Photooxidative damage to lysosomes of cultured macrophages by acridine orange

Isoxazole based nucleosides induce autophagy through the production of ROS and the suppression of the β-catenin pathway in human colorectal carcinoma cells

β-catenin is frequently implicated in signaling pathways that regulate autophagy, and the production of reactive oxygen species (ROS) has been linked to autophagy activation. Isoxazole-based nucleoside compounds have demonstrated anti-cancer properties. In this study, we report the identification of novel isoxazole-nucleosides as anti-tumor agents and their impact on autophagy in human colorectal carcinoma (CRC) cells. Among the ITP series, ITP-7 and ITP-9 (ITP-7/9) exhibited significant cytotoxicity compared to other compounds. Treatment with ITP-7/9 upregulated the expression of key autophagy-related proteins, including LC3 II, Atg7, and phosphorylated Beclin-1. Additionally, ITP-7/9 promoted the formation of LC3 II puncta and increased the number of AO-stained and MDC-stained cells, indicating enhanced autophagy. ROS levels were elevated following ITP-7/9 exposure, and treatment with N-acetyl l-cysteine (NAC), a ROS inhibitor, reduced the ITP-7/9-induced expression of LC3 II. Furthermore, ITP-7/9 inhibited β-catenin's role as a transcription factor, as observed in ICC assays. Moreover, cells with β-catenin gene deletion exhibited stronger autophagy when treated with ITP-7/9 compared to those treated with ITP-7/9 alone. These findings suggest that ITP-7/9 induces autophagy and promotes CRC cell death by downregulating β-catenin.

An antioxidant screen identifies ascorbic acid for prevention of light-induced mitotic prolongation in live cell imaging

Phototoxicity is an important issue in fluorescence live imaging of light-sensitive cellular processes such as mitosis. Among several approaches to reduce phototoxicity, the addition of antioxidants to the media has been used as a simple method. Here, we analyzed the impact of phototoxicity on the mitotic progression in fluorescence live imaging of human cells and performed a screen to identify the most efficient antioxidative agents that reduce it. Quantitative analysis shows that high amounts of light illumination cause various mitotic defects such as prolonged mitosis and delays of chromosome alignment and centrosome separation. Among several antioxidants, our screen reveals that ascorbic acid significantly alleviates these phototoxic effects in mitosis. Furthermore, we demonstrate that adding ascorbic acid to the media enables fluorescence imaging of mitotic events at very high temporal resolution without obvious photodamage. Thus, this study provides an optimal method to effectively reduce the phototoxic effects in fluorescence live cell imaging.

Cholesterol-Depletion-Induced Membrane Repair Carries a Raft Conformer of P-Glycoprotein to the Cell Surface, Indicating Enhanced Cholesterol Trafficking in MDR Cells, Which Makes Them Resistant to Cholesterol Modifications

The human P-glycoprotein (P-gp), a transporter responsible for multidrug resistance, is present in the plasma membrane's raft and non-raft domains. One specific conformation of P-gp that binds to the monoclonal antibody UIC2 is primarily associated with raft domains and displays heightened internalization in cells overexpressing P-gp, such as in NIH-3T3 MDR1 cells. Our primary objective was to investigate whether the trafficking of this particular P-gp conformer is dependent on cholesterol levels. Surprisingly, depleting cholesterol using cyclodextrin resulted in an unexpected increase in the proportion of raft-associated P-gp within the cell membrane, as determined by UIC2-reactive P-gp. This increase appears to be a compensatory response to cholesterol loss from the plasma membrane, whereby cholesterol-rich raft micro-domains are delivered to the cell surface through an augmented exocytosis process. Furthermore, this exocytotic event is found to be part of a complex trafficking mechanism involving lysosomal exocytosis, which contributes to membrane repair after cholesterol reduction induced by cyclodextrin treatment. Notably, cells overexpressing P-gp demonstrated higher total cellular cholesterol levels, an increased abundance of stable lysosomes, and more effective membrane repair following cholesterol modifications. These modifications encompassed exocytotic events that involved the transport of P-gp-carrying rafts. Importantly, the enhanced membrane repair capability resulted in a durable phenotype for MDR1 expressing cells, as evidenced by significantly improved viabilities of multidrug-resistant Pgp-overexpressing immortal NIH-3T3 MDR1 and MDCK-MDR1 cells compared to their parents when subjected to cholesterol alterations.

Macro-microporous ZIF-8 MOF complexed with lysosomal pH-adjusting hexadecylsulfonylfluoride as tumor vaccine delivery systems for improving anti-tumor cellular immunity

Tumor vaccine therapy, which can induce tumor antigen-specific cellular immune responses to directly kill tumor cells, is considered to be one of the most promising tumor immunotherapies. How to elicit effective tumor antigen-specific cellular immunity is the key for the development of tumor vaccines. However, current tumor vaccines with conventional antigen delivery systems mainly induce humoral immunity but not effective cellular immunity. In this study, based on pH-sensitive, ordered macro-microporous zeolitic imidazolate framework-8 (SOM-ZIF-8) and hexadecylsulfonylfluoride (HDSF), an intelligent tumor vaccine delivery system SOM-ZIF-8/HDSF was developed to elicit potent cellular immunity. Results demonstrated that the SOM-ZIF-8 particles could efficiently encapsulate antigen into the macropores, promote antigen uptake by antigen-presenting cells, facilitate lysosomal escape, and enhance antigen cross-presentation and cellular immunity. In addition, the introduction of HDSF could up-regulate the lysosomal pH to protect antigens from acid degradation, which further promoted antigen cross-presentation and cellular immunity. The immunization tests showed that the tumor vaccines based on the delivery system improved antigen-specific cellular immune response. Moreover, the tumor vaccines significantly inhibited tumor growth in B16 melanoma-bearing C57BL/6 mice. These results indicate that SOM-ZIF-8/HDSF as an intelligent vaccine delivery system could be used for the development of novel tumor vaccines.

The effect of A2E on lysosome membrane permeability during blue light-induced human RPEs apoptosis

BACKGROUND

To investigate the effect of N-retinyl-N-retinylidene ethanolamine (A2E) on lysosome membrane permeability (LMP) during blue light-induced human retinal pigment epithelium cells (RPEs) apoptosis.

METHODS

By building an A2E and blue light irradiation inducing RPEs damage model, the CCK-8 assay was used to detect RPEs viability loaded with different concentrations of A2E after different culturing time to determine the optimum A2E loading concentration. And the RPEs fluorescence intensity changes were observed by fluorescence microscopy loaded with different concentration of A2E. The RPEs were divided into four groups randomly: control group, A2E-loaded group, blue light irradiation group, and A2E-loaded + blue light irradiation group. Annexin V-FITC/PI and TUNEL/DAPI methods were used to detect RPEs apoptotic rate. Laser scanning confocal microscopy (LSCM) was used to observe RPEs LMP changes stained by acridine orange (AO) method.

RESULTS

The CCK-8 result showed a downward trend in cells viability of RPEs loaded with increasing concentration of A2E and extending culturing time. The optimum A2E loading concentration was determined at 25 μmol/L. With increasing A2E loading concentrations, the intensity of fluorescence in RPEs decreased gradually. The RPEs apoptotic rate in blue light irradiation + A2E-loaded group was significantly higher than those in other three groups detected by Annexin V-FITC/PI method, which was similar to TUNEL/DAPI's result. After AO staining, cytoplasmic and nucleolar RNAs emits green fluorescence; lysosomes emit red fluorescence. Through the interference of A2E and blue light on RPEs, red fluorescent leakage from the lysosomes (means LMP increasing) can be observed. The mean red fluorescence intensity was chosen as the statistics indicator to estimate LMP change in RPEs cultured in vitro. Compared with the control group, the red fluorescence intensity decreased in A2E-loaded group, blue light irradiation group, and blue light irradiation + A2E-loaded group. Meanwhile, the mean red fluorescence intensity in blue light irradiation + A2E-loaded group was the lowest.

CONCLUSIONS

Both A2E-loaded and blue light irradiation could induce human RPEs apoptosis, and the two factors had a synergistic effect. In addition, both A2E and blue light can lead to LMP increasing, which indicated LMP change might be the upstream part in inducing mitochondrion-dependent apoptotic pathway. These data provided evidence that A2E as the most important auto-fluorescence substance in lipofuscin is an initiator of blue light-mediated damage of RPEs and participate in pathogenesis of retinal degenerative diseases in humans.

Lysosomal Changes in Mitosis

The recent discovery demonstrating that the leakage of cathepsin B from mitotic lysosomes assists mitotic chromosome segregation indicates that lysosomal membrane integrity can be spatiotemporally regulated. Unlike many other organelles, structural and functional alterations of lysosomes during mitosis remain, however, largely uncharted. Here, we demonstrate substantial differences in lysosomal proteome, lipidome, size, and pH between lysosomes that were isolated from human U2OS osteosarcoma cells either in mitosis or in interphase. The combination of pharmacological synchronization and mitotic shake-off yielded ~68% of cells in mitosis allowing us to investigate mitosis-specific lysosomal changes by comparing cell populations that were highly enriched in mitotic cells to those mainly in the G1 or G2 phases of the cell cycle. Mitotic cells had significantly reduced levels of lysosomal-associated membrane protein (LAMP) 1 and the active forms of lysosomal cathepsin B protease. Similar trends were observed in levels of acid sphingomyelinase and most other lysosomal proteins that were studied. The altered protein content was accompanied by increases in the size and pH of LAMP2-positive vesicles. Moreover, mass spectrometry-based shotgun lipidomics of purified lysosomes revealed elevated levels of sphingolipids, especially sphingomyelin and hexocylceramide, and lysoglyserophospholipids in mitotic lysosomes. Interestingly, LAMPs and acid sphingomyelinase have been reported to stabilize lysosomal membranes, whereas sphingomyelin and lysoglyserophospholipids have an opposite effect. Thus, the observed lysosomal changes during the cell cycle may partially explain the reduced lysosomal membrane integrity in mitotic cells.

Isocyanide Substitution in Acridine Orange Shifts DNA Damage-Mediated Phototoxicity to Permeabilization of the Lysosomal Membrane in Cancer Cells

Simple Summary

Aside from tissue cell renewal, tumor cells are also produced every day. In ordinary conditions, immunologically controlled cell death mechanisms limit cancer development. There are several cell death processes used for how normal and tumor cells are eliminated at the end of their lifespan. In cancer therapy, cells dying via immunological death are more efficiently eradicated than cells dying by classical apoptosis. Photodynamic treatments with some photosensitizers target lysosomes. Lysosomal death diverts apoptosis to the immunologically more pertinent necrosis-like death pathways. Acridine orange (AO), a well-known photosensitizer, targets lysosomes as well. We have synthesized a new compound abbreviated as DM, a modified AO, and examined details of intracellular processes leading to photodynamic cell death. We have proven that DM targets lysosomes better than AO. Remarkably, with DM, we could visualize an abrupt nuclear DNA release from cells during the photodynamic process. Our work highlights which cellular events may enhance immunological cell death.

Abstract

In cancer therapy, immunogenic cell death eliminates tumor cells more efficiently than conventional apoptosis. During photodynamic therapy (PDT), some photosensitizer (PS) targeting lysosomes divert apoptosis to the immunologically more relevant necrosis-like cell death. Acridine orange (AO) is a PS targeting lysosome. We synthesized a new compound, 3-N,N-dimethylamino-6-isocyanoacridine (DM), a modified AO, aiming to target lysosomes better. To compare DM and AO, we studied optical properties, toxicity, cell internalization, and phototoxicity. In addition, light-mediated effects were monitored by the recently developed QUINESIn method on nuclei, and membrane stability, morphology, and function of lysosomes utilizing fluorescent probes by imaging cytometry in single cells. DM proved to be a better lysosomal marker at 405 nm excitation and lysed lysosomes more efficiently. AO injured DNA and histones more extensively than DM. Remarkably, DM’s optical properties helped visualize shockwaves of nuclear DNA released from cells during the PDT. The asymmetric polar modification of the AO leads to a new compound, DM, which has increased efficacy in targeting and disrupting lysosomes. Suitable AO modification may boost adaptive immune response making PDT more efficient.

Peroxisome proliferator-activated receptor δ rescues xCT-deficient cells from ferroptosis by targeting peroxisomes

Ferroptosis is a recently recognized process of cell death characterized by accumulation of iron-dependent lipid peroxides. Herein, we demonstrate that peroxisome proliferator-activated receptor δ (PPARδ) inhibits ferroptosis of mouse embryonic fibroblasts (MEFs) derived from cysteine/glutamate transporter (xCT)-knockout mice. Activation of PPARδ by the specific ligand GW501516 led to a dose-dependent decrease in ferroptotic cell death triggered by xCT deficiency, along with decreased levels of intracellular iron accumulation and lipid peroxidation. These effects of GW501516 were abolished by PPARδ-targeting small interfering RNA (siRNA) and the PPARδ inhibitor GSK0660, indicating that PPARδ inhibits xCT deficiency-induced ferroptosis. In addition, GW501516-activated PPARδ time- and dose-dependently upregulated catalase expression at both the mRNA and protein levels. This PPARδ-mediated upregulation of catalase was markedly attenuated in cells treated with PPARδ-targeting siRNA and GSK0660, indicating that expression of catalase is dependent on PPARδ. Consistently, the effects of GW501516 on ferroptosis of xCT-deficient MEFs were counteracted in the presence of 3-amino-1,2,4-triazole, a specific inhibitor of catalase, suggesting that catalase is essential for the effect of PPARδ on ferroptosis triggered by xCT deficiency. GW501516-activated PPARδ stabilized peroxisomes through catalase upregulation by targeting peroxisomal hydrogen peroxide-mediated lysosomal rupture, which led to ferroptosis of xCT-deficient MEFs. Collectively, these results demonstrate that PPARδ modulates ferroptotic signals in xCT-deficient MEFs by regulating catalase expression.

Oxidative damage of lysosomes in regulated cell death systems: Pathophysiology and pharmacologic interventions

Lysosomes are small specialized organelles containing a variety of different hydrolase enzymes that are responsible for degradation of all macromolecules, entering the cells through the endosomal system or originated from the internal sources. This allows for transport and recycling of nutrients and internalization of surface proteins for antigen presentation as well as maintaining cellular homeostasis. Lysosomes are also important storage compartments for metal ions and nutrients. The integrity of lysosomal membrane is central to maintaining their normal function, but like other cellular membranes, lysosomal membrane is subject to damage mediated by reactive oxygen species. This results in spillage of lysosomal enzymes into the cytoplasm, leading to proteolytic damage to cellular systems and organelles. Several forms of lysosomal dependent cell death have been identified in diseases. Examination of these events are important for finding treatment strategies relevant to cancer or neurodegenerative diseases as well as autoimmune deficiencies. In this review, we have examined the current literature on involvement of lysosomes in induction of programed cell death and have provided an extensive list of therapeutic approaches that can modulate cell death. Exploitation of these mechanisms can lead to novel therapies for cancer and neurodegenerative diseases.

Reliability evaluation of biomarker reference ranges for mesocosm and field conditions: Cellular innate immunomarkers in Gasterosteus aculeatus

Due to their sensitivity to environmental contamination and their link with fish health status, innate immunomarkers are of great interest for environmental risk assessment studies. Nevertheless, the lack of knowledge about the effect of confounding factors can lead to data misinterpretation and false diagnostics. So, the determination of reference values was of huge interest for the integration of biomarkers in biomonitoring programs. Laboratory immunomarker reference ranges (including cellular mortality, leucocyte distribution, phagocytosis activity, respiratory burst and lysosomal presence) that consider three confounding factors (season, sex and body size) were previously developed in three-spined stickleback, Gasterosteus aculeatus, from our husbandry. Usefulness of these reference ranges in biomonitoring programs depends on how they can be transposed to various experimental levels, such as mesocosm (outdoor artificial pond) and field conditions. Immunomarkers were therefore measured every 2 months over 1 year in one mesocosm and in one site assumed to uncontaminated (Houdancourt, field). Differences between immunomarker seasonal variations in mesocosm and field fish on one side and laboratory fish on the other side were quantified: in some cases, seasonal trends were not significant or did not differ between mesocosm and laboratory conditions, but overall, models developed based on data obtained in laboratory conditions were poorly predictive of data obtained in mesocosm or field conditions. To propose valuable field reference ranges, mesocosm and field data were integrated in innate immunomarker modelling in order to strengthen the knowledge on the effect of confounding factors. As in laboratory conditions, sex was overall a confounding factor only for necrotic cell percentage and granulocyte-macrophage distribution and size was a confounding factor only for cellular mortality, leucocyte distribution and phagocytosis activity. Confounding factors explained a large proportion of immunomarker variability in particular for phagocytosis activity and lysosomal presence. Further research is needed to test the field models in a biomonitoring program to compare the sensitivity of immunomarkers to the confounding factors identified in this study and the sensitivity to various levels of pollution.

Assessment of DNA Susceptibility to Denaturation as a Marker of Chromatin Structure

The susceptibility of DNA in situ to denaturation is modulated by its interactions with histone and nonhistone proteins, as well as with other chromatin components related to the maintenance of the 3D nuclear structure. Measurement of DNA proclivity to denature by cytometry provides insight into chromatin structure and thus can be used to recognize cells in different phases of the cell cycle, including mitosis, quiescence (G₀ ), and apoptosis, as well as to identify the effects of drugs that modify chromatin structure. Particularly useful is the method's ability to detect chromatin changes in sperm cells related to DNA fragmentation and infertility. This article presents a flow cytometric procedure for assessing DNA denaturation based on application of the metachromatic property of acridine orange (AO) to differentially stain single- versus double-stranded DNA. This approach circumvents limitations of biochemical methods of examining DNA denaturation, in particular the fact that the latter destroy higher orders of chromatin structure and that, being applied to bulk cell populations, they cannot detect heterogeneity of individual cells. Because the metachromatic properties of AO have also found application in other cytometric procedures, such as differential staining of RNA versus DNA and assessment of lysosomal proton pump including autophagy, to avert confusion between these approaches and the use of this dye in the DNA denaturation assay, these AO applications are briefly outlined in this unit as well. © 2019 by John Wiley & Sons, Inc. Basic Protocol: Differential staining of single- versus double-stranded DNA with acridine orange.

Mitochondrial respiratory chain deficiency inhibits lysosomal hydrolysis

Mitochondria are key organelles for cellular metabolism, and regulate several processes including cell death and macroautophagy/autophagy. Here, we show that mitochondrial respiratory chain (RC) deficiency deactivates AMP-activated protein kinase (AMPK, a key regulator of energy homeostasis) signaling in tissue and in cultured cells. The deactivation of AMPK in RC-deficiency is due to increased expression of the AMPK-inhibiting protein FLCN (folliculin). AMPK is found to be necessary for basal lysosomal function, and AMPK deactivation in RC-deficiency inhibits lysosomal function by decreasing the activity of the lysosomal Ca²⁺ channel MCOLN1 (mucolipin 1). MCOLN1 is regulated by phosphoinositide kinase PIKFYVE and its product PtdIns(3,5)P₂, which is also decreased in RC-deficiency. Notably, reactivation of AMPK, in a PIKFYVE-dependent manner, or of MCOLN1 in RC-deficient cells, restores lysosomal hydrolytic capacity. Building on these data and the literature, we propose that downregulation of the AMPK-PIKFYVE-PtdIns(3,5)P₂-MCOLN1 pathway causes lysosomal Ca²⁺ accumulation and impaired lysosomal catabolism. Besides unveiling a novel role of AMPK in lysosomal function, this study points to the mechanism that links mitochondrial malfunction to impaired lysosomal catabolism, underscoring the importance of AMPK and the complexity of organelle cross-talk in the regulation of cellular homeostasis.

Abbreviation: ΔΨ_m: mitochondrial transmembrane potential; AMP: adenosine monophosphate; AMPK: AMP-activated protein kinase; ATG5: autophagy related 5; ATP: adenosine triphosphate; ATP6V0A1: ATPase, H+ transporting, lysosomal, V0 subbunit A1; ATP6V1A: ATPase, H+ transporting, lysosomal, V0 subbunit A; BSA: bovine serum albumin; CCCP: carbonyl cyanide-m-chlorophenylhydrazone; CREB1: cAMP response element binding protein 1; CTSD: cathepsin D; CTSF: cathepsin F; DMEM: Dulbecco’s modified Eagle’s medium; DMSO: dimethyl sulfoxide; EBSS: Earl’s balanced salt solution; ER: endoplasmic reticulum; FBS: fetal bovine serum; FCCP: carbonyl cyanide-p-trifluoromethoxyphenolhydrazone; GFP: green fluorescent protein; GPN: glycyl-L-phenylalanine 2-naphthylamide; LAMP1: lysosomal associated membrane protein 1; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MCOLN1/TRPML1: mucolipin 1; MEF: mouse embryonic fibroblast; MITF: melanocyte inducing transcription factor; ML1N*2-GFP: probe used to detect PtdIns(3,5)P₂ based on the transmembrane domain of MCOLN1; MTORC1: mechanistic target of rapamycin kinase complex 1; NDUFS4: NADH:ubiquinone oxidoreductase subunit S4; OCR: oxygen consumption rate; PBS: phosphate-buffered saline; pcDNA: plasmid cytomegalovirus promoter DNA; PCR: polymerase chain reaction; PtdIns3P: phosphatidylinositol-3-phosphate; PtdIns(3,5)P₂: phosphatidylinositol-3,5-bisphosphate; PIKFYVE: phosphoinositide kinase, FYVE-type zinc finger containing; P/S: penicillin-streptomycin; PVDF: polyvinylidene fluoride; qPCR: quantitative real time polymerase chain reaction; RFP: red fluorescent protein; RNA: ribonucleic acid; SDS-PAGE: sodium dodecyl sulfate polyacrylamide gel electrophoresis; shRNA: short hairpin RNA; siRNA: small interfering RNA; TFEB: transcription factor EB; TFE3: transcription factor binding to IGHM enhancer 3; TMRM: tetramethylrhodamine, methyl ester, perchlorate; ULK1: unc-51 like autophagy activating kinase 1; ULK2: unc-51 like autophagy activating kinase 2; UQCRC1: ubiquinol-cytochrome c reductase core protein 1; v-ATPase: vacuolar-type H+-translocating ATPase; WT: wild-type

Concurrent detection of lysosome and tissue transglutaminase activation in relation to cell cycle position during apoptosis induced by different anticancer drugs

Described is the new cytometric approach do detect either stimulation or a collapse of lysosomal proton pump (lysosomes rupture) combined with activation of transglutaminase 2 (TG2) during induction of apoptosis. Apoptosis of human lymphoblastoid TK6 cells was induced by combination of 2-deoxyglucose with the isoquinoline alkaloid berberine, by DNA topoisomerase I inhibitor camptothecin, its analog topotecan, topoisomerase II inhibitors etoposide or mitoxantrone, as well as by the cytotoxic anticancer ribonuclease ranpirnase (onconase). Activity of the proton pump of lysosomes was assessed by measuring entrapment and accumulation of the basic fluorochrome acridine orange (AO) resulting in its metachromatic red luminescence (F_>640 ) within these organelles. Activation of TG2 was detected in the same cell subpopulation by the evidence of crosslinking of cytoplasmic proteins revealed by the increased intensity of the side light scatter (SSC) as well as following cell lysis by detergent, by its red fluorescence after staining by sulforhodamine 101. Because at low AO concentration nuclear DNA of the lysed cells was stoichiometrically stained green (F₅₃₀ ) its quantity provided information on effects of the drug treatments on cell cycle in relation to activation of TG2. The data reveal that activation of lysosomal proton pump was evident in subpopulations of cells treated with 2-deoxyglucose plus berberine, topotecan, etoposide and mitoxantrone but not with ranpirnase. The collapse of lysosomal proton pump possibly reporting rupture of these organelles was observed in definite cell subpopulations after treatment with each of the studied drugs. Because regardless of the inducer of apoptosis TG2 activation invariably was correlated with lysosomes rupture it is likely that it was triggered by calcium ions or protons released from the ruptured lysosomes. This new methodological approach offers the means to investigate mechanisms and factors affecting autophagic lysosomes proton pump activity vis-à-vis TG2 activation that are common in several pathological states. © 2019 International Society for Advancement of Cytometry.

Efficient lysis of B-chronic lymphocytic leukemia cells by the plant-derived sesquiterpene alcohol α-bisabolol, a dual proapoptotic and antiautophagic agent

The sesquiterpene α-bisabolol (α-BSB) is a cytotoxic agent against acute leukemia and chronic myeloid leukemia cells. Here the profile of α-BSB citotoxicity was evaluated ex vivo in primary mononuclear blood cells isolated from 45 untreated B-chronic lymphocytic leukemia (B-CLL) patients. We studied the effects of α-BSB by flow cytometric and western blotting techniques with the following findings: (1) α-BSB was an effective proapoptotic agent against B-CLL cells (IC50 42 ± 15 μM). It was also active, but to a lesser extent, on normal residual B cells and monocytes (IC50 68 ± 34 and 74 ± 28 μM, respectively; p < 0.01), while T-cells, though not achieving IC50, were nevertheless decreased. (2) Lipid raft content positively correlated with α-BSB cell sensitivity, while neither the phenotype of B-CLL cells nor the disease clinical stage did affect the sensitivity to α-BSB. (3) Flow cytometry analysis evidenced the induction of pores in mitochondrial and lysosomal membrane after 3- to 5-hour exposure of B-CLL cells to α-BSB, leading to apoptosis; in contrast, western blotting analysis showed inhibition of the autophagic flux. Therefore, according to cellular selectivity, α-BSB is a cytotoxic agent preferentially active against leukemic cells, while its lower activity on normal B cells, monocytes and T cells may account for an additive anti-inflammatory effect targeting the leukemia-associated pro-inflammatory microenvironment. Consistent with the observed effects on intracellular processes, α-BSB should be regarded as a dual agent, both activating mitochondrial-based apoptosis and inhibiting autophagy by disrupting lysosomes.

Aloe-Emodin Influence on the Lysosomal Compartment of Hela Cells

Background: Aloe-emodin belongs to the group of anthraquinones having extremely high biological activity. The aim of this study was to evaluate the range of morphological and biochemical changes in HeLa cells treated with aloe-emodin, especially with regard to the lysosomal compartment. Methods: Marking of lysosomes was performed with neutral red staining for conventional light microscopy and acridine orange staining for confocal microscopy. To evaluate ctivity of lysosomal enzymes and permeability of the lysosomal membrane, spectrophotometric techniques were employed. Results: Aloe-emodin caused increased permeability of lysosomal membranes in HeLa cells, expressed inter alia by extinction of the orange color of acridine orange (lysosomal marker) and in reduction of neutral red uptake by lysosomes. These changes are accompanied by release of cathepsins from the interior of the lysosomes with a simultaneous highly significant increase in their activity in the cytoplasm. Conclusion: The results indicate that aloeemodin can activate lysosomal pathway-dependent apoptosis in HeLa cells.

Phototriggered N2-Generating Submicron Particles for Selective Killing of Cancer Cells

Killing of cancer cells by applying mechanical disruption has been an appealing emerging strategy for cancer treatment in recent years. In this study, photoresponsive submicron particles based on diazo-resin that are able to release N₂ under UV irradiation were prepared through a polyamine-salt aggregation method. After surface modification with hyaluronic acid, the particles could be internalized selectively by cancer cells and were mainly located in lysosomes after 6 h incubation. The viability of cancer cells decreased obviously after they were co-cultured with photoresponsive particles and UV irradiation due to the integrity damage of lysosomes by phototriggered N₂ generation and the subsequent increased number of reactive oxygen species.

Preparation of photo-responsive poly(ethylene glycol) microparticles and their influence on cell viability

Intelligent colloidal particles have been widely used as carriers for delivery of bioactive molecules due to the ability of controlled release. However, attention is mainly paid to the effects of their payloads, whereas the impacts of carriers are largely ignored. In this study, photo-responsive polyethylene glycol (PEG) microparticles were fabricated by using 8-arm-PEG with terminal amine groups (8-arm-PEG-NH₂) and a photo-cleavable cross-linker. Due to the cleavable CO bond in the cross-linker, under UV irradiation the PEG particles could be decomposed gradually, leading to particle swelling and eventual disappearance. The PEG particles could be internalized by smooth muscle cells and HepG2 cells, and located in lysosomes. Their intracellular photo-response induced significant decrease of cell viability and increase of reactive oxygen species level.

Natural extracellular nanovesicles and photodynamic molecules: is there a future for drug delivery?

Photodynamic molecules represent an alternative approach for cancer therapy for their property (i) to be photo-reactive; (ii) to be not-toxic for target cells in absence of light; (iii) to accumulate specifically into tumour tissues; (iv) to be activable by a light beam only at the tumour site and (v) to exert cytotoxic activity against tumour cells. However, to date their clinical use is limited by the side effects elicited by systemic administration. Extracellular vesicles are endogenous nanosized-carriers that have been recently introduced as a natural delivery system for therapeutic molecules. We have recently shown the ability of human exosomes to deliver photodynamic molecules. Therefore, this review focussed on extracellular vesicles as a novel strategy for the delivery of photodynamic molecules at cancer sites. This completely new approach may enhance the delivery and decrease the toxicity of photodynamic molecules, therefore, represent the future for photodynamic therapy for cancer treatment.

Acridine orange exhibits photodamage in human bladder cancer cells under blue light exposure

Human bladder cancer (BC) cells exhibit a high basal level of autophagic activity with accumulation of acridine-orange(AO)-stained acidic vesicular organelles. The rapid AO relocalization was observed in treated BC cells under blue-light emission. To investigate the cytotoxic effects of AO on human BC cell lines under blue-light exposure, human immortalized uroepithelial (SV-Huc-1) and BC cell lines (5637 and T24) were treated with indicated concentrations of AO or blue-light exposure alone and in combination. The cell viability was then determined using WST-1, time-lapse imaging with a Cytosmart System and continuous quantification with a multi-mode image-based reader. Treatment of AO or blue-light exposure alone did not cause a significant loss of viability in BC cells. However, AO exhibited a dose-dependent increment of cytotoxicity toward BC cells under blue-light exposure. Furthermore, the tumor formation of BC cells with treatment was significantly reduced when evaluated in a mouse xenograft model. The photodamage caused by AO was nearly neglected in SV-Huc-1 cells, suggesting a differential effect of this treatment between cancer and normal cells. In summary, AO, as a photosensitizer, disrupts acidic organelles and induces cancer cell death in BC cells under blue-light irradiation. Our findings may serve as a novel therapeutic strategy against human BC.

Live Cell Imaging: Assessing the Phototoxicity of 488 and 546 nm Light and Methods to Alleviate it

In live cell imaging of fluorescent proteins, phototoxicity of the excitation light can be problematical. Cell death is obvious, but reduced cell viability can make the interpretation of observations error prone. We characterized the phototoxic consequences of 488 and 546 nm light on untransformed human cells and tested methods that have or could be used to alleviate photodamage. Unlabeled RPE1 cells were given single 0.5-2.5 min irradiations in early G1 from a mercury arc lamp on a fluorescence microscope. Four hundred eighty-eight nanometer light produced a dose-dependent decrease in the percentage of cells that progressed to mitosis, slowing of the cell cycle for some of those entering mitosis, and a ∼12% incidence of cell death for the highest dose. For 546 nm light we found a 10-15% reduction in the percentage of cells entering mitosis, no strong dose dependency, and a ∼2% incidence of cell death for the longest irradiations. For cells expressing GFP-centrin1 or mCherry-centrin1, fewer entered mitosis for each dose than unlabeled cells. For constant total dose 488 nm light irradiations of unlabeled cells, reducing the intensity 10-fold or spreading the exposures out as a series of 10 sec pulses at 1 min intervals produced a minor and not consistent improvement in the percentage of cells entering mitosis. Reducing oxidative processes, by culturing at ∼3% oxygen or adding the reducing agent Trolox noticeably increased the fraction of cells entering mitosis. Thus, for long-term imaging there can be value to using RFP constructs and for GFP-tagged proteins reducing oxidative processes. J. Cell. Physiol. 232: 2461-2468, 2017. © 2016 Wiley Periodicals, Inc.

Fluorescent Dye Labeling of Erythrocytes and Leukocytes for Studying the Flow Dynamics in Mouse Retinal Circulation

The retinal and choroidal blood flow dynamics may provide insight into the pathophysiology and sequelae of various ocular diseases, such as glaucoma, diabetic retinopathy, age-related macular degeneration (AMD) and other ocular inflammatory conditions. It may also help to monitor the therapeutic responses in the eye. The proper labeling of the blood cells, coupled with live-cell imaging of the labeled cells, allows for the investigation of the flow dynamics in the retinal and choroidal circulation. Here, we describe the standardized protocols of 1.5% indocyanine green (ICG) and 1% sodium fluorescein labeling of mice erythrocytes and leukocytes, respectively. Scanning laser ophthalmoscopy (SLO) was applied to visualize the labeled cells in the retinal circulation of C57BL/6J mice (wild type). Both methods demonstrated distinct fluorescently labeled cells in the mouse retinal circulation. These labeling methods can have wider applications in various ocular disease models.

Acridine Orange/exosomes increase the delivery and the effectiveness of Acridine Orange in human melanoma cells: A new prototype for theranostics of tumors

Specifically targeted drug delivery systems with low immunogenicity and toxicity are deemed to increase efficacy of cancer chemotherapy. Acridine Orange (AO) is an acidophilic dye with a strong tumoricidal action following excitation with a light source at 466 nm. However, to date the clinical use of AO is limited by the potential side effects elicited by systemic administration. The endogenous nanocarrier exosomes have been recently introduced as a natural delivery system for therapeutic molecules. In this article, we show the outcome of the administration to human melanoma cells of AO charged Exosomes (Exo-AO), in both monolayer and spheroid models. The results showed an extended drug delivery time of Exo-AO to melanoma cells as compared to the free AO, improving the cytotoxicity of AO. This study shows that Exo-AO have a great potential for a real exploitation as a new theranostic approach against tumors based on AO delivered through the exosomes.

Zinc Chelation Mediates the Lysosomal Disruption without Intracellular ROS Generation

We report the molecular mechanism for zinc depletion caused by TPEN (N,N,N′,N′-Tetrakis(2-pyridylmethyl)ethylenediamine) in neuroblastoma cells. The activation of p38 MAP kinase and subsequently caspase 3 is not due to or followed by redox imbalance or ROS generation, though these are commonly observed in literature. We found that TPEN is not responsible for ROS generation and the mechanism involves essentially lysosomal disruption caused by intracellular zinc depletion. We also observed a modest activation of Bax and no changes in the Bcl-2 proteins. As a result, we suggest that TPEN causes intracellular zinc depletion which can influence the breakdown of lysosomes and cell death without ROS generation.

Effect of glutamate on lysosomal membrane permeabilization in primary cultured cortical neurons

Glutamate is the principal neurotransmitter in the central nervous system. Glutamate-mediated excitotoxicity is the predominant cause of cerebral damage. Recent studies have shown that lysosomal membrane permeabilization (LMP) is involved in ischemia-associated neuronal death in non-human primates. This study was designed to investigate the effect of glutamate on lysosomal stability in primary cultured cortical neurons. Glutamate treatment for 30 min induced the permeabilization of lysosomal membranes as assessed by acridine orange redistribution and immunofluorescence of cathepsin B in the cytoplasm. Inhibition of glutamate excitotoxicity by the NMDA receptor antagonist MK-801 and the calcium chelator ethylene glycolbis (2-aminoethylether)-N, N, N′, N′-tetraacetic acid, rescued lysosomes from permeabilization. The role of calpain and reactive oxygen species (ROS) in inducing LMP was also investigated. Ca²⁺ overload following glutamate treatment induced the activation of calpain and the production of ROS, which are two major contributors to neuronal death. It has been reported that lysosomal-associated membrane protein 2 (LAMP2) and heat shock protein (HSP)70 are two calpain substrates that promote LMP in cancer cells; however, it was found that calpains were activated by glutamate, but only LAMP2 was subsequently degraded. Furthermore, LMP was not alleviated by treatment with the calpain inhibitors calpeptin and SJA6017, which blocked the cleavage of the calpain substrate α-fodrin. It was demonstrated that LMP was significantly alleviated by treatment with the antioxidant N-Acetyl-L-cysteine, indicating that LMP involvement in early glutamate excitotoxicity may be mediated partly by ROS rather than calpain activation. Overall, these data shed light on the role of ROS-mediated LMP in early glutamate excitotoxicity.

Reliable Screening of Dye Phototoxicity by Using a Caenorhabditis elegans Fast Bioassay

Phototoxicity consists in the capability of certain innocuous molecules to become toxic when subjected to suitable illumination. In order to discover new photoactive drugs or characterize phototoxic pollutants, it would be advantageous to use simple biological tests of phototoxicy. In this work, we present a pilot screening of 37 dyes to test for phototoxic effects in the roundworm Caenorhabditis elegans. Populations of this nematode were treated with different dyes, and subsequently exposed to 30 min of white light. Behavioral outcomes were quantified by recording the global motility using an infrared tracking device (WMicrotracker). Of the tested compounds, 17 dyes were classified as photoactive, being phloxine B, primuline, eosin Y, acridine orange and rose Bengal the most phototoxic. To assess photoactivity after uptake, compounds were retested after washing them out of the medium before light irradiation. Dye uptake into the worms was also analyzed by staining or fluorescence. All the positive drugs were incorporated by animals and produced phototoxic effects after washing. We also tested the stress response being triggered by the treatments through reporter strains. Endoplasmic reticulum stress response (hsp-4::GFP strain) was activated by 22% of phototoxic dyes, and mitochondrial stress response (hsp-6::GFP strain) was induced by 16% of phototoxic dyes. These results point to a phototoxic perturbation of the protein functionality and an oxidative stress similar to that reported in cell cultures. Our work shows for the first time the feasibility of C. elegans for running phototoxic screenings and underscores its application on photoactive drugs and environmental pollutants assessment.

Ferritin-stimulated lipid peroxidation, lysosomal leak, and macroautophagy promote lysosomal "metastability" in primary hepatocytes determining in vitro cell survival

Several pathologies are associated with elevated levels of serum ferritin, for which growth inhibitory properties have been reported; however, the underlying mechanisms are still poorly defined. Previously we have described cytotoxic properties of isoferritins released from primary hepatocytes in vitro, which induce apoptosis in an iron and oxidative stress-dependent mode. Here we show that this ferritin species stimulates endosome clustering and giant endosome formation in primary hepatocytes accompanied by enhanced lysosomal membrane permeability (LMP). In parallel, protein modification by lipid peroxidation-derived 4-hydroxynonenal (HNE) is strongly promoted by ferritin, the HNE-modified proteins (HNE-P) showing remarkable aggregation. Emphasizing the prooxidant context, GSH is rapidly depleted and the GSH/GSSG ratio is substantially declining in ferritin-treated cells. Furthermore, ferritin triggers a transient upregulation of macroautophagy which is abolished by iron chelation and apparently supports HNE-P clearance. Macroautophagy inhibition by 3-methyladenine strongly amplifies ferritin cytotoxicity in a time- and concentration-dependent mode, suggesting an important role of macroautophagy on cellular responses to ferritin endocytosis. Moreover, pointing at an involvement of lysosomal proteolysis, ferritin cytotoxicity and lysosome fragility are aggravated by the protease inhibitor leupeptin. In contrast, EGF which suppresses ferritin-induced cell death attenuates ferritin-mediated LMP. In conclusion, we propose that HNE-P accumulation, lysosome dysfunction, and macroautophagy stimulated by ferritin endocytosis provoke lysosomal "metastability" in primary hepatocytes which permits cell survival as long as in- and extrinsic determinants (e.g., antioxidant availability, damage repair, EGF signaling) keep the degree of lysosomal destabilization below cell death-inducing thresholds.

WIN induces apoptotic cell death in human colon cancer cells through a block of autophagic flux dependent on PPARγ down-regulation

Cannabinoids have been reported to possess anti-tumorigenic activity in cancer models although their mechanism of action is not well understood. Here, we show that the synthetic cannabinoid WIN55,212-2 (WIN)-induced apoptosis in colon cancer cell lines is accompanied by endoplasmic reticulum stress induction. The formation of acidic vacuoles and the increase in LC3-II protein indicated the involvement of autophagic process which seemed to play a pro-survival role against the cytotoxic effects of the drug. However, the enhanced lysosomal membrane permeabilization (LMP) blocked the autophagic flux after the formation of autophagosomes as demonstrated by the accumulation of p62 and LC3, two markers of autophagic degradation. Data also provided evidence for a role for nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) in cannabinoid signalling. PPARγ expression, at both protein and mRNA levels, was significantly down-regulated after WIN treatment and its inhibition, either by specific antagonists or by down-regulation via gene silencing, induced effects on cell viability as well as on ER stress and autophagic markers similar to those obtained in the presence of WIN. Moreover, the observation that the increase in p62 level and the induction of LMP were also modified by PPARγ antagonists seemed to indicate that PPARγ down-regulation was crucial to determinate the block of autophagic flux, thus confirming the critical role of PPARγ in WIN action. In conclusion, at our knowledge, our results are the first to show that the reduction of PPARγ levels contributes to WIN-induced colon carcinoma cell death by blocking the pro-survival autophagic response of cells.

Oxidative stress-dependent activation of the eIF2α–ATF4 unfolded protein response branch by skin sensitizer 1-fluoro-2,4-dinitrobenzene modulates dendritic-like cell maturation and inflammatory status in a biphasic manner [corrected]

The pathogenesis of allergic contact dermatitis, the most common manifestation of immunotoxicity in humans, is intimately connected to hapten-induced maturation of dendritic cells (DC). The molecular mechanisms driving this maturational program are not completely known; however, initial danger signals such as the generation of reactive oxygen species (ROS) were shown to play a critical role. Recent evidence linking ROS production, endoplasmic reticulum (ER) stress, and the pathogenesis of several inflammatory diseases led us to analyze, in the present work, the ability of the skin sensitizer 1-fluoro-2,4-dinitrobenzene (DNFB) to evoke ER stress in DC-like THP-1 cells and the concomitant consequences to their immunobiology. We found that DNFB triggers a ROS-dependent activation of the PERK-eIFα-ATF4 unfolded protein response (UPR) branch conferring cytoprotection and modulating the maturation/proinflammatory cell status in a biphasic manner. Early DNFB induction of ATF4 positively modulates autophagy-related genes MAP1LC3B and ATG3 and stabilizes the transcription factor Nrf2, causing a strong induction of the HMOX1-detoxifying gene. Moreover, we observed that in a first phase, DNFB-induced ATF4 upregulates IL8 mRNA levels while blocking CD86, IL1B, IL12B, and CXL10 transcription. Later, following ATF4 decay, HMOX1 and IL8 transcription drastically decrease and CD86, IL1B, and Il12B are upregulated. Overall, our results evidence a connection between sensitizer-induced redox imbalance and the establishment of ER stress in DC-like cells and provide new insights into the role of UPR effectors such as ATF4 to the complex DC maturational program.

Lysosome size, motility and stress response regulated by fronto-temporal dementia modifier TMEM106B

Fronto-temporal lobar degeneration with TDP-43 (FTLD-TDP) is a fatal neurodegeneration. TMEM106B variants are linked to FTLD-TDP risk, and TMEM106B is lysosomal. Here, we focus on neuronal TMEM106B, and demonstrate co-localization and traffic with lysosomal LAMP-1. pH-sensitive reporters demonstrate that the TMEM106B C-terminus is lumenal. The TMEM106B N-terminus interacts with endosomal adaptors and other TMEM106 proteins. TMEM106B knockdown reduces neuronal lysosomal number and diameter by STED microscopy, and overexpression enlarges LAMP-positive structures. Reduction of TMEM106B increases axonally transported lysosomes, while TMEM106B elevation inhibits transport and yields large lysosomes in the soma. TMEM106B overexpression alters lysosomal stress signaling, causing a translocation of the mTOR-sensitive transcription factor, TFEB, to neuronal nuclei. TMEM106B loss-of-function delays TFEB translocation after Torin-1-induced stress. Enlarged TMEM106B-overexpressing lysosomes maintain organelle integrity longer after lysosomal photodamage than do control lysosomes, while small TMEM106B-knockdown lysosomes are more sensitive to illumination. Thus, neuronal TMEM106B plays a central role in regulating lysosomal size, motility and responsiveness to stress, highlighting the possible role of lysosomal biology in FTLD-TDP.

Palladacycle (BPC) antitumour activity against resistant and metastatic cell lines: the relationship with cytosolic calcium mobilisation and cathepsin B activity

The search for new compounds that induce p53-independent apoptosis is the focus of many studies in cancer biology because these compounds could be more specific and would overcome chemotherapy resistance. In this study, we evaluated the in vitro antitumour activity of a Biphosphinic Palladacycle Complex (BPC) and extended preclinical studies to an in vivo model. Saos-2 cells, a p53-null human osteosarcoma drug-resistant cell line, were treated with BPC in the presence or absence of a cathepsin B inhibitor and a calcium chelator (CA074 and BAPTA-AM, respectively), and several parameters related to apoptosis were evaluated. Preclinical studies were performed with mice that were intravenously inoculated with murine melanoma B16F10-Nex2 cells and treated intraperitoneally (i.p.) with BPC (8 mg/kg/day) for ten consecutive days, when lung metastatic nodules were counted. In vitro data show that BPC induces cell death in Saos-2 cells mainly by apoptosis, which was accompanied by the effector caspase-3 activation. These events are most likely related to Bax translocation and increased cytosolic calcium mobilisation, mainly from intracellular compartments. Lysosomal Membrane Permeabilisation (LMP) was also observed after 12 h of BPC exposure. Interestingly, BAPTA-AM and CA074 significantly decreased BPC cytotoxicity, suggesting that both calcium and cathepsin B are required for BPC antitumour activity. In vivo studies demonstrated that BPC protects mice against murine metastatic melanoma. In conclusion, BPC complex is an effective anticancer compound against metastatic murine melanoma. This complex is cytotoxic to the drug-resistant osteosarcoma Saos-2 human tumour cells by inducing apoptosis triggered by calcium signalling and a lysosomal-dependent pathway.

A simple method to visualize and assess the integrity of lysosomal membrane in mammalian cells using a fluorescent dye

Fluorescent dyes have been used as "nanosensors" for visualization and determination of various processes occurring inside a cell, or intracellular events, such as cell cycle progression and intracellular trafficking. Here, we describe a novel use of acridine orange to visualize lysosomes and discriminate cells with healthy lysosomes from cells with damaged lysosomes in two different types of mammalian cells: fibroblasts and macrophages. This method allows assessment of lysosomal membrane integrity upon exposure to various foreign particles, i.e., engineered nanoparticles. The uniqueness of this method enables investigators to acquire fluorescent images with a dye that is susceptible to photo-bleaching under UV light. These acquired images bolster the quantitative data, providing a visual representation of the cell morphology as well as assess its nucleus and lysosomes.

Flow cytometry detection of lysosomal presence and lysosomal membrane integrity in the three-spined stickleback (Gasterosteus aculeatus L.) immune cells: applications in environmental aquatic immunotoxicology

The neutral red retention assay has been proposed to determine the lysosomal membrane stability in immune cells. Nevertheless, this assay implies many examinations under a microscope at short time intervals and therefore the analysis of few samples. The present study proposes two more rapid, efficient, and sensitive sample analyses using flow cytometry method. Lysosomal presence and lysosomal membrane integrity (LMI) were evaluated on the three-spined stickleback, Gasterosteus aculeatus (L.), a well-described model fish species for aquatic ecotoxicology studies. After development of the two biomarkers, they were validated by ex vivo contamination with endosulfan and copper and by in situ sampling. These immunomarkers were clearly modulated by pollutants and their variations seemed to be correlated with leucocyte mortality. Thus, from a practical point of view, lysosomal presence and LMI may provide novel and efficient means of evaluating immune capacities and indicating the toxic effects of environmental pollution.

Sensitivity to lysosome-dependent cell death is directly regulated by lysosomal cholesterol content

Alterations in lipid homeostasis are implicated in several neurodegenerative diseases, although the mechanisms responsible are poorly understood. We evaluated the impact of cholesterol accumulation, induced by U18666A, quinacrine or mutations in the cholesterol transporting Niemann-Pick disease type C1 (NPC1) protein, on lysosomal stability and sensitivity to lysosome-mediated cell death. We found that neurons with lysosomal cholesterol accumulation were protected from oxidative stress-induced apoptosis. In addition, human fibroblasts with cholesterol-loaded lysosomes showed higher lysosomal membrane stability than controls. Previous studies have shown that cholesterol accumulation is accompanied by the storage of lipids such as sphingomyelin, glycosphingolipids and sphingosine and an up regulation of lysosomal associated membrane protein-2 (LAMP-2), which may also influence lysosomal stability. However, in this study the use of myriocin and LAMP deficient fibroblasts excluded these factors as responsible for the rescuing effect and instead suggested that primarily lysosomal cholesterol content determineD the cellular sensitivity to toxic insults. Further strengthening this concept, depletion of cholesterol using methyl-β-cyclodextrin or 25-hydroxycholesterol decreased the stability of lysosomes and cells became more prone to undergo apoptosis. In conclusion, cholesterol content regulated lysosomal membrane permeabilization and thereby influenced cell death sensitivity. Our data suggests that lysosomal cholesterol modulation might be used as a therapeutic strategy for conditions associated with accelerated or repressed apoptosis.

Gene expression profiling of macrophages: implications for an immunosuppressive effect of dissolucytotic gold ions

Background

Gold salts has previously been used in the treatment of rheumatoid arthritis but have been replaced by biologicals such as TNF-α inhibitors. The mechanisms behind the anti-inflammatory effect of metallic gold ions are still unknown, however, recent data showed that charged gold atoms are released from pure metallic gold implants by macrophages via a dissolucytosis membrane, and that gold ions are taken up by local macrophages, mast cells and to some extent fibroblasts. These findings open the question of possible immunomodulatory effects of metallic gold and motivate efforts on a deeper understanding of the effect of metallic gold on key inflammatory cells as macrophages.

Methods

Human macrophage cells (cell line THP-1) were grown on gold foils and intracellular uptake was analysed by autometallography. The impact of phagocytised gold ions on viability of THP-1 cells was investigated by trypan blue staining and TUNEL assay. The global gene expression profile of THP-1 cells after incorporation of gold ions was studied using microarray analysis comprising approximately 20,000 genes. The gene expression data was confirmed by measurement of secreted proteins.

Results

Autometallography showed intracellular uptake of gold ions into THP-1 cells. No significant effect on viability of THP-1 cells was demonstrated. Our data revealed a unique gene expression signature of dissolucytotic THP-1 cells that had taken up gold ions. A large number of regulated genes were functionally related to immunomodulation. Gold ion uptake induced downregulation of genes involved in rheumatoid arthritis such as hepatocyte growth factor, tenascin-C, inhibitor of DNA binding 1 and 3 and matrix metalloproteinase 13.

Conclusion

The data obtained in this study offer new insights into the mode of action of gold ions and suggest for the investigation of effects on other key cells and a possible future role of metallic gold as implants in rheumatoid arthritis or other inflammatory conditions.

A quantitative method for measuring phototoxicity of a live cell imaging microscope

Fluorescence-based imaging regimes require exposure of living samples under study to high intensities of focused incident illumination. An often underestimated, overlooked, or simply ignored fact in the design of any experimental imaging protocol is that exposure of the specimen to these excitation light sources must itself always be considered a potential source of phototoxicity. This can be problematic, not just in terms of cell viability, but much more worrisome in its more subtle manifestation where phototoxicity causes anomalous behaviors that risk to be interpreted as significant, whereas they are mere artifacts. This is especially true in the case of microbial pathogenesis, where host-pathogen interactions can prove especially fragile to light exposure in a manner that can obscure the very processes we are trying to observe. For these reasons, it is important to be able to bring the parameter of phototoxicity into the equation that brings us to choose one fluorescent imaging modality, or setup, over another. Further, we need to be able to assess the risk that phototoxicity may occur during any specific imaging experiment. To achieve this, we describe here a methodological approach that allows meaningful measurement, and therefore relative comparison of phototoxicity, in most any variety of different imaging microscopes. In short, we propose a quantitative approach that uses microorganisms themselves to reveal the range over which any given fluorescent imaging microscope will yield valid results, providing a metrology of phototoxic damage, distinct from photobleaching, where a clear threshold for phototoxicity is identified. Our method is widely applicable and we show that it can be adapted to other paradigms, including mammalian cell models.

Role of oxidative stress in lysosomal membrane permeabilization and apoptosis induced by gentamicin, an aminoglycoside antibiotic

Gentamicin, an aminoglycoside antibiotic used to treat severe bacterial infections, may cause acute renal failure. At therapeutic concentrations, gentamicin accumulates in lysosomes and induces apoptosis in kidney proximal tubular cells. In gentamicin-treated renal LLC-PK1 cells, acridine orange release from lysosomes, previously interpreted as lysosomal membrane permeabilization, precedes the apoptotic cascade that develops during incubation with gentamicin. However, the link between gentamicin lysosomal accumulation and apoptosis remains unclear. We here examined if reactive oxygen species (ROS) production could account for gentamicin-induced acridine orange release and apoptosis, and the implication of iron in these events. We found that gentamicin induced ROS production prior to, and at lower drug concentrations than required for, acridine orange release and apoptosis. ROS antioxidant or scavenger, catalase, and N-acetylcysteine largely prevented these events. Vital confocal imaging revealed that gentamicin-induced ROS production occurs in lysosomes. Deferoxamine, an iron chelator, which is endocytosed and accumulates in lysosomes, largely prevented gentamicin-induced ROS production as well as apoptosis. Direct evidence for gentamicin-induced permeabilization of lysosomal membrane was provided by showing the release into the cytosol of Lucifer yellow, a membrane-impermeant endocytic tracer with a comparable molecular weight as gentamicin. Altogether, our data demonstrate a key role of lysosomal iron and early ROS production in gentamicin-induced lysosomal membrane permeabilization and apoptosis.

Cell death causes relocalization of photosensitizing fluorescent probes

When cultured cells are treated with fluorescent organelle probes or photosensitizer agents, a characteristic redistribution of fluorescence in cell structures occurs frequently after light irradiation. It is currently assumed that such changes, referred to as relocalizations of the fluorescent compounds, represent an important aspect of the photodynamic process, which is based on the excitation of photosensitizers by light in the presence of oxygen. As cell damage and death result from the oxidative stress induced by photodynamic treatments, we have studied here the redistribution of acridine orange (AO) and 3,3'-dimethyl-oxacarbocyanine (DiOC(1)(3)) fluorescence after incubation of HeLa cell cultures with these compounds followed by blue light irradiation to achieve lethal effects. The relocalization of dyes from their original labeling sites (AO: lysosomes, DiOC(1)(3): mitochondria) to nucleic acid-containing structures (cytoplasm, nuclei and nucleoli) appeared clearly associated with cell death. Therefore, the relocalization phenomenon simply reflects fluorescence changes due to the different affinity of these dyes for living and damaged or dead cells. As fluorescent probes are often photosensitizers, prolonged light exposures using fluorescence microscopy will produce lethal photodynamic effects with relocalization of the fluorescent signal and changes in the cell morphology.

Nanomaterial cytotoxicity is composition, size, and cell type dependent

Background

Despite intensive research efforts, reports of cellular responses to nanomaterials are often inconsistent and even contradictory. Additionally, relationships between the responding cell type and nanomaterial properties are not well understood. Using three model cell lines representing different physiological compartments and nanomaterials of different compositions and sizes, we have systematically investigated the influence of nanomaterial properties on the degrees and pathways of cytotoxicity. In this study, we selected nanomaterials of different compositions (TiO₂ and SiO₂ nanoparticles, and multi-wall carbon nanotubes [MWCNTs]) with differing size (MWCNTs of different diameters < 8 nm, 20-30 nm, > 50 nm; but same length 0.5-2 μm) to analyze the effects of composition and size on toxicity to 3T3 fibroblasts, RAW 264.7 macrophages, and telomerase-immortalized (hT) bronchiolar epithelial cells.

Results

Following characterization of nanomaterial properties in PBS and serum containing solutions, cells were exposed to nanomaterials of differing compositions and sizes, with cytotoxicity monitored through reduction in mitochondrial activity. In addition to cytotoxicity, the cellular response to nanomaterials was characterized by quantifying generation of reactive oxygen species, lysosomal membrane destabilization and mitochondrial permeability. The effect of these responses on cellular fate - apoptosis or necrosis - was then analyzed. Nanomaterial toxicity was variable based on exposed cell type and dependent on nanomaterial composition and size. In addition, nanomaterial exposure led to cell type dependent intracellular responses resulting in unique breakdown of cellular functions for each nanomaterial: cell combination.

Conclusions

Nanomaterials induce cell specific responses resulting in variable toxicity and subsequent cell fate based on the type of exposed cell. Our results indicate that the composition and size of nanomaterials as well as the target cell type are critical determinants of intracellular responses, degree of cytotoxicity and potential mechanisms of toxicity.

Photodynamic therapy with acridine orange in musculoskeletal sarcomas

Limb salvage involving wide resection and reconstruction is now well established for managing musculoskeletal sarcomas. However, involvement of major nerves and vessels with a large volume of muscle and skin may result in a useless limb, contributing to depression and a low quality of life. We have been studying alternative treatments for musculoskeletal sarcoma since 1990, and have recently established a regime using photodynamic surgery with cells labelled with acridine orange, photodynamic therapy with cells treated similarly and radiodynamic treatment using the effect of X-rays on such cells. These techniques have been used after marginal or intralesional resection of tumours since 1999 and have enabled maintenance of excellent limb function in patients with sarcomas.

What does the commonly used DCF test for oxidative stress really show?

H2DCF-DA (dihydrodichlorofluorescein diacetate) is widely used to evaluate ‘cellular oxidative stress’. After passing through the plasma membrane, this lipophilic and non-fluorescent compound is de-esterified to a hydrophilic alcohol [H2DCF (dihydrodichlorofluorescein)] that may be oxidized to fluorescent DCF (2′,7′-dichlorofluorescein) by a process usually considered to involve ROS (reactive oxygen species). It is, however, not always recognized that, being a hydrophilic molecule, H2DCF does not cross membranes, except for the outer fenestrated mitochondrial ones. It is also not generally realized that oxidation of H2DCF is dependent either on Fenton-type reactions or on unspecific enzymatic oxidation by cytochrome c, for neither superoxide, nor H2O2, directly oxidizes H2DCF. Consequently, oxidation of H2DCF requires the presence of either cytochrome c or of both redox-active transition metals and H2O2. Redox-active metals exist mainly within lysosomes, whereas cytochrome c resides bound to the outer side of the inner mitochondrial membrane. Following exposure to H2DCF-DA, weak mitochondrial fluorescence was found in both the oxidation-resistant ARPE-19 cells and the much more sensitive J774 cells. This fluorescence was only marginally enhanced following short exposure to H2O2, showing that by itself it is unable to oxidize H2DCF. Cells that were either exposed to the lysosomotropic detergent MSDH (O-methylserine dodecylamide hydrochloride), exposed to prolonged oxidative stress, or spontaneously apoptotic showed lysosomal permeabilization and strong DCF-induced fluorescence. The results suggest that DCF-dependent fluorescence largely reflects relocation to the cytosol of lysosomal iron and/or mitochondrial cytochrome c.

A new class of naphthalimide-based antitumor agents that inhibit topoisomerase II and induce lysosomal membrane permeabilization and apoptosis

Based on the advantages of multitarget drugs for cancer treatment, a new class of naphthalimides was designed, synthesized, and proved to inhibit topoisomerase II (topo II), induced lysosomal membrane permeabilization (LMP), and ultimately caused apoptosis and cell death. The majority of compounds 7a-d and 8a-d potently inhibited the growth of the five tested cancer cell lines with IC(50) values ranging from 2 to 10 microM and are more active than amonafide, a naphthalimide that was in phase III clinical trials. These compounds were tested for their interactions with DNA and their cell-free topo II inhibition activities, which demonstrated these compounds were weak DNA binders but modest topo II inhibitors. Furthermore, compounds 7b-d were found to notably induce LMP and exhibited better antiproliferative activity compared with their single-target analogues. All of the newly synthesized compounds were demonstrated to efficiently induce apoptosis via a mitochondrial pathway. Accordingly, a new paradigm was suggested for the design of novel multitarget anticancer drugs.

Lysosomal-mitochondrial axis in zoledronic acid-induced apoptosis in human follicular lymphoma cells

Bisphosphonates (BPs) are potent inhibitors of osteoclast function, widely used to treat excessive bone resorption associated with bone metastases, that also have anti-tumor activity. Zoledronic acid (ZOL) represents a potential chemotherapeutic agent for the treatment of cancer. ZOL is the most potent nitrogen-containing BPs, and it inhibits cell growth and induces apoptosis in a variety of cancer cells. Recently we demonstrated that accumulation of isopentenyl pyrophosphate and the consequent formation of a new type of ATP analog (ApppI) after mevalonate pathway inhibition by nitrogen-containing BPs strongly correlates with ZOL-induced cell death in cancer cells in vitro. In this study we show that ZOL-induced apoptosis in HF28RA human follicular lymphoma cells occurs exclusively via the mitochondrial pathway, involves lysosomes, and is dependent on mevalonate pathway inhibition. To define the exact signaling pathway connecting them, we used modified HF28RA cell lines overexpressing either BclXL or dominant-negative caspase-9. In both mutant cells, mitochondrial and lysosomal membrane permeabilization (MMP and LMP) were totally prevented, indicating signaling between lysosomes and mitochondria and, additionally, an amplification loop for MMP and/or LMP regulated by caspase-9 in association with farnesyl pyrophosphate synthetase inhibition. Additionally, the lysosomal pathway in ZOL-induced apoptosis plays an additional/amplification role of the intrinsic pathway independently of caspase-3 activation. Moreover, we show a potential regulation by Bcl-XL and caspase-9 on cell cycle regulators of S-phase. Our findings provide a molecular basis for new strategies concomitantly targeting cell death pathways from multiple sites.