up to the brim of the glans corona, which can also be accompanied by foreskin ventral deficiency. For the most part, a limited number of cases have known etiology. We have followed a high-throughput proteomics approach to study the proteome in mild hypospadias patients. Methods: Foreskin samples from patients with mild hypospadias were collected during urethroplasty, while control samples were collected during elective circumcision (n = 5/group). A high-throughput, quantitative proteomics approach based on multiplexed peptide stable isotope labeling (SIL) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis was used to ascertain protein abundance changes in hypospadias patients when compared to control samples. Results: A total of 4,815 proteins were quantitated (2,522 with at least two unique peptides). One hundred and thirty-three proteins from patients with mild hypospadias showed significant abundance changes with respect to control samples, where 38 proteins were increased, and 95 proteins were decreased. Unbiased functional biological analysis revealed that both mitochondrial energy production and apoptotic signaling pathways were enriched in mild hypospadias. Conclusions: This first comprehensive proteomics characterization of mild hypospadias shows molecular changes associated with essential cellular processes related to energy production and apoptosis. Further evaluation of the proteome may expand the search of novel candidates in the etiology of mild hypospadias and could also lead to the identification of biomarkers for this congenital urogenital condition.

Ferula L. Plant Extracts and Dose-Dependent Activity of Natural Sesquiterpene Ferutinin: From Antioxidant Potential to Cytotoxic Effects

The employment studies of natural extracts in the prevention and treatment of several diseases highlighted the role of different species of genus Ferula L., belonging to the Apiaceae family, dicotyledonous plants present in many temperate zones of our planet. Ferula communis L. is the main source of sesquiterpene ferutinin, a bioactive compound studied both in vitro and in vivo, because of different effects, such as phytoestrogenic, antioxidant, anti-inflammatory, but also antiproliferative and cytotoxic activity, performed in a dose-dependent and cell-dependent way. The present review will focus on the molecular mechanisms involved in the different activities of Ferutinin, starting from its antioxidant potential at low doses until its ionophoric property and the subsequent mitochondrial dysfunction induced through administration of high doses, which represent the key point of its anticancer action. Furthermore, we will summarize the data acquired from some experimental studies on different cell types and on several diseases. The results obtained showed an important antioxidant and phytoestrogenic regulation with lack of typical side effects related to estrogenic therapy. The preferential cell death induction for tumor cell lines suggests that ferutinin may have anti-neoplastic properties, and may be used as an antiproliferative and cytotoxic agent in an estrogen dependent and independent manner. Nevertheless, more data are needed to clearly understand the effect of ferutinin in animals before using it as a phytoestrogen or anticancer drug.

Skeletal Phenotypes Due to Abnormalities in Mitochondrial Protein Homeostasis and Import

Mitochondrial disease represents a collection of rare genetic disorders caused by mitochondrial dysfunction. These disorders can be quite complex and heterogeneous, and it is recognized that mitochondrial disease can affect any tissue at any age. The reasons for this variability are not well understood. In this review, we develop and expand a subset of mitochondrial diseases including predominantly skeletal phenotypes. Understanding how impairment ofdiverse mitochondrial functions leads to a skeletal phenotype will help diagnose and treat patients with mitochondrial disease and provide additional insight into the growing list of human pathologies associated with mitochondrial dysfunction. The underlying disease genes encode factors involved in various aspects of mitochondrial protein homeostasis, including proteases and chaperones, mitochondrial protein import machinery, mediators of inner mitochondrial membrane lipid homeostasis, and aminoacylation of mitochondrial tRNAs required for translation. We further discuss a complex of frequently associated phenotypes (short stature, cataracts, and cardiomyopathy) potentially explained by alterations to steroidogenesis, a process regulated by mitochondria. Together, these observations provide novel insight into the consequences of impaired mitochondrial protein homeostasis.

The protective role of corilagin on renal calcium oxalate crystal-induced oxidative stress, inflammatory response, and apoptosis via PPAR-γ and PI3K/Akt pathway in rats

Kidney stones, also known as calcium oxalate (CaOx) nephrolithiasis, are often asymptomatic, leading to kidney injury and renal failure complications. Corilagin is a gallotannin found in various plants and is known to elicit various biological activities. The present study aimed to elucidate the renoprotective effect of corilagin against the rats' renal stones deposition. The rats were induced for nephrolithiasis (CaOx deposition) using 0.75% ethylene glycol in their drinking water. Then, they were treated with corilagin at 50 and 100 mg/kg/day for 4 weeks. At the end of the experimental period, the rats were killed; blood and renal tissues were collected for various histological, biochemical, and gene expression analyses. The results demonstrated that the rats had renal calculi displaying a significant increase in serum creatinine (59.39 μmol/L) and blood urea nitrogen (19.03 mmol/L) levels compared with controls. Moreover, the malondialdehyde (13.29 nmol/mg) level was found to increase with a profound reduction in antioxidants' activities with upregulated inflammatory cytokines. In contrast, the RT-PCR and immunohistochemistry analysis demonstrated a substantial reduction in cell survival markers PPAR-γ and PI3K/Akt with an apparent increase in apoptosis markers genes expressions in rats suffering from renal stones. Thus, the present study results suggest that corilagin could suppress renal CaOx crystal-induced oxidative stress, inflammatory response, and apoptosis via PPAR-γ and PI3K/Akt-mediated pathway.

Peptide Fibrillar Assemblies Exhibit Membranolytic Effects and Antimetastatic Activity on Lung Cancer Cells

Cancer metastasis is a central oncology concern that worsens patient conditions and increases mortality in a short period of time. During metastatic events, mitochondria undergo specific physiological alterations that have emerged as notable therapeutic targets to counter cancer progression. In this study, we use drug-free, cationic peptide fibrillar assemblies (PFAs) formed by poly(L-Lysine)-block-poly(L-Threonine) (Lys-b-Thr) to target mitochondria. These PFAs interact with cellular and mitochondrial membranes via electrostatic interactions, resulting in membranolysis. Charge repulsion and hydrogen-bonding interactions exerted by Lys and Thr segments dictate the packing of the peptides and enable the PFAs to display enhanced membranolytic activity toward cancer cells. Cytochrome c (cyt c), endonuclease G, and apoptosis-inducing factor were released from mitochondria after treatment of lung cancer cells, subsequently inducing caspase-dependent and caspase-independent apoptotic pathways. A metastatic xenograft mouse model was used to show how the PFAs significantly suppressed lung metastasis and inhibited tumor growth, while avoiding significant body weight loss and mortality. Antimetastatic activities of PFAs are also demonstrated by in vitro inhibition of lung cancer cell migration and clonogenesis. Our results imply that the cationic PFAs achieved the intended and targeted mitochondrial damage, providing an efficient antimetastatic therapy.

