A chimerical phagocytosis model reveals the recruitment by Sertoli cells of autophagy for the degradation of ingested illegitimate substrates

Phagocytosis and autophagy are typically dedicated to degradation of substrates of extrinsic and intrinsic origins respectively. Although overlaps between phagocytosis and autophagy were reported, the use of autophagy for ingested substrate degradation by nonprofessional phagocytes has not been described. Blood-separated tissues use their tissue-specific nonprofessional phagocytes for homeostatic phagocytosis. In the testis, Sertoli cells phagocytose spermatid residual bodies produced during germ cell differentiation. In the retina, pigmented epithelium phagocytoses shed photoreceptor tips produced during photoreceptor renewal. Spermatid residual bodies and shed photoreceptor tips are phosphatidylserine-exposing substrates. Activation of the tyrosine kinase receptor MERTK, which is implicated in phagocytosis of phosphatidylserine-exposing substrates, is a common feature of Sertoli and retinal pigmented epithelial cell phagocytosis. The major aim of our study was to investigate to what extent phagocytosis by Sertoli cells may be tissue specific. We analyzed in Sertoli cell cultures that were exposed to either spermatid residual bodies (legitimate substrates) or retina photoreceptor outer segments (illegitimate substrates) the course of the main phagocytosis stages. We show that whereas substrate binding and ingestion stages occur similarly for legitimate or illegitimate substrates, the degradation of illegitimate but not of legitimate substrates triggers autophagy as evidenced by the formation of double-membrane wrapping, MAP1LC3A-II/LC3-II clustering, SQSTM1/p62 degradation, and by marked changes in ATG5, ATG9 and BECN1/Beclin 1 protein expression profiles. The recruitment by nonprofessional phagocytes of autophagy for the degradation of ingested cell-derived substrates is a novel feature that may be of major importance for fundamentals of both apoptotic substrate clearance and tissue homeostasis

Semaphorin, neuropilin and VEGF expression in glial tumours: SEMA3G, a prognostic marker?

Gliomas are characterised by local infiltration, migration of tumour cells across long distances and sustained angiogenesis; therefore, proteins involved in these processes are most likely important. Such candidates are semaphorins involved in axon guidance and cell migration. In addition, semaphorins regulate tumour progression and angiogenesis. For cell signalling, class-4 semaphorins bind directly to plexins, whereas class-3 semaphorins require additional neuropilin (NRP) receptors that also bind VEGF165. The anti-angiogenic activity of class-3 semaphorins can be explained by competition with VEGF165 for NRP binding. In this study, we analysed the expressions of seven semaphorins of class-3, SEMA4D, VEGF and the NRP1 and NRP2 receptors in 38 adult glial tumours. In these tumours, SEMA3B, SEMA3G and NRP2 expressions were related to prolonged survival. In addition, SEMA3D expression was reduced in high-grade as compared with low-grade gliomas. In contrast, VEGF correlated with higher grade and poor survival. Thus, our data suggest a function for a subset of class-3 semaphorins as inhibitors of tumour progression, and the prognostic value of the VEGF/SEMA3 balance in adult gliomas. Moreover, in multivariate analysis, SEMA3G was found to be the only significant prognostic marker

Optimal design of dependable control system architectures using temporal sequences of failures

Designing a dependable control system requires accurate methods to evaluate efficiently the dependability level of one given component architecture. This evaluation is crucial to determine the risks associated with system failures, and the remaining properties after fault occurrences. The dependability level of a control system depends not only on the kind of component failures that may occur, but also on the ordered sequences of the failure appearance. Classical evaluation methods, i.e. Fault Trees or Failure Mode and Effect Analysis, are not appropriate to handle these sequences. Our paper contributes on this aspect, and proposes a complete design methodology for dependable systems. This methodology uses ordered sequences of multiple failures to evaluate accurately the dependability level of all possible system's equipment architectures. Starting with the hierarchical functional decomposition of the system, the first step is to identify the dreaded events. Thus, the faulty behaviors of all possible system architectures are characterized with temporal operators. The set of system's operational architectures is finally determined by solving an optimization problem that considers both dependability objectives, and cost constraints. This methodology is applied to design a fire detection system for a railroad transportation system. In this paper, a complete methodology to design dependable control systems is presented. The innovative feature of this methodology is that it attempts to take into account time ordered sequences of failures. A new representation, called improved multi-fault tree, is defined. This tool allows us first to model failure relationships between functions, and second to evaluate the dependability level of a set of equipment architectures by the use of time ordered sequences of failures. Our design method provides a set of optimal architectures with given costs, and dependability levels. The designer can choose among these solutions tradin- g among the costs, and dependability level specifications. The comparison between the new approach and the classical dependability method shows that the set of solutions for the multi-fault tree is smaller than the set of solutions for the classical one. The set is smaller, but the solutions are better because the new approach integrates temporal functions, and evaluates more precisely the level of dependability than with the traditional one

A self-immolative dendritic glucuronide prodrug of doxorubicin

International audienceThe first self-immolative dendritic glucuronide prodrug of doxorubicin was studied with the aim to target beta-glucuronidase overexpressed in the microenvironment of numerous tumors. This compound includes a chemical amplifier programmed to release two molecules of doxorubicin after a single enzymatic activation step. Upon beta-glucuronidase activation, the dendritic prodrug was twice more toxic than its monomeric counterpart against H661 lung cancer cell

Shared or divergent practices of safety integrity level allocation in the railway domain

Les conditions de conception et d'exploitation des systèmes ferroviaires au sein de l'U.E sont régies par des directives, des règlements et des décrets. Cependant, chaque état membre de l'U.E. a développé ses propres règles de sécurité en se basant sur ses propres concepts techniques et opérationnels et aboutissant, au final, à des pratiques divergentes entre états. L'allocation des SIL (Safety Integrity Level) utilisée afin de réduire le risque résiduel ne fait pas exception à ce constat. Le travail présenté résume les points faisant consensus et les points de divergence liés à cette allocation puis propose une méthodologie d'allocation homogène des SIL.In the E.U, safety railway system design and operational terms are governed by directives, regulations and decrees. However, based on its own technical and operational concepts, each state member of the E.U. has developed its own safety rules leading to divergent practices between states. Used to reduce residual risks, the SIL (Safety Integrity Level) concept has the same problem. This research work summarizes shared and divergent points related to the SIL allocation and proposes a homogeneous allocation methodology applied to SIL

Synthesis and biological evaluations of a monomethylauristatin E glucuronide prodrug for selective cancer chemotherapy

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An enzyme-responsive system programmed for the double release of bioactive molecules through an intracellular chemical amplification process

International audienceThe rise of chemical biology has led to the development of sophisticated molecular devices designed to explore and manipulate biological processes. Within this framework, we developed the first chemical system programmed for the selective internalization and subsequent enzyme-catalyzed double release of bioactive compounds inside a targeted population of cells. This system is composed of five distinct units including a targeting ligand, an enzymatic trigger, a self-immolative linker and two active compounds articulated around a chemical amplifier. Designed as such, this molecular assembly is capable in an autonomous manner to recognize a selected population of cells, penetrate into the intracellular medium through endocytosis and transform a single enzymatic activation step into the release of two active units. Demonstrating that an enzyme-catalyzed amplification process can occur spontaneously under the conditions prevailing within the cells could be an important step toward the development of innovative molecular systems fora diverse range of applications spanning drug delivery biological sensors and diagnostic

Enhancing tumor response to targeted chemotherapy through up-regulation of folate receptor α expression induced by dexamethasone and valproic acid

International audienceSeveral folate-drug conjugates are currently undergoing clinical trials for application in oncology. However, the efficacy of folate-targeted therapy strongly depends on the folate receptor (FR) abundance at the surface of cancer cells. Recently, it has been postulated that up-regulation of FRα by means of chemo-sensitizing agents could enhance the anticancer activity of FR-drug conjugates. In this study, we demonstrate in vitro that a combination of dexamethasone (Dexa) and valproic acid (VPA) increases FRα expression selectively at the surface of FR-overexpressing cancer cells. The same stimulation was observed in vivo in KB-tumor xenografts when mice are treated with this combined treatment. This effect is reversible since treatment interruption induces the return of FR expression at basal level. When incubated with Dexa and VPA, the β-galactosidaseresponsive folate-monomethyl auristatin E (MMAE) conjugate, called MGAF, exhibits higher cytotoxic activity on several FR-positive human cancer cell lines, compared to its administration as a single agent. This improved toxicity results from the enhanced concentration of MMAE released within cancer cells after internalization and subsequent enzymatic activation of MGAF. Higher deposition of MMAE is also observed in vivo after up-regulation of FR expression level in tumor xenografts, induced by the prior administration of the Dexa/VPA combination. In this model, MGAF/Dexa/VPA combined therapy results in an 81% inhibition of tumor growth compared to the control group, while MGAF used in monotherapy is inefficient. Since Dexa and VPA are currently used in humans, this finding could be of great interest for further development of folate-drug conjugates, in particular for those that are presently under clinical investigation