Le peptide oncolytique LTX-315 a été développé comme un peptide cationique amphipathique qui tue les cellules cancéreuses et qui se révèle stimulant pour la réponse anti-cancer immune quand il est localement injecté dans des tumeurs présentent chez des souris immunocompétentes. La microscopie électronique par transmission révélées que LTX-315 a échoué à induire la condensation nucléaire apoptotique mais induit plutôt un phénotype nécrotique. Par conséquent, LTX-315 a échoué à stimuler l'activation de caspase-3, et l'inhibition des caspases par le biais de Z-VAD-fmk n'a pas été capable de réduire la mort cellulaire par LTX-315. En outre, deux inhibiteurs importants de la nécroptose, nommés necrostatin-1 et cycospotin-A, ont échoué à réduire la mort cellulaire par LTX-315. En conclusion, il semble que LTX-315 déclenche une nécrose non-régulée, qui peut contribuer à ses effets pro-inflammatoires et pro-immunitaires. Le fractionnement subcellulaire des cellules traitées par LTX-315, suivie par une quantification spectrométrique massive, a révélé que cet agent était enrichi en mitochondries. LTX-315 a causé un arrêt immédiat de la respiration mitochondriale sans aucun effet majeur de découplage. Par conséquent, LTX-315 a interrompu le réseau mitochondrial, a dissipé le potentiel mitochondrial de la membrane interne, et a causé la libération des protéines inter-membranaires mitochondriales dans le cytosol. LTX-315 était relativement inefficace dans la mitophagie stimulante. Les cellules dépourvues de deux pro-apoptotiques protéines à domaines multiples BAX et BAK, étaient moins susceptibles de mourir par LTX-315. De plus, les cellules conçues pour perdre leurs mitochondries étaient relativement résistantes à LTX-315, soulignant l'importance de cet organite pour la cytotoxicité induite par LTX-315. Au total, ces résultats soutiennent la notion que LTX-315 tue les cellules cancéreuses par sa vertue à perméabiliser les membranes mitochondriales. Nous avons observé que LTX-315 induit toutes les charactéristiques d'ICD connues. Cette conclusion a étévalidée par diverses méthodes indépendantes incluant la teinture par immunofluorence, dosage par bioluminescence, immunodosages, RT-PCRs. Quand il a été injecté dans des cancers créés, LTX-315 a causé une nécrose focale transitoirement hémorragique accompagnée d'une libération massive de HMGB1, aussi bien que l'activation de caspase-3 dans une partie des cellules. LTX-315 était au moins aussi efficace que le controle positif, l' anthracycline mitoxantrone en induisant une inflammation locale par infitration de cellules myéloïdes et de lymphocytes T. Collectivement, ces résultats appuient l'idée que LTX-315 peut induire l'ICD, expliquant sa capacité à induire des effets thérapeutiques immuno-dépendants.L'autre Lytix composé LTX-401 est un acide aminé oncolytique dérivé avec des propriétés immunogéniques potentielles. Nous démontrons que LTX-401 détruit sélectivement la strucutre du dispositif Golgi. Le fractionnement subcellulaire suivi par une détection spectométrique massive a révélé que LTX-401 a enrichi sélectivement dans le Golgi mieux que dans la mitochondrie ou dans le cytosol. Lagent Golgi-dissociant Brefeldin A a réduit la mort cellulaire par LTX-401 comme cela a partiellement inhibé la libération mitochondrial induite par LTX-401 de cytochrome C et l'activation de BAX. L'effet cytotoxique de LTX-401 a été atténué par la double suppression de BAX et BAK, comme la déplétion mitophagique forcée de la mitochondrie, déjà réfractaire à l'inhibition de caspase. LTX-401 induit toutes les caractéristiques majeures de la mort cellulaire immunogénique. En outre, les tumeurs traitées par LTX-401 ont manifesté une forte infiltration lymphoïde. Ensemble, ces résultats soutiennent l'idée que LTX-401 peut stimuler la mort immunogétique des cellules à travers un passage dans lequel LTX-401 localisé sur Golgi opère en amont de la perméabilisation de la membrane mitochondriale. / The oncolytic peptide LTX-315 has been developed as an amphipathic cationic peptide that kills cancer cells and turned out to stimulate anticancer immune responses when locally injected into tumors established in immunocompetent mice. We investigated whether LTX-315 induces apoptosis or necrosis. Transmission electron microscopy or morphometric analysis of chromatin-stained tumor cells revealed that LTX-315 failed to induce apoptotic nuclear condensation and rather induced a necrotic phenotype. Accordingly, LTX-315 failed to stimulate the activation of caspase-3. Moreover, inhibition of caspases by Z-VAD-fmk was unable to reduce cell killing by LTX-315. In addition, two prominent inhibitors of necroptosis, necrostatin-1 and cyclosporin A, failed to reduce LTX-315-induced cell death. In conclusion, it appears that LTX-315 triggers unregulated necrosis, which may contribute to its pro-inflammatory and pro-immune effects. Subsequently, we investigated the putative involvement of mitochondria in the cytotoxic action of LTX-315. Subcellular fractionation of LTX-315-treated cells, followed by mass spectrometric quantification, revealed that the agent was enriched in mitochondria. LTX-315 caused an immediate arrest of mitochondrial respiration without any major uncoupling effect. Accordingly, LTX-315 disrupted the mitochondrial network, dissipated the mitochondrial inner transmembrane potential, and caused the release of mitochondrial intermembrane proteins into the cytosol. LTX-315 was relatively inefficient in stimulating mitophagy. Cells lacking the two pro-apoptotic multidomain proteins BAX and BAK, were less susceptible to LTX-315-mediated killing. Moreover, cells engineered to lose their mitochondria were relatively resistant against LTX-315, underscoring the importance of this organelle for LTX-315-mediated cytotoxicity. Altogether, these results support the notion that LTX-315 kills cancer cells by virtue of its capacity to permeabilize mitochondrial membranes. Following, we investigated whether LTX-315 may elicit the hallmarks of immunogenic cell death (ICD). Overally, we observed that LTX-315 induces all known ICD characteristics. This conclusion was validated by several independent methods including immunofluorescence staining, bioluminescence assays, immunoassays, and RT-PCRs. The injection of LTX-315 into established cancers resulted in transiently hemorrhagic focal necrosis that was accompanied by massive release of HMGB1, as well as caspase-3 activation in a fraction of the cells. LTX-315 was equal or more efficient as the positive control, the anthracycline mitoxantrone (MTX), in inducing local inflammation with infiltration by myeloid cells and T lymphocytes. Collectively, these results support the idea that LTX-315 can induce ICD, explaining its capacity to mediate immune-dependent therapeutic effects. The second Lytix compound investigated, LTX-401, is an oncolytic amino acid derivative with potential immunogenic properties. We demonstrated that LTX-401 selectively destroys the structure of the Golgi apparatus. Subcellular fractionation followed by mass spectrometric detection revealed that LTX-401 was selectively enriched in the Golgi rather than in the mitochondria or in the cytosol. The Golgi-dissociating agent Brefeldin A (BFA) reduced cell killing by LTX-401 as it partially inhibited LTX-401-induced mitochondrial release of cytochrome c and the activation of BAX. The cytotoxic effect of LTX-401 was attenuated by the double knockout of BAX and BAK, as well as the mitophagy-enforced depletion of mitochondria, yet was refractory to caspase inhibition. LTX-401 induced all major hallmarks of immunogenic cell death. Moreover, LTX-401-treated tumors manifested a strong lymphoid infiltration. Altogether, these results support the contention that LTX-401 can stimulate immunogenic cell death through a pathway in which Golgi-localized LTX-401 operates upstream of mitochondrial membrane permeabilization.

L’arrivée des nanobiotechnologies en cancérologie apporte un nouveau souffle dans le traitement des cancers. Les travaux réalisés par Olivier Tillement et ses collaborateurs ont permis de montrer que les nanoparticules de gadolinium (GdBN) sont capables d’augmenter d’une part la qualité d’imagerie par résonance magnétique (IRM) mais également d’augmenter les effets des rayonnements ionisants (IR) sur les tumeurs. Des études précliniques sur des tumeurs de glioblastome greffées sur des souris C57BL/6 ont permis de révéler la capacité de la combinaison GdBN+IR à favoriser une régression tumorale. Néanmoins, les processus de morts cellulaires impliqués sont partiellement connus. Nos résultats ont permis de démontrer que ce traitement produit un stress oxydatif généré par une NADPH oxydase. Ce stress oxydatif déclenche un arrêt de la prolifération des cellules qui dépend de la protéine p21 et qui déclenche un processus de sénescence cellulaire et le cannibalisme des cellules irradiées. Le cannibalisme cellulaire ainsi déclenché aboutit à l’élimination de cellules internalisées. Ainsi, l’ensemble de ces résultats nous a permis de révéler que la combinaison des GdBN et de l’irradiation contribue à l’élimination de cellules cancéreuses en déclenchant la sénescence des cellules irradiées ainsi qu’un mécanisme original de mort cellulaire, le cannibalisme cellulaire. / The nanotechnology aims to help in the cancer treatment. Olivier Tillement and his colleagues have demonstrated that the Gadolinium-Based Nanoparticle (GdBN) can improve Magnetic Resonance Imaging (MRI) and increase radiotherapy effects. Pre-clinical studies show that the combination of GdBN with ionizing radiation is associated with tumor regression. However, the molecular and cellular processes involved this biological effect remain to be elucidated. Our results show that the combination of GdBN with IR generates oxidative stress through NADPH oxidase-dependent mechanisms, leads to cellular senescence and induces the cannibalistic activity of irradiated cells. Altogether, these results reveal that the combination of GdBN with IR promotes the killing of irradiated cells through the induction of cellular senescence and cellular cannibalism.

Orientador: Fábio Ermínio Mingatto / Resumo: O imidacloprido (IMD) é um inseticida neonicotinóide de uso veterinário e agronômico utilizado mundialmente em larga escala. Este composto, apresenta toxicidade seletiva para os receptores pós-sinápticos da acetilcolina (nAChRs) em insetos e baixa toxicidade para mamíferos. Porém, dados na literatura demonstram efeitos nocivos induzidos pela substância em vários animais, sendo o fígado apontado como o principal órgão afetado. Nesse sentido, o objetivo deste trabalho foi avaliar os efeitos do IMD em células de hepatoblastoma humano (HepG2) para elucidar os mecanismos envolvidos na ação tóxica da substância. As células HepG2 foram expostas ao IMD (250 - 2000μM) durante 24 e 48 horas. Após a exposição o IMD causou perda da viabilidade celular a partir da concentração de 500 μM no tempo 24 horas e a partir de 250 μM no tempo 48 horas de forma concentração e tempo-dependente. A capacidade metabólica das células, avaliada pelo teste do MTT, também foi afetada em ambos os tempos investigados resultando em uma diminuição a partir da concentração de 250 μM no tempo 24 horas, enquanto que no tempo de 48 horas esse resultado só foi significante a partir da concentração de 500 μM. O IMD diminuiu o potencial de membrana mitocondrial nas células HepG2 apenas na maior concentração testada (2000 μM) em ambos os tempos de incubação e induziu danos na membrana celular conforme observado pelos aumentos significantes na liberação da enzima lactato desidrogenase em relação ao controle a partir da... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

Neuroblastoma is the most common extracranial solid tumor that occurs during infancy. Despite the great progress has been made in contemporary clinic medicine some forms of neuroblastoma disease are still found very difficult to treat . This work focuses on the effects of histone deacetylase inhibitors (HDAC) in the neuroblastoma cell lines. It is known that HDAC inhibitors may contribute to recurrence of the tumor cells by affecting the chromatin structure and thus increase the expression of critical tumor suppressor genes. These genes activate apoptotic pathways that may even be independent of caspases. We observed the efficiency of used HDAC inhibitors as under standard conditions an in hypoxia (1 % O2). Inadequate amount of oxygen supply is one of the characteristic features of tumors and it also may contribute to chemoresistance. With the hypoxia-induced chemoresistance of tumor cells, the influence of HIF-1α is expected. Some HDAC inhibitors reduce the amount of HIF-1α in hypoxia and thus HIF transcription factor activity. Thus, the first part of this study is concerned with the acquisition of suitable experimental arrangement for the monitoring of induction of cellular death in human neuroblastoma cell lines SK-N-AS and UKF-NB-3. Secondly, this paper provides the evaluation of the influence...

CD4 T cell death or survival following initial HIV infection is crucial for the development of viral reservoirs and latent infection, making its evaluation critical in devising strategies for HIV cure. Here we infected primary CD4 T cells with a wild-type HIV-1 and investigated the death and survival mechanisms in productively infected and bystander cells during early HIV infection. We found that HIV-infected cells exhibited increased programmed cell death, such as apoptosis, pyroptosis, and ferroptosis, than uninfected cells. However, productively infected (p24+) cells and bystander (p24-) cells displayed different patterns of cell death due to differential expression of pro-/anti-apoptotic proteins and signaling molecules. Cell death was triggered by an aberrant DNA damage response (DDR), as evidenced by increases in γH2AX levels, which inversely correlated with telomere length and telomerase levels during HIV infection. Mechanistically, HIV-infected cells exhibited a gradual shortening of telomeres following infection. Notably, p24+ cells had longer telomeres compared to p24- cells, and telomere length positively correlated with the telomerase, pAKT, and pATM expressions in HIV-infected CD4 T cells. Importantly, blockade of viral entry attenuated the HIV-induced inhibition of telomerase, pAKT, and pATM as well as the associated telomere erosion and cell death. Moreover, ATM inhibition promoted survival of HIV-infected CD4 T cells, especially p24+ cells, and rescued telomerase and AKT activities by inhibiting cell activation, HIV infection, and DDR. These results indicate that productively infected and bystander CD4 T cells employ different mechanisms for their survival and death, suggesting a possible pro-survival, pro-reservoir mechanism during early HIV infection.

A biochemical characterization of ubiquitin (Ub)-proteasome pathway activity was conducted in <I>Zinnia</I> mesophyll cell cultures to examine potential differences between differentiating cells of tracheary element (TE) cultures and non-differentiating cells of control cultures. The pathway is highly active throughout development of differentiating TEs, a programmed cell death (PCD) process during which the majority of cellular proteins and biochemical processes are expected to be down-regulated in activity and/or expression. Addition of the proteasome inhibitors <I>clasto</I>-lactacystin Beta-lactone (LAC) and carbobenzoxy-leucinyl-leucinyl-leucinal (LLL) at culture initiation prevented TE differentiation in this system. Proteasome inhibition at 48h did not alter the final percentage of TEs compared to controls. However, proteasome inhibition at 48 h delayed the differentiation program by approximately 24 h, as indicated by examination of morphological markers and the expression of putative autolytic cysteine proteases.These results suggest that proteasome activity is required both for induction of TE differentiation and for progression of the TE program in committed cells. Treatment at 48 h with LLL resulted in partial uncoupling of autolysis from differentiation. Results of protease activity gel analysis suggest that incomplete autolysis was due to the ability of LLL to inhibit TE cysteine proteases. A characterization of phytohormone-stimulated growth of non-differentiating cultured <I>Zinnia</I> cells is also presented. Differential effects on radial cell expansion versus cell elongation were observed for the four plant growth regulators examined. Auxin (naphthaleneacetic acid, NAA) and a brassinosteroid (2,4-epibrassinolide, BI) stimulate only cell elongation. Cytokinin (N-6-benzyladenine, BA) has a greater effect on growth in cell girth rather than length. Gibberellic acid (GA₃) has equivalent effects on expansion in both dimensions. These results demonstrate that radial cell expansion and cell elongation can be uncoupled, and therefore, may be controlled by different mechanisms. Additionally, this study establishes the utility of <I>Zinnia</I> suspension cultures as a valuable model for studies of cell expansion. Finally, we modified <I>Arabidopsis</I> plant growth conditions to promote proliferation of secondary tissues, permitting the separation of secondary xylem from bark (phloem plus nonvascular) tissues using hypocotyl-root segments. Dissected tissues were used for semi-quantitative and quantitative RT-PCR and for the construction of bark and xylem cDNA libraries for PCR-based screening of several Ub pathway components, including Ub-conjugating enzymes (<I>UBCs</I>), deubiquitinating enzymes (DUBs), and an Alpha (<I>PAF1</I>) and Beta (<I>PAF1</I>) subunit of the proteasome. All targeted <I>UBC</I> families, candidate <I>UBCs</I> and DUBs, and proteasome subunits are expressed in secondary xylem and bark in this system. / Ph. D.

Background: STAT3 is increasingly becoming known for its non-transcriptional regulation of mitochondrial bioenergetic function upon activation of its S727 residue (S727-STAT3). Lengthy mitochondrial dysfunction can lead to cell death. We tested whether an integrin-FAK-STAT3 signaling pathway we recently discovered regulates mitochondrial function and cell survival, and treatments thereof. Methods: Cultured mouse brain bEnd5 endothelial cells were treated with integrin, FAK or STAT3 inhibitors, FAK siRNA, as well as integrin and STAT3 activators. STAT3 null cells were transfected with mutant STAT3 plasmids. Outcome measures included oxygen consumption rate for mitochondrial bioenergetics, Western blotting for protein phosphorylation, mitochondrial membrane potential for mitochondrial integrity, ROS production, and cell counts. Results: Vitronectin-dependent mitochondrial basal respiration, ATP production, and maximum reserve and respiratory capacities were suppressed within 4 h by RGD and αvβ3 integrin antagonist peptides. Conversely, integrin ligands vitronectin, laminin and fibronectin stimulated mitochondrial function. Pharmacological inhibition of FAK completely abolished mitochondrial function within 4 h while FAK siRNA treatments confirmed the specificity of FAK signaling. WT, but not S727A functionally dead mutant STAT3, rescued bioenergetics in cells made null for STAT3 using CRISPR-Cas9. STAT3 inhibition with stattic in whole cells rapidly reduced mitochondrial function and mitochondrial pS727-STAT3. Stattic treatment of isolated mitochondria did not reduce pS727 whereas more was detected upon phosphatase inhibition. This suggests that S727-STAT3 is activated in the cytoplasm and is short-lived upon translocation to the mitochondria. FAK inhibition reduced pS727-STAT3 within mitochondria and reduced mitochondrial function in a non-transcriptional manner, as shown by co-treatment with actinomycin. Treatment with the small molecule bryostatin-1 or hepatocyte growth factor (HGF), which indirectly activate S727-STAT3, preserved mitochondrial function during FAK inhibition, but failed in the presence of the STAT3 inhibitor. FAK inhibition induced loss of mitochondrial membrane potential, which was counteracted by bryostatin, and increased superoxide and hydrogen peroxide production. Bryostatin and HGF reduced the substantial cell death caused by FAK inhibition over a 24 h period. Conclusion: These data suggest that extracellular matrix molecules promote STAT3-dependent mitochondrial function and cell survival through integrin-FAK signaling. We furthermore show a new treatment strategy for cell survival using S727-STAT3 activators.