Hesperetin Promotes Cisplatin-Induced Apoptosis of Gastric Cancer In Vitro and In Vivo by Upregulating PTEN Expression

As one of the most common malignant gastrointestinal tumors, gastric cancer (GC) has a high incidence and poor prognosis. Cisplatin (DDP) is often used as chemotherapy for advanced GC; however, the high incidence of drug resistance remains a problem. The use of several anti-tumor drugs as combined chemotherapy is an effective strategy. Hesperetin has anti-tumor ability via its pro-apoptotic effect on various human cancers, both in vitro and in vivo, with no significant toxicity. However, a combination of DDP and hesperetin in GC has not been reported. The present study aimed to investigate the in vitro and in vivo chemosensitization effect and mechanism of hesperetin-augmented DDP-induced apoptosis of GC. The proliferation of GC ty -60cells was inhibited significantly in a time and dose-dependent manner by combined treatment of DDP with hesperetin. Hesperetin markedly increased DDP-induced apoptosis of GC cell lines. In a xenograft tumor mouse model, markedly better tumor suppression was observed after treatment with DDP plus hesperetin compared with that of either agent alone. Additionally, the combination of DDP and hesperetin remarkably increased the expression levels of phosphatase and tensin homolog (PTEN) and Cytochrome C (Cyt C), and significantly decreased the levels of phosphorylated protein kinase B (p-AKT) and CyclinD1. DDP and hesperetin also induced significant increases in apoptosis inducing factor (AIF), BCL2 associated X, apoptosis regulator (BAX), cleaved caspase-9, and cleaved caspase-3, and decreased B-cell lymphoma 2 (BCL2), caspase-9, and caspase-3 levels. Thus, we demonstrated that hesperetin could inhibit the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/AKT signaling pathway and induce the mitochondrial pathway via upregulating PTEN expression, thereby significantly enhancing DDP’s anti-tumor effect on GC. Hesperetin is a potential chemotherapeutic agent for GC and merits further clinical investigation.

Apoptosis inducing factor and mitochondrial NADH dehydrogenases: redox-controlled gear boxes to switch between mitochondrial biogenesis and cell death

The mitochondrial complex I serves as entry point for NADH into the electron transport chain. In animals, fungi and plants, additional NADH dehydrogenases carry out the same electron transfer reaction, however they do not pump protons. The apoptosis inducing factor (AIF, AIFM1 in humans) is a famous member of this group as it was the first pro-apoptotic protein identified that can induce caspase-independent cell death. Recent studies on AIFM1 and the NADH dehydrogenase Nde1 of baker's yeast revealed two independent and experimentally separable activities of this class of enzymes: On the one hand, these proteins promote the functionality of mitochondrial respiration in different ways: They channel electrons into the respiratory chain and, at least in animals, promote the import of Mia40 (named MIA40 or CHCHD4 in humans) and the assembly of complex I. On the other hand, they can give rise to pro-apoptotic fragments that are released from the mitochondria to trigger cell death. Here we propose that AIFM1 and Nde1 serve as conserved redox switches which measure metabolic conditions on the mitochondrial surface and translate it into a binary life/death decision. This function is conserved among eukaryotic cells and apparently used to purge metabolically compromised cells from populations.

Mesenchymal stem cell‑derived extracellular vesicles prevent neural stem cell hypoxia injury via promoting miR‑210‑3p expression

Neural stem cells (NSCs) have the potential to give rise to offspring cells and hypoxic injury can impair the function of NSCs. The present study investigated the effects of mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) on NSC injury, as well as the underlying mechanisms. MSC-EVs were isolated and identified via morphological and particle size analysis. Cobalt chloride was used to establish a hypoxic injury model in NSCs. Terminal deoxynucleotidyl transferase dUTP nick end labeling assay was conducted to detect apoptosis. Reverse transcription-quantitative PCR was performed to detect the expression levels of miR-210-3p, and western blotting was used to detect the expression levels of apoptosis-inducing factor (AIF) and Bcl-2 19 kDa interacting protein (BNIP3). Compared with the control group, NSC apoptosis, and the expression of miR-210-3p, AIF and BNIP3 were significantly higher in the cobalt chloride-induced hypoxia group. By contrast, treatment with MSC-EVs further increased miR-210-3p expression levels, but reduced NSC apoptosis and the expression levels of AIF and BNIP3 compared with the model group (P<0.05). In addition, miR-210-3p inhibitor reduced miR-210-3p expression, but promoted hypoxia-induced apoptosis and the expression levels of AIF and BNIP3 compared with the model group (P<0.05). Collectively, the results suggested that MSC-EVs prevented NSC hypoxia injury by promoting miR-210-3p expression, which might reduce AIF and BNIP3 expression levels and NSC apoptosis.

MicroRNA Expression Profiling of Bone Marrow-Derived Proangiogenic Cells (PACs) in a Mouse Model of Hindlimb Ischemia: Modulation by Classical Cardiovascular Risk Factors

Background

Classical cardiovascular risk factors (CRFs) are associated with impaired angiogenic activities of bone marrow–derived proangiogenic cells (PACs) related to peripheral artery diseases (PADs) and ischemia-induced neovascularization. MicroRNAs (miRs) are key regulators of gene expression, and they are involved in the modulation of PAC function and PAC paracrine activity. However, the effects of CRFs on the modulation of miR expression in PACs are unknown.

Aims and Methods

We used a model of hindlimb ischemia and next-generation sequencing to perform a complete profiling of miRs in PACs isolated from the bone marrow of mice subjected to three models of CRFs: aging, smoking (SMK) and hypercholesterolemia (HC).

Results

Approximately 570 miRs were detected in PACs in the different CRF models. When excluding miRs with a very low expression level (<100 RPM), 40 to 61 miRs were found to be significantly modulated by aging, SMK, or HC. In each CRF condition, we identified downregulated proangiogenic miRs and upregulated antiangiogenic miRs that could contribute to explain PAC dysfunction. Interestingly, several miRs were similarly downregulated (e.g., miR-542-3p, miR-29) or upregulated (e.g., miR-501, miR-92a) in all CRF conditions. In silico approaches including Kyoto Encyclopedia of Genes and Genomes and cluster dendogram analyses identified predictive effects of these miRs on pathways having key roles in the modulation of angiogenesis and PAC function, including vascular endothelial growth factor signaling, extracellular matrix remodeling, PI3K/AKT/MAPK signaling, transforming growth factor beta (TGFb) pathway, p53, and cell cycle progression.

Conclusion

This study describes for the first time the effects of CRFs on the modulation of miR profile in PACs related to PAD and ischemia-induced neovascularization. We found that several angiogenesis-modulating miRs are similarly altered in different CRF conditions. Our findings constitute a solid framework for the identification of miRs that could be targeted in PACs in order to improve their angiogenic function and for the future development of novel therapies to improve neovascularization and reduce tissue damage in patients with severe PAD.

Oxidation of apoptosis-inducing factor (AIF) to disulfide-linked conjugates

Apoptosis-inducing factor (AIF) is a flavoprotein and essential partner of the CHCHD4 redox protein during the mitochondrial intermembrane space import machinery. Mammalian AIF has three cysteine residues, which have received little attention. Previous reports have evidenced a redox interaction between AIF and thioredoxin 1 (Trx1), particularly after oxidant conditions. Therefore, we asked whether the cysteine residues of the human AIF could be oxidized. Our data showed that endogenous AIF could be oxidized to disulfide-linked conjugates (DLC). Overexpressed WT AIF in HEK293T cells, as well as recombinant WT AIF, formed DLC. Expression of C256S, C317S or C441S AIF mutants severely inhibited DLC formation in cells exposed to oxidants. In vitro, DLC formation was completely precluded with C256S and C441S AIF mutants and partially inhibited with the C317S mutant. DLC was shown to enhance cellular susceptibility to apoptosis induced by staurosporine, likely by preventing AIF to maintain mitochondrial oxidative phosphorylation. Cells with decreased expression of Trx1 produced more AIF DLC than those with normal Trx1 levels, and in vitro, Trx1 was able to decrease the amount of AIF DLC. Finally, confocal analysis, as well as immunoblotting of mitochondrial fraction, indicated that a fraction of Trx1 is present in mitochondria. Overall, these data provide evidence that all three cysteine residues of AIF can be oxidized to DLC, which can be disrupted by mitochondrial Trx1.

Quantitative proteomics analysis of young and elderly skin with DIA mass spectrometry reveals new skin aging-related proteins

Skin aging is a specific manifestation of the physiological aging process that occurs in virtually all organisms. In this study, we used data independent acquisition mass spectrometry to perform a comparative analysis of protein expression in volar forearm skin samples from of 20 healthy young and elderly Chinese individuals. Our quantitative proteomic analysis identified a total of 95 differentially expressed proteins (DEPs) in aged skin compared to young skin. Enrichment analyses of these DEPs (57 upregulated and 38 downregulated proteins) based on the GO, KEGG, and KOG databases revealed functional clusters associated with immunity and inflammation, oxidative stress, biosynthesis and metabolism, proteases, cell proliferation, cell differentiation, and apoptosis. We also found that GAPDH, which was downregulated in aged skin samples, was the top hub gene in a protein-protein interaction network analysis. Some of the DEPs identified herein had been previously correlated with aging of the skin and other organs, while others may represent novel age-related entities. Our non-invasive proteomics analysis of human epidermal proteins may guide future research on skin aging to help develop treatments for age-related skin conditions and rejuvenation.

Cell cycle arrest and apoptosis are not dependent on p53 prior to p53-dependent embryonic stem cell differentiation

Previous efforts to determine whether or not the transcription factor and tumor suppressor protein p53 is required for DNA damage-induced apoptosis in pluripotent embryonic stem cells (ESCs) produced contradictory conclusions. To resolve this issue, p53+/+ and p53-/- ESCs derived by two different methods were used to quantify time-dependent changes in nuclear DNA content; annexin-V binding; cell permeabilization; and protein expression, modification, and localization. The results revealed that doxorubicin (Adriamycin [ADR]) concentrations 10 to 40 times less than commonly used in previous studies induced the DNA damage-dependent G2-checkpoint and completed apoptosis within the same time frame, regardless of the presence or absence of p53, p21, and PUMA. Increased ADR concentrations delayed initiation of apoptosis in p53-/- ESCs, but the rates of apoptosis remained equivalent. Similar results were obtained by inducing apoptosis with either staurosporine inhibition of kinase activities or WX8 disruption of lysosome homeostasis. Differentiation of ESCs by LIF deprivation revealed p53-dependent formation of haploid cells, increased genomic stability, and suppression of the G2-checkpoint. Minimal induction of DNA damage now resulted in p53-facilitated apoptosis, but regulation of pluripotent gene expression remained p53-independent. Primary embryonic fibroblasts underwent p53-dependent total cell cycle arrest (a prelude to cell senescence), and p53-independent apoptosis occurred in the presence of 10-fold higher levels of ADR, consistent with previous studies. Taken together, these results reveal that the multiple roles of p53 in cell cycle regulation and apoptosis are first acquired during pluripotent stem cell differentiation.

Riboflavin Deficiency-Implications for General Human Health and Inborn Errors of Metabolism

As an essential vitamin, the role of riboflavin in human diet and health is increasingly being highlighted. Insufficient dietary intake of riboflavin is often reported in nutritional surveys and population studies, even in non-developing countries with abundant sources of riboflavin-rich dietary products. A latent subclinical riboflavin deficiency can result in a significant clinical phenotype when combined with inborn genetic disturbances or environmental and physiological factors like infections, exercise, diet, aging and pregnancy. Riboflavin, and more importantly its derivatives, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), play a crucial role in essential cellular processes including mitochondrial energy metabolism, stress responses, vitamin and cofactor biogenesis, where they function as cofactors to ensure the catalytic activity and folding/stability of flavoenzymes. Numerous inborn errors of flavin metabolism and flavoenzyme function have been described, and supplementation with riboflavin has in many cases been shown to be lifesaving or to mitigate symptoms. This review discusses the environmental, physiological and genetic factors that affect cellular riboflavin status. We describe the crucial role of riboflavin for general human health, and the clear benefits of riboflavin treatment in patients with inborn errors of metabolism.

The nuclear envelope: target and mediator of the apoptotic process

Apoptosis is characterized by the destruction of essential cell organelles, including the cell nucleus. The nuclear envelope (NE) separates the nuclear interior from the cytosol. During apoptosis, the apoptotic machinery, in particular caspases, increases NE permeability by cleaving its proteins, such as those of the nuclear pore complex (NPC) and the nuclear lamina. This in turns leads to passive diffusion of cytosolic apoptogenic proteins, such as caspases and nucleases, through NPCs into the nucleus and the subsequent breakdown of the NE and destruction of the nucleus. However, NE leakiness at early stages of the apoptotic process can also occur in a caspase-independent manner, where Bax, by a non-canonical action, promotes transient and repetitive localized generation and subsequent rupture of nuclear protein-filled nuclear bubbles. This NE rupture leads to discharge of apoptogenic nuclear proteins from the nucleus to the cytosol, a process that can contribute to the death process. Therefore, the NE may play a role as mediator of cell death at early stages of apoptosis. The NE can also serve as a platform for assembly of complexes that regulate the death process. Thus, the NE should be viewed as both a mediator of the cell death process and a target.

Increased Protein S-Glutathionylation in Leber's Hereditary Optic Neuropathy (LHON)

Leber’s hereditary optic neuropathy (LHON, MIM#535000) is the most common form of inherited optic neuropathies and mitochondrial DNA-related diseases. The pathogenicity of mutations in genes encoding components of mitochondrial Complex I is well established, but the underlying pathomechanisms of the disease are still unclear. Hypothesizing that oxidative stress related to Complex I deficiency may increase protein S-glutathionylation, we investigated the proteome-wide S-glutathionylation profiles in LHON (n = 11) and control (n = 7) fibroblasts, using the GluICAT platform that we recently developed. Glutathionylation was also studied in healthy fibroblasts (n = 6) after experimental Complex I inhibition. The significantly increased reactive oxygen species (ROS) production in the LHON group by Complex I was shown experimentally. Among the 540 proteins which were globally identified as glutathionylated, 79 showed a significantly increased glutathionylation (p < 0.05) in LHON and 94 in Complex I-inhibited fibroblasts. Approximately 42% (33/79) of the altered proteins were shared by the two groups, suggesting that Complex I deficiency was the main cause of increased glutathionylation. Among the 79 affected proteins in LHON fibroblasts, 23% (18/79) were involved in energetic metabolism, 31% (24/79) exhibited catalytic activity, 73% (58/79) showed various non-mitochondrial localizations, and 38% (30/79) affected the cell protein quality control. Integrated proteo-metabolomic analysis using our previous metabolomic study of LHON fibroblasts also revealed similar alterations of protein metabolism and, in particular, of aminoacyl-tRNA synthetases. S-glutathionylation is mainly known to be responsible for protein loss of function, and molecular dynamics simulations and 3D structure predictions confirmed such deleterious impacts on adenine nucleotide translocator 2 (ANT2), by weakening its affinity to ATP/ADP. Our study reveals a broad impact throughout the cell of Complex I-related LHON pathogenesis, involving a generalized protein stress response, and provides a therapeutic rationale for targeting S-glutathionylation by antioxidative strategies.

Inhibiting the interaction between apoptosis-inducing factor and cyclophilin A prevents brain injury in neonatal mice after hypoxia-ischemia

The interaction between apoptosis-inducing factor (AIF) and cyclophilin A (CypA) has been shown to contribute to caspase-independent apoptosis. Blocking the AIF/CypA interaction protects against glutamate-induced neuronal cell death in vitro, and the purpose of this study was to determine the in vivo effect of an AIF/CypA interaction blocking peptide (AIF(370-394)-TAT) on neonatal mouse brain injury after hypoxia-ischemia (HI). The pups were treated with AIF (370-394)-TAT peptide intranasally prior to HI. Brain injury was significantly reduced at 72 h after HI in the AIF(370-394)-TAT peptide treatment group compared to vehicle-only treatment for both the gray matter and the subcortical white matter, and the neuroprotection was more pronounced in males than in females. Neuronal cell death was evaluated in males at 8 h and 24 h post-HI, and it was decreased significantly in the CA1 region of the hippocampus and the nucleus habenularis region after AIF(370-394)-TAT treatment. Caspase-independent apoptosis was decreased in the cortex, striatum, and nucleus habenularis after AIF(370-394)-TAT treatment, but no significant change was found on caspase-dependent apoptosis as indicated by the number of active caspase-3-labeled cells. Further analysis showed that both AIF and CypA nuclear accumulation were decreased after treatment with the AIF(370-394)-TAT peptide. These results suggest that AIF(370-394)-TAT inhibited AIF/CypA translocation to the nucleus and reduced HI-induced caspase-independent apoptosis and brain injury in young male mice, suggesting that blocking AIF/CypA might be a potential therapeutic target for neonatal brain injury.

Perturbed mitochondrial dynamics, an emerging aspect of epithelial-microbe interactions

Mitochondria exist in a complex network that is constantly remodeling via the processes of fission and fusion in response to intracellular conditions and extracellular stimuli. Excessive fragmentation of the mitochondrial network because of an imbalance between fission and fusion reduces the cells' capacity to generate ATP and can be a forerunner to cell death. Given the critical roles mitochondria play in cellular homeostasis and innate immunity, it is not surprising that many microbial pathogens can disrupt mitochondrial activity. Here we note the putative contribution of mitochondrial dysfunction to gut disease and review data showing that infection with microbial pathogens can alter the balance between mitochondrial fragmentation and fusion, preventing normal remodeling (i.e., dynamics) and can lead to cell death. Current data indicate that infection of epithelia or macrophages with microbial pathogens will ultimately result in excessive fragmentation of the mitochondrial network. Concerted research efforts are required to elucidate fully the processes that regulate mitochondrial dynamics, the mechanisms by which microbes affect epithelial mitochondrial fission and/or fusion, and the implications of this for susceptibility to infectious disease. We speculate that the commensal microbiome of the gut may be important for normal epithelial mitochondrial form and function. Drugs designed to counteract the effect of microbial pathogen interference with mitochondrial dynamics may be a new approach to infectious disease at mucosal surfaces.

AIF meets the CHCHD4/Mia40-dependent mitochondrial import pathway

In the mitochondria of healthy cells, Apoptosis-Inducing factor (AIF) is required for the optimal functioning of the respiratory chain machinery, mitochondrial integrity, cell survival, and proliferation. In all analysed species, it was revealed that the downregulation or depletion of AIF provokes mainly the post-transcriptional loss of respiratory chain Complex I protein subunits. Recent progress in the field has revealed that AIF fulfils its mitochondrial pro-survival function by interacting physically and functionally with CHCHD4, the evolutionarily-conserved human homolog of yeast Mia40. The redox-regulated CHCHD4/Mia40-dependent import machinery operates in the intermembrane space of the mitochondrion and controls the import of a set of nuclear-encoded cysteine-motif carrying protein substrates. In addition to their participation in the biogenesis of specific respiratory chain protein subunits, CHCHD4/Mia40 substrates are also implicated in the control of redox regulation, antioxidant response, translation, lipid homeostasis and mitochondrial ultrastructure and dynamics. Here, we discuss recent insights on the AIF/CHCHD4-dependent protein import pathway and review current data concerning the CHCHD4/Mia40 protein substrates in metazoan. Recent findings and the identification of disease-associated mutations in AIF or in specific CHCHD4/Mia40 substrates have highlighted these proteins as potential therapeutic targets in a variety of human disorders.

AIF knockdown induce apoptosis and mitochondrial dysfunction in cochlear spiral ganglion neurons in vitro

The underlying mechanism involved in auditory neuropathy spectrum disorder (ANSD) remains largely unclear. It has been previously reported that mutations in the apoptosis-inducing factor (AIF) gene are associated with auditory neuropathy and delayed peripheral neuropathy, which can eventually cause ANSD. In the present study, the regulatory effects of AIF knockdown on the cellular functions of spiral ganglion neurons (SNGs) and the molecular mechanism(s) of AIF knockdown in inducing cell apoptosis in SGNs were further investigated. The results showed that the AIF knockdown via siRNA transfection resulted in high levels of oxidative stress, and impaired mitochondrial respiration activity and membrane potential in SGNs. Western blotting further proved that the knockdown of AIF can decrease the content of anti-apoptotic and anti-oxidative proteins, as well as mitochondrial respiratory chain Complex I proteins. The present experimental data suggested that the abnormal expression of AIF may affect SGNs cellular function, and may contribute to the progress of ANSD.

Overexpression of apoptosis inducing factor aggravates hypoxic-ischemic brain injury in neonatal mice

Apoptosis inducing factor (AIF) has been shown to be a major contributor to neuron loss in the immature brain after hypoxia-ischemia (HI). Indeed, mice bearing a hypomorphic mutation causing reduced AIF expression are protected against neonatal HI. To further investigate the possible molecular mechanisms of this neuroprotection, we generated an AIF knock-in mouse by introduction of a latent transgene coding for flagged AIF protein into the Rosa26 locus, followed by its conditional activation by a ubiquitously expressed Cre recombinase. Such AIF transgenic mice overexpress the pro-apoptotic splice variant of AIF (AIF1) at both the mRNA (5.9 times higher) and protein level (2.4 times higher), but not the brain-specific AIF splice-isoform (AIF2). Excessive AIF did not have any apparent effects on the phenotype or physiological functions of the mice. However, brain injury (both gray and white matter) after neonatal HI was exacerbated in mice overexpressing AIF, coupled to enhanced translocation of mitochondrial AIF to the nucleus as well as enhanced caspase-3 activation in some brain regions, as indicated by immunohistochemistry. Altogether, these findings corroborate earlier studies demonstrating that AIF plays a causal role in neonatal HI brain injury.

Apoptotic Markers in the Midbrain of the Human Neonate After Perinatal Hypoxic/Ischemic Injury

Our previous postmortem studies on neonates with neuropathological injury of perinatal hypoxia/ischemia (PHI) showed a dramatic reduction of tyrosine hydroxylase expression (dopamine synthesis enzyme) in substantia nigra (SN) neurons, with reduction of their cellular size. In order to investigate if the above observations represent an early stage of SN degeneration, we immunohistochemically studied the expression of cleaved caspase-3 (CCP3), apoptosis inducing factor (AIF), and DNA fragmentation by using terminal deoxynucleotidyltransferase-mediated dUTP-biotin 3'-end-labeling (TUNEL) technique in the SN of 22 autopsied neonates (corrected age ranging from 34 to 46.5 gestational weeks), in relation to the severity/duration of PHI injury, as estimated by neuropathological criteria. No CCP3-immunoreactive neurons and a limited number of apoptotic TUNEL-positive neurons with pyknotic characteristics were found in the SN. Nuclear AIF staining was revealed only in few SN neurons, indicating the presence of early signs of AIF-mediated degeneration. By contrast, motor neurons of the oculomotor nucleus showed higher cytoplasmic AIF expression and nuclear translocation, possibly attributed to the combined effect of developmental processes and increased oxidative stress induced by antemortem and postmortem factors. Our study indicates the activation of AIF, but not CCP3, in the SN and oculomotor nucleus of the human neonate in the developmentally critical perinatal period.

FAD/NADH Dependent Oxidoreductases: From Different Amino Acid Sequences to Similar Protein Shapes for Playing an Ancient Function

Flavoprotein oxidoreductases are members of a large protein family of specialized dehydrogenases, which include type II NADH dehydrogenase, pyridine nucleotide-disulphide oxidoreductases, ferredoxin-NAD+ reductases, NADH oxidases, and NADH peroxidases, playing a crucial role in the metabolism of several prokaryotes and eukaryotes. Although several studies have been performed on single members or protein subgroups of flavoprotein oxidoreductases, a comprehensive analysis on structure-function relationships among the different members and subgroups of this great dehydrogenase family is still missing. Here, we present a structural comparative analysis showing that the investigated flavoprotein oxidoreductases have a highly similar overall structure, although the investigated dehydrogenases are quite different in functional annotations and global amino acid composition. The different functional annotation is ascribed to their participation in species-specific metabolic pathways based on the same biochemical reaction, i.e., the oxidation of specific cofactors, like NADH and FADH₂. Notably, the performed comparative analysis sheds light on conserved sequence features that reflect very similar oxidation mechanisms, conserved among flavoprotein oxidoreductases belonging to phylogenetically distant species, as the bacterial type II NADH dehydrogenases and the mammalian apoptosis-inducing factor protein, until now retained as unique protein entities in Bacteria/Fungi or Animals, respectively. Furthermore, the presented computational analyses will allow consideration of FAD/NADH oxidoreductases as a possible target of new small molecules to be used as modulators of mitochondrial respiration for patients affected by rare diseases or cancer showing mitochondrial dysfunction, or antibiotics for treating bacterial/fungal/protista infections.

Systematic spatiotemporal mapping reveals divergent cell death pathways in three mouse models of hereditary retinal degeneration

Calcium (Ca²⁺ ) dysregulation has been linked to neuronal cell death, including in hereditary retinal degeneration. Ca²⁺ dysregulation is thought to cause rod and cone photoreceptor cell death. Spatial and temporal heterogeneities in retinal disease models have hampered validation of this hypothesis. We examined the role of Ca²⁺ in photoreceptor degeneration, assessing the activation pattern of Ca²⁺ -dependent calpain proteases, generating spatiotemporal maps of the entire retina in the cpfl1 mouse model for primary cone degeneration, and in the rd1 and rd10 models for primary rod degeneration. We used Gaussian process models to distinguish the temporal sequences of degenerative molecular processes from other variability sources.In the rd1 and rd10 models, spatiotemporal pattern of increased calpain activity matched the progression of primary rod degeneration. High calpain activity coincided with activation of the calpain-2 isoform but not with calpain-1, suggesting differential roles for both calpain isoforms. Primary rod loss was linked to upregulation of apoptosis-inducing factor, although only a minute fraction of cells showed activity of the apoptotic marker caspase-3. After primary rod degeneration concluded, caspase-3 activation appeared in cones, suggesting apoptosis as the dominant mechanism for secondary cone loss. Gaussian process models highlighted calpain activity as a key event during primary rod photoreceptor cell death. Our data suggest a causal link between Ca²⁺ dysregulation and primary, nonapoptotic degeneration of photoreceptors and a role for apoptosis in secondary degeneration of cones, highlighting the importance of the spatial and temporal location of key molecular events, which may guide the evaluation of new therapies.

Brain oxidative damage in murine models of neonatal hypoxia/ischemia and reoxygenation

The brain is one of the main organs affected by hypoxia and reoxygenation in the neonatal period and one of the most vulnerable to oxidative stress. Hypoxia/ischemia and reoxygenation leads to impairment of neurogenesis, disruption of cortical migration, mitochondrial damage and neuroinflammation. The extent of the injury depends on the clinical manifestation in the affected regions. Preterm newborns are highly vulnerable, and they exhibit severe clinical manifestations such as intraventricular hemorrhage (IVH), retinopathy of prematurity (ROP) and diffuse white matter injury (DWMI) among others. In the neonatal period, the accumulation of high levels of reactive oxygen species exacerbated by the immature antioxidant defense systems in represents cellular threats that, if they exceed or bypass physiological counteracting mechanisms, are responsible of significant neuronal damage. Several experimental models in mice mimic the consequences of perinatal asphyxia and the use of oxygen in the reanimation process that produce brain injury. The aim of this review is to highlight brain damage associated with oxidative stress in different murine models of hypoxia/ischemia and reoxygenation.

Resveratrol Protects against Restraint Stress Effects on Stomach and Spleen in Adult Male Mice

The objectives were to investigate whether restraint stress (which is known as a mixture of psychologic and physical stress) exerts negative effects on the stomach and spleen, and whether the phenolic compound resveratrol (RES) exerts any protective roles. Fifty adult male mice were divided into five groups, with 10 mice per group as follows: control (C), restraint stress (RS), RS with vehicle (RS + V), RS with 2 mg/kg of resveratrol (RS + 2 mg RES), and RS with 20 mg/kg of resveratrol (RS + 20 mg RES). Mice were restrained in conical centrifuge tubes for 4 h daily to establish the RS model. RS + 2 mg RES, RS + 20 mg RES, and RS + V groups were given an oral dose of resveratrol or vehicle for 15 consecutive days, while the control group was not exposed to restraint stress. Herein, we showed that restraint stress decreased body weight and food and water consumption in stressed groups RS and RS + V compared to controls, while the groups treated with resveratrol showed improvements. Moreover, restraint stress caused acute damage to the morphology of gastric cells and reduced the quantitative distribution of parietal cells along with their decreased size and diameter, pointing to gastritis or ulcer. Furthermore, the antibody against the apoptosis-inducing factor (AIF) was highly attached in the RS groups. Splenic size, weight, and length were also greatly augmented in the stressed groups compared to the controls, while these phenomena were not observed in the RS + 2 mg RES group. Our findings proved significant ameliorating effects of resveratrol against restraint stress in adult male mice.

Purine-Metabolising Enzymes and Apoptosis in Cancer

The enzymes of both de novo and salvage pathways for purine nucleotide synthesis are regulated to meet the demand of nucleic acid precursors during proliferation. Among them, the salvage pathway enzymes seem to play the key role in replenishing the purine pool in dividing and tumour cells that require a greater amount of nucleotides. An imbalance in the purine pools is fundamental not only for preventing cell proliferation, but also, in many cases, to promote apoptosis. It is known that tumour cells harbour several mutations that might lead to defective apoptosis-inducing pathways, and this is probably at the basis of the initial expansion of the population of neoplastic cells. Therefore, knowledge of the molecular mechanisms that lead to apoptosis of tumoural cells is key to predicting the possible success of a drug treatment and planning more effective and focused therapies. In this review, we describe how the modulation of enzymes involved in purine metabolism in tumour cells may affect the apoptotic programme. The enzymes discussed are: ectosolic and cytosolic 5'-nucleotidases, purine nucleoside phosphorylase, adenosine deaminase, hypoxanthine-guanine phosphoribosyltransferase, and inosine-5'-monophosphate dehydrogenase, as well as recently described enzymes particularly expressed in tumour cells, such as deoxynucleoside triphosphate triphosphohydrolase and 7,8-dihydro-8-oxoguanine triphosphatase.

The roles of mitochondria-associated membranes in mitochondrial quality control under endoplasmic reticulum stress

The endoplasmic reticulum (ER) and mitochondria are two important organelles in cells. Mitochondria-associated membranes (MAMs) are lipid raft-like domains formed in the ER membranes that are in close apposition to mitochondria. They play an important role in signal transmission between these two essential organelles. When cells are exposed to internal or external stressful stimuli, the ER will activate an adaptive response called the ER stress response, which has a significant effect on mitochondrial function. Mitochondrial quality control is an important mechanism to ensure the functional integrity of mitochondria and the effect of ER stress on mitochondrial quality control through MAMs is of great significance. Therefore, in this review, we introduce ER stress and mitochondrial quality control, and discuss how ER stress signals are transmitted to mitochondria through MAMs. We then review the important roles of MAMs in mitochondrial quality control under ER stress.

Astragaloside IV Protects Ethanol-Induced Gastric Mucosal Injury by Preventing Mitochondrial Oxidative Stress and the Activation of Mitochondrial Pathway Apoptosis in Rats

Alcohol consumption affects gastric mucosa by multiple and complex mechanisms depending either by direct contact of ethanol or by indirect biological damage induced by its metabolite acetaldehyde. The present study aims at further investigating the mechanism of ethanol-induced gastric mucosa injury and the protective effect of astragaloside IV (AS-IV) in an aspect of mitochondrial oxidative stress and mitochondrial pathway of apoptosis. Using an array of experimental approaches, we have shown that the development of mitochondrial oxidative stress and associated apoptosis play crucial roles in the pathogenesis of gastric injury induced by ethanol. AS-IV inhibits mitochondrial oxidative stress by scavenging accumulation of malondialdehyde and decreasing the consumption of glutathione. AS-IV also prevents ethanol-induced apoptosis by modulating the activity of caspase-3 and caspase-9, the expression of Bax/Bcl-2, and the release of cytochrome C and apoptosis inducing factor. Moreover, AS-IV reduces ethanol-mediated activation of caspase-8 and breakage of Bid. This study thus indicates that AS-IV prevented ethanol-induced gastric damage by blocking activation of mitochondrial oxidative stress and mitochondrial pathway of apoptosis induced by ethanol in the gastric mucosa.

Porphyromonas gingivalis degrades integrin β1 and induces AIF-mediated apoptosis of epithelial cells

Background: Porphyromonas gingivalis, a major pathogen of chronic periodontitis, adheres to and invades epithelial cells via an interaction between fimbriae and integrin. P. gingivalis proliferation and infection may affect the survival of cells. In this study, we further examined alternative signaling pathways mediating epithelial-cell death induced by P. gingivalis and the role of the cell-adhesion molecule integrin. Methods: Human epithelial KB cells interacted with P. gingivalis to evaluate cell death by Annexin V-propidium iodide (PI) staining. JC-1 staining was used to measure mitochondrial membrane potential (MMP). The mRNA and protein of integrin β1, apoptosis-inducing factor (AIF) and caspase-3 were detected by real-time PCR and western blot. Caspase-3 activity was analyzed by spectrophotometry. Results: P. gingivalis infection downregulated integrin β1 and led to cell detachment in a dose and time-dependent manner. Large amount of P. gingivalis induced MMP depolarization and apoptosis in KB cells. Moreover, P. gingivalis up-regulated AIF, but not activate caspase-3 during apoptosis. In addition, AIF inhibitor N-Phenylmaleimide almost inhibited the P. gingivalis-induced apoptosis. Conclusions: P. gingivalis disrupts epithelial-cell adhesion by degrading integrin β1 and induces caspase-independent, AIF-mediated mitochondrial apoptosis, which may promote the damage of oral tissue.

Epigenome-wide DNA methylation in placentas from preterm infants: association with maternal socioeconomic status

This study evaluated the hypothesis that prenatal maternal socioeconomic status (SES) adversity is associated with DNA methylation in the placenta. SES adversity was defined by the presence of, as well as a summative count of, four factors: less than college education, single marital status, food and nutritional service assistance, and public health insurance. Epigenome-wide DNA methylation was assessed using the Illumina EPIC array in 426 placentas from a sample of infants born < 28 weeks of gestation from the Extremely Low Gestational Age Newborn cohort. Associations between SES adversity and DNA methylation were assessed with robust linear regressions adjusted for covariates and controlled the false discovery rate at < 10%. We also examined whether such associations were sex specific. Indicators of SES adversity were associated with differential methylation at 33 CpG sites. Of the 33 identified CpG sites, 19 (57.6%) displayed increased methylation, and 14 (42.4%) displayed decreased methylation in association with at least one of the SES adversity factors. Sex differences were observed in DNA methylation associated with summative SES score; in which placentas derived from female pregnancies showed more robust differential CpG methylation than placentas from male pregnancies. Maternal SES adversity was associated with differential methylation of genes with key role in gene transcription and placental function, potentially altering immunity and stress response. Further investigation is needed to evaluate the role of epigenetic differences in mediating the association between maternal socioeconomic status during pregnancy and later life health outcomes in children.

Cytoplasmic upregulation of Cyto c and AIF serve as biomarkers of mechanical asphyxia death

The certification of death due to mechanical asphyxia has been a complex problem in some cases. The use of protein expression to identify mechanical asphyxia death has recently attracted attention. Asphyxia creates an extremely hypoxic environment for cells, which should reactivate the mitochondria in the cells. Cyto c and AIF, located in the mitochondria, are transferred to the cytoplasm under hypoxia to trigger the apoptotic process. Based this phenomenon, we designed the animal asphyxia model and cell hypoxia model to examine whether Cyto c and AIF are expressed in the cytoplasm, and we used human samples to verify the results. We found that the two proteins were detectably expressed in the cytoplasm of mechanical asphyxia groups and were hardly detected in the cytoplasm of other groups. This is a promising finding that may shed light on the precise mechanisms associated with mechanical asphyxia.

Identification of Chaetocin as a Potent non-ROS-mediated Anticancer Drug Candidate for Gastric Cancer

Chaetocin, a natural product extracted from Chaetomium species, possesses anticancer effects in several kinds of tumors. However, it remains unclear whether the potential indication for chaetocin could also include human gastric cancer. We found here that chaetocin induced caspase-dependent and -independent apoptosis in human gastric cancer cell lines, which greatly depended on BID-mediated AIF translocation. Despite not increasing the intercellular ROS levels in gastric cancer cells, chaetocin did cause a reduction in mitochondrial membrane potential probably through its regulation on the expression of Bcl-2 and BAX. Chaetocin could also induce autophagy in gastric cancer cells; blocking autophagy by chloroquine enhanced the cytotoxicity of chaetocin. Chaetocin was further found to suppress the growth of gastric cancer xenograft in nude mice. Therefore, our study provides first evidence that chaetocin has an anticancer efficacy against gastric cancer and the combined use of chaetocin with autophagy inhibitors may enhance the therapeutic effect for gastric cancer. As chronic and exorbitant ROS levels instigate drug resistance, chaetocin, which eradicates gastric cancer cells without increasing ROS levels, may initiate a new line of non-ROS-mediated anti-tumor strategy.

Downregulation of AIF-2 Inhibits Proliferation, Migration, and Invasion of Human Glioma Cells via Mitochondrial Dysfunction

Glioma remains the leading cause of brain tumor-related death worldwide. Apoptosis inducing factor (AIF) is a family of mitochondrial oxidoreductases that play important roles in mitochondrial metabolism and redox control. AIF-1 has been demonstrated to exert cell-killing effect via apoptosis in cancer cells, whereas the role of AIF-2 in cancer cells has not been determined. This study aimed to investigate the role of AIF-2 in human glioma cells. We found that AIF-2 was upregulated in human glioma tissues and cell lines, especially in U251 cells. Downregulation of AIF-2 using specific siRNA (Si-AIF-2) significantly reduced cell proliferation, induced G1 cell cycle arrest and differently regulated the expression of cell cycle regulator proteins in U251 cells. In addition, the results of Matrigel invasion assay and live-cell tracking assay showed that knockdown of AIF-2 inhibited cell invasion and migration. The results of immunocytochemistry indicated that knockdown of AIF-2 significantly attenuated the nuclear translocation of AIF-1, which was confirmed by western blot analysis. Furthermore, downregulation of AIF-2 resulted in mitochondrial dysfunction in U251 cells, as evidenced by reduced mitochondrial membrane potential (MMP), mitochondrial complex I activity, and mitochondrial Ca2+ buffering capacity. In conclusion, we found that AIF-2 plays a key role in promoting cell proliferation, invasion, and migration via regulating AIF-1-related mitochondrial cascades. Downregulation of the candidate oncogene AIF-2 might constitute a strategy to kill human glioma cells.

Cathepsin B mediated scramblase activation triggers cytotoxicity and cell cycle arrest by andrographolide to overcome cellular resistance in cisplatin resistant human hepatocellular carcinoma HepG2 cells

Andrographolide regimen in single or in combination with anticancer drugs is a promising new strategy to reverse chemoresistance in heaptocellular carcinoma. Apoptosis inducing factor (AIF) may regulate a complementary, cooperative or redundant pathway, along with caspase cascades. Despite these findings, mechanisms underlying caspase-dependent and-independent signaling pathways in andrographolide -induced apoptosis in cisplatin-resistant human hepatocellular carcinoma cell line (HepG2CR) remain unclear. Andrographolide treatment effectively reduced NF-κβ nuclear localization by modulating protein kinase A- protein phosphatase 2 A- Iκβ kinase (PKA/PP2 A/IKK) axis that in turn maintains initiator caspase8 activity. Lysosomal distribution of tBid stimulates cytosolic cathepsin B resulting accumulation of truncated-AIF with induction in scramblase mediated phosphatidylserine exposure in HepG2CR cells. Andrographolide treatment thereby switch on subG1 phase arrest by modulating cellular check points (cyclin A, B, cyclin dependent kinase-1) cueing to the apoptosis event. Collectively, this study suggested antineoplastic potential of andrographolide through PKA/PP2 A/IKK pathway in HepG2CR cells.

Signal-induced PARP1-Erk synergism mediates IEG expression

A recently disclosed Erk-induced PARP1 activation mechanism mediates the expression of immediate early genes (IEGs) in response to a variety of extra- and intracellular signals implicated in memory acquisition, development and proliferation. Here, we review this mechanism, which is initiated by stimulation-induced binding of PARP1 to phosphorylated Erk translocated into the nucleus. This binding maintains long-lasting synergistic activity of these proteins, which offers a new pattern for targeted therapy.

Phyla nodiflora L. Extracts Induce Apoptosis and Cell Cycle Arrest in Human Breast Cancer Cell Line, MCF-7

Phyla nodiflora L. has been used as medicinal remedies for various ailments due to its antioxidant, anti-inflammatory, anti-bacterial, anti-tumor activity. Previously, we found that the plant extracts induced DNA fragmentation in MCF-7. This study was to investigate the modes of action of P. nodiflora in inhibiting breast cancer cells using leaf ethyl acetate (EA leaf), stem ethyl acetate (EA stem) and stem methanol (Met stem) extracts. The MTT assay showed that the anti-proliferative effects of P. nodiflora extracts were selective towards MCF-7 with a minimal effect on MCF10A. Morphological changes such as cell shrinkage and nuclear condensation were observed in treated cells. We found that induction of apoptosis by EA leaf and EA stem was mitochondrial-dependent while loss of mitochondrial membrane potential was not found in Met stem-treated cells. In addition, the expression levels of AIFM1, CASP9, CFLAR, and IGF1R were altered after treatment. Decreased BCL-2 expression was found in treated cells while BAX and caspases' expression was upregulated or maintained. All extracts caused perturbation of cell cycle at S phase by dysregulating the expression of cell cycle regulators such as CDKs and cyclins. Our findings indicate that P. nodiflora inhibits MCF-7 cells by inducing apoptosis and perturbing cell cycle.

Oxeiptosis: a discreet way to respond to radicals

One of the best-studied cellular responses to toxic signals and pathogens is programmed cell death. Over the past years, it became apparent that the specific mechanisms of cell death have tremendous influence at both cellular and organismal level, highlighting the importance of sensors and pathways involved in this decision-making process. Central signalling molecules involved in a variety of cell death pathways are reactive oxygen species (ROS). However, the molecular mechanisms regulating differential responses and cellular fates to distinct ROS levels remain incompletely understood. Recently, we uncovered a caspase-independent cell-death pathway named 'oxeiptosis', which links the ROS sensing capacity of KEAP1 to a cell death pathway involving PGAM5 and AIFM1. Alike apoptosis, oxeiptosis is anti-inflammatory when activated by increased intracellular ROS levels and upon pathogens encounter. Here we discuss the potential impact of oxeiptosis in pathogens clearance and teratogenic cells.

A disease-associated Aifm1 variant induces severe myopathy in knockin mice

OBJECTIVE

Mutations in the AIFM1 gene have been identified in recessive X-linked mitochondrial diseases. Functional and molecular consequences of these pathogenic AIFM1 mutations have been poorly studied in vivo.

METHODS/RESULTS

Here we provide evidence that the disease-associated apoptosis-inducing factor (AIF) deletion arginine 201 (R200 in rodents) causes pathology in knockin mice. Within a few months, posttranslational loss of the mutant AIF protein induces severe myopathy associated with a lower number of cytochrome c oxidase-positive muscle fibers. At a later stage, Aifm1 (R200 del) knockin mice manifest peripheral neuropathy, but they do not show neurodegenerative processes in the cerebellum, as observed in age-matched hypomorphic Harlequin (Hq) mutant mice. Quantitative proteomic and biochemical data highlight common molecular signatures of mitochondrial diseases, including aberrant folate-driven one-carbon metabolism and sustained Akt/mTOR signaling.

CONCLUSION

Our findings indicate metabolic defects and distinct tissue-specific vulnerability due to a disease-causing AIFM1 mutation, with many pathological hallmarks that resemble those seen in patients.