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Results show that apoptotic cells secrete a chemotactic signal, which attracts monocytic cells and primary macrophages in a caspase-3-dependent manner. Data indicate that the chemotactic signal molecule is the phospholipid lysophosphatidyl choline and the involvement of phospholipase A(sub)2 in the caspase-3-mediated generation of the phospholipid.

Graphical abstract Endogenous vitronectin (VN) promotes the vascularization of PPE biomaterial (left, mid). Additional surface coating with recombinant VN accelerates and intensifies this process (right). Abstract Rapid implant vascularization is a prerequisite for successful biomaterial engraftment. Vitronectin (VN) is a matricellular glycoprotein well known for its capability to interact with growth factors, proteases, and protease inhibitors/receptors. Since such proteins are highly relevant for angiogenic processes, we hypothesized that VN contributes to the tissue integration of biomaterials. Employing different in vivo and ex vivo microscopy techniques, engraftment of porous polyethylene (PPE) implants was analyzed in the dorsal skinfold chamber model in wild-type (WT) and VN−/− mice. Upon PPE implantation, vascularization of this biomaterial was severely compromised in animals lacking this matricellular protein. Proteome profiling revealed that VN deficiency does not cause major changes in angiogenic protein composition in the implants suggesting that VN promotes PPE vascularization via mechanisms modulating the activity of angiogenic factors rather than by directly enriching them in the implant. Consequently, surface coating with recombinant VN (embedded in Matrigel®) accelerated implant vascularization in WT mice by enhancing the maturation of a vascular network. Thus, VN contributes to the engraftment of PPE implants by promoting the vascularization of this biomaterial. Surface coating with VN might provide a promising strategy to improve the vascularization of PPE implants without affecting the host's integrity. Statement of Significance Porous polyethylene (PPE) is a biomaterial frequently used in reconstructive surgery. The proper vascularization of PPE implants is a fundamental prerequisite for its successful engraftment in host tissue. Although the overall biocompatibility of PPE is good, there are less favorable application sites for its use in tissue reconstruction mostly characterized by low blood supply. Employing advanced in vivo microscopy methods and proteomic analyses in genetically engineered mice, we here describe a previously unrecognized function of vitronectin (VN) that enables this abundantly present glycoprotein to particularly promote the vascularization of PPE biomaterial. These properties of VN specifically facilitate the formation of a dense vessel network within the implant which relies on modulating the activity of angiogenic mediators rather than on the enrichment of these factors in the implant. Consequently, surface coating with this matricellular protein effectively accelerated and intensified implant vascularization which might be beneficial for its implementation at unfavorable sites for implantation without affecting the host's integrity. [ABSTRACT FROM AUTHOR]

Radiotherapy represents an essential treatment option for the majority of cancer patients in different stages of their disease. Physical achievements of the recent years led to the implementation of high precision treatment planning procedures, and image-guided dose delivery is current state of the art. Yet, radiotherapy still faces several limitations with cancer intrinsic radioresistance being a key driver of therapeutic failure. Accordingly, the mechanisms orchestrating radioresistance and their therapeutic targeting by combined modality approaches are in the center of attention of numerous radiation oncologists. In the present review, we summarize and discuss therapeutic approaches that exploit the heat shock response, either by hyperthermia or by pharmacological heat shock protein inhibition, in combination with radiotherapy. These strategies appear particularly promising, since they sensitize cancer cells to irradiation-induced cell death and at the same time have proven the potential to promote systemic anti-tumor immune mechanisms, which may target not only locally surviving tumor cells, but also distant out-of-field metastases. [ABSTRACT FROM AUTHOR]

: ObjectiveDendritic cells (DC) are professional antigen-presenting cells playing a pivotal role in the induction of immunological responses. There is evidence that DC survival during ongoing immune responses is finite. However, little is known about the mechanisms regulating apoptosis in these cells. Here, we have investigated the effects of the anti-inflammatory cyclopentenone prostaglandins on human monocyte-derived DC.: Materials and MethodsPhenotype of DC was determined by flow cytometry and their allostimulatory potential in mixed leukocyte reaction. Induction of apoptosis in DC was monitored by staining with annexin-V-FITC and propidium iodide, propidium iodide staining of cell nuclei, and fluorimetric assay of caspase activity. Induction of maturation in DC was obtained by stimulation with TNF-α, LPS, IFN-γ, CD40-ligand, or different combinations of these stimuli. PPAR-γ expression in DC was determined by RT-PCR.: ResultsExposure of immature DC to cyclopentenone prostaglandins blunted their allostimulatory capacity and skewed their phenotype by downregulating CD1a and costimulatory molecules. These effects were due to activation of caspases and induction of apoptotic cell death in DC by cyclopentenone prostaglandins. Mature DC showed enhanced susceptibility to apoptosis via cyclopentenone prostaglandins as compared with immature DC. Although DC express PPAR-γ, the corresponding receptor for some of these metabolites, PPAR-γ activation by a synthetic high-affinity agonist failed to impair DC viability.: ConclusionsCyclopentenone prostaglandins induce apoptosis of human DC by a PPAR-γ-independent mechanism. Since these compounds are released during an inflammatory event and show anti-inflammatory properties, they may contribute to the downregulation of DC function through apoptotic cell death. [Copyright &y& Elsevier]