β-arrestins, a family of regulatory and scaffold proteins, are well-known negative regulators of G-protein-coupled receptors (GPCRS) including opioid receptors. Recent studies have shown that β-arrestin2 plays a potential role in inhibiting cell death. It has been reported that opioids such as morphine induce cell death at high concentrations (>500 μM for 24 hours), which is similar to morphine plasma concentrations in cancer patients receiving chronic morphine treatment for pain relievers. However, the role of β-arrestin2 in opioid-induced cell death remains to be elucidated. We report here that β-arrestin2 significantly blocks morphine-induced number of cell death in human breast cancer MCF-7 and MDA-MB231 cells. Suppression of endogenous β-arrestin2 by specific RNA interfering (RNAi) and morphine treatment significantly attenuates the levels of phosphorylated Akt compared with inhibition of β-arrestin2 or morphine treatment alone. However, blockade of morphine-induced cell death by β-arrestin2 seems to be dependent on the inhibition of caspase-8, as inhibition of β-arrestin2 and morphine treatment significantly enhanced the levels of cleaved caspase-8. These studies show for the first time that β-arrestin2 blocks morphine-induced cell death through anti-apoptotic Akt and pro-apoptotic caspase-8 pathways. Therefore, targeting β-arrestin2 may be useful for treating side effects of opioids as pain relievers for cancer patients.

To understand the physiological function of glutaredoxin, a thiotransferase catalyzing the reduction of mixed disulfides of protein and glutathione, we generated a line of knockout mice deficient in the cytosolic glutaredoxin 1 (Grx1). To our surprise, mice deficient in Grx1 were not more susceptible to acute oxidative insults in models of heart and lung injury induced by ischemia/reperfusion and hyperoxia, respectively, suggesting that either changes in S-glutathionylation status of cytosolic proteins are not the major cause of such tissue injury or developmental adaptation in the Glrx1-knockout animals alters the response to oxidative insult. In contrast, mouse embryonic fibroblasts (MEFs) isolated from Grx1-deficient mice displayed an increased vulnerability to diquat and paraquat, but they were not more susceptible to cell death induced by hydrogen peroxide (H2O2) and diamide. A deficiency in Grx1 also sensitized MEFs to protein S-glutathionylation in response to H2O2 treatment and retarded deglutathionylation of the S-glutathionylated proteins, especially for a single prominent protein band. Additional experiments showed that MEFs lacking Grx1 were more tolerant to apoptosis induced by tumor necrosis factor αplus actinomycin D. These findings suggest that various oxidants may damage the cells via distinct mechanisms in which the action of Grx1 may or may not be protective and Grx1 may exert its function on specific target proteins.

Angiopoietin-1 (Ang-1) is essential for the maturation of blood vessels during vasculogenesis. Besides angiogenesis, recent publications indicate that Ang-1 is also a potent survival factor for endothelial cells; however, the mechanisms by which pathways remain elusive. Doxorubicin (DOX) is a powerful anticancer drug, but its use is severely restricted by its cardiotoxicity. The authors report here that Ang-1 inhibits DOX-induced cell death in human umbilical vein endothelial cells (HUVECs). Interestingly, the DOX-induced up-regulation in Fas (CD95/APO-1) and Fas ligand expression could be blocked by Ang-1, indicating a pivotal role of Ang-1 in DOX-induced Fas and Fas ligand expression. In addition, the prevention of cell death in this model system seems to be dependent on the activation of phosphatidylinositol 3-kinase (PI3K)/Akt, as Ang-1 fails to inhibit DOX-induced cell death while PI3K/Akt pathway was blocked by the PI3K inhibitor LY294002. Moreover, Ang-1 inhibits DOX-induced up-regulation of p53 through PI3K/Akt. Therefore, Ang-1 is a potent inhibitor for DOX-induced cell death through Fas and PI3K/Akt-mediated pathways.