The caspase-3 precursor has a cytosolic and mitochondrial distribution: implications for apoptotic signaling

Gasdermin-D activation promotes NLRP3 activation and host resistance to Leishmania infection

Intracellular parasites from the Leishmania genus cause Leishmaniasis, a disease affecting millions of people worldwide. NLRP3 inflammasome is key for disease outcome, but the molecular mechanisms upstream of the inflammasome activation are still unclear. Here, we demonstrate that despite the absence of pyroptosis, Gasdermin-D (GSDMD) is active at the early stages of Leishmania infection in macrophages, allowing transient cell permeabilization, potassium efflux, and NLRP3 inflammasome activation. Further, GSDMD is processed into a non-canonical 25 kDa fragment. Gsdmd-/- macrophages and mice exhibit less NLRP3 inflammasome activation and are highly susceptible to infection by several Leishmania species, confirming the role of GSDMD for inflammasome-mediated host resistance. Active NLRP3 inflammasome and GSDMD are present in skin biopsies of patients, demonstrating activation of this pathway in human leishmaniasis. Altogether, our findings reveal that Leishmania subverts the normal functions of GSDMD, an important molecule to promote inflammasome activation and immunity in Leishmaniasis.

Protective Effects of Several Common Amino Acids, Vitamins, Organic Acids, Flavonoids and Phenolic Acids against Hepatocyte Damage Caused by Alcohol

With the increase in alcohol consumption, more and more people are suffering from alcoholic liver disease (ALD). Therefore, it is necessary to elaborate the pathogenesis of ALD from the aspects of alcohol metabolism and harm. In this study, we established an alcoholic liver injury model in vitro by inducing L02 cells with different concentration of ethanol and acetaldehyde. Results showed that the metabolism of ethanol can promote the content of ROS, MDA, TNF-α, IL-6, and caspase 3, causing oxidative and inflammatory stress and membrane permeability changes. However, unmetabolized ethanol and acetaldehyde had little effect on cell membrane permeability and inflammation, indicating that ethanol metabolites were the main reason for cell membrane damage. We also evaluated the effects of amino acids (taurine and methionine), vitamins (E and vitamin D), organic acids (malic acid and citric acid), flavonoids (rutin and quercetin), and phenolic acids (ferulic acid and chlorogenic acid) on alcohol-induced cell membrane damage of L02 cells. Chlorogenic acid, taurine, vitamin E, and citric acid had remarkable effects on improving cell membrane damage. Malic acid, rutin, quercetin, and ferulic acid had obvious therapeutic effects, while vitamin D and methionine had poor therapeutic effects. The relationship between the structure and effect of active ingredients can be further studied to reveal the mechanism of action, and monomers can be combined to explore whether there is a synergistic effect between functional components, in order to provide a certain theoretical basis for the actual study of liver protection.

Cinchona officinalis Phytochemicals-Loaded Iron Oxide Nanoparticles Induce Cytotoxicity and Stimulate Apoptosis in MCF-7 Human Breast Cancer Cells

The present study aimed to synthesize iron oxide nanoparticles loaded with quinine and alkaloids-rich Cinchona officinalis (Peruvian bark) stem bark extract, and further evaluate their cytotoxic effect and apoptosis mechanisms in MCF-7 breast cancer cells. Nanoparticles were prepared by biological reduction of iron oxide with Cinchona officinalis extract, using the green synthesis method. The nanoparticles were characterized by XRD, FT-IR, and UV-vis spectroscopy and transmission electron microscopy (TEM). In vitro cytotoxicity analyses of Cinchona officinalis extract, ferrous oxide, and Cinchona officinalis extract-loaded iron oxide nanoparticles (CO-NPs) were carried out using the MTT test for 24 h and 48 h. We found that CO-NPs reduced the MCF-7 cell viability with IC₅₀ values of 16.2 and 9 µg/mL in 24 h and 48 h, respectively. In addition, CO-NPs were tested with normal hMSCs to determine their toxicity, and we did not find noticeable cytotoxicity. Confocal fluorescent microscopy revealed that CO-NPs efficiently increased the nuclear condensation and chromatin damage in propidium iodide staining; meanwhile, there was decreased mitochondrial membrane potential in CO-NPs-treated MCF-7 cells. In addition, AO-EB staining confirmed the late apoptotic and apoptotic morphology of cancer cells. Further gene expression analysis confirmed that the upregulation of tumor suppressors, Cdkn1A, Prb, and p53 was significantly increased, and inflammatory traits such as TNF-α and Nf-κb were increased in cancer cells treated with CO-NPs. Apoptotic stimulators such as Bax and caspase-3 expression were highly significantly increased, while mdm-2 and Bcl-2 were significantly decreased. Overall, the enhanced cytotoxic potential of the Cinchona officianlis stem bark extract loaded CO-NPs versus free Cinchona officianlis extract might be due to the functional stabilization of bioactive compounds, such as alkaloids, quinine, flavonoids, phenolics, etc., into the iron oxide, providing bioavailability and internalization of cinchona metabolites intracellularly.

Breast cancer growth and proliferation is suppressed by the mitochondrial targeted furazano[3,4-b]pyrazine BAM15

BACKGROUND

Enhanced metabolic plasticity and diversification of energy production is a hallmark of highly proliferative breast cancers. This contributes to poor pharmacotherapy efficacy, recurrence, and metastases. We have previously identified a mitochondrial-targeted furazano[3,4-b]pyrazine named BAM15 that selectively reduces bioenergetic coupling efficiency and is orally available. Here, we evaluated the antineoplastic properties of uncoupling oxidative phosphorylation from ATP production in breast cancer using BAM15.

METHODS

The anticancer effects of BAM15 were evaluated in human triple-negative MDA-MB-231 and murine luminal B, ERα-negative EO771 cells as well as in an orthotopic allograft model of highly proliferative mammary cancer in mice fed a standard or high fat diet (HFD). Untargeted transcriptomic profiling of MDA-MB-231 cells was conducted after 16-h exposure to BAM15. Additionally, oxidative phosphorylation and electron transfer capacity was determined in permeabilized cells and excised tumor homogenates after treatment with BAM15.

RESULTS

BAM15 increased proton leak and over time, diminished cell proliferation, migration, and ATP production in both MDA-MB-231 and EO771 cells. Additionally, BAM15 decreased mitochondrial membrane potential, while inducing apoptosis and reactive oxygen species accumulation in MDA-MB-231 and EO771 cells. Untargeted transcriptomic profiling of MDA-MB-231 cells further revealed inhibition of signatures associated with cell survival and energy production by BAM15. In lean mice, BAM15 lowered body weight independent of food intake and slowed tumor progression compared to vehicle-treated controls. In HFD mice, BAM15 reduced tumor growth relative to vehicle and calorie-restricted weight-matched controls mediated in part by impaired cell proliferation, mitochondrial respiratory function, and ATP production. LC-MS/MS profiling of plasma and tissues from BAM15-treated animals revealed distribution of BAM15 in adipose, liver, and tumor tissue with low abundance in skeletal muscle.

CONCLUSIONS

Collectively, these data indicate that mitochondrial uncoupling may be an effective strategy to limit proliferation of aggressive forms of breast cancer. More broadly, these findings highlight the metabolic vulnerabilities of highly proliferative breast cancers which may be leveraged in overcoming poor responsiveness to existing therapies.

Algae-meditated route to cuprous oxide (Cu2O) nanoparticle: differential expression profile of MALAT1 and GAS5 LncRNAs and cytotoxic effect in human breast cancer

Background

Breast cancer (BC), as the most widely recognized disease in women worldwide, represents about 30% of all cancers impacting women. This study was aimed to synthesize Cu2O nanoparticles from the cystoseira myrica algae (CM-Cu2O NPs) assess their antimicrobial activity against pathogenic bacteria and fungi. We evaluated the expression levels of lncRNAs (MALAT1 and GAS5) and apoptosis genes (p53, p27, bax, bcl2 and caspase3), their prognostic roles.

Methods

In this study, CM-Cu2O NPs synthesized by cystoseira myrica algae extraction used to evaluate its cytotoxicity and apoptotic properties on MDA-MB-231, SKBR3 and T-47D BC cell lines compared to HDF control cell line. The CM-Cu2O NPs was characterized by UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM). The antimicrobial activity of CM-Cu2O NPs was assessed against pathogenic bacteria, staphylococcus aureus (S. aureus) PTCC 1112 bacteria as a standard gram-positive bacteria and pseudomonas aeruginosa (P. aeruginosa) PTCC 1310 as a standard gram-negative bacterium. Expression profile of MALAT1 and GAS5 lncRNAs and apoptosis genes, i.e., p27, bax, bcl2 and caspase3 genes, were calculated utilizing qRT-PCR. The changes in the expression levels were determined using the DDCT method.

Results

MALAT1 was upregulated in MDA-MB-231, SKBR3 and T-47D BC (p < 0.01), while GAS5 was downregulated in SKBR3 and T-47D cell lines tested compared with HDF control cell line (p < 0.05) was found. The results revealed that, p27, bax and caspase3 were significantly upregulated in BC cell lines as compared with normal cell line. Bcl2 expression was also significantly increased in MDA-MB-231 and T47D cell lines compared with normal cell line, but bcl2 levels were downregulated in SKBR3 cell line.

Conclusions

Our results confirm the beneficial cytotoxic effects of green-synthesized CM-Cu2O NPs on BC cell lines. This nanoparticle decreased angiogenesis and induces apoptosis, so we conclude that CM-Cu2O NPs can be used as a supplemental drug in cancer treatments. Significantly, elevated circulating lncRNAs were demonstrated to be BC specific and could differentiate BC cell lines from the normal cell lines. It was demonstrated that lncRNAs used in this study and their expression profiles can be created as biomarkers for early diagnosis and prognosis of BC. Further studies utilizing patients would give recognizable identification of lncRNAs as key players in intercellular interactions.

Striatin translocates to the cytosol of apoptotic cells and is proteolytically cleaved in a caspase 3-dependent manner

Striatin (STRN) is a multivalent protein holding great therapeutic potentials in view of its interaction with dynamic partners implicated in apoptosis. Although striatin-3 and striatin-4, that share high structural similarities with STRN, have been linked to apoptosis, the dynamics of STRN in apoptotic cells remain unclear. Herein, we report that the amount of STRN (110 kDa) is reduced in apoptotic cells, in response to various chemotherapeutic agents, thereby yielding a major polypeptide fragment at ~65 kDa, and three minor products at lower molecular weights. While STRN siRNA reduced the 65 kDa derivative fragment, the overexpression of a Myc-tagged STRN precipitated a novel fragment that was detected slightly higher than 65 kDa (due to the Myc-DDK tag on the cleaved fragment), confirming the cleavage of STRN during apoptosis. Interestingly, STRN cleavage was abrogated by the general caspase inhibitor Z-VAD.fmk. Cell fractionation revealed that the STRN pool, mainly distributed in the non-cytosolic fragment of naïve cells, translocates to the cytosol where it is proteolytically cleaved during apoptosis. Interestingly, the ectopic expression of caspase 3 in MCF-7 cells (deprived of caspase 3) induced STRN cleavage under apoptotic conditions. Inhibition of caspase 3 (Ac-DEVD-CHO) conferred a dose-dependent protection against the proteolytic cleavage of STRN. Collectively, our data provide cogent proofs that STRN translocates to the cytosol where it undergoes proteolytic cleavage in a caspase 3-dependent manner during apoptosis. Thus, this study projects the cleavage of STRN as a novel marker for apoptosis to serve pharmacological strategies targeting this particular form of cell death.

Redox modulation of muscle mass and function

Muscle mass and strength are very important for exercise performance. Training-induced musculoskeletal injuries usually require periods of complete immobilization to prevent any muscle contraction of the affected muscle groups. Disuse muscle wasting will likely affect every sport practitioner in his or her lifetime. Even short periods of disuse results in significant declines in muscle size, fiber cross sectional area, and strength. To understand the molecular signaling pathways involved in disuse muscle atrophy is of the utmost importance to develop more effective countermeasures in sport science research.

We have divided our review in four different sections. In the first one we discuss the molecular mechanisms involved in muscle atrophy including the main protein synthesis and protein breakdown signaling pathways. In the second section of the review we deal with the main cellular, animal, and human atrophy models. The sources of reactive oxygen species in disuse muscle atrophy and the mechanism through which they regulate protein synthesis and proteolysis are reviewed in the third section of this review. The last section is devoted to the potential interventions to prevent muscle disuse atrophy with especial consideration to studies on which the levels of endogenous antioxidants enzymes or dietary antioxidants have been tested.

Astragaloside IV Supplementation Promotes A Neuroprotective Effect in Experimental Models of Neurological Disorders: A Systematic Review

Background:

Neurological disorders constitute a growing worldwide concern due to the progressive aging of the population and the risky behavior they represent. Herbal medicines have scientific relevance in the treatment of these pathol-ogies. One of these substances, Astragaloside IV (AS-IV), is the main active compound present in the root of Astragalus membranaceus (Fisch.) Bge, a Chinese medicinal herb with neuroprotective properties.

Objective:

In the present study we performed a systematic review that sought to comprehend the neuroprotective effect pre-sented by AS-IV in experimental models of neurological disorders.

Method:

This study is a systematic review, where an electronic search in United States National Library of Medicine (Pub-Med), Science Direct, Cochrane Library, Scientific Electronic Library Online (SciELO), Scopus, Web of Science, Medline via Proquest and Periodicos Capes databases covering the years between 2007 and 2017, using “Astragaloside IV” and “Neurodegenerative diseases”; “Astragaloside IV” and “ Neurological disorders” as reference terms was made.

Results:

A total of 16 articles were identified, in which the efficacy of AS-IV was described in experimental models of Par-kinson’s disease, Alzheimer’s disease, cerebral ischemia and autoimmune encephalomyelitis, by improving motor deficits and/or neurochemical activity, especially antioxidant systems, reducing inflammation and oxidative stress.

Conclusion:

The findings of the present study indicate that the administration of AS-IV can improve behavioral and neuro-chemical deficits largely due to its antioxidant, antiapoptotic and anti-inflammatory properties, emerging as an alternative therapeutic approach for the treatment of neurological disorders.

Development of Activity-Based Reporter Gene Technology for Imaging of Protease Activity with an Exquisite Specificity in a Single Live Cell

Imaging of an active protease with an exquisite specificity in the presence of highly homologous proteins within a living cell is a very challenging task. Herein, we disclose a new method called "Activity-based Reporter Gene Technology" (AbRGT). This method provides an opportunity to study the function of "active protease" with an unprecedented specificity. As a proof-of-concept, we have applied this method to study the function of individual caspase protease in both intrinsic and extrinsic apoptosis signaling pathways. The versatility of this method is demonstrated by studying the function of both the initiator and effector caspases, independently. The modular fashion of this technology provides the opportunity to noninvasively image the function of cathepsin-B in a caspase-dependent cell death pathway. As a potential application, this method is used as a tool to screen compounds that are potent inhibitors of caspases and cathepsin-B proteases. The fact that this method can be readily applied to any protease of interest opens up huge opportunities for this technology in the area of target validation, high-throughput screening, in vivo imaging, diagnostics, and therapeutic intervention.

The role of suboptimal mitochondrial function in vulnerability to post-traumatic stress disorder

Post-traumatic stress disorder remains the most significant psychiatric condition associated with exposure to a traumatic event, though rates of traumatic event exposure far outstrip incidence of PTSD. Mitochondrial dysfunction and suboptimal mitochondrial function have been increasingly implicated in several psychopathologies, and recent genetic studies have similarly suggested a pathogenic role of mitochondria in PTSD. Mitochondria play a central role in several physiologic processes underlying PTSD symptomatology, including abnormal fear learning, brain network activation, synaptic plasticity, steroidogenesis, and inflammation. Here we outline several potential mechanisms by which inherited (genetic) or acquired (environmental) mitochondrial dysfunction or suboptimal mitochondrial function, may contribute to PTSD symptomatology and increase susceptibility to PTSD. The proposed pathogenic role of mitochondria in the pathophysiology of PTSD has important implications for prevention and therapy, as antidepressants commonly prescribed for patients with PTSD have been shown to inhibit mitochondrial function, while alternative therapies shown to improve mitochondrial function may prove more efficacious.

Cardioprotective Regimen of Adaptation to Chronic Hypoxia Diversely Alters Myocardial Gene Expression in SHR and SHR-mtBN Conplastic Rat Strains

Adaptation to continuous normobaric hypoxia (CNH) protects the heart against acute ischemia/reperfusion injury. Recently, we have demonstrated the infarct size-limiting effect of CNH also in hearts of spontaneously hypertensive rats (SHR) and in conplastic SHR-mt^BN strain characterized by the selective replacement of the mitochondrial genome of SHR with that of more ischemia-resistant Brown Norway rats. Importantly, cardioprotective effect of CNH was more pronounced in SHR-mt^BN than in SHR. Thus, here we aimed to identify candidate genes which may contribute to this difference between the strains. Rats were adapted to CNH (FiO₂ 0.1) for 3 weeks or kept at room air as normoxic controls. Screening of 45 transcripts was performed in left ventricles using Biomark Chip. Significant differences between the groups were analyzed by univariate analysis (ANOVA) and the genes contributing to the differences between the strains unmasked by CNH were identified by multivariate analyses (PCA, SOM). ANOVA with Bonferroni correction revealed that transcripts differently affected by CNH in SHR and SHR-mt^BN belong predominantly to lipid metabolism and antioxidant defense. PCA divided four experimental groups into two main clusters corresponding to chronically hypoxic and normoxic groups, and differences between the strains were more pronounced after CNH. Subsequently, the following 14 candidate transcripts were selected by PCA, and confirmed by SOM analyses, that can contribute to the strain differences in cardioprotective phenotype afforded by CNH: Alkaline ceramidase 2 (Acer2), Fatty acid translocase (Cd36), Aconitase 1 (Aco1), Peroxisome proliferator activated receptor gamma (Pparg), Hemoxygenase 2 (Hmox2), Phospholipase A2 group IIA (Ppla2g2a), Dynamin-related protein (Drp), Protein kinase C epsilon (Pkce), Hexokinase 2 (Hk2), Sphingomyelin synthase 2 (Sgms2), Caspase 3 (Casp3), Mitofussin 1 (Mfn1), Phospholipase A2 group V (Pla2g5), and Catalase (Cat). Our data suggest that the stronger cardioprotective phenotype of conplastic SHR-mt^BN strain afforded by CNH is associated with either preventing the drop or increasing the expression of transcripts related to energy metabolism, antioxidant response and mitochondrial dynamics.

Ferulic acid promoting apoptosis in human osteosarcoma cell lines

OBJECTIVE

To explore the promoting apoptosis and antitumor activities of ferulic acid (FA) in human osteosarcoma and its potential mechanism.

METHODS

The SaOS-2 and MG63 osteosarcoma cell lines were opted to experiment and these cells were, respectively, cultured with various concentrations of FA (0 μM, 10 μM, 20 μM, 40 μM) for 72 hours at 37°C. The viabilities of the FA treated cells were monitored by MTT. Apoptosis cells were evaluated using annexin V/PI by flow cytometry. Apoptosis proteins caspase-3, procaspase-3, Bcl-2 and Bax were detected by western blot. Expressions of apoptotic genes Bcl-2 and Bax were quantified by qPCR.

RESULTS

The cell viabilities were critically declined in the concentration-dependent manner in FA groups (P < 0.01). The apoptosis cells were increased proportionately with the concentration of FA (P < 0.05). The procaspase-3 protein contents, and Bcl-2 mRNA and protein contents were significantly decreased while caspase-3 protein contents, and Bax mRNA and protein contents were concomitantly increased in the concentration-dependent manner in FA groups (P < 0.05). The response to FA by the SaOS-2 osteosarcoma cell was similar with the MG63 osteosarcoma cell (P > 0.05).

CONCLUSION

Ferulic acid could significantly descend osteosarcoma cell viability through the promoting apoptosis pathway in which FA activates both caspase-3 and Bax and inactivates Bcl-2.

Epigallocatechin-3-gallate protects against hepatic ischaemia-reperfusion injury by reducing oxidative stress and apoptotic cell death

Objective

To investigate the protective effects of epigallocatechin-3-gallate (EGCG), a major polyphenol source in green tea, against hepatic ischaemia–reperfusion injury in mice.

Methods

The partial hepatic ischaemia–reperfusion injury model was created by employing the hanging-weight method in C57BL/6 male mice. EGCG (50 mg/kg) was administered via an intraperitoneal injection 45 min before performing the reperfusion. A number of markers of inflammation, oxidative stress, apoptosis and liver injury were measured after the ischaemia–reperfusion injury had been induced.

Results

The treatment groups were: sham-operated (Sham, n = 10), hepatic ischaemia–reperfusion injury (IR, n = 10), and EGCG with ischaemia–reperfusion injury (EGCG-treated IR, n = 10). Hepatic ischaemia–reperfusion injury increased the levels of biochemical and histological markers of liver injury, increased the levels of malondialdehyde, reduced the glutathione/oxidized glutathione ratio, increased the levels of oxidative stress and lipid peroxidation markers, decreased B-cell lymphoma 2 levels, and increased the levels of Bax, cytochrome c, cleaved caspase-3, and cleaved caspase-9. Pretreatment with EGCG ameliorated all of these changes.

Conclusion

The antioxidant and antiapoptotic effects of EGCG protected against hepatic ischaemia–reperfusion injury in mice.

Decrease of mitochondrial p53 during late apoptosis is linked to its dephosphorylation on serine 20

Following a genotoxic stress, the tumor suppressor p53 translocates to mitochondria to take part in direct induction of apoptosis, via interaction with BCL-2 family members such as BAK and BAX. We determined the kinetics of the mitochondrial translocation of p53 in HCT-116 and PA-1 cells exposed to different genotoxic stresses (doxorubicin, camptothecin, UVB). This analysis revealed an early escalation in the amount of mitochondrial p53, followed by a peak amount and a decrease of mitochondrial p53 at later time points. We show that the serine 20 phosphorylated form of p53 is present at the mitochondria and that the decrease of p53 mitochondrial level during late apoptosis correlates with a decrease of Ser-20 phosphorylation. Moreover, the S20A p53 mutant translocates well to mitochondria after a genotoxic stress but its mitochondrial localization is very low during late apoptosis when compared to wt p53. The S20A mutant also appears to be compromised for interaction with BAK. We propose here that the level of serine 20 phosphorylation is influential on p53 mitochondrial localization during late apoptosis. Additionally, we report the presence of a new ≃45 kDa caspase-cleaved fragment of p53 in the cytosolic and mitochondrial fractions of apoptotic cells.

Edaravone improves survival and neurological outcomes after CPR in a ventricular fibrillation model of rats

OBJECTIVE

Overproduction of free radicals is a main factor contributing to cerebral injury after cardiac arrest (CA)/cardiopulmonary resuscitation (CPR). We sought to evaluate the impact of edaravone on the survival and neurological outcomes after CA/CPR in rats.

METHODS

Rats were subjected to CA following CPR. For survival study, the rats with restoration of spontaneous circulation (ROSC) were randomly allocated to one of the two groups (edaravone and saline group, n=20/each group) to received Edaravone (3 mg/kg) or normal saline. Another 10 rats without experiencing CA and CPR served as the sham group. Survival was observed for 72 hours and the neurological deficit score (NDS) was calculated at 12, 24, 48, and 72 hours after ROSC. For the neurological biochemical analysis study, rats were subjected to the same experimental procedures. Then, edaravone group (n=24), saline group (n=24) and sham group (n=16) were further divided into 4 subgroups according to the different time intervals (12, 24, 48, and 72 hours following ROSC). Brain tissues were harvested at relative time intervals for evaluation of oxidative stress, TUNEL staining and apoptotic gene expression.

RESULTS

Edaravone improved postresuscitative survival time and neurological deficit, decreased brain malonylaldehyde level, increased superoxide dismutase activities, decreased proapoptotic gene expression of capase-8, capase-3, and Bax, and increased antiapoptotic Bcl-2 expression at 12, 24, 48, and 72 hours after ROSC.

CONCLUSIONS

Edaravone improves survival and neurological outcomes following CPR via antioxidative and antiapoptotic effects in rats.

The antioxidant and antiapoptotic effects of crocin pretreatment on global cerebral ischemia reperfusion injury induced by four vessels occlusion in rats

AIMS

Cerebral ischemia reperfusion (IR) injury is a process in which oxidative and apoptotic mechanisms play a part. Neuroprotective agents to be found could work out well for the efficient and safe minimization of cerebral IR injury. Crocin is a strong antioxidant agent; however the influence of this agent on the experimental cerebral ischemia model has not been studied extensively and thus it is not well-known. The objective of our study was to investigate the antioxidant, antiapoptotic and protective effects of crocin on the global cerebral IR induced by four-vessel occlusion.

MAIN METHODS

A total of 30 adult female Sprague-Dawley rats were equally and randomly separated into three groups as follows: sham, IR and IR+crocin (40mg/kg/day orally for 10days). 24h after electrocauterization of bilateral vertebral arteries, bilateral common carotid arteries were occluded for 30min and reperfused for 30min. Oxidative stress parameters (TAS, TOS, OSI), haematoxylin and eosin staining, caspase-3 and hypoxia-inducible factor-1 alpha (HIF-1α) expressions and TUNEL methods were investigated.

KEY FINDINGS

There was a significant difference between the IR and sham groups by means of OSI level, histopathological scoring, caspase-3, HIF-1α and TUNEL-positive cell parameters. We have also observed that pre-treatment with crocin reduced these parameter levels back to the baseline.

SIGNIFICANCE

The data obtained from the present study suggest that crocin may exert antiapoptotic, antioxidant and protective effects in IR-mediated brain injury induced by four-vessel occlusion. To the best of our knowledge, this would be the first study to be conducted in this field.

Grb7 and Hax1 may colocalize partially to mitochondria in EGF-treated SKBR3 cells and their interaction can affect Caspase3 cleavage of Hax1

Growth factor receptor bound protein 7 (Grb7) is a signal-transducing adaptor protein that mediates specific protein-protein interactions in multiple signaling pathways. Grb7, with Grb10 and Grb14, is members of the Grb7 protein family. The topology of the Grb7 family members contains several protein-binding domains that facilitate the formation of protein complexes, and high signal transduction efficiency. Grb7 has been found overexpressed in several types of cancers and cancer cell lines and is presumed involved in cancer progression through promotion of cell proliferation and migration via interactions with the erythroblastosis oncogene B 2 (human epidermal growth factor receptor 2) receptor, focal adhesion kinase, Ras-GTPases, and other signaling partners. We previously reported Grb7 binds to Hax1 (HS1 associated protein X1) isoform 1, an anti-apoptotic protein also involved in cell proliferation and calcium homeostasis. In this study, we confirm that the in vitro Grb7/Hax1 interaction is exclusive to these two proteins and their interaction does not depend on Grb7 dimerization state. In addition, we report Grb7 and Hax1 isoform 1 may colocalize partially to mitochondria in epidermal growth factor-treated SKBR3 cells and growth conditions can affect this colocalization. Moreover, Grb7 can affect Caspase3 cleavage of Hax1 isoform 1 in vitro, and Grb7 expression may slow Caspase3 cleavage of Hax1 isoform 1 in apoptotic HeLa cells. Finally, Grb7 is shown to increase cell viability in apoptotic HeLa cells in a time-dependent manner. Taken together, these discoveries provide clues for the role of a Grb7/Hax1 protein interaction in apoptosis pathways involving Hax1. Copyright © 2016 John Wiley & Sons, Ltd.

Escin reduces cell proliferation and induces apoptosis on glioma and lung adenocarcinoma cell lines

Aesculus hippocastanum (the horse chestnut) seed extract has a wide variety of biochemical and pharmacological effects including anti-inflammatory, antianalgesic, and antipyretic activities. The main active compound of this plant is escin. It is known that several medicinal herbs with anti-inflammatory properties have been found to have a role in the prevention and treatment of cancer. In the present study, the cytotoxic effects of escin in the C6 glioma and A549 cell lines were analyzed by MTT. Apoptotic effects of escin on both cell lines were evaluated by Annexin V binding capacity with flow cytometric analysis. Structural and ultrastructural changes were also evaluated using transmission electron microscopy. The results indicated that escin has potent antiproliferative effects against C6 glioma and A549 cells. These effects are both dose and time dependent. Taken together, escin possesses cell cycle arrest on G0/G1 phase and selective apoptotic activity on A549 cells as indicated by increased Annexin V-binding capacity, bax protein expression, caspase-3 activity and morphological changes obtained from micrographs by transmission electron microscopy.

Antiproliferative Activity of Aqueous Leaf Extract of Annona muricata L. on the Prostate, BPH-1 Cells, and Some Target Genes

Background. Annona muricata L. has been reported to possess antitumor and antiproliferative properties. Not much work has been done on its effect on BPH-1 cell lines, and no in vivo studies targeting the prostate organ exist. The study determined the effect of A muricata on human BPH-1 cells and prostate organ. Methods. The MTT assay was performed on BPH-1 cells using the aqueous leaf extract of A muricata. Cells (1 × 105 per well) were challenged with 0.5, 1.0, and 1.5 mg/mL extract for 24, 48, and 72 hours. Cell proliferation and morphology were examined microscopically. BPH-1 cells (1 × 104 per well) were seeded into 6-well plates and incubated for 48 hours with 0.5, 1.0, and 1.5 mg/mL A muricata extract. Reverse transcriptase polymerase chain reaction was performed using mRNA extracted from the cells. Possible target genes, Bax and Bcl-2, were examined. Twenty F344 male rats (≈200 g) were gavaged 30 mg/mL (10 rats) and 300 mg/mL (10 rats) and fed ad libitum alongside 10 control rats. Rats were sacrificed after 60 days. The prostate, seminal vesicles, and testes were harvested for histological examination. Results. Annona muricata demonstrated antiproliferative effects with an IC50 of 1.36 mg/mL. Best results were obtained after 48 hours, with near cell extinction at 72 hours. Bax gene was upregulated, while Bcl-2 was downregulated. Normal histological architecture was observed for all testes. Seminal vesicle was significantly reduced in test groups ( P < .05) and demonstrated marked atrophy with increased cellularity and the acinii, empty of secretion. Prostate of test groups were reduced with epithelial lining showing pyknotic nucleus, condensation, and marginalization of the nuclear material, characteristic of apoptosis of the glandular epithelium. Furthermore, scanty prostatic secretion with flattening of acinar epithelial lining occurred. Conclusion. Annona muricata has antiproliferative effects on BPH-1 cells and reduces prostate size, possibly through apoptosis.

Pre- and posttreatment with edaravone protects CA1 hippocampus and enhances neurogenesis in the subgranular zone of dentate gyrus after transient global cerebral ischemia in rats

Edaravone is clinically used for treatment of patients with acute cerebral infarction. However, the effect of double application of edaravone on neurogenesis in the hippocampus following ischemia remains unknown. In the present study, we explored whether pre- and posttreatment of edaravone had any effect on neural stem/progenitor cells (NSPCs) in the subgranular zone of hippocampus in a rat model of transient global cerebral ischemia and elucidated the potential mechanism of its effects. Male Sprague-Dawley rats were divided into three groups: sham-operated (n = 15), control (n = 15), and edaravone-treated (n = 15) groups. Newly generated cells were labeled by 5-bromo-2-deoxyuridine. Immunohistochemistry was used to detect neurogenesis. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling was used to detect cell apoptosis. Reactive oxygen species (ROS) were detected by 2,7-dichlorofluorescien diacetate assay in NSPCs in vitro. Hypoxia-inducible factor-1α (HIF-1α) and cleaved caspase-3 proteins were quantified by western blot analysis. Treatment with edaravone significantly increased the number of NSPCs and newly generated neurons in the subgranular zone (p < .05). Treatment with edaravone also decreased apoptosis of NSPCs (p < .01). Furthermore, treatment with edaravone significantly decreased ROS generation and inhibited HIF-1α and cleaved caspase-3 protein expressions. These findings indicate that pre- and posttreatment with edaravone enhances neurogenesis by protecting NSPCs from apoptosis in the hippocampus, which is probably mediated by decreasing ROS generation and inhibiting protein expressions of HIF-1α and cleaved caspase-3 after cerebral ischemia.

A flavonoid isolated from Streptomyces sp. (ERINLG-4) induces apoptosis in human lung cancer A549 cells through p53 and cytochrome c release caspase dependant pathway

The aim of this study was to investigate the anticancer activity of a flavonoid type of compound isolated from soil derived filamentous bacterium Streptomyces sp. (ERINLG-4) and to explore the molecular mechanisms of action. Cytotoxic properties of ethyl acetate extract was carried out against A549 lung cancer cell line using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Cytotoxic properties of isolated compound were investigated in A549 lung cancer cell line, COLO320DM cancer cell line and Vero cells. The compound showed potent cytotoxic properties against A549 lung cancer cell line and moderate cytotoxic properties against COLO320DM cancer cell line. Isolated compound showed no toxicity up to 2000 μg/mL in Vero cells. So we have chosen the A549 lung cancer cell line for further anticancer studies. Intracellular visualization was done by using a laser scanning confocal microscope. Apoptosis was measured using DNA fragmentation technique. Treatment of the A549 cancer cells with isolated compound significantly reduced cell proliferation, increased formation of fragmented DNA and apoptotic body. Activation of caspase-9 and caspase-3 indicated that compound may be inducing intrinsic and extrinsic apoptosis pathways. Bcl-2, p53, pro-caspases, caspase-3, caspase-9 and cytochrome c release were detected by western blotting analysis after compound treatment (123 and 164 μM). The activities of pro-caspases-3, caspase-9 cleaved to caspase-3 and caspase-9 gradually increased after the addition of isolated compound. But Bcl-2 protein was down regulated after treatment with isolated compound. Molecular docking studies showed that the compound bound stably to the active sites of caspase-3 and caspase-9. These results strongly suggest that the isolated compound induces apoptosis in A549 cancer cells via caspase activation through cytochrome c release from mitochondria. The present results might provide helpful suggestions for the design of antitumor drugs toward lung cancer treatment.

Traumatic white matter injury and glial activation: from basic science to clinics

An improved understanding and characterization of glial activation and its relationship with white matter injury will likely serve as a novel treatment target to curb post injury inflammation and promote axonal remyelination after brain trauma. Traumatic brain injury (TBI) is a significant public healthcare burden and a leading cause of death and disability in the United States. Particularly, traumatic white matter (WM) injury or traumatic axonal injury has been reported as being associated with patients' poor outcomes. However, there is very limited data reporting the importance of glial activation after TBI and its interaction with WM injury. This article presents a systematic review of traumatic WM injury and the associated glial activation, from basic science to clinical diagnosis and prognosis, from advanced neuroimaging perspective. It concludes that there is a disconnection between WM injury research and the essential role of glia which serve to restore a healthy environment for axonal regeneration following WM injury. Particularly, there is a significant lack of non-invasive means to characterize the complex pathophysiology of WM injury and glial activation in both animal models and in humans. An improved understanding and characterization of the relationship between glia and WM injury will likely serve as a novel treatment target to curb post injury inflammation and promote axonal remyelination.

The effects of bioactive compounds from plant foods on mitochondrial function: a focus on apoptotic mechanisms

Mitochondria are essential organelles for cellular integrity and functionality maintenance and their imparement is implicated in the development of a wide range of diseases, including metabolic, cardiovascular, degenerative and hyperproliferative pathologies. The identification of different compounds able to interact with mitochondria for therapeutic purposes is currently becoming of primary importance. Indeed, it is well known that foods, particularly those of vegetable origin, present several constituents with beneficial effects on health. This review summarizes and updates the most recent findings concerning the mechanisms through which different dietary compounds from plant foods affect mitochondria functionality in healthy and pathological in vitro and in vivo models, paying particular attention to the pathways involved in mitochondrial biogenesis and apoptosis.

A novel polysaccharide from Ganoderma atrum exerts antitumor activity by activating mitochondria-mediated apoptotic pathway and boosting the immune system

Ganoderma is a precious health-care edible medicinal fungus in China. A novel Ganoderma atrum polysaccharide (PSG-1) is the main bioactive component. We investigated the antitumor effect and molecular mechanisms of PSG-1. It exhibited no significant effect on cell proliferation directly. In contrast, administration of PSG-1 markedly suppressed tumor growth in CT26 tumor-bearing mice. It was observed that PSG-1 caused apoptosis in CT26 cells. Apoptosis was associated with loss of mitochondrial membrane potential, enhancement of mitochondrial cytochrome c release and intracellular ROS production, elevation of p53 and Bax expression, downregulation of Bcl-2, and the activation of caspase-9 and -3. Moreover, PSG-1 enhanced immune organ index and promoted lymphocyte proliferation as well as cytokine levels in serum. Taken together, our data indicate that PSG-1 has potential antitumor activity in vivo by inducing apoptosis via mitochondria-mediated apoptotic pathway and enhances host immune system function. Therefore, PSG-1 could be a safe and effective antitumor, bioactive agent or functional food.

Role of stress, depression, and aging in cognitive decline and Alzheimer's disease

Late-onset Alzheimer's disease (AD) is a chronic neurodegenerative disorder and the most common cause of progressive cognitive dysfunction and dementia. Despite considerable progress in elucidating the molecular pathology of this disease, we are not yet close to unraveling its etiopathogenesis. A battery of neurotoxic modifiers may underpin neurocognitive pathology via deleterious heterogeneous pathologic impact in brain regions, including the hippocampus. Three important neurotoxic factors being addressed here include aging, stress, and depression. Unraveling "upstream pathologies" due to these disparate neurotoxic entities, vis-à-vis cognitive impairment involving hippocampal dysfunction, is of paramount importance. Persistent systemic inflammation triggers and sustains neuroinflammation. The latter targets several brain regions including the hippocampus causing upregulation of amyloid beta and neurofibrillary tangles, synaptic and neuronal degeneration, gray matter volume atrophy, and progressive cognitive decline. However, what is the fundamental source of this peripheral inflammation in aging, stress, and depression? This chapter highlights and delineates the inflammatory involvement-i.e., from its inception from gut to systemic inflammation to neuroinflammation. It highlights an upregulated cascade in which gut-microbiota-related dysbiosis generates lipopolysaccharides (LPS), which enhances inflammation and gut's leakiness, and through a Web of interactions, it induces stress and depression. This may increase neuronal dysfunction and apoptosis, promote learning and memory impairment, and enhance vulnerability to cognitive decline.

Cell survival and apoptosis signaling as therapeutic target for cancer: marine bioactive compounds

Inhibition of apoptosis leads to activation of cell survival factors (e.g., AKT) causes continuous cell proliferation in cancer. Apoptosis, the major form of cellular suicide, is central to various physiological processes and the maintenance of homeostasis in multicellular organisms. A number of discoveries have clarified the molecular mechanism of apoptosis, thus clarifying the link between apoptosis and cell survival factors, which has a therapeutic outcome. Induction of apoptosis and inhibition of cell survival by anticancer agents has been shown to correlate with tumor response. Cellular damage induces growth arrest and tumor suppression by inducing apoptosis, necrosis and senescence; the mechanism of cell death depends on the magnitude of DNA damage following exposure to various anticancer agents. Apoptosis is mainly regulated by cell survival and proliferating signaling molecules. As a new therapeutic strategy, alternative types of cell death might be exploited to control and eradicate cancer cells. This review discusses the signaling of apoptosis and cell survival, as well as the potential contribution of marine bioactive compounds, suggesting that new therapeutic strategies might follow.

Stress-inducible caspase substrate TRB3 promotes nuclear translocation of procaspase-3

Pseudokinase TRB3 is a stress-inducible nuclear protein, which has recently been shown to be involved in ER stress-induced apoptosis. However, it remains unclear how TRB3 contributes to the process. We recently demonstrated that TRB3 was cleaved by caspase-3 (CASP3) in vitro and also in apoptosis-induced cells. Thus, we investigate the role of TRB3 cleavage in the apoptotic process to address the above question. Overexpression studies revealed that the cleavage of TRB3 promoted CASP3/7 activation and apoptosis. In contrast, the anti-apoptotic effects were found under TRB3 non-cleavable conditions, such as ER stress, and also when the CASP3/7 activation was enhanced by knockdown of endogenous TRB3 expression. Interestingly, nuclear translocation of procaspase-3 (proCASP3) was observed in cells either overexpressing TRB3 or under tunicamycin-induced ER stress. Although forced cytoplasmic expression of proCASP3 enhanced apoptosis significantly, its nuclear expression did not produce any pro-apoptotic effect, suggesting that nuclear distribution of proCASP3 is not critical for the execution of apoptosis. Thus, TRB3 might prevent cytoplasmic activation of CASP3 by promoting proCASP3 entry into the nucleus, and thereby inhibit apoptosis. Taken together, our results suggest that TRB3, through its own cleavage, functions as a molecular switch between the cell survival and apoptotic pathways under stressful conditions.

Biology of mitochondria in neurodegenerative diseases

Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS) are the most common human adult-onset neurodegenerative diseases. They are characterized by prominent age-related neurodegeneration in selectively vulnerable neural systems. Some forms of AD, PD, and ALS are inherited, and genes causing these diseases have been identified. Nevertheless, the mechanisms of the neuronal degeneration in these familial diseases, and in the more common idiopathic (sporadic) diseases, are unresolved. Genetic, biochemical, and morphological analyses of human AD, PD, and ALS, as well as their cell and animal models, reveal that mitochondria could have roles in this neurodegeneration. The varied functions and properties of mitochondria might render subsets of selectively vulnerable neurons intrinsically susceptible to cellular aging and stress and the overlying genetic variations. In AD, alterations in enzymes involved in oxidative phosphorylation, oxidative damage, and mitochondrial binding of Aβ and amyloid precursor protein have been reported. In PD, mutations in mitochondrial proteins have been identified and mitochondrial DNA mutations have been found in neurons in the substantia nigra. In ALS, changes occur in mitochondrial respiratory chain enzymes and mitochondrial programmed cell death proteins. Transgenic mouse models of human neurodegenerative disease are beginning to reveal possible principles governing the biology of selective neuronal vulnerability that implicate mitochondria and the mitochondrial permeability transition pore. This chapter reviews several aspects of mitochondrial biology and how mitochondrial pathobiology might contribute to the mechanisms of neurodegeneration in AD, PD, and ALS.

Dexamethasone and Aβ₂₅-₃₅ accelerate learning and memory impairments due to elevate amyloid precursor protein expression and neuronal apoptosis in 12-month male rats

Alzheimer's disease (AD) is an irreversible, progressive brain disorder of the elderly characterized by learning and memory impairment. Stress level glucocorticoids (GCs) and β-amyloid (Aβ) peptides deposition are found to be correlated with dementia progression in patients with AD. However, little is known about the simultaneous effects of glucocorticoids and Aβ on learning and memory impairment and its mechanism. In this study, 12-month-old male rats were chronically treated with Aβ(25-35) (10 μg/rat, hippocampal CA1 injection) and dexamethasone (DEX, 1.5mg/kg) for 14 days to investigate the effects of DEX and Aβ(25-35) treatment on learning and memory impairments, pathological changes, neuronal ultrastructure, amyloid precursor protein (APP) processing and neuronal cell apoptosis. Our results showed that DEX or Aβ(25-35) treatment alone for 14 days had caused slight damage on learning and memory impairments and hippocampal neurons, but damages were significantly increased with DEX+Aβ(25-35) treatment. And the mRNA levels of the APP, β-secretase and caspase 3 were significantly increased after DEX+Aβ(25-35) treatment. The immunohistochemistry demonstrated that APP, Aβ(1-40), caspase 3 and cytochrome c in hippocampus CA1 were significantly increased. Furthermore, Hoechst 33258 staining and Aβ(1-40) ELISA results showed that DEX+Aβ(25-35) treatment induced hippocampus CA1 neuron apoptosis and increased the level of Aβ(1-40). The results suggest that the simultaneous effects of GCs and Aβ may have important roles in the etiopathogenesis of AD, and demonstrate that stressful life events and GC therapy may increase the toxicity of Aβ and have cumulative impacts on the course of AD development and progression.

Roles of reactive oxygen and nitrogen species in pain

Peroxynitrite (PN; ONOO⁻) and its reactive oxygen precursor superoxide (SO; O₂•⁻) are critically important in the development of pain of several etiologies including pain associated with chronic use of opiates such as morphine (also known as opiate-induced hyperalgesia and antinociceptive tolerance). This is now an emerging field in which considerable progress has been made in terms of understanding the relative contributions of SO, PN, and nitroxidative stress in pain signaling at the molecular and biochemical levels. Aggressive research in this area is poised to provide the pharmacological basis for development of novel nonnarcotic analgesics that are based upon the unique ability to selectively eliminate SO and/or PN. As we have a better understanding of the roles of SO and PN in pathophysiological settings, targeting PN may be a better therapeutic strategy than targeting SO. This is because, unlike PN, which has no currently known beneficial role, SO may play a significant role in learning and memory. Thus, the best approach may be to spare SO while directly targeting its downstream product, PN. Over the past 15 years, our team has spearheaded research concerning the roles of SO and PN in pain and these results are currently leading to the development of solid therapeutic strategies in this important area.

Flow cytometric analysis of ca-induced membrane permeability transition of isolated rat liver mitochondria

The membrane permeability transition (MPT) of mitochondria plays an important role in the mechanism of apoptotic cell death in various cells. Classic type MPT is induced by Ca²⁺ in the presence of inorganic phosphate and respiratory substrate, and is characterized by various events including generation of reactive oxygen species (ROS), membrane depolarization, swelling, release of Ca²⁺ and high sensitivity to cyclosporine A. However, the sequence of these events and the effect of antioxidants on their events remain obscure. Flow cytometry is a convenient method to investigate the order of events among various functions occurring in MPT using a limited amount of mitochondria (200 µl of 0.02 mg protein/ml) without contamination by other organelles. Flow cytometric analysis revealed that Ca²⁺ sequentially induced ROS generation, depolarization, swelling and Ca²⁺ release in mitochondria by a cyclosporine A-inhibitable mechanism. These results were supported by the finding that Ca²⁺-induced MPT was inhibited by antioxidants, such as glutathione and N-acetylcysteine. It was also revealed that various inhibitors of Ca²⁺-induced phospholipase A₂ suppressed all of the events associated with Ca²⁺-induced MPT. These results suggested that ROS generation and phospholipase A₂ activation by Ca²⁺ underlie the mechanism of the initiation of MPT.

Immunohistochemical expression of procaspase-3 and its clinical significance in childhood non-Hodgkin lymphomas

Previous studies have shown differences in expression levels of apoptosis regulatory proteins in non-Hodgkin lymphomas (NHLs) and indicated the correlation of procaspase-3 (proC-3) and caspase-3 activation to the response of chemotherapy. We investigated whether proC-3 expression in tumor biopsies of childhood NHLs is related to clinical outcome. Formalin-fixed paraffin-embedded tissues from 58 children with NHL were evaluated for proC-3 expression by immunochemistry analysis. The study included 20 cases of Burkitt lymphoma, 7 cases of diffuse large B-cell lymphoma, 18 cases of anaplastic large cell lymphoma (ALCL), and 13 cases of precursor lymphoblastic lymphoma. The highest expression level of proC-3 was observed in ALCL. In the multivariate analysis the higher clinical stage of disease and higher expression level of proC-3 were independent and appear to be significant prognostic factors of treatment failure. Our results suggest that the high expression level of proC-3 may be a powerful independent predictor of response to chemotherapy and progression-free survival in childhood NHLs.

Protective effect of extract of Astragalus on learning and memory impairments and neurons' apoptosis induced by glucocorticoids in 12-month-old male mice

Alzheimer's disease (AD) is a chronic neurodegenerative disorder marked by a progressive loss of memory and cognitive function. Stress-level glucocorticoids are correlated with dementia progression in patients with AD. In this study, 12-month male mice were chronically treated with stress-level dexamethasone (DEX, 5 mg/kg) and extract of Astragalus (EA, 10, 20, and 40 mg/kg) or Ginsenoside Rg1 (Rg1, 6.5 mg/kg) for 21 days. We investigated the protective effect of EA against DEX injury in mice and its action mechanism. Our results indicate that DEX can induce learning and memory impairments and neuronal cell apoptosis. The mRNA levels of caspase-3 are selectively increased after DEX administration. The results of immunohistochemistry demonstrate that caspase-3 and cytochrome c in hippocampus (CA1, CA3) and neocortex are significantly increased. Furthermore, DEX treatment increased the activity of caspase-9 and caspase-3. Treatment groups with EA (20 and 40 mg/kg) or Rg1 (6.5 mg/kg) significantly improve learning and memory, downregulate the mRNA level of caspase-3, decrease expression of caspase-3 and cytochrome c in hippocampus (CA1, CA3) and neocortex, and inhibit activity of caspase-9 and caspase-3. The present findings highlight a possible mechanism by which stress level of DEX accelerates learning and memory impairments and increases neuronal apoptosis and the potential neuronal protection of EA.

Wild-type and mutant p53 proteins interact with mitochondrial caspase-3

Caspases play a key role in the apoptotic pathway by virtue of their ability to cleave key protein substrates within the dying cell. Caspases are produced as inactive zymogens, and need to become proteolytically processed in order to become active. A key executioner caspase, caspase-3, has previously been found to exist in both the cytosol and the mitochondria. At the mitochondria, caspase-3 is associated with both the inner and outer mitochondrial membranes, where it interacts with heat shock proteins Hsp60 and Hsp10. Like caspase-3, a small portion of the p53 tumor suppressor protein is localized to mitochondria, particularly after genotoxic stress. p53 interacts with various members of the Bcl2 family at the mitochondria, and this interaction is key to its ability to induce apoptosis. In this study, we sought to determine the identity of other mitochondrial p53-interacting proteins. Using immunoprecipitation from purified mitochondria followed by mass spectrometry we identified caspase-3 as a mitochondrial p53-interacting protein. Interestingly, we find that tumor-derived mutant forms of p53 retain the ability to interact with mitochondrial caspase-3. Further, we find evidence that these mutant forms of p53 may interfere with the ability of procaspase-3 to become proteolytically activated by caspase-9. The combined data suggest that tumor-derived mutants of p53 may be selected for in tumor cells due to their ability to bind and inhibit the activation of caspase-3.

Polygonatum cyrtonema lectin induces murine fibrosarcoma L929 cell apoptosis via a caspase-dependent pathway as compared to Ophiopogon japonicus lectin

Galanthus nivalis agglutinin (GNA)-related lectin family, a superfamily of strictly mannose-binding specific lectins, has been well-known to possess several biological functions including apoptosis-inducing activities. However, the precise mechanisms of GNA-related lectins to induce apoptosis remains to be clarified. In this study, we showed that Polygonatum cyrtonema lectin (PCL) and Ophiopogon japonicus lectin (OJL), the two mannose-binding GNA-related lectins, could induce murine fibrosarcoma L929 cell apoptosis. In addition, we found that there was a close link between their sugar-binding and apoptosis-inducing activities. Interestingly, we further confirmed that the mechanism of lectin-induced apoptosis was a caspase-dependent pathway. Moreover, we found that the two lectins could amplify tumor necrosis factor α (TNFα)-induced apoptosis. Taken together, these findings would open a new perspective for GNA-related lectins as potential anti-tumor agents.

Processing of metacaspase into a cytoplasmic catalytic domain mediating cell death in Leishmania major

Metacaspases are cysteine peptidases that could play a role similar to caspases in the cell death programme of plants, fungi and protozoa. The human protozoan parasite Leishmania major expresses a single metacaspase (LmjMCA) harbouring a central domain with the catalytic dyad histidine and cysteine as found in caspases. In this study, we investigated the processing sites important for the maturation of LmjMCA catalytic domain, the cellular localization of LmjMCA polypeptides, and the functional role of the catalytic domain in the cell death pathway of Leishmania parasites. Although LmjMCA polypeptide precursor form harbours a functional mitochondrial localization signal (MLS), we determined that LmjMCA polypeptides are mainly localized in the cytoplasm. In stress conditions, LmjMCA precursor forms were extensively processed into soluble forms containing the catalytic domain. This domain was sufficient to enhance sensitivity of parasites to hydrogen peroxide by impairing the mitochondrion. These data provide experimental evidences of the importance of LmjMCA processing into an active catalytic domain and of its role in disrupting mitochondria, which could be relevant in the design of new drugs to fight leishmaniasis and likely other protozoan parasitic diseases.

Increased expression but not sensitivity to Fas/CD95 in glioblastoma cells depleted of mitochondrial DNA

Mitochondria and Fas (CD95) play a role in tumorigenicity and apoptosis. In the present study, the functional relationship of mitochondria to Fas in mediating apoptosis was investigated. Glioblastoma cells (DBTRGO5MG, U87) were depleted of mitochondrial DNA (mtDNA) by treatment with ethidium bromide (Rho(-) cells). Compared to Rho(+) cells, Rho(-) cells showed enhanced expression of Fas at the cell surface. Indeed, when Rho(+) cells were treated with mitochondrial respiratory chain complex inhibitors, Fas cell surface expression was noted to increase in a similar fashion to the depletion of mtDNA in both cell lines. However, when cells were evaluated for sensitivity to apoptosis using Fas-engagement, there was no difference between the Rho(+) and Rho(-) cells in either cell line. By contrast, sensitivity to the cytotoxic agent cis-diammine-dichloroplatinum (cisplatin) was markedly increased in the Rho(-) cells, which expressed higher levels of cell surface Fas. Expression of Fas is increased with the depletion of mtDNA and respiratory complex inhibitors. However, this increase in expression does not necessarily translate to an increase in sensitivity to Fas-engagement, although there is an increase in the sensitivity of depleted cells to cytotoxic agents such as cisplatin.

Apoptogenic factors released from mitochondria

When cells kill themselves, they usually do so by activating mechanisms that have evolved specifically for that purpose. These mechanisms, which are broadly conserved throughout the metazoa, involve two processes: activation in the cytosol of latent cysteine proteases (termed caspases), and disruption of mitochondrial functions. These processes are linked in a number of different ways. While active caspases can cleave proteins in the mitochondrial outer membrane, and cleave and thereby activate certain pro-apoptotic members of the Bcl-2 family, proteins released from the mitochondria can trigger caspase activation and antagonise IAP family proteins. This review will focus on the pro-apoptotic molecules that are released from the mitochondria of cells endeavouring to kill themselves. This article is part of a Special Issue entitled Mitochondria: the deadly organelle.

Response of IMCD3 cells to hypertonic challenges as analyzed by electron microscopy

This work defines the ultrastructural responses of immortalized cells from the inner medullary collecting duct cells (IMCD3 cells) to hypertonic challenges. The cultured cells were either acutely exposed to hypertonic medium (550 mOsm/kgH₂O) for 24-72 h or gradually adapted to 600 or 900 mOsm/kgH₂O media with sodium chloride. After short (24 h) hypertonic challenges, there was an expansion of the Golgi apparatus with distinct expression of the γ subunit of Na,K-ATPase. The frequency of active caspase-3-positive cells was unchanged as was also the measured activity of caspase-3. Immunoelectron microscopy showed that active caspase-3 in the positive cells was localized in cytoplasmic bodies 0.5-1 μm in diameter but not in other structures. Apoptotic bodies with the nuclei were only rarely observed following acute hypertonicity for 24 to 72 h. Following prolonged hypertonic challenges, some cells showed condensation of the chromatin but still few apoptotic bodies. Gradual hypertonicity to 900 mOsm/kgH₂O led to a decrease of microvilli, dilated cisternae of the endoplasmic reticulum (ER), increased abundance of free ribosomes and longitudinal mitochondrial cristae. Virus particles were present inside and outside the cells in all experimental conditions and appeared unrelated to the apoptotic process. The results suggest that cultured IMCD3 cells are resistant to short hypertonic challenge or gradual adaptation to moderate hypertonicity and only rarely exhibit more ultrastructural apoptotic changes than control cells. The presence of caspase-3-containing bodies is a novel finding, and we suggest that they arise from the ER and are involved in the apoptotic signaling system.