The NALP3 inflammasome is activated by low intracellular potassium concentrations [K+]i, leading to the secretion of the proinflammatory cytokine IL-1β. However, the mechanism of [K+]i lowering after phagocytosis of monosodium urate crystals is still elusive. Here, we propose that endosomes containing monosodium urate crystals fuse with acidic lysosomes. The low pH in the phagolysosome causes a massive release of sodium and raises the intracellular osmolarity. This process is balanced by passive water influx through aquaporins leading to cell swelling. This process dilutes [K+]i to values below the threshold of 90 mm known to activate NALP3 inflammasomes without net loss of cytoplasmic potassium ions. In vitro, the inhibitors of lysosomal acidification (ammonium chloride, chloroquine) and of aquaporins (mercury chloride, phloretin) all significantly decreased the production of IL-1β. In vivo, only the pharmacological inhibitor of lysosome acidification chloroquine could be used which again significantly reduced the IL-1β production. As a translational aspect one may consider the use of chloroquine for the anti-inflammatory treatment of refractory gout. [ABSTRACT FROM AUTHOR]

Human epithelial cell adhesion molecule (HEPCAM) is a tumor-associated antigen frequently expressed in carcinomas, which promotes proliferation after regulated intramembrane proteolysis. Here, we describe extracellular shedding of HEPCAM at two α-sites through a disintegrin and metalloprotease (ADAM) and at one β-site through BACE1. Transmembrane cleavage by γ-secretase occurs at three γ-sites to generate extracellular A β-like fragments and at two ε-sites to release human EPCAM intracellular domain HEPICD, which is efficiently degraded by the proteasome. Mapping of cleavage sites onto three-dimensional structures of HEPEX cis-dimer predicted conditional availability of α- and β-sites. Endocytosis of HEP-CAM warrants acidification in cytoplasmic vesicles to dissociate protein cis-dimers required for cleavage by BACE1 at low pH values. Intramembrane cleavage sites are accessible and not part of the structurally important transmembrane helix dimer crossing region. Surprisingly, neither chemical inhibition of cleavage nor cellular knock-out of HEPCAM using CRISPR-Cas9 technology impacted the adhesion of carcinoma cell lines. Hence, a direct function of HEPCAM as an adhesion molecule in carcinoma cells is not supported and appears to be questionable. [ABSTRACT FROM AUTHOR]

Radiotherapy is an essential part of multi-modal treatment for soft tissue sarcomas. Treatment failure is commonly attributed to radioresistance, but comprehensive analyses of radiosensitivity are not available, and suitable biomarkers or candidates for targeted radiosensitization are scarce. Here, we systematically analyzed the intrinsic radioresistance of a panel of soft tissue sarcoma cell lines, and extracted scores of radioresistance by principal component analysis (PCA). To identify molecular markers of radioresistance, transcriptomic profiling of DNA damage response regulators was performed. The expression levels of HSP90 and its clients ATR, ATM, and NBS1 revealed strong, positive correlations with the PCA-derived radioresistance scores. Their functional involvement was addressed by HSP90 inhibition, which preferentially sensitized radioresistant sarcoma cells and was accompanied by delayed γ-H2AX foci clearance and HSP90 client protein degradation. The induction of apoptosis and necrosis was not significantly enhanced, but increased levels of basal and irradiation-induced senescence upon HSP90 inhibition were detected. Finally, evaluation of our findings in the TCGA soft tissue sarcoma cohort revealed elevated expression levels of HSP90, ATR, ATM, and NBS1 in a relevant subset of cases with particularly poor prognosis, which might preferentially benefit from HSP90 inhibition in combination with radiotherapy in the future. [ABSTRACT FROM AUTHOR]

Highlights: [•] Nanomedical formulations allow for treatment of atherosclerosis in animal models. [•] Such formulations can target lipid metabolism, inflammation, or mechanisms of destabilization. [•] Clinical trials are hampered by possible toxic and immunostimulatory/-suppressive properties. [Copyright &y& Elsevier]

Inappropriate clearance of apoptotic remnants is considered to be the primary cause of systemic autoimmune diseases, like systemic lupus erythematosus. Here we demonstrate that apoptotic cells release distinct types of subcellular membranous particles (scMP) derived from the endoplasmic reticulum (ER) or the plasma membrane. Both types of scMP exhibit desialylated glycotopes resulting from surface exposure of immature ER-derived glycoproteins or from surface-borne sialidase activity, respectively. Sialidase activity is activated by caspase-dependent mechanisms during apoptosis. Cleavage of sialidase Neu1 by caspase 3 was shown to be directly involved in apoptosisrelated increase of surface sialidase activity. ER-derived blebs possess immature mannosidic glycoepitopes and are prioritized by macrophages during clearance. Plasma membrane-derived blebs contain nuclear chromatin (DNA and histones) but not components of the nuclear envelope. Existence of two immunologically distinct types of apoptotic blebs may provide new insights into clearance-related diseases. [ABSTRACT FROM AUTHOR]

Abstract: In multicellular organisms apoptotic cells are rapidly and efficiently removed by professional or semi-professional phagocytes. The molecular mechanisms and the key players involved in this highly coordinate process, as well as its immunological outcome constitute a vividly expanding field of scientific interest. A plethora of studies provided a detailed understanding of the interaction site between the dying cell and the phagocyte, as well as to the current concept that apoptotic cell removal leads to a non- or anti-inflammatory response, whereas necrotic cell removal stimulates a pro-inflammatory reaction. In contrast, our current knowledge about the soluble factors released from apoptotic cells is rather limited, although meanwhile it is generally accepted that not only the dying cell itself but also the substances, which are liberated during cell death, contribute to the process of corpse clearance and the subsequent immune response. This review is intended to summarize the up-to-date knowledge about apoptotic cell-derived attraction signals, their function as phagocytic chemoattractants, their influence on the immune system, and the receptors, which are engaged in this scenario. [Copyright &y& Elsevier]

Abstract: ZM447439 (ZM) is a potent and selective inhibitor of aurora-A and -B kinase with putative anti-tumoral activity. Inhibitors of aurora kinases were shown to induce apoptosis in vitro and in vivo. To investigate the underlying mechanisms, cell death pathways triggered by ZM was analysed in HCT-116 colorectal cancer cells. Through correlation of polyploidization and apoptosis in different knockout cells, the interrelation of these cellular responses to ZM was investigated. ZM induced apoptosis in a concentration- and time-dependent manner. ZM-induced apoptosis was associated with an upregulation of p53, breakdown of the mitochondrial membrane potential (ΔΨm) and activation of caspase-3. To precisely define key components for ZM-induced apoptosis, knockout cells lacking p53, Bak, Bax or both Bak and Bax were used. Lack of p53 reduced ZM-induced apoptosis and breakdown of ΔΨm, while lack of Bak, Bax or both almost completely inhibited apoptosis and breakdown of ΔΨm. Since no difference in apoptosis induction was detectable between HCT-116 cells lacking Bak, Bax or both, apoptosis induction depended non-redundantly on both Bak and Bax. Phenomenally, ZM induced notable polyploidization in all examined cells, especially in p53−/− cells. A correlation between polyploidization and apoptosis was observed in wild-type, and also in p53−/− cells, albeit with a modest extent of apoptosis. Moreover, in Bak−/−, Bax−/− and Bak/Bax−/− cells apoptosis was totally inhibited in spite of the strongest polyploidization, suggesting apoptosis may be a secondary event following polyploidization in HCT-116 cells. Thus ZM-induced apoptosis depends not only on polyploidization, but also on the intracellular apoptotic signaling. [Copyright &y& Elsevier]

Phagocytosis of apoptotic cells is fundamentally important throughout life, because non-cleared cells become secondarily necrotic and release intracellular contents, thus instigating inflammatory and autoimmune responses. Secreted "find-me" and exposed "eat-me" signals displayed by the dying cell in concert with the phagocyte receptors comprise the phagocytic synapse of apoptotic cell clearance. In this scenario, lysophospholipids (lysoPLs) are assumed to act as find-me signals for the attraction of phagocytes. However, both the identity of the lyso-PLs released from apoptotic cells and the nature of the phagocyte receptor are largely unknown. By a detailed analysis of the structural requirements we show here that lysophosphatidylcholine (lysoPC), but none of the lysoPC metabolites or other lysoPLs, represents the essential apoptotic attraction signal able to trigger a phagocyte chemotactic response. Furthermore, using RNA interference and expression studies, we demonstrate that the G-protein-coupled receptor G2A, unlike its relative GPR4, is involved in the chemotaxis of monocytic cells. Thus, our study identifies lysoPC and G2A as the crucial receptor/ligand system for the attraction of phagocytes to apoptotic cells and the prevention of autoimmunity. [ABSTRACT FROM AUTHOR]