[Which patient for TAVI in 2019?] / À quel patient proposer un TAVI en 2019 ?

The therapeutic management of aortic stenosis has been drastically changed by the advent of percutaneous valve replacement (TAVI). Since the first implantation, the indications have progressively been extended from the inoperable patient to the patient at low surgical risk. The main objective of this review is to describe the currently recommended main indications of TAVI depending on an individualized assessment of each patient's risk, technical characteristics and anatomical valvular criteria.

Cytochrome c is released in a single step during apoptosis.

Release of cytochrome c from mitochondria is a central event in apoptotic signaling. In this study, we utilized a cytochrome c fusion that binds fluorescent biarsenical ligands (cytochrome c-4CYS (cyt. c-4CYS)) as well as cytochrome c-green fluorescent protein (cyt. c-GFP) to measure its release from mitochondria in different cell types during apoptosis. In single cells, the kinetics of cyt. c-4CYS release was indistinguishable from that of cyt. c-GFP in apoptotic cells expressing both molecules. Lowering the temperature by 7 degrees C did not affect this corelease, but further separated cytochrome c release from the subsequent decrease in mitochondrial membrane potential (DeltaPsi(m)). Cyt. c-GFP rescued respiration in cells lacking endogenous cytochrome c, and the duration of cytochrome c release was approximately 5 min in a variety of cell types induced to die by various forms of cellular stress. In addition, we could observe no evidence of caspase-dependent amplification of cytochrome c release or changes in DeltaPsi(m) preceding the release of cyt. c-GFP. We conclude that there is a general mechanism responsible for cytochrome c release that proceeds in a single step that is independent of changes in DeltaPsi(m).

Hyperthermic intraperitoneal chemotherapy leads to an anticancer immune response via exposure of cell surface heat shock protein 90.

The occurrence of peritoneal carcinomatosis is a major cause of treatment failure in colorectal cancer and is considered incurable. However, new therapeutic approaches have been proposed, including cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy (HIPEC). Although HIPEC has been effective in selected patients, it is not known how HIPEC prolongs a patient's lifespan. Here, we have demonstrated that HIPEC-treated tumor cells induce the activation of tumor-specific T cells and lead to vaccination against tumor cells in mice. We have established that this effect results from the HIPEC-mediated exposure of heat shock protein (HSP) 90 at the plasma membrane. Inhibition or blocking of HSP90, but not HSP70, prevented the HIPEC-mediated antitumoral vaccination. Our work raises the possibility that the HIPEC procedure not only kills tumor cells but also induces an efficient anticancer immune response, therefore opening new opportunities for cancer treatment.

Cleavage of Fyn and Lyn in their N-terminal unique regions during induction of apoptosis: a new mechanism for Src kinase regulation.

The members of the Src kinase family are expressed in a wide variety of tissues, but some of them such as Blk, Hck, Fgr, Lck and Lyn are found primarily in hematopoietic cells. In the present study, we have undertaken experiments to test whether Src kinase cleavage and relocation is a general mechanism during induction of apoptosis. Our results indicate that Fyn and Lyn are efficiently cleaved in their unique region in hematopoietic cells undergoing apoptosis. Fyn cleavage occurred in Fas-stimulated Jurkat T cells but Fyn and Lyn were also processed in the SKW6.4 B cell line. Inhibition of caspases by Z-VAD-fmk or Ac-DEVD-CHO totally prevented Fyn and Lyn cleavage in both intact cells and in vitro. Fyn and Lyn but not Lck, Src and Hck were processed in vitro by human recombinant caspase 3 and by cellular extracts prepared from Fas-stimulated cells. Single mutation of Asp 19 or Asp 18 in the unique N-terminal domains of Fyn and Lyn respectively abolished their cleavage and relocation into the cytoplasm of apoptotic cells. When immunoprecipitated from COS cells N-terminal deleted Src kinases exhibited increased enzymatic kinase activity toward enolase. Thus, cleavage of Fyn and Lyn during induction of apoptosis represents a new mechanism for the regulation of Src kinases that may have important functional and physiological consequences.

Cleavage and relocation of the tyrosine kinase P59FYN during Fas-mediated apoptosis in T lymphocytes.

Ligation of Fas with its natural ligand or with anti-Fas antibodies induces an apoptotic program in Fas sensitive cells. We report here the identification of the tyrosine kinase p59Fyn as a substrate for CPP32-like proteinases and more particularly caspase 3 during Fas-mediated apoptosis in Jurkat T cells. Inhibition of CPP32-like proteinases by Ac-Asp-Glu-Val-Asp-aldehyde but not by Ac-Tyr-Val-Ala-Asp-aldehyde prevents CPP32, PARP and p59Fyn cleavage indicating that CPP32 or CPP32-like proteinases are responsible for the cleavage of p59Fyn. Cleavage occurs in the N-terminal domain of p59Fyn between Asp19 and Gly20 and is accompanied by relocation of an active p57Fyn kinase to cytoplasm of Fas-stimulated Jurkat cells as judged by both biochemical and confocal microscopy experiments. Thus, p59Fyn relocation and activity may play an important role during Fas-mediated cell death in human T lymphocytes.

Differential requirements for ERK1/2 and P38 MAPK activation by thrombin in T cells. Role of P59Fyn and PKCepsilon.

Activation of the mitogen-activated protein kinase (MAPK) cascade is a well documented mechanism for the G-protein-coupled receptors. Here, we have analysed the requirements for ERKs and p38 MAPK activation by thrombin in Jurkat T cells. We show that thrombin-mediated ERKs activation requires both PTK and PKC activities, whereas p38 MAPK activation is dependent only on PTKs. Thrombin-induced ERK and p38 MAPK activation was more pronounced in p56Lck deficient cells indicating that this PTK exerts a negative control on MAPK activity. Accordingly, overexpression of p50 Csk a kinase that inactivates p56Lck induced constitutive activation of ERKs. Requirement for a Src kinase was evidenced by expression of a constitutively active form of p59Fyn in Jurkat cells. Besides its effect on tyrosine phosphorylation events, thrombin also triggered a rapid and robust redistribution of PKCepsilon and delta from the cytosol to the membrane. Expression of constitutively active and dominant negative PKCepsilon demonstrates the pivotal role of this PKC isoform in ERKs activation by thrombin. These data are consistent with a model where thrombin induces ERK activation via both PKC-dependent and independent pathways, whereas p38 MAPK activation requires only PTKs. The PKC-independent pathway requires Src kinases other than p56Lck more likely p59Fyn, while the PKC-dependent mechanism depends on PKCepsilon

T and B leukemic cell lines exhibit different requirements for cell death: correlation between caspase activation, DFF40/DFF45 expression, DNA fragmentation and apoptosis in T cell lines but not in Burkitt's lymphoma.

The execution phase of apoptosis occurs through the activation and function of caspases which cleave key substrates that orchestrate the death process. Here, we have compared the sensitivity of various T and B cell lines to death receptor or staurosporine-induced apoptosis. First, we found a lack of correlation between death receptor expression and sensitivity to Fas or Trail. By contrast, a correlation between caspase activation, DNA fragmentation and cell death in T cell lines was evidenced. Among T cells, CEM underwent apoptosis in response to CH11 but were resistant to Trail in agreement with the absence of Trail receptors (DR4 and DR5) on their surface. The B cell line SKW 6.4 was sensitive to CH11 and staurosporine but resistant to Trail. As B cell lines expressed significant levels of DR4 and DR5, resistance to Trail in SKW 6.4 is likely due to the expression of the decoy receptor DcR1. Burkitt's lymphoma such as RPMI 8866 and Raji did not exhibit DNA fragmentation in response to CH11, Trail or staurosporine but showed long-term caspase-dependent loss of viability upon effector treatment. The B cell lines used in this study express very weak or undetectable levels of DFF40 and relatively high levels of DFF45. Interestingly, cytosolic extracts from RPMI 88.66 but not other B lymphoma exhibit altered levels of cytochrome c-dependent caspase activation. Taken together, our results show that: (1) death receptor expression does not correlate with sensitivity to apoptosis; (2) the very low ratio of DFF40 vs. DFF45 is unlikely to explain by itself the lack of DNA fragmentation observed in certain B cell lines; and (3) a defective cytochrome c-dependent caspase activation might account at least in part for the insensitivity of certain Burkitt's lymphoma (RPMI 88.66) to apoptosis. Thus it seems that resistance of Burkitt's lymphoma to apoptosis is not governed by a general mechanism, but is rather multifactorial and differs from one cell line to another.

[Unusual consequences of foam sclerotherapy]. / Des conséquences insolites d'une sclérothérapie à la mousse.

Neurological disorders are rare complications of foam sclerotherapy. Visual disturbances and headache are the most commonly reported events and are thought to be equivalent to migraine with aura. Exceptionally, strokes have been reported. Papillary fibroelastoma is a rare cardiac tumor, which may embolize in cerebral arteries. We report the case of a patient in whom neurological disorders occurred during a session of foam sclerotherapy, and led to the discovery of a cardiac fibroelastoma.

GAPDH enhances the aggressiveness and the vascularization of non-Hodgkin's B lymphomas via NF-κB-dependent induction of HIF-1α.

Deregulated expression of glycolytic enzymes contributes not only to the increased energy demands of transformed cells but also has non-glycolytic roles in tumors. However, the contribution of these non-glycolytic functions in tumor progression remains poorly defined. Here, we show that elevated expression of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), but not of other glycolytic enzymes tested, increased aggressiveness and vascularization of non-Hodgkin's lymphoma. Elevated GAPDH expression was found to promote nuclear factor-κB (NF-κB) activation via binding to tumor necrosis factor receptor-associated factor-2 (TRAF2), enhancing the transcription and the activity of hypoxia-inducing factor-1α (HIF-1α). Consistent with this, inactive mutants of GAPDH failed to bind TRAF2, enhance HIF-1 activity or promote lymphomagenesis. Furthermore, elevated expression of gapdh mRNA in biopsies from diffuse large B-cell non-Hodgkin's lymphoma patients correlated with high levels of hif-1α, vegf-a, nfkbia mRNA and CD31 staining. Collectively, these data indicate that deregulated GAPDH expression promotes NF-κB-dependent induction of HIF-1α and has a key role in lymphoma vascularization and aggressiveness.

NIK promotes tissue destruction independently of the alternative NF-κB pathway through TNFR1/RIP1-induced apoptosis.

NF-κB-inducing kinase (NIK) is well-known for its role in promoting p100/NF-κB2 processing into p52, a process defined as the alternative, or non-canonical, NF-κB pathway. Here we reveal an unexpected new role of NIK in TNFR1-mediated RIP1-dependent apoptosis, a consequence of TNFR1 activation observed in c-IAP1/2-depleted conditions. We show that NIK stabilization, obtained by activation of the non-death TNFRs Fn14 or LTßR, is required for TNFα-mediated apoptosis. These apoptotic stimuli trigger the depletion of c-IAP1/2, the phosphorylation of RIP1 and the RIP1 kinase-dependent assembly of the RIP1/FADD/caspase-8 complex. In the absence of NIK, the phosphorylation of RIP1 and the formation of RIP1/FADD/caspase-8 complex are compromised while c-IAP1/2 depletion is unaffected. In vitro kinase assays revealed that recombinant RIP1 is a bona fide substrate of NIK. In vivo, we demonstrated the requirement of NIK pro-death function, but not the processing of its substrate p100 into p52, in a mouse model of TNFR1/LTßR-induced thymus involution. In addition, we also highlight a role for NIK in hepatocyte apoptosis in a mouse model of virus-induced TNFR1/RIP1-dependent liver damage. We conclude that NIK not only contributes to lymphoid organogenesis, inflammation and cell survival but also to TNFR1/RIP1-dependent cell death independently of the alternative NF-κB pathway.

Lack of effect of Presenilin 1, betaAPP and their Alzheimer's disease-related mutated forms on Xenopus oocytes membrane currents.

The effect of the microinjection of Xenopus oocytes with various cRNAs coding for Presenilin 1 and four mutated presenilins linked to early onset familial forms of Alzheimer's disease was examined. These cRNAs were injected either alone or in combination with the cRNA encoding betaAPP751 and the Swedish mutated form of betaAPP751 known to produce exacerbated amount of Abeta. Current-voltage relationships generated by voltage step were recorded. None of the cRNA injected alone or in combination displayed the ability to modify the current recorded with naive cells. Altogether, this study shows that Presenilin 1 does not mediate membrane currents and is more likely involved in the physiopathological maturation of betaAPP.

A Jurkat T cell variant resistant to death receptor-induced apoptosis. Correlation with heat shock protein (Hsp) 27 and 70 levels.

Ligation of Fas induces an apoptotic program in Jurkat cells (Jd). We describe a Jurkat T cell variant (Jr) which shows total resistance to Fas-mediated apoptosis but which exhibits sensitivity to non-death-receptor pro-apoptotic stimuli such as staurosporine. Resistance to Fas-induced apoptosis in Jr cells is correlated with high expression of Hsps. A prior heat-shock increases Hsp27 and 70 expression and protects Jd and Jr cells from Fas- and staurosporine-induced apoptosis. Staurosporine, but not the anti-Fas antibody CH11, abrogates constitutive Hsp70 expression at 37 degrees C and staurosporine also inhibit Hsp27 expression in Jd and Jr cells at 42 degrees C. These data suggest that constitutive expression of Hsp27 inhibits Fas-mediated apoptosis, but only induced expression of Hsp70 can protect T cells from staurosporine-induced apoptosis. Thus, Hsp27 could play a role in the regulation of death receptor-mediated apoptosis, while Hsp70 could regulate mitochondrial-dependent cell death.

Glucose metabolism is inhibited by caspases upon the induction of apoptosis.

Rapidly proliferating cells, such as cancer cells, have adopted aerobic glycolysis rather than oxidative phosphorylation to supply their energy demand; this phenomenon is known as 'the Warburg effect'. It is now widely accepted that during apoptosis the loss of energy production, orchestrated by caspases, contributes to the dismantling of the dying cell. However, how this loss of energy production occurs is still only partially known. In the present work, we established that during apoptosis the level of cellular ATP decreased in a caspase-dependent manner. We demonstrated that this decrease in ATP content was independent of any caspase modification of glucose uptake, ATP consumption or reactive oxygen species production but was dependent on a caspase-dependent inhibition of glycolysis. We found that the activity of the two glycolysis-limiting enzymes, phosphofructokinase and pyruvate kinase, were affected by caspases, whereas the activity of phosphoglycerate kinase was not, suggesting specificity of the effect. Finally, using a metabolomic analysis, we observed that caspases led to a decrease in several key metabolites, including phosphoserine, which is a major regulator of pyruvate kinase muscle isozyme activity. Thus, we have established that during apoptosis, caspases can shut down the main energy production pathway in cancer cells, leading to the impairment in the activity of the two enzymes controlling limiting steps of glycolysis.

GAPDH binds to active Akt, leading to Bcl-xL increase and escape from caspase-independent cell death.

Increased glucose catabolism and resistance to cell death are hallmarks of cancers, but the link between them remains elusive. Remarkably, under conditions where caspases are inhibited, the process of cell death is delayed but rarely blocked, leading to the occurrence of caspase-independent cell death (CICD). Escape from CICD is particularly relevant in the context of cancer as apoptosis inhibition only is often not sufficient to allow oncogenic transformation. While most glycolytic enzymes are overexpressed in tumors, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is of particular interest as it can allow cells to recover from CICD. Here, we show that GAