Apoptotic volume decrease as a geometric determinant for cell dismantling into apoptotic bodies

Employing Piezoelectric Mg2+-Doped Hydroxyapatite to Target Death Receptor-Mediated Necroptosis: A Strategy for Amplifying Immune Activation

Although immunogenic cell death (ICD) inducers evidently enhance the effectiveness of immunotherapy, their potential is increasingly restricted by the development of apoptosis resistance in tumor cells, poor immunogenicity, and low T-cell immune responsiveness. In this study, for the first time, piezoelectrically catalyzed Mg2+-doped hydroxyapatite (Mg-HAP) nanoparticles, which are coated with a mesoporous silica layer and loaded with ONC201 as an agonist to specifically target the death receptor DR5 on tumor cells, ultimately developing an Mg-HAP@MS/ONC201 nanoparticle (MHMO NP) system, are engineered. Owing to its excellent piezoelectric properties, MHMO facilitates the release of a significant amount of reactive oxygen species and Ca2+ within tumor cells, effectively promoting the upregulation of DR5 expression and inducing tumor cell necroptosis to ultimately overcome apoptosis resistance. Concurrently, Mg2+ released in the tumor microenvironment promotes CD8+ T receptor activation in response to the antitumor immune reaction induced by ICD. Using RNA-seq analysis, it is elucidated that MHMO can activate the NF-κB pathway under piezoelectric catalysis, thus inducing M1-type macrophage polarization. In summary, a dual-targeting therapy system that targets both tumor cells and the tumor microenvironment under piezoelectric catalysis is designed. This system holds substantial potential for advancements in tumor immunotherapy.

Silica-coated LiYF4:Yb3+, Tm3+ upconverting nanoparticles are non-toxic and activate minor stress responses in mammalian cells

Lanthanide-doped upconverting nanoparticles (UCNPs) are ideal candidates for use in biomedicine. The interaction of nanomaterials with biological systems determines whether they are suitable for use in living cells. In-depth knowledge of the nano-bio interactions is therefore a pre-requisite for the development of biomedical applications. The current study evaluates fundamental aspects of the NP-cell interface for square bipyramidal UCNPs containing a LiYF4:Yb3+, Tm3+ core and two different silica surface coatings. Given their importance for mammalian physiology, fibroblast and renal proximal tubule epithelial cells were selected as cellular model systems. We have assessed the toxicity of the UCNPs and measured their impact on the homeostasis of living non-malignant cells. Rigorous analyses were conducted to identify possible toxic and sub-lethal effects of the UCNPs. To this end, we examined biomarkers that reveal if UCNPs induce cell killing or stress. Quantitative measurements demonstrate that short-term exposure to the UCNPs had no profound effects on cell viability, cell size or morphology. Indicators of oxidative, endoplasmic reticulum, or nucleolar stress, and the production of molecular chaperones varied with the surface modification of the UCNPs and the cell type analyzed. These differences emphasize the importance of evaluating cells of diverse origin that are relevant to the intended use of the nanomaterials. Taken together, we established that short-term, our square bipyramidal UCNPs are not toxic to non-malignant fibroblast and proximal renal epithelial cells. Compared with established inducers of cellular stress, these UCNPs have minor effects on cellular homeostasis. Our results build the foundation to explore square bipyramidal UCNPs for future in vivo applications.

Modulation of autophagy and apoptosis can contribute to the anticancer effect of Abemaciclib/Celecoxib combination in colon cancer cells

Drug resistance and recurrence represent a great challenge in colorectal cancer management, highlighting the urgent need for novel therapeutics. Our objective is to evaluate the influence of Abemaciclib, Celecoxib, and their combination on both the autophagic and apoptotic machinery in an attempt to unravel the interplay between them in HCT-116 and Caco-2 cell lines. The MTT assay was used to assess the GI50 of the drugs. ELIZA was used to determine the protein levels of Beclin-1, LC3, Cox-2, and Bcl-2. Active Caspase-3 was determined by a colorimetric assay. Gene expression levels of ATG5, LC3, Beclin-1, and p62 were assessed by quantitative real-time PCR. In HCT-116 cells, the GI50s for Abemaciclib and Celecoxib were 15.86 and 92.67 μM, respectively, while for Caco-2 cells, the GI50s were 7.85 and 49.02 μM for Abemaciclib and Celecoxib, respectively. Upon treatment of HCT-116 and Caco-2 cells with Abemaciclib, Celecoxib, and their combinations, ATG5, p62, LC3, and Beclin-1 gene expression levels were up-regulated. The protein levels of Beclin-1, LC3, and Caspase-3 were significantly increased, while Bcl-2 was decreased in both cell lines due to single and combined treatments. Both drugs, either alone or in combination, decreased the migration ability of the cells in both cell lines. To conclude, the treatment protocol has the potential to induce cell cycle arrest, diminish the potentiality of cells for migration, and initiate apoptotic and autophagic cell death. Further research is recommended to unravel the potential antitumor effects of Abemaciclib/Celecoxib combination in different cancer types.

Advances in biological functions and applications of apoptotic vesicles

BACKGROUND

Apoptotic vesicles are extracellular vesicles generated by apoptotic cells that were previously regarded as containing waste or harmful substances but are now thought to play an important role in signal transduction and homeostasis regulation.

METHODS

In the present review, we reviewed many articles published over the past decades on the subtypes and formation of apoptotic vesicles and the existing applications of these vesicles.

RESULTS

Apoptotic bodies were once regarded as vesicles released by apoptotic cells, however, apoptotic vesicles are now regarded to include apoptotic bodies, apoptotic microvesicles and apoptotic exosomes, which exhibit variation in terms of biogenesis, sizes and properties. Applications of apoptotic vesicles were first reported long ago, but such reports have been rarer than those of other extracellular vesicles. At present, apoptotic vesicles have been utilized mainly in four aspects, including in direct therapeutic applications, in their engineering as carriers, in their construction as vaccines and in their utilization in diagnosis.

CONCLUSION

Building on a deeper understanding of their composition and characteristics, some studies have utilized apoptotic vesicles to treat diseases in more novel ways. However, their limitations for clinical translation, such as heterogeneity, have also emerged. In general, apoptotic vesicles have great application potential, but there are still many barriers to overcome in their investigation. Video Abstract.

Intracranial pressure for clinicians: it is not just a number

BACKGROUND

Invasive intracranial pressure (ICP) monitoring is a standard practice in severe brain injury cases, where it allows to derive cerebral perfusion pressure (CPP); ICP-tracing can also provide additional information about intracranial dynamics, forecast episodes of intracranial hypertension and set targets for a tailored therapy to prevent secondary brain injury. Nevertheless, controversies about the advantages of an ICP clinical management are still debated.

FINDINGS

This article reviews recent research on ICP to improve the understanding of the topic and uncover the hidden information in this signal that may be useful in clinical practice. Parameters derived from time-domain as well as frequency domain analysis include compensatory reserve, autoregulation estimation, pulse waveform analysis, and behavior of ICP in time. The possibility to predict the outcome and apply a tailored therapy using a personalised perfusion pressure target is also described.

CONCLUSIONS

ICP is a crucial signal to monitor in severely brain injured patients; a bedside computer can empower standard monitoring giving new metrics that may aid in clinical management, establish a personalized therapy, and help to predict the outcome. Continuous collaboration between engineers and clinicians and application of new technologies to healthcare, is vital to improve the accuracy of current metrics and progress towards better care with individualized dynamic targets.

Pterostilbene induces apoptosis in hepatocellular carcinoma cells: Biochemical, pathological, and molecular markers

Worldwide, hepatocellular carcinoma (HCC) is considered the sixth most prevalent cancer and ranked third in causes leading to death. Pterostilbene (PTE), a dimethylated analog of resveratrol, is a phytochemical found in fruits such as blueberries and grapes, and is known for its anticancer effect. The current study intended to investigate the effect of PTE on HepG2 cells. Cell viability, colony-forming potential, lipid peroxidation, catalase enzyme (CAT), superoxide dismutase (SOD), and caspase 3 activities, histone release, and expression levels of mTOR, S6K1, p53, and STAT3 proteins were assessed in PTE-treated HepG2 cells. In addition, the cellular and ultrastructural alterations were evaluated by light and transmission electron microscopy. PTE induced a significant reduction in HepG2 viability in a dose-dependent manner (IC₅₀ of PTE = 74 ± 6 μM), accompanied by a decrease in colony formation potential. PTE-treated cancer cells exhibited a decrease in lipid peroxidation and CAT activity, and an increase in histone release, caspase-3, and SOD activities. Ultrastructurally, PTE-treated cells exhibited notable cell shrinkage, reduced number of filopodia, increased vacuolization, apoptotic bodies, accumulation of lipid droplets, enlarged mitochondria, dilated endoplasmic reticulum, pyknotic nuclei, and cellular fragmentation. mTOR, S6K1, and STAT3 levels were downregulated, however p53 level was modulated in PTE-treated cells. The anticancer potential of PTE might be related to its ability to alter the ultrastructure morphology, reduce mitotic activity, and modulate some key protein required for cell proliferation, suggesting its potential to trigger cancer cells towards apoptosis.

Apoptotic bodies: bioactive treasure left behind by the dying cells with robust diagnostic and therapeutic application potentials

Apoptosis, a form of programmed cell death, is essential for growth and tissue homeostasis. Apoptotic bodies (ApoBDs) are a form of extracellular vesicles (EVs) released by dying cells in the last stage of apoptosis and were previously regarded as debris of dead cells. Recent studies unraveled that ApoBDs are not cell debris but the bioactive treasure left behind by the dying cells with an important role in intercellular communications related to human health and various diseases. Defective clearance of ApoBDs and infected-cells-derived ApoBDs are possible etiology of some diseases. Therefore, it is necessary to explore the function and mechanism of the action of ApoBDs in different physiological and pathological conditions. Recent advances in ApoBDs have elucidated the immunomodulatory, virus removal, vascular protection, tissue regenerative, and disease diagnostic potential of ApoBDs. Moreover, ApoBDs can be used as drug carriers enhancing drug stability, cellular uptake, and targeted therapy efficacy. These reports from the literature indicate that ApoBDs hold promising potential for diagnosis, prognosis, and treatment of various diseases, including cancer, systemic inflammatory diseases, cardiovascular diseases, and tissue regeneration. This review summarizes the recent advances in ApoBDs-related research and discusses the role of ApoBDs in health and diseases as well as the challenges and prospects of ApoBDs-based diagnostic and therapeutic applications.

Inhibition of autophagy reduces the rate of fluoride-induced LS8 apoptosis via regulating ATG5 and ATG7

Excessive fluoride affects ameloblast differentiation and tooth development. The fate of fluorinated ameloblasts is determined by multiple signaling pathways in response to a range of stimuli. Both autophagy and apoptosis are involved in the regulation of dental fluorosis as well as in protein synthesis and enamel mineralization. Emerging evidence suggests that autophagy and apoptosis are interconnected and that their interaction greatly influences cell death. However, the effect of autophagy on apoptosis in fluoride-treated ameloblasts is unclear. Here, we employed an in vitro cellular model of fluorosis in mouse ameloblast-like LS8 cells and induced autophagy using sodium fluoride (NaF). Our findings suggest that NaF treatment induces autophagy in LS8 cells, and ATG5 and ATG7 are important molecules involved in this process. We also showed that NaF treatment reduced cell viability in Atg5/7 siRNA and autophagy inhibitor-treated LS8 cells. More importantly, NaF-induced apoptosis can be reversed by inhibiting early stage of autophagy. In conclusion, our study shows that autophagy is closely related to dental fluorosis, and inhibition of autophagy, especially ATG5/7, reduces fluoride-induced cell death and apoptosis.

In search of cytotoxic selectivity on cancer cells with biogenically synthesized Ag/AgCl nanoparticles

Green synthesis may be a useful approach to achieve selective cytotoxicity of silver nanoparticles on cancer cells and healthy cells. In this study, the concomitant biosynthesis of silver (Ag)/silver chloride (AgCl) nanoparticles from pineapple peel extracts and their behavior on the breast cancer cell line MCF-7 is shown. Bioreactions were monitored at different temperatures. Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis), thermogravimetric analysis (TGA), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) techniques were used to characterize nanoparticle development. The breast cancer cell line MCF-7 was used as a test model to study the cytotoxic behavior of Ag/AgCl nanoparticles and, as a counterpart, the nanoparticles were also tested on mononuclear cells. Ag/AgCl nanoparticles with spherical and triangular morphology were obtained. The size of the nanoparticles (10-70 nm) and the size distribution depended on the reaction temperature. A dose close to 20 µg/mL of Ag/AgCl nanoparticles considerably decreased the cell viability of the MCF-7 line. The best cytotoxicity effects on cancer cells were obtained with nanoparticles at 60 and 80 °C where cell viability was reduced up to 80% at a concentration of 50 µg/mL. A significant preference was observed in the cytotoxic effect of Ag/AgCl nanoparticles against cancer cells in comparison to monocytes.

Mesenchymal Stem Cell-Derived Apoptotic Bodies: Biological Functions and Therapeutic Potential

Mesenchymal stem cells (MSCs) are non-hematopoietic progenitor cells with self-renewal ability and multipotency of osteogenic, chondrogenic, and adipogenic differentiation. MSCs have appeared as a promising approach for tissue regeneration and immune therapies, which are attributable not only to their differentiation into the desired cells but also to their paracrine secretion. MSC-sourced secretome consists of soluble components including growth factors, chemokines, cytokines, and encapsulated extracellular vesicles (EVs). Apoptotic bodies (ABs) are large EVs (diameter 500𠀓2000 nm) harboring a variety of cellular components including microRNA, mRNA, DNA, protein, and lipids related to the characteristics of the originating cell, which are generated during apoptosis. The released ABs as well as the genetic information they carry are engulfed by target cells such as macrophages, dendritic cells, epithelial cells, and fibroblasts, and subsequently internalized and degraded in the lysosomes, suggesting their ability to facilitate intercellular communication. In this review, we discuss the current understanding of the biological functions and therapeutic potential of MSC-derived ABs, including immunomodulation, tissue regeneration, regulation of inflammatory response, and drug delivery system.

Cellular enlargement - A new hallmark of aging?

Years of important research has revealed that cells heavily invest in regulating their size. Nevertheless, it has remained unclear why accurate size control is so important. Our recent study using hematopoietic stem cells (HSCs) in vivo indicates that cellular enlargement is causally associated with aging. Here, we present an overview of these findings and their implications. Furthermore, we performed a broad literature analysis to evaluate the potential of cellular enlargement as a new aging hallmark and to examine its connection to previously described aging hallmarks. Finally, we highlight interesting work presenting a correlation between cell size and age-related diseases. Taken together, we found mounting evidence linking cellular enlargement to aging and age-related diseases. Therefore, we encourage researchers from seemingly unrelated areas to take a fresh look at their data from the perspective of cell size.

Apoptotic bodies for advanced drug delivery and therapy

Extracellular vesicles (EVs) have emerged as promising candidates for multiple biomedical applications. Major types of EVs include exosomes, microvesicles, and apoptotic bodies (ABs). ABs are conferred most properties from parent cells in the final stages of apoptosis. A wide variety of sources and stable morphological features are endowed to ABs by the rigorous apoptotic program. ABs accommodate more functional biomolecules by relying on the larger volume and maintaining their naturalness in circulation. The predominant body surface ratio of ABs facilitates their recognition by recipient cells and is advantageous for interactions with microenvironments. ABs can modulate and alleviate symptoms of numerous diseases for their origins, circulation, and high biocompatibility. In addition, ABs have been emerging in disease diagnosis, immunotherapy, regenerative therapy, and drug delivery. Here, we aim to present a thorough discussion on current knowledge about ABs. Of particular interest, we will summarize the application of AB-based strategies for diagnosis and disease therapy. Perspectives for the development of ABs in biomedical applications are highlighted.

A Promising Method for the Determination of Cell Viability: The Membrane Potential Cell Viability Assay

Determining the viability of cells is fraught with many uncertainties. It is often difficult to determine whether a cell is still alive, approaching the point of no return, or dead. Today, there are many methods for determining cell viability. Most rely on an indirect determination of cell death (metabolism, molecular transport, and leakage, to name a few). In contrast, we have developed a promising novel method for a “direct” determination of cell viability. The potential method assesses cell membrane integrity (which is essential for all viable cells) by measuring the electrical potential of the cell membrane. To test the assay, we chose two different cell types, blood macrophages (TLT) and breast cancer epithelial cells (MCF 7). We exposed them to seven different toxic scenarios (arsenic (V), UV light, hydrogen peroxide, nutrient starvation, Tetrabromobisphenol A, fatty acids, and 5-fluorouracil) to induce different cell death pathways. Under controlled test conditions, the assay showed good accuracy when comparing the toxicity assessment with well-established methods. Moreover, the method showed compatibility with live cell imaging. Although we know that further studies are needed to confirm the performance of the assay in other situations, the results obtained are promising for their wider application in the future.

Advances in the Therapeutic Effects of Apoptotic Bodies on Systemic Diseases

Apoptosis plays an important role in development and in the maintenance of homeostasis. Apoptotic bodies (ApoBDs) are specifically generated from apoptotic cells and can contain a large variety of biological molecules, which are of great significance in intercellular communications and the regulation of phagocytes. Emerging evidence in recent years has shown that ApoBDs are essential for maintaining homeostasis, including systemic bone density and immune regulation as well as tissue regeneration. Moreover, studies have revealed the therapeutic effects of ApoBDs on systemic diseases, including cancer, atherosclerosis, diabetes, hepatic fibrosis, and wound healing, which can be used to treat potential targets. This review summarizes current research on the generation, application, and reconstruction of ApoBDs regarding their functions in cellular regulation and on systemic diseases, providing strong evidence and therapeutic strategies for further insights into related diseases.

Passiflora mollissima Seed Extract Induced Antiproliferative and Cytotoxic Effects on CAL 27 Spheroids

Multicellular tumor spheroids are used as models in drug development due to their characteristics simulating in vivo tumors. Likewise, antiproliferative properties of extracts derived from fruits have been widely described. Peels and seeds can be used as a matrix to obtain different compounds. Recently, a study demonstrated the antiproliferative activity from a P. mollissima extract (PME) on human colon cancer cells; however, its effect on oral spheroids is unknown. Objective. To evaluate the antiproliferative potential of an extract obtained from P. mollissima seeds on the spheroid-type-3D culture model of CAL 27. Methods. CAL 27-spheroids were treated with three concentrations of PME (10, 50, and 100 μg/ml). After 72 hr incubation, morphology and cellular changes, cytotoxic and proapoptotic effect, gene expression, and metastasis were determined. Additionally, changes in the cell cycle phases responded to the PME concentrations. Comparisons between groups were made through a U Mann-Whitney test. Results. It was shown that 100 μg/ml PE affects CAL 27 cells proliferation grown in spheroids through cell cycle arrest and gene regulation of p53, HIF 1α, and CDH1. However, none of the treatments employed induced MMP9 gene expression. Conclusion. Our study shows that PME inhibits the growth and proliferation of oral tumor cells cultured in spheroids through the positive regulation of cell death and metastasis genes.

Stability of Intracellular Protein Concentration under Extreme Osmotic Challenge

Cell volume (CV) regulation is typically studied in short-term experiments to avoid complications resulting from cell growth and division. By combining quantitative phase imaging (by transport-of-intensity equation) with CV measurements (by the exclusion of an external absorbing dye), we were able to monitor the intracellular protein concentration (PC) in HeLa and 3T3 cells for up to 48 h. Long-term PC remained stable in solutions with osmolarities ranging from one-third to almost twice the normal. When cells were subjected to extreme hypoosmolarity (one-quarter of normal), their PC did not decrease as one might expect, but increased; a similar dehydration response was observed at high concentrations of ionophore gramicidin. Highly dilute media, or even moderately dilute in the presence of cytochalasin, caused segregation of water into large protein-free vacuoles, while the surrounding cytoplasm remained at normal density. These results suggest that: (1) dehydration is a standard cellular response to severe stress; (2) the cytoplasm resists prolonged dilution. In an attempt to investigate the mechanism behind the homeostasis of PC, we tested the inhibitors of the protein kinase complex mTOR and the volume-regulated anion channels (VRAC). The initial results did not fully elucidate whether these elements are directly involved in PC maintenance.

Propionic acid induces apoptosis-like death in Escherichia coli O157

Propionic acid (PPA), utilized in the manufacture of cellulose acetate propionate, is known to exhibit antimicrobial effects, but its mechanism in Escherichia coli O157 is still unknown. In general, antimicrobial activity is associated with reactive oxygen species (ROS), but ROS generation is not observed under PPA treatment. In addition to ROS, experiments were conducted to observe changes in trehalose and ion balance to discover factors that may affect the cell proliferation. Bacteria use trehalose, a sugar used for stabilization due to stress factors, which contradicts PPA concentration. Discrepancy in homeostasis follows as a result of ion imbalance. PPA causes interruption in bacterial internal stability in a dose-dependent manner. Membrane damage by ion imbalance occurs due to the binding ability of ionized PPA and divalent ions, which induce membrane depolarization, leading to a reduction in cell viability. Considering the lethal impact of membrane depolarization on cell death in bacteria, DNA fragmentation and phosphatidylserine exposure in apoptosis are confirmed. Due to severe damage in DNA, the activation of caspase-like protein is observed. Apoptosis-like death (ALD), a novel programmed cell death in bacteria, occurs eventually. In conclusion, ALD in E. coli O157 is induced via the contribution of homeostasis disruption in a ROS-independent manner.

Extracellular Vesicles in Acute Leukemia: A Mesmerizing Journey With a Focus on Transferred microRNAs

Despite their small size, the membrane-bound particles named extracellular vesicles (EVs) seem to play an enormous role in the pathogenesis of acute leukemia. From oncogenic hematopoietic stem cells (HSCs) to become leukemic cells to alter the architecture of bone marrow (BM) microenvironment, EVs are critical components of leukemia development. As a carrier of essential molecules, especially a group of small non-coding RNAs known as miRNA, recently, EVs have attracted tremendous attention as a prognostic factor. Given the importance of miRNAs in the early stages of leukemogenesis and also their critical parts in the development of drug-resistant phenotype, it seems that the importance of EVs in the development of leukemia is more than what is expected. To be familiar with the clinical value of leukemia-derived EVs, this review aimed to briefly shed light on the biology of EVs and to discuss the role of EV-derived miRNAs in the development of acute myeloid leukemia and acute lymphoblastic leukemia. By elaborating the advances and challenges concerning the isolation of EVs, we discuss whether EVs could have a prognostic value in the clinical setting for leukemia.

Urinary TCP1-eta: A Cortical Damage Marker for the Pathophysiological Diagnosis and Prognosis of Acute Kidney Injury

Acute kidney injury (AKI) is a serious syndrome with increasing incidence and health consequences, and high mortality rate among critically ill patients. Acute kidney injury lacks a unified definition, has ambiguous semantic boundaries, and relies on defective diagnosis. This, in part, is due to the absence of biomarkers substratifying AKI patients into pathophysiological categories based on which prognosis can be assigned and clinical treatment differentiated. For instance, AKI involving acute tubular necrosis (ATN) is expected to have a worse prognosis than prerenal, purely hemodynamic AKI. However, no biomarker has been unambiguously associated with tubular cell death or is able to provide etiological distinction. We used a cell-based system to identify TCP1-eta in the culture medium as a noninvasive marker of damaged renal tubular cells. In rat models of AKI, TCP1-eta was increased in the urine co-relating with renal cortical tubule damage. When kidneys from ATN rats were perfused in situ with Krebs-dextran solution, a portion of the urinary TCP1-eta protein content excreted into urine disappeared, and another portion remained within the urine. These results indicated that TCP1-eta was secreted by tubule cells and was not fully reabsorbed by the damaged tubules, both effects contributing to the increased urinary excretion. Urinary TCP1-eta is found in many etiologically heterogeneous AKI patients, and is statistically higher in patients partially recovered from severe AKI. In conclusion, urinary TCP1-eta poses a potential, substratifying biomarker of renal cortical damage associated with bad prognosis.

MRCK: a master regulator of tissue remodeling or another 'ROCK' in the epithelial block?

The epithelium forms a smart barrier to the external environment that can remodel whilst maintaining tissue integrity, a feature important for development, homeostasis, and function. Its dysregulation can lead to diseases ranging from cancer to vision loss. Epithelial remodeling requires reorganization of a thin sheet of actomyosin cortex under the plasma membrane of polarized cells that form basolateral contacts with neighboring cells and the extracellular matrix (ECM). Rho GTPases act as spatiotemporal molecular switches in this process, controlling localized actomyosin dynamics. However, the molecular mechanisms that control actomyosin dynamics at the apical cortex are poorly understood. This review focusses on a growing body of evidence that suggest myotonic dystrophy kinase-related Cdc42-binding kinase (MRCK) plays a conserved role in morphogenetic signaling at the apical cortex in diverse cell and tissue remodeling processes. The possible molecular and mechanistic basis for the diverse functions of MRCK at the apical pole will also be discussed.

Biogenesis, Membrane Trafficking, Functions, and Next Generation Nanotherapeutics Medicine of Extracellular Vesicles

Extracellular vesicles (EVs) are a heterogeneous group of membrane-limited vesicles and multi-signal messengers loaded with biomolecules. Exosomes and ectosomes are two different types of EVs generated by all cell types. Their formation depends on local microdomains assembled in endocytic membranes for exosomes and in the plasma membrane for ectosomes. Further, EV release is a fundamental process required for intercellular communication in both normal physiology and pathological conditions to transmit/exchange bioactive molecules to recipient cells and the extracellular environment. The unique structure and composition of EVs enable them to serve as natural nanocarriers, and their physicochemical properties and biological functions can be used to develop next-generation nano and precision medicine. Knowledge of the cellular processes that govern EVs biology and membrane trafficking is essential for their clinical applications. However, in this rapidly expanding field, much remains unknown regarding EV origin, biogenesis, cargo sorting, and secretion, as well as EV-based theranostic platform generation. Hence, we present a comprehensive overview of the recent advances in biogenesis, membrane trafficking, and functions of EVs, highlighting the impact of nanoparticles and oxidative stress on EVs biogenesis and release and finally emphasizing the role of EVs as nanotherapeutic agents.

Size-controlled human adipose-derived stem cell spheroids hybridized with single-segmented nanofibers and their effect on viability and stem cell differentiation

BACKGROUND

Fabrication of three-dimensional stem cell spheroids have been studied to improve stem cell function, but the hypoxic core and limited penetration of nutrients and signaling cues to the interior of the spheroid were challenges. The incorporation of polymers such as silica and gelatin in spheroids resulted in relatively relaxed assembly of composite spheroids, and enhancing transport of nutrient and biological gas. However, because of the low surface area between cells and since the polymers were heterogeneously distributed throughout the spheroid, these polymers cannot increase the cell to extracellular matrix interactions needed to support differentiation.

METHODS

We developed the stem cell spheroids that incorporate poly(ι-lactic acid) single-segmented fibers synthesized by electrospinning and physical and chemical fragmentation. The proper mixing ratio was 2000 cells/μg fibers (average length of the fibers was 50 μm - 100 μm). The SFs were coated with polydopamine to increase cell binding affinity and to synthesize various-sized spheroids. The function of spheroids was investigated by in vitro analysis depending on their sizes. For statistical analysis, Graphpad Prism 5 software (San Diego, CA, USA) was used to perform one-way analysis of variance ANOVA with Tukey's honest significant difference test and a Student's t-test (for two variables) (P < 0.05).

RESULTS

Spheroids of different sizes were created by modulating the amount of cells and fibers (0.063 mm2-0.322 mm2). The fibers in the spheroid were homogenously distributed and increased cell viability, while cell-only spheroids showed a loss of DNA contents, internal degradation, and many apoptotic signals. Furthermore, we investigated stemness and various functions of various-sized fiber-incorporated spheroids. In conclusion, the spheroid with the largest size showed the greatest release of angiogenic factors (released VEGF: 0.111 ± 0.004 pg/ng DNA), while the smallest size showed greater effects of osteogenic differentiation (mineralized calcium: 18.099 ± 0.271 ng/ng DNA).

CONCLUSION

The spheroids incorporating polydopamine coated single-segmented fibers showed enhanced viability regardless of sizes and increased their functionality by regulating the size of spheroids which may be used for various tissue reconstruction and therapeutic applications.

Mechanisms for Modulating Anoikis Resistance in Cancer and the Relevance of Metabolic Reprogramming

The attachment of cells to the extracellular matrix (ECM) is the hallmark of structure–function stability and well-being. ECM detachment in localized tumors precedes abnormal dissemination of tumor cells culminating in metastasis. Programmed cell death (PCD) is activated during tumorigenesis to clear off ECM-detached cells through “anoikis.” However, cancer cells develop several mechanisms for abrogating anoikis, thus promoting their invasiveness and metastasis. Specific factors, such as growth proteins, pH, transcriptional signaling pathways, and oxidative stress, have been reported as drivers of anoikis resistance, thus enhancing cancer proliferation and metastasis. Recent studies highlighted the key contributions of metabolic pathways, enabling the cells to bypass anoikis. Therefore, understanding the mechanisms driving anoikis resistance could help to counteract tumor progression and prevent metastasis. This review elucidates the dynamics employed by cancer cells to impede anoikis, thus promoting proliferation, invasion, and metastasis. In addition, the authors have discussed other metabolic intermediates (especially amino acids and nucleotides) that are less explored, which could be crucial for anoikis resistance and metastasis.

Cellular alterations and damage to the renal tissue of marine catfish Arius arius following Cd exposure and the possible sequestrant role of Metallothionein

Cd is a non-degradable heavy metal pollutant with no known biological role. When taken up by living organisms from the environment, it causes extensive tissue damage. Here, we studied the effects of exposure to 20 mg/L^-1CdCl₂for 0, 24, 48, and 72 h on the renal tissue of marine catfish Arius arius. Cd uptake, metallothionein (MT) induction, microarchitectural alterations, DNA fragmentation, and caspase-3 activity were studied. Cd and MT levels were time-dependent and positively correlated. The diameter of the Bowman's capsule and tubules was significantly increased. Meanwhile, the density, diameter, and volume of the glomerulus as well as the density and volume of tubules decreased. Cd induced apoptosis though elevatedcaspase-3 activity. These results support the notion that exposure to sublethal Cd levels induces oxidative stress, leading to structural and functional impairment of the kidneys. Cd uptake and MT induction can serve as useful environmental biomarkers.

An Annexin V-FITC-Propidium Iodide-Based Method for Detecting Apoptosis in a Non-Small Cell Lung Cancer Cell Line

Annexin V and propidium iodide staining is widely used for determining the cellular death through apoptosis. In the presence of Ca²⁺ ions, annexin V has a strong binding affinity for phosphatidylserine, a membrane phospholipid that during apoptosis is translocated from the inner side of the cell membrane to its outer side. On the other hand, propidium iodide has ability for DNA binding and it can only enter into necrotic or late apoptotic cells. This chapter describes a commonly used method for detection of apoptosis in a non-small cell lung cancer cell line using annexin V and propidium iodide dye. We describe the detection of different stages of apoptosis in the A549 lung cancer cell line treated with dihydroartemisinin (DHA). This apoptosis detection method can be used to determine the efficacy of different kinds of drugs on cultured cancer cell lines.

Glial Chloride Channels in the Function of the Nervous System Across Species

In the nervous system, the concentration of Cl- in neurons that express GABA receptors plays a key role in establishing whether these neurons are excitatory, mostly during early development, or inhibitory. Thus, much attention has been dedicated to understanding how neurons regulate their intracellular Cl- concentration. However, regulation of the extracellular Cl- concentration by other cells of the nervous system, including glia and microglia, is as important because it ultimately affects the Cl- equilibrium potential across the neuronal plasma membrane. Moreover, Cl- ions are transported in and out of the cell, via either passive or active transporter systems, as counter ions for K+ whose concentration in the extracellular environment of the nervous system is tightly regulated because it directly affects neuronal excitability. In this book chapter, we report on the Cl- channel types expressed in the various types of glial cells focusing on the role they play in the function of the nervous system in health and disease. Furthermore, we describe the types of stimuli that these channels are activated by, the other solutes that they may transport, and the involvement of these channels in processes such as pH regulation and Regulatory Volume Decrease (RVD). The picture that emerges is one of the glial cells expressing a variety of Cl- channels, encoded by members of different gene families, involved both in short- and long-term regulation of the nervous system function. Finally, we report data on invertebrate model organisms, such as C. elegans and Drosophila, that are revealing important and previously unsuspected functions of some of these channels in the context of living and behaving animals.

An update to the Monro-Kellie doctrine to reflect tissue compliance after severe ischemic and hemorrhagic stroke

High intracranial pressure (ICP) can impede cerebral blood flow resulting in secondary injury or death following severe stroke. Compensatory mechanisms include reduced cerebral blood and cerebrospinal fluid volumes, but these often fail to prevent raised ICP. Serendipitous observations in intracerebral hemorrhage (ICH) suggest that neurons far removed from a hematoma may shrink as an ICP compliance mechanism. Here, we sought to critically test this observation. We tracked the timing of distal tissue shrinkage (e.g. CA1) after collagenase-induced striatal ICH in rat; cell volume and density alterations (42% volume reduction, 34% density increase; p < 0.0001) were highest day one post-stroke, and rebounded over a week across brain regions. Similar effects were seen in the filament model of middle cerebral artery occlusion (22% volume reduction, 22% density increase; p ≤ 0.007), but not with the Vannucci-Rice model of hypoxic-ischemic encephalopathy (2.5% volume increase, 14% density increase; p ≥ 0.05). Concerningly, this 'tissue compliance' appears to cause sub-lethal damage, as revealed by electron microscopy after ICH. Our data challenge the long-held assumption that 'healthy' brain tissue outside the injured area maintains its volume. Given the magnitude of these effects, we posit that 'tissue compliance' is an important mechanism invoked after severe strokes.

Mesenchymal stem cell-derived small extracellular vesicles and bone regeneration

Mesenchymal stem cells (MSCs) and MSC‐derived small extracellular vesicles (sEVs) are promising candidates for cell‐based and cell‐free regenerative medicine, respectively. By virtue of their multiple lineage differentiation capacity, MSCs have been implicated as an ideal tool for bone and cartilage regeneration. However, later observations attributed such regenerative effects to MSC‐secreted paracrine factors. Exosomes, endosomal originated sEVs carrying lipid, protein and nucleic acid cargoes, were identified as components of the MSC secretome and propagated the key regenerative and immunoregulatory characteristics of parental MSCs. Here, exosome biogenesis, the molecular composition of exosomes, sEV‐cell interactions and the effects on key bone homeostasis cells are reviewed. MSC‐derived sEVs show to promote neovascularization and bone and cartilage regeneration in preclinical disease models. The mechanisms include the transfer of molecules, including microRNAs, mRNAs and proteins, to other key cells. MSC‐derived sEVs are interesting candidates as biopharmaceuticals for drug delivery and for the engineering of biologically functionalized materials. Although major exploratory efforts have been made for therapeutic development, the secretion, distribution and biological effects of MSC‐derived sEVs in bone and cartilage regeneration are not fully understood. Moreover, techniques for high‐yield production, purity and storage need to be optimized before effective and safe MSC‐derived sEVs therapies are realized.

Apoptosis-inducing activity of a fluorescent barrel-rosette M+/Cl- channel

Synthetic transmembrane ion transport systems are emerging as new tools for anticancer therapy. Here, a series of 2-hydroxy-N 1,N 3-diarylisophthalamide-based fluorescent ion channel-forming compounds are reported. Ion transport studies across large unilamellar vesicles confirmed that the compound with two 3,5-bis(trifluoromethyl)phenyl arms is the most efficient transporter among the series and it facilitates M+/Cl- symport. The compound formed supramolecular ion channels with a single-channel conductance of 100 ± 2 pS, a diameter of 5.06 ± 0.16 Å and a permeability ratio, P Cl- /P K+ , of 8.29 ± 1. The molecular dynamics simulations of the proposed M2.11 channel (i.e. 11 coaxial layers of a dimeric rosette) with K+ and Cl- in the preequilibrated POPC lipid bilayer with water molecules illustrated various aspects of channel formation and ion permeation. Cell viability assay with the designed compounds indicated that cell death is being induced by the individual compounds which follow the order of their ion transport activity and chloride and cations play roles in cell death. The inherent fluorescence of the most active transporter was helpful to monitor its permeation in cells by confocal microscopy. The apoptosis-inducing activity upon perturbation of intracellular ionic homeostasis was established by monitoring mitochondrial membrane depolarization, generation of reactive oxygen species, cytochrome c release, activation of the caspase 9 pathway, and finally the uptake of the propidium iodide dye in the treated MCF7 cells.

A Comprehensive Picture of Extracellular Vesicles and Their Contents. Molecular Transfer to Cancer Cells

Critical processes such as growth, invasion, and metastasis of cancer cells are sustained via bidirectional cell-to-cell communication in tissue complex environments. Such communication involves the secretion of soluble factors by stromal cells and/or cancer cells within the tumor microenvironment (TME). Both stromal and cancer cells have been shown to export bilayer nanoparticles: encapsulated regulatory molecules that contribute to cell-to-cell communication. These nanoparticles are known as extracellular vesicles (EVs) being classified into exosomes, microvesicles, and apoptotic bodies. EVs carry a vast repertoire of molecules such as oncoproteins and oncopeptides, DNA fragments from parental to target cells, RNA species (mRNAs, microRNAs, and long non-coding RNA), and lipids, initiating phenotypic changes in TME. According to their specific cargo, EVs have crucial roles in several early and late processes associated with tumor development and metastasis. Emerging evidence suggests that EVs are being investigated for their implication in early cancer detection, monitoring cancer progression and chemotherapeutic response, and more relevant, the development of novel targeted therapeutics. In this study, we provide a comprehensive understanding of the biophysical properties and physiological functions of EVs, their implications in TME, and highlight the applicability of EVs for the development of cancer diagnostics and therapeutics.

Apoptosis and apoptotic body: disease message and therapeutic target potentials

Apoptosis is widely known as programmed cell death eliciting no inflammatory responses. The intricacy of apoptosis has been a focus of an array of researches, accumulating a wealth of knowledge which led to not only a better understanding of the fundamental process, but also potent therapies of diseases. The classic intrinsic and extrinsic signaling pathways of apoptosis, along with regulatory factors have been well delineated. Drugs and therapeutic measures designed based on current understanding of apoptosis have long been employed. Small-molecule apoptosis inducers have been clinically used for eliminating morbid cells and therefore treating diseases, such as cancer. Biologics with improved apoptotic efficacy and selectivity, such as recombinant proteins and antibodies, are being extensively researched and some have been approved by the FDA. Apoptosis also produces membrane-bound vesicles derived from disassembly of apoptotic cells, now known as apoptotic bodies (ApoBDs). These little sealed sacs containing information as well as substances from dying cells were previously regarded as garbage bags until they were discovered to be capable of delivering useful materials to healthy recipient cells (e.g., autoantigens). In this review, current understandings and knowledge of apoptosis were summarized and discussed with a focus on apoptosis-related therapeutic applications and ApoBDs.

Diphenylethylenediamine-Based Potent Anionophores: Transmembrane Chloride Ion Transport and Apoptosis Inducing Activities

Synthetic anion transporters have been recognized as one of the potential therapeutic agents for the treatment of diseases including cystic fibrosis, myotonia, and epilepsy that originate due to the malfunctioning of natural Cl^- ion transport systems. Recent studies showed that the synthetic Cl^- ion transporters can also disrupt cellular ion-homeostasis and induce apoptosis in cancer cell lines, leading to a revived attention for synthetic Cl^- ion transporters. Herein, we report the development of conformationally controlled 1,2-diphenylethylenediamine-based bis(thiourea) derivatives as a new class of selective Cl^- ion carrier. The strong Cl^- ion binding properties ( K_d = 3.87-6.66 mM) of the bis(thiourea) derivatives of diamine-based compounds correlate well with their transmembrane anion transport activities (EC₅₀ = 2.09-4.15 nM). The transport of Cl^- ions via Cl^-/NO₃^- antiport mechanism was confirmed for the most active molecule. Perturbation of Cl^- ion homeostasis by this anion carrier induces cell death by promoting the caspase-mediated intrinsic pathway of apoptosis.

Opening of the CLC-3 chloride channel induced by dihydroartemisinin contributed to early apoptotic events in human poorly differentiated nasopharyngeal carcinoma cells

Nasopharyngeal carcinoma (NPC) is a specific type of head and neck cancer that is prevalent in Southeast Asia. Dihydroartemisinin (DHA), a semisynthetic derivative of artemisinin, has specific anticancer activity. Here, we aimed to investigate the role of the CLC-3 chloride channel in the anticancer effect of DHA in poorly differentiated NPC CNE-2Z cells. First, we observed that DHA could specifically inhibit the proliferation, induce apoptosis, and increase cleaved caspase-3 expression in the CNE-2Z cells. Then, we found that DHA could activate chloride channels, which led to Cl^- efflux and apoptotic volume decrease (AVD) in the early stage in the CNE-2Z cells. DHA also specifically increased CLC-3 chloride channel protein expression in the CNE-2Z cells. Silencing of the CLC-3 protein expression depleted the Cl^- currents, and decreased the AVD capacity and cell apoptosis induced by DHA. Finally, we revealed that the [Ca²⁺ ]_i increased after around 6 hours of treatment with DHA, which was also inhibited by silencing of the CLC-3 protein expression. Our data demonstrated that the selective antitumor activities of DHA in NPC may occur through the specific activation of the CLC-3 Cl^- channel, leading to Cl^- efflux, and induced AVD, then led to [Ca²⁺ ]_i accumulation and caspase-3 activation, and finally induced apoptosis. The activation of the CLC-3 chloride channel played an essential and proximal upstream role in the antitumor activities of DHA.

Methamphetamine Induces Apoptosis of Microglia via the Intrinsic Mitochondrial-Dependent Pathway

Methamphetamine (METH) is a drug of abuse, the acute and chronic use of which induces neurotoxic responses in the human brain, ultimately leading to neurocognitive disorders. Our goals were to understand the impact of METH on microglial mitochondrial respiration and to determine whether METH induces the activation of the mitochondrial-dependent intrinsic apoptosis pathway in microglia. We assessed the expression of pro- apoptosis genes using qPCR of RNA extracted from a human microglial cell line (HTHU). We examined the apoptosis-inducing effects of METH on microglial cells using digital holographic microscopy (DHM) to quantify real-time apoptotic volume decrease (AVD) in microglia in a noninvasive manner. METH treatment significantly increased AVD, activated Caspase 3/7, increased the gene expression levels of the pro- apoptosis proteins, APAF-1 and BAX, and decreased mitochondrial DNA content. Using immunofluorescence analysis, we found that METH increased the expression of the mitochondrial proteins cytochrome c and MCL-1, supporting the activation of mitochondrion-dependent (intrinsic) apoptosis pathway. Cellular bio-energetic flux analysis by Agilent Seahorse XF Analyzer revealed that METH treatment increased both oxidative and glycolytic respiration after 3 h, which was sustained for at least 24 h. Several events, such as oxidative stress, neuro-inflammatory responses, and mitochondrial dysfunction, may converge to mediate METH-induced apoptosis of microglia that may contribute to neurotoxicity of the CNS. Our study has important implications for therapeutic strategies aimed at preserving mitochondrial function in METH abusing patients.

Metabolic reprogramming of acute lymphoblastic leukemia cells in response to glucocorticoid treatment

Glucocorticoids (GCs) are metabolic hormones with immunosuppressive effects that have proven effective drugs against childhood acute lymphoblastic leukemia (ALL). Yet, the role of metabolic reprogramming in GC-induced ALL cell death is poorly understood. GCs efficiently block glucose uptake and metabolism in ALL cells, but this does not fully explain the observed induction of autophagy and cell death. Here, we have performed parallel time-course proteomics, metabolomics, and isotope-tracing studies to examine in detail the metabolic effects of GCs on ALL cells. We observed metabolic events associated with growth arrest, autophagy, and catabolism prior to onset of apoptosis: nucleotide de novo synthesis was reduced, while certain nucleobases accumulated; polyamine synthesis was inhibited; and phosphatidylcholine synthesis was induced. GCs suppressed not only glycolysis but also entry of both glucose and glutamine into the TCA cycle. In contrast, expression of glutamine-ammonia ligase (GLUL) and cellular glutamine content was robustly increased by GC treatment, suggesting induction of glutamine synthesis, similar to nutrient-starved muscle. Modulating medium glutamine and dimethyl-α-ketoglutarate (dm-αkg) to favor glutamine synthesis reduced autophagosome content of ALL cells, and dm-αkg also rescued cell viability. These data suggest that glutamine synthesis affects autophagy and possibly onset of cell death in response to GCs, which should be further explored to understand mechanism of action and possible sources of resistance.

Tetracaine induces apoptosis through a mitochondrion-dependent pathway in human corneal stromal cells in vitro

PURPOSE

Tetracaine is a local anesthetic widely used in ocular diagnosis and ophthalmic surgery and may lead to some adverse effects and complications at a clinical dose. To assess the cytotoxicity and molecular toxicity mechanisms of tetracaine, we used human corneal stromal (HCS) cells as an in vitro model to study the effects of tetracaine on HCS cells.

MATERIALS AND METHODS

The cytotoxicity of tetracaine on HCS cells was investigated by examining the changes of cell growth, morphology, viability and cell cycle progressing when HCS cells were treated with tetracaine at concentrations from 10 g/L to 0.078125 g/L. To prove the hypothesis that the cytotoxicity of tetracaine on HCS cells was related with apoptosis induction, we further detected multiple changes in HCS cells, including plasma membrane (PM) permeability, phosphatidylserine (PS) orientation, genomic DNA integrality, and cell ultrastrcuture after treated with tetracaine. Furthermore, the pro-apoptotic signalling pathway induced by tetracaine was explored through detecting the activation of various caspases, the changes of mitochondrial transmembrane potential (MTP), the expression level of Bcl-2 family proteins and the amount of mitochondria-released apoptosis regulating proteins in cytoplasm.

RESULTS

Tetracaine at concentrations above 0.15625 g/L had a dose- and time-dependent cytotoxicity to HCS cells, which resulted cell growth inhibition, proliferation retardation, morphological abnormalities and decreased viability. Meanwhile, we found that the HCS cells treated with tetracaine had typical features associated with apoptosis, including an increase in PM permeability, PS externalization, DNA fragmentation and apoptotic body formation. Tetracaine not only resulted in caspase-3, caspase-8 and caspase-9 activation and disruption of MTP but also downregulated Bcl-2 and Bcl-xL and upregulated Bad and Bax, along with the upregulation of cytoplasmic cytochrome c (Cyt. c) and apoptosis-inducing factor (AIF).

CONCLUSIONS

These results suggested that tetracaine-induced apoptosis might be triggered through Fas death receptors and mediated by Bcl-2 family proteins in the mitochondria-dependent pathway. Our findings identified the cytotoxicity and molecular mechanisms of tetracaine, which could provide a reference value for the safety of this medication and prospective therapeutic interventions in eye clinic.

Viability assessment of primary growth oocytes following ovarian tissue vitrification of neotropical teleost pacu (Piaractus mesopotamicus)

Vitrification of ovarian tissue containing immature oocytes provides an important tool for protecting the endangered species and genetic diversity in aquatic species. Therefore, the main objective was to assess primary growth (PG) oocytes viability following ovarian tissue vitrification using histological analysis, two staining protocols (trypan blue or fluorescein diacetate combined with propidium iodide) and mitochondrial activity assay (MTT assay). In addition, oocyte histomorphometry was performed to evaluate the morphometric parameters after vitrification and the relationship with the occurrence of damage (nucleus and/or membrane) in PG oocytes. There was no significant difference among the vitrified oocytes using trypan blue dye or FDA + IP staining. Oocyte viability assessed using histological analysis showed that vitrification solution 2.0 M Me₂SO + 2.5 M etilenoglycol +0.5 M sucrose (VS3; 66.43 ± 4.68%) and 1.5 M methanol + 5.5 M Me₂SO + 0.5 M sucrose (VS5; 74.14 ± 3.71%) had the lowest viability rate. Similar results were observed in MTT assay where VS3 (1.63 ± 0.12) and VS5 (1.58 ± 0.09) had the lowest averages when compare with VS1 (2.39 ± 0.14), VS2 (1.78 ± 0.06) and VS4 (2.34 ± 0.19) (P = 0.0002). In membrane damage evaluation by histology, there was no difference among vitrified oocytes and control. However, the highest percentages of nucleus damage were observed in treatments VS3 (26.00 ± 5.55) and VS5 (26.00 ± 5.55). Oocyte diameter did not change after vitrification; however, nucleus diameter was significantly higher in control group (49.03 ± 1.07). Oocyte viability by histological analysis was positive-correlated to the occurrence of nucleus (r² = 0.78) and membrane (r² = 0.45) damage after vitrification/warming. The high viability of PG oocytes obtained after ovarian tissue vitrification of Piaractus mesopotamicus suggests that the protocol applied here might be used successfully in other teleost species for food production.

MRCKα is activated by caspase cleavage to assemble an apical actin ring for epithelial cell extrusion

Apoptotic cell extrusion is critical for the maintenance of epithelial functionality and relies on complex morphological events mediated by the actomyosin cytoskeleton. Gagliardi et al. show that caspase-mediated cleavage of MRCKα triggers the assembly of an apical actin ring and apoptotic epithelial extrusion.

Extrusion of apoptotic cells from epithelial tissues requires orchestrated morphological rearrangements of the apoptotic cell and its neighbors. However, the connections between the apoptotic cascade and events leading to extrusion are not fully understood. Here, we characterize an apoptotic extrusion apical actin ring (EAAR) that is assembled within the apoptotic cell and drives epithelial extrusion. Caspase-mediated cleavage of myotonic dystrophy kinase–related CDC42-binding kinase-α (MRCKα) triggers a signaling pathway that leads to the assembly of EAAR that pulls actin bundles, resulting in the compaction and removal of the cell body. We provide a detailed portrait of the EAAR including F-actin flow, the contribution of myosin contraction, and actin polymerization at bundles' terminals when the product of MRCKα cleavage is expressed. These results add to our understanding of the mechanisms controlling the process of epithelial extrusion by establishing a causal relationship between the triggering events of apoptosis, the activation of MRCKα, and its subsequent effects on the dynamics of actomyosin cytoskeleton rearrangement.

Reassessing apoptosis in plants

Cell death can be driven by a genetically programmed signalling pathway known as programmed cell death (PCD). In plants, PCD occurs during development as well as in response to environmental and biotic stimuli. Our understanding of PCD regulation in plants has advanced significantly over the past two decades; however, the molecular machinery responsible for driving the system remains elusive. Thus, whether conserved PCD regulatory mechanisms include plant apoptosis remains enigmatic. Animal apoptotic regulators, including Bcl-2 family members, have not been identified in plants but expression of such regulators can trigger or suppress plant PCD. Moreover, plants exhibit nearly all of the biochemical and morphological features of apoptosis. One difference between plant and animal PCD is the absence of phagocytosis in plants. Evidence is emerging that the vacuole may be key to removal of unwanted plant cells, and may carry out functions that are analogous to animal phagocytosis. Here, we provide context for the argument that apoptotic-like cell death occurs in plants.

Phosphatidylserine externalization, "necroptotic bodies" release, and phagocytosis during necroptosis

Necroptosis is a regulated, nonapoptotic form of cell death initiated by receptor-interacting protein kinase-3 (RIPK3) and mixed lineage kinase domain-like (MLKL) proteins. It is considered to be a form of regulated necrosis, and, by lacking the “find me” and “eat me” signals that are a feature of apoptosis, necroptosis is considered to be inflammatory. One such “eat me” signal observed during apoptosis is the exposure of phosphatidylserine (PS) on the outer plasma membrane. Here, we demonstrate that necroptotic cells also expose PS after phosphorylated mixed lineage kinase-like (pMLKL) translocation to the membrane. Necroptotic cells that expose PS release extracellular vesicles containing proteins and pMLKL to their surroundings. Furthermore, inhibition of pMLKL after PS exposure can reverse the process of necroptosis and restore cell viability. Finally, externalization of PS by necroptotic cells drives recognition and phagocytosis, and this may limit the inflammatory response to this nonapoptotic form of cell death. The exposure of PS to the outer membrane and to extracellular vesicles is therefore a feature of necroptotic cell death and may serve to provide an immunologically-silent window by generating specific “find me” and “eat me” signals.

Necroptosis, a recently discovered regulated form of cell death, is widely considered to be inflammatory due to the absence of specific “find me” and “eat me” signals prior to lytic death. Here, we demonstrate that necroptotic cells generate “find me” and “eat me” signals by exposure of phosphatidylserine on their outer plasma membrane. This was further associated with the release of extracellular vesicles (“necroptotic bodies”) that contain phosphatidylserine, pMLKL (a key necroptotic marker), as well as other proteins. These signals drive recognition and phagocytosis of necroptotic cells to modulate the immune response. The exposure of phosphatidylserine and release of “necroptotic bodies” indicate that apoptosis and necroptosis share some common biochemical and cellular features and highlight the need for new biomarkers to distinguish apoptotic and necroptotic cell death.

Caspase involvement in autophagy

Caspases are a family of cysteine proteases widely known as the principal mediators of the apoptotic cell death response, but considerably less so as the contributors to the regulation of pathways outside cellular demise. In regards to autophagy, the modulatory roles of caspases have only recently begun to be adequately described. In contrast to apoptosis, autophagy promotes cell survival by providing energy and nutrients through the lysosomal degradation of cytoplasmic constituents. Under basal conditions autophagy and apoptosis cross-regulate each other through an elaborate network of interconnections which also includes the interplay between autophagy-related proteins (ATGs) and caspases. In this review we focus on the effects of this crosstalk at the cellular level, as we aim to concentrate the main observations from research conducted so far on the fine-tuning of autophagy by caspases. Several members of this protease-family have been found to directly interact with key ATGs involved in different tiers across the autophagic cascade. Therefore, we firstly outline the core mechanism of macroautophagy in brief. In an effort to emphasize the importance of the intricate cross-regulation of ATGs and caspases, we also present examples of autophagy's contribution to apoptotic cell death during development.

Mouse Lung Fibroblast Resistance to Fas-Mediated Apoptosis Is Dependent on the Baculoviral Inhibitor of Apoptosis Protein 4 and the Cellular FLICE-Inhibitory Protein

A characteristic feature of idiopathic pulmonary fibrosis (IPF) is accumulation of apoptotic resistant fibroblasts/myofibroblasts in the fibroblastic foci. As caveolin (Cav)-null mice develop pulmonary fibrosis (PF), we hypothesized that the participating fibroblasts display an apoptosis-resistant phenotype. To test this hypothesis and identify the molecular mechanisms involved we isolated lung fibroblasts from Cav-null mice and examined the expression of several inhibitors of apoptosis (IAPs), of c-FLIP, of Bcl-2 proteins and of the death receptor CD95/Fas. We found significant increase in XIAP and c-FLIP constitutive protein expression with no alteration of Bcl-2 and lower levels of CD95/Fas. The isolated fibroblasts were then treated with the CD95/Fas ligand (FasL) to induce apoptosis. While the morphological and biochemical alterations induced by FasL were similar in wild-type (wt) and Cav-null mouse lung fibroblasts, the time course and the extent of the alterations were greater in the Cav-null fibroblasts. Several salient features of Cav-null fibroblasts response such as loss of membrane potential, fragmentation of the mitochondrial continuum concurrent with caspase-8 activation, and subsequent Bid cleavage, prior to caspase-3 activation were detected. Furthermore, M30 antigen formation, phosphatidylserine expression and DNA fragmentation were caspase-3 dependent. SiRNA-mediated silencing of XIAP and c-FLIP, individually or combined, enhanced the sensitivity of lung fibroblasts to FasL-induced apoptosis. Pharmacological inhibition of Bcl-2 had no effect. Together our findings support a mechanism in which CD95/Fas engagement activates caspase-8, inducing mitochondrial apoptosis through Bid cleavage. XIAP and c-FLIP fine tune this process in a cell-type specific manner.

Anodically Grown Titania Nanotube Induced Cytotoxicity has Genotoxic Origins

Nanoarchitectures of titania (TiO₂) have been widely investigated for a number of medical applications including implants and drug delivery. Although titania is extensively used in the food, drug and cosmetic industries, biocompatibility of nanoscale titania is still under careful scrutiny due to the conflicting reports on its interaction with cellular matter. For an accurate insight, we performed in vitro studies on the response of human dermal fibroblast cells toward pristine titania nanotubes fabricated by anodic oxidation. The nanotubes at low concentrations were seen to induce toxicity to the cells, whereas at higher concentrations the cell vitality remained on par with controls. Further investigations revealed an increase in the G₀ phase cell population depicting that majority of cells were in the resting rather than active phase. Though the mitochondrial set-up did not exhibit any signs of stress, significantly enhanced reactive oxygen species production in the nuclear compartment was noted. The TiO₂ nanotubes were believed to have gained access to the nuclear machinery and caused increased stress leading to genotoxicity. This interesting property of the nanotubes could be utilized to kill cancer cells, especially if the nanotubes are functionalized for a specific target, thus eliminating the need for any chemotherapeutic agents.

Contribution of Maladaptive Adipose Tissue Expansion to Development of Cardiovascular Disease

The overweight and obesity epidemic has led to an increase in the metabolic syndrome and associated cardiovascular disease (CVD). These abnormalities include insulin resistance, type 2 diabetes mellitus, vascular stiffness, hypertension, stroke, and coronary heart disease. Visceral white adipocyte tissue (WAT) expansion and associated fibrosis/stiffness of WAT promote insulin resistance and CVD through increases in proinflammatory adipokines, oxidative stress, activation of renin-angiotensin-aldosterone system, dysregulation of adipocyte apoptosis and autophagy, dysfunctional immune modulation, and adverse changes in the gut microbiome. The expansion of WAT is partly determined by activation of peroxisome proliferator-activated receptor gamma and mammalian target of rapamycin/ribosomal S6 kinase signaling pathways. Further, the chronic activation of these signaling pathways may not only induce adipocyte hypertrophy and fibrosis, but also contribute to systemic inflammation, and impairment of insulin metabolic signaling in fat, liver, and skeletal muscle tissue. Therefore, the interplay of adipocyte dysfunction, maladaptive immune and inflammatory responses, and associated metabolic disorders often coexist leading to systemic low-grade inflammation and insulin resistance that are associated with increased CVD in obese individuals. © 2017 American Physiological Society. Compr Physiol 7:253-262, 2017.

Cell apoptosis, autophagy and necroptosis in osteosarcoma treatment

Osteosarcoma is the most common primary bone tumor in children and adolescents. Although combined therapy including surgery and multi-agent chemotherapy have resulted in great improvements in the overall survival of patients, chemoresistance remains an obstacle for the treatment of osteosarcoma. Molecular targets or effective agents that are actively involved in cell death including apoptosis, autophagy and necroptosis have been studied. We summarized how these agents (novel compounds, miRNAs, or proteins) regulate apoptotic, autophagic and necroptotic pathways; and discussed the current knowledge on the role of these new agents in chemotherapy resistance in osteosarcoma.