ABSTRACT
Levamisole (LMS) is a small molecule used in the treatment of idiopathic nephrotic syndrome (INS). The pathogenesis of INS remains unknown, but evidence points toward an immunological basis of the disease. Recently, LMS has been shown to increase the relapse-free survival in INS patients. While LMS has been hypothesized to exert an immunomodulatory effect, its mechanism of action remains unknown. Here, we show that LMS decreased activation and proliferation of human T cells. T-cell activation-associated cytokines such as IL-2, TNF-α, and IFN-γ were reduced upon LMS treatment, whereas IL-4 and IL-13 were increased. Gene expression profiling confirmed that the suppressive effects of LMS as genes involved in cell cycle progression were downregulated. Furthermore, genes associated with p53 activation were upregulated by LMS. In agreement, LMS treatment resulted in p53 phosphorylation and increased expression of the p53 target gene FAS. Accordingly, LMS sensitized activated T cells for Fas-mediated apoptosis. LMS treatment resulted in a mid-S phase cell cycle arrest accompanied by γH2AX-foci formation and phosphorylation of CHK1. Our findings indicate that LMS acts as an immunosuppressive drug that directly affects the activation and proliferation of human T cells by induction of DNA damage and the activation of a p53-dependent DNA damage response.
Subject(s)
Levamisole , Tumor Suppressor Protein p53 , Humans , Levamisole/pharmacology , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/metabolism , Cell Division , Apoptosis , T-Lymphocytes , DNA DamageABSTRACT
Temporary elevation of tumor temperature, also known as hyperthermia, is a safe and well-tolerated treatment modality. The efficacy of hyperthermia can be improved by efficient thermosensitizers, and various candidate drugs, including inhibitors of the heat stress response, have been explored in vitro and in animal models, but clinically relevant thermosensitizers are lacking. Here, we employ unbiased in silico approaches to uncover new mechanisms and compounds that could be leveraged to increase the thermosensitivity of cancer cells. We then focus on elesclomol, a well-performing compound, which amplifies cell killing by hyperthermia by 5- to 20-fold in cell lines and outperforms clinically applied chemotherapy when combined with hyperthermia in vitro. Surprisingly, our findings suggest that the thermosensitizing effects of elesclomol are independent of its previously reported modes of action but depend on copper shuttling. Importantly, we show that, like elesclomol, multiple other copper shuttlers can thermosensitize, suggesting that disturbing copper homeostasis could be a general strategy for improving the efficacy of hyperthermia.
Subject(s)
Copper , Hydrazines , Neoplasms , Animals , Temperature , Fever , Hyperthermia , Neoplasms/drug therapyABSTRACT
The majority of the proteins involved in processing of DNA double-strand breaks (DSBs) accumulate at the damage sites. Real-time imaging and analysis of these processes, triggered by the so-called microirradiation using UV lasers or heavy particle beams, yielded valuable insights into the underlying DSB repair mechanisms. To study the temporal organization of DSB repair responses triggered by a more clinically-relevant DNA damaging agent, we developed a system coined X-ray multi-microbeam microscope (XM3), capable of simultaneous high dose-rate (micro)irradiation of large numbers of cells with ultra-soft X-rays and imaging of the ensuing cellular responses. Using this setup, we analyzed the changes in real-time kinetics of MRE11, MDC1, RNF8, RNF168 and 53BP1-proteins involved in the signaling axis of mammalian DSB repair-in response to X-ray and UV laser-induced DNA damage, in non-cancerous and cancer cells and in the presence or absence of a photosensitizer. Our results reveal, for the first time, the kinetics of DSB signaling triggered by X-ray microirradiation and establish XM3 as a powerful platform for real-time analysis of cellular DSB repair responses.
Subject(s)
DNA Breaks, Double-Stranded , DNA Repair , DNA-Binding Proteins/metabolism , Time-Lapse Imaging/methods , X-Rays , Adaptor Proteins, Signal Transducing/metabolism , Animals , Cell Cycle Proteins/metabolism , Cell Line , Humans , MRE11 Homologue Protein , Microscopy, Electron, Scanning , Osteosarcoma/metabolism , Pigment Epithelium of Eye/metabolism , Signal Transduction , Tumor Suppressor p53-Binding Protein 1/metabolism , Ubiquitin-Protein Ligases/metabolism , Ultraviolet RaysABSTRACT
Histatins are multifunctional histidine-rich peptides secreted by the salivary glands and exclusively present in the saliva of higher primates, where they play a fundamental role in the protection of the oral cavity. Our previously published results demonstrated that histatin-1 (Hst1) promotes cell-substrate adhesion in various cell types and hinted that it could also be involved in cell-cell adhesion, a process of fundamental importance to epithelial and endothelial barriers. Here we explore the effects of Hst1 on cellular barrier function. We show that Hst1 improved endothelial barrier integrity, decreased its permeability for large molecules, and prevented translocation of bacteria across epithelial cell layers. These effects are mediated by the adherens junction protein E-cadherin (E-cad) and by the tight junction protein zonula occludens 1, as Hst1 increases the levels of zonula occludens 1 and of active E-cad. Hst1 may also promote epithelial differentiation as Hst1 induced transcription of the epithelial cell differentiation marker apolipoprotein A-IV (a downstream E-cad target). In addition, Hst1 counteracted the effects of epithelial-mesenchymal transition inducers on the outgrowth of oral cancer cell spheroids, suggesting that Hst1 affects processes that are implicated in cancer progression.-Van Dijk, I. A., Ferrando, M. L., van der Wijk, A.-E., Hoebe, R. A., Nazmi, K., de Jonge, W. J., Krawczyk, P. M., Bolscher, J. G. M., Veerman, E. C. I., Stap, J. Human salivary peptide histatin-1 stimulates epithelial and endothelial cell adhesion and barrier function.
Subject(s)
Endothelial Cells/physiology , Epithelial Cells/physiology , Gene Expression Regulation/physiology , Histatins/metabolism , Cell Line , Histatins/genetics , HumansABSTRACT
The paper presents a camera comprising 512 × 128 pixels capable of single-photon detection and gating with a maximum frame rate of 156 kfps. The photon capture is performed through a gated single-photon avalanche diode that generates a digital pulse upon photon detection and through a digital one-bit counter. Gray levels are obtained through multiple counting and accumulation, while time-resolved imaging is achieved through a 4-ns gating window controlled with subnanosecond accuracy by a field-programmable gate array. The sensor, which is equipped with microlenses to enhance its effective fill factor, was electro-optically characterized in terms of sensitivity and uniformity. Several examples of capture of fast events are shown to demonstrate the suitability of the approach.
ABSTRACT
The structural maintenance of chromosomes (SMC) protein complexes shape and regulate the structure and dynamics of chromatin, thereby controlling many chromosome-based processes such as cell cycle progression, differentiation, gene transcription and DNA repair. The SMC5/6 complex is previously described to promote DNA double-strand breaks (DSBs) repair by sister chromatid recombination, and found to be essential for resolving recombination intermediates during meiotic recombination. Moreover, in budding yeast, SMC5/6 provides structural organization and topological stress relief during replication in mitotically dividing cells. Despite the essential nature of the SMC5/6 complex, the versatile mechanisms by which SMC5/6 functions and its molecular regulation in mammalian cells remain poorly understood. By using a human osteosarcoma cell line (U2OS), we show that after the CRISPR-Cas9-mediated removal of the SMC5/6 subunit NSMCE2, treatment with the topoisomerase II inhibitor etoposide triggered an increased sensitivity in cells lacking NSMCE2. In contrast, NSMCE2 appeared not essential for a proper DNA damage response or cell survival after DSB induction by ionizing irradiation (IR). Interestingly, by way of immunoprecipitations (IPs) and mass spectrometry, we found that the SMC5/6 complex physically interacts with the DNA topoisomerase II α (TOP2A). We therefore propose that the SMC5/6 complex functions in resolving TOP2A-mediated DSB-repair intermediates generated during replication.
Subject(s)
Cell Cycle Proteins/metabolism , DNA Breaks, Double-Stranded , DNA Repair , Ligases/metabolism , Antigens, Neoplasm/metabolism , CRISPR-Cas Systems , Cell Cycle Proteins/genetics , Cell Line, Tumor , Cell Survival/radiation effects , Chromosomal Proteins, Non-Histone , DNA Breaks, Double-Stranded/drug effects , DNA Breaks, Double-Stranded/radiation effects , DNA Topoisomerases, Type II/metabolism , DNA-Binding Proteins/metabolism , Etoposide/adverse effects , Humans , Ligases/genetics , Poly-ADP-Ribose Binding Proteins , Protein Interaction Maps , Topoisomerase II Inhibitors/adverse effectsABSTRACT
DNA double-strand breaks initiate the DNA damage response (DDR), leading to the accumulation of repair proteins at break sites and the formation of the-so-called foci. Various microscopy methods, such as wide-field, confocal, electron, and super-resolution microscopy, have been used to study these structures. However, the impact of different DNA-damaging agents on their (nano)structure remains unclear. Utilising GSDIM super-resolution microscopy, here we investigated the distribution of fluorescently tagged DDR proteins (53BP1, RNF168, MDC1) and γH2AX in U2OS cells treated with γ-irradiation, etoposide, cisplatin, or hydroxyurea. Our results revealed that both foci structure and their nanoscale ultrastructure, including foci size, nanocluster characteristics, fluorophore density and localisation, can be significantly altered by different inducing agents, even ones with similar mechanisms. Furthermore, distinct behaviours of DDR proteins were observed under the same treatment. These findings have implications for cancer treatment strategies involving these agents and provide insights into the nanoscale organisation of the DDR.
Subject(s)
DNA Repair , Microscopy , DNA Damage , Tumor Suppressor p53-Binding Protein 1/metabolism , DNA , Discoidin Domain Receptors/genetics , Discoidin Domain Receptors/metabolismABSTRACT
In the rapidly evolving field of bioimaging, the integration and orchestration of findable, accessible, interoperable, and reusable (FAIR) image analysis workflows remains a challenge. We introduce BIOMERO (bioimage analysis in OMERO), a bridge connecting OMERO, a renowned bioimaging data management platform; FAIR workflows; and high-performance computing (HPC) environments. BIOMERO facilitates seamless execution of FAIR workflows, particularly for large datasets from high-content or high-throughput screening. BIOMERO empowers researchers by eliminating the need for specialized knowledge, enabling scalable image processing directly from OMERO. BIOMERO notably supports the sharing and utilization of FAIR workflows between OMERO, Cytomine/BIAFLOWS, and other bioimaging communities. BIOMERO will promote the widespread adoption of FAIR workflows, emphasizing reusability, across the realm of bioimaging research. Its user-friendly interface will empower users, including those without technical expertise, to seamlessly apply these workflows to their datasets, democratizing the utilization of AI by the broader research community.
ABSTRACT
BACKGROUND: A predictive assay for late radiation toxicity would allow more personalized treatment planning, reducing the burden of toxicity for the more sensitive minority, and improving the therapeutic index for the majority. In a previous study in prostate cancer patients, the γ-H2AX foci decay ratio (γ-FDR) was the strongest predictor of late radiation toxicity. The current study aimed to validate this finding in a more varied group of patients with pelvic cancer. Additionally, the potential correlation between the γ-FDR and patient-reported outcomes was investigated. METHODS: Prostate and gynecological cancer patients with ≥ 24 months of follow-up were included in the current analysis. Toxicity was evaluated by physician (CTCAE version 4) and patient (EORTC questionnaires). γ-FDRs were determined in ex vivo irradiated lymphocytes. Correlation between γ-FDR and toxicity was assessed using both linear and logistic regression analyses. The highest toxicity grade recorded during follow-up was used. The association between global quality of life and γ-FDR was tested by comparing the change in quality of life over time in patients with γ-FDR < or ≥ 3.41, a previously established threshold. RESULTS: Eighty-eight patients were included. Physician-assessed and patient-reported cumulative grade ≥ 2 toxicity was 25% and 29%, respectively; which is much lower than in the previous cohort (i.e., 51% CTCAE grade ≥ 2). Patients with toxicity exhibited less favorable dose-volume parameters. In men, these parameters showed significant improvement compared to the previous cohort. The proportion of patients with a low γ-FDR increased with severity of toxicity, but this trend was not statistically significant. In addition, a γ-FDR < 3.41 was not correlated with the development of moderate to severe toxicity. Post-treatment decline in global quality of life was minimal, and similar for patients with γ-FDR < or ≥ 3.41. CONCLUSIONS: In the present study, the γ-H2AX foci decay ratio could not be validated as a predictor of late radiation toxicity in patients with pelvic cancer. Improved radiotherapy techniques with smaller irradiated bladder and bowel volumes have probably resulted in less toxicities. Future studies on genetic markers of toxicity should be powered on these lower incidences. We further recommend taking persistency, next to severity, into consideration.
Subject(s)
Histones , Prostatic Neoplasms , Quality of Life , Radiation Injuries , Radiotherapy, Image-Guided , Humans , Male , Female , Aged , Radiotherapy, Image-Guided/methods , Radiotherapy, Image-Guided/adverse effects , Middle Aged , Prostatic Neoplasms/radiotherapy , Prostatic Neoplasms/pathology , Histones/genetics , Histones/analysis , Radiation Injuries/etiology , Aged, 80 and over , Genital Neoplasms, Female/radiotherapy , Adult , Follow-Up Studies , Pelvic Neoplasms/radiotherapy , Biomarkers, Tumor/genetics , PrognosisABSTRACT
The Clonogenic Survival Assay (CSA) is a fundamental tool employed to assess cell survival and proliferative potential in cancer research. Despite its importance, CSA faces limitations, primarily its time- and labor-intensive nature and its binary output. To overcome these limitations and enhance CSA's utility, several approaches have been developed, focusing on increasing the throughput. However, achieving both high-content and high-throughput analyses simultaneously has remained a challenge. In this paper, we introduce LeGO-CSA, an extension of the classical CSA that employs the imaging of cell nuclei barcoded with fluorescent lentiviral gene ontology markers, enabling both high-content and high-throughput analysis. To validate our approach, we contrasted it with results from a classical assay and conducted a proof-of-concept screen of small-molecule inhibitors targeting various pathways relevant to cancer treatment. Notably, our results indicate that the classical CSA may underestimate clonogenicity and unveil intriguing aspects of clonal cell growth. We demonstrate the potential of LeGO-CSA to offer a robust approach for assessing cell survival and proliferation with enhanced precision and throughput, with promising implications for accelerating drug discovery and contributing to a more comprehensive understanding of cellular behavior in cancer.
ABSTRACT
Clonal growth and competition underlie processes of key relevance in etiology, progression and therapy response across all cancers. Here, we demonstrate a novel experimental approach, based on multi-color, fluorescent tagging of cell nuclei, in combination with picoliter droplet deposition, to study the clonal dynamics in two- and three-dimensional cell cultures. The method allows for the simultaneous visualization and analysis of multiple clones in individual multi-clonal colonies, providing a powerful tool for studying clonal dynamics and identifying clonal populations with distinct characteristics. Results of our experiments validate the utility of the method in studying clonal dynamics in vitro, and reveal differences in key aspects of clonal behavior of different cancer cell lines in monoculture conditions, as well as in co-cultures with stromal fibroblasts.
Subject(s)
Cell Culture Techniques , Neoplasms , Humans , Clone Cells , Cell Line , Coculture TechniquesABSTRACT
Hyperthermia is being used as a radio- and chemotherapy sensitizer for a growing range of tumor subtypes in the clinic. Its potential is limited, however, by the ability of cancer cells to activate a protective mechanism known as the heat stress response (HSR). The HSR is marked by the rapid overexpression of molecular chaperones, and recent advances in drug development make their inhibition an attractive option to improve the efficacy of hyperthermia-based therapies. Our previous in vitro work showed that a single, short co-treatment with a HSR (HSP90) inhibitor ganetespib prolongs and potentiates the effects of hyperthermia on DNA repair, enhances hyperthermic sensitization to radio- and chemotherapeutic agents, and reduces thermotolerance. In the current study, we first validated these results using an extended panel of cell lines and more robust methodology. Next, we examined the effects of hyperthermia and ganetespib on global proteome changes. Finally, we evaluated the potential of ganetespib to boost the efficacy of thermo-chemotherapy and thermo-radiotherapy in a xenograft murine model of cervix cancer. Our results revealed new insights into the effects of HSR inhibition on cellular responses to heat and show that ganetespib could be employed to increase the efficacy of hyperthermia when combined with radiation.
ABSTRACT
Huntington's disease is an autosomal dominant heritable disorder caused by an expanded CAG trinucleotide repeat at the N-terminus of the Huntingtin (HTT) gene. Lowering the levels of soluble mutant HTT protein prior to aggregation through increased degradation by the proteasome would be a therapeutic strategy to prevent or delay the onset of disease. Native PAGE experiments in HdhQ150 mice and R6/2 mice showed that PA28αß disassembles from the 20S proteasome during disease progression in the affected cortex, striatum and hippocampus but not in cerebellum and brainstem. Modulating PA28αß activated proteasomes in various in vitro models showed that PA28αß improved polyQ degradation, but decreased the turnover of mutant HTT. Silencing of PA28αß in cells lead to an increase in mutant HTT aggregates, suggesting that PA28αß is critical for overall proteostasis, but only indirectly affects mutant HTT aggregation.
Subject(s)
Huntington Disease , Mice , Animals , Huntington Disease/metabolism , Cerebellum/metabolism , Proteasome Endopeptidase Complex/genetics , Proteasome Endopeptidase Complex/metabolism , Proteostasis , Brain Stem/metabolism , Huntingtin Protein/genetics , Huntingtin Protein/metabolism , Disease Models, Animal , Brain/metabolismABSTRACT
BACKGROUND: The nuclear lamina provides structural support to the nucleus and has a central role in defining nuclear organization. Defects in its filamentous constituents, the lamins, lead to a class of diseases collectively referred to as laminopathies. On the cellular level, lamin mutations affect the physical integrity of nuclei and nucleo-cytoskeletal interactions, resulting in increased susceptibility to mechanical stress and altered gene expression. METHODS: In this study we quantitatively compared nuclear deformation and chromatin mobility in fibroblasts from a homozygous nonsense LMNA mutation patient and a Hutchinson-Gilford progeria syndrome patient with wild type dermal fibroblasts, based on the visualization of mCitrine labeled telomere-binding protein TRF2 with light-economical imaging techniques and cytometric analyses. RESULTS: Without application of external forces, we found that the absence of functional lamin A/C leads to increased nuclear plasticity on the hour and minute time scale but also to increased intranuclear mobility down to the second time scale. In contrast, progeria cells show overall reduced nuclear dynamics. Experimental manipulation (farnesyltransferase inhibition or lamin A/C silencing) confirmed that these changes in mobility are caused by abnormal or reduced lamin A/C expression. CONCLUSIONS: These observations demonstrate that A-type lamins affect both nuclear membrane and telomere dynamics. GENERAL SIGNIFICANCE: Because of the pivotal role of dynamics in nuclear function, these differences likely contribute to or represent novel mechanisms in laminopathy development.
Subject(s)
Codon, Nonsense , Fibroblasts/physiology , Lamin Type A/genetics , Nuclear Envelope/genetics , Progeria/genetics , Cell Line , Cell Shape , Fibroblasts/pathology , Humans , Immunohistochemistry , Lamin Type A/deficiency , Nuclear Envelope/metabolism , Nuclear Proteins/genetics , Nuclear Proteins/metabolism , Polymorphism, Single Nucleotide , Progeria/metabolism , Progeria/pathology , Protein Precursors/genetics , Protein Precursors/metabolism , Reference Values , Skin/cytology , Skin Physiological PhenomenaABSTRACT
Cellular responses to DNA double-strand breaks (DSBs) not only promote genomic integrity in healthy tissues, but also largely determine the efficacy of many DNA-damaging cancer treatments, including X-ray and particle therapies. A growing body of evidence suggests that activation of the mechanisms that detect, signal and repair DSBs may depend on the complexity of the initiating DNA lesions. Studies focusing on this, as well as on many other radiobiological questions, require reliable methods to induce DSBs of varying complexity, and to visualize the ensuing cellular responses. Accelerated particles of different energies and masses are exceptionally well suited for this task, due to the nature of their physical interactions with the intracellular environment, but visualizing cellular responses to particle-induced damage - especially in their early stages - at particle accelerator facilities, remains challenging. Here we describe a straightforward approach for real-time imaging of early response to particle-induced DNA damage. We rely on a transportable setup with an inverted fluorescence confocal microscope, tilted at a small angle relative to the particle beam, such that cells can be irradiated and imaged without any microscope or beamline modifications. Using this setup, we image and analyze the accumulation of fluorescently-tagged MDC1, RNF168 and 53BP1-key factors involved in DSB signalling-at DNA lesions induced by 254 MeV α-particles. Our results provide a demonstration of technical feasibility and reveal asynchronous initiation of accumulation of these proteins at different individual DSBs.
Subject(s)
DNA Damage , Microscopy, Fluorescence/instrumentation , Particle Accelerators , Retinal Pigment Epithelium/radiation effects , Adaptor Proteins, Signal Transducing/analysis , Cell Cycle Proteins/analysis , Cell Line , DNA Breaks, Double-Stranded/radiation effects , Equipment Design , Humans , Microscopy, Confocal/instrumentation , Microscopy, Confocal/methods , Microscopy, Fluorescence/methods , Molecular Imaging/instrumentation , Molecular Imaging/methods , Proof of Concept Study , Retinal Pigment Epithelium/cytology , Tumor Suppressor p53-Binding Protein 1/analysis , Ubiquitin-Protein Ligases/analysisABSTRACT
Atherosclerosis is associated with a compromised endothelial barrier, facilitating the accumulation of immune cells and macromolecules in atherosclerotic lesions. In this study, we investigate endothelial barrier integrity and the enhanced permeability and retention (EPR) effect during atherosclerosis progression and therapy in Apoe-/- mice using hyaluronan nanoparticles (HA-NPs). Utilizing ultrastructural and en face plaque imaging, we uncover a significantly decreased junction continuity in the atherosclerotic plaque-covering endothelium compared to the normal vessel wall, indicative of disrupted endothelial barrier. Intriguingly, the plaque advancement had a positive effect on junction stabilization, which correlated with a 3-fold lower accumulation of in vivo administrated HA-NPs in advanced plaques compared to early counterparts. Furthermore, by using super-resolution and correlative light and electron microscopy, we trace nanoparticles in the plaque microenvironment. We find nanoparticle-enriched endothelial junctions, containing 75% of detected HA-NPs, and a high HA-NP accumulation in the endothelium-underlying extracellular matrix, which suggest an endothelial junctional traffic of HA-NPs to the plague. Finally, we probe the EPR effect by HA-NPs in the context of metabolic therapy with a glycolysis inhibitor, 3PO, proposed as a vascular normalizing strategy. The observed trend of attenuated HA-NP uptake in aortas of 3PO-treated mice coincides with the endothelial silencing activity of 3PO, demonstrated in vitro. Interestingly, the therapy also reduced the plaque inflammatory burden, while activating macrophage metabolism. Our findings shed light on natural limitations of nanoparticle accumulation in atherosclerotic plaques and provide mechanistic insight into nanoparticle trafficking across the atherosclerotic endothelium. Furthermore, our data contribute to the rising field of endothelial barrier modulation in atherosclerosis.
Subject(s)
Arteries/pathology , Atherosclerosis/metabolism , Atherosclerosis/therapy , Disease Progression , Endothelium, Vascular/pathology , Nanoparticles/chemistry , Animals , Atherosclerosis/pathology , Entropy , Europium/chemistry , Mice , Probability , TemperatureABSTRACT
Re-scan confocal microscopy (RCM) is a new super-resolution technique based on a standard confocal microscope extended with a re-scan unit in the detection path that projects the emitted light onto a sensitive camera. In this paper the fundamental properties of RCM, lateral resolution, axial resolution and signal-to-noise ratio, are characterized and compared with properties of standard confocal microscopy. The results show that the lateral resolution of RCM is ~170 nm compared to ~240 nm of confocal microscopy for 488 nm excitation and 1.49 NA. As the theory predicts, this improved lateral resolution is independent of the pinhole diameter. In standard confocal microscopy, the same lateral resolution can only be achieved with an almost closed pinhole and, consequently, with a major loss of signal. We show that the sectioning capabilities of the standard confocal microscope are preserved in RCM and that the axial resolution of RCM is slightly better (~15%) than the standard confocal microscope. Furthermore, the signal-to-noise ratio in RCM is a factor of 2 higher than in standard confocal microscopy, also due to the use of highly sensitive modern cameras. In case the pinhole of a confocal microscope is adjusted in such way that the lateral resolution is comparable to that of RCM, the signal-to-noise ratio in RCM is 4 times higher than standard confocal microscopy. Therefore, RCM offers a good alternative to standard confocal microscopy for higher lateral resolution with the main advantage of strongly improved sensitivity.
ABSTRACT
sCMOS imagers are currently utilized (replacing EMCCD imagers) to increase the acquisition speed in super resolution localization microscopy. Single-photon avalanche diode (SPAD) imagers feature frame rates per bit depth comparable to or higher than sCMOS imagers, while generating microsecond 1-bit-frames without readout noise, thus paving the way to in-depth time-resolved image analysis. High timing resolution can also be exploited to explore fluorescent dye blinking and other photophysical properties, which can be used for dye optimization. We present the methodology for the blinking analysis of fluorescent dyes on experimental data. Furthermore, the recent use of microlenses has enabled a substantial increase of SPAD imager overall sensitivity (12-fold in our case), reaching satisfactory values for sensitivity-critical applications. This has allowed us to record the first super resolution localization microscopy results obtained with a SPAD imager, with a localization uncertainty of 20 nm and a resolution of 80 nm.
ABSTRACT
The efficacy of photodynamic therapy (PDT) in some solid tumors is limited by the poor biodistributive properties of conventional photosensitizers and a natural predisposition of tumor cells to survive hypoxia and oxidative stress. This study investigated the therapeutic potential of a third-generation photosensitizer, liposomal zinc phthalocyanine (ZnPC), in combination with the hypoxic cytotoxin tirapazamine (TPZ). TPZ induces DNA double strand breaks (DSBs) under hypoxic conditions and subsequent apoptosis via p53 signaling. Experiments were performed in tumor cells with functional p53 (Sk-Cha1) and dysfunctional p53 (A431). The combination therapy of TPZ and PDT induced DNA DSBs and cell cycle stalling and enhanced the cytotoxicity of PDT by exacerbating apopotic and non-apoptotic tumor cell death. These phenomena occurred regardless of oxygen tension and the mechanism of cell death differed per cell line. Liposomes containing both ZnPC and TPZ exhibited no dark toxicity but were more lethal to both cell types after PDT compared to ZnPC-liposomes lacking TPZan effect that was more pronounced under hypoxic conditions. In conclusion, TPZ is a suitable pharmaceutical compound to increase PDT efficacy by exploiting the post-PDT tumor hypoxia. The inclusion of TPZ and ZnPC into a single liposomal delivery system was feasible. The PDT strategy described in this study may be valuable for the treatment of PDT-recalcitrant tumors.
Subject(s)
Antineoplastic Agents/pharmacology , DNA Damage/drug effects , Indoles/pharmacology , Liposomes/pharmacology , Organometallic Compounds/pharmacology , Photochemotherapy/methods , Triazines/pharmacology , Antineoplastic Agents/chemistry , Cell Death/drug effects , Cell Line, Tumor , Cell Survival/drug effects , Humans , Indoles/chemistry , Isoindoles , Liposomes/chemistry , Neoplasms/metabolism , Organometallic Compounds/chemistry , Oxidative Stress/drug effects , Photosensitizing Agents/chemistry , Photosensitizing Agents/pharmacology , Reactive Oxygen Species , Tirapazamine , Triazines/chemistry , Zinc CompoundsABSTRACT
Hyaluronan is a biologically active polymer, which can be formulated into nanoparticles. In our study, we aimed to probe atherosclerosis-associated inflammation by using hyaluronan nanoparticles and to determine whether they can ameliorate atherosclerosis. Hyaluronan nanoparticles (HA-NPs) were prepared by reacting amine-functionalized oligomeric hyaluronan (HA) with cholanic ester and labeled with a fluorescent or radioactive label. HA-NPs were characterized in vitro by several advanced microscopy methods. The targeting properties and biodistribution of HA-NPs were studied in apoe-/- mice, which received either fluorescent or radiolabeled HA-NPs and were examined ex vivo by flow cytometry or nuclear techniques. Furthermore, three atherosclerotic rabbits received 89Zr-HA-NPs and were imaged by PET/MRI. The therapeutic effects of HA-NPs were studied in apoe-/- mice, which received weekly doses of 50 mg/kg HA-NPs during a 12-week high-fat diet feeding period. Hydrated HA-NPs were ca. 90 nm in diameter and displayed very stable morphology under hydrolysis conditions. Flow cytometry revealed a 6- to 40-fold higher uptake of Cy7-HA-NPs by aortic macrophages compared to normal tissue macrophages. Interestingly, both local and systemic HA-NP-immune cell interactions significantly decreased over the disease progression. 89Zr-HA-NPs-induced radioactivity in atherosclerotic aortas was 30% higher than in wild-type controls. PET imaging of rabbits revealed 6-fold higher standardized uptake values compared to the muscle. The plaques of HA-NP-treated mice contained 30% fewer macrophages compared to control and free HA-treated group. In conclusion, we show favorable targeting properties of HA-NPs, which can be exploited for PET imaging of atherosclerosis-associated inflammation. Furthermore, we demonstrate the anti-inflammatory effects of HA-NPs in atherosclerosis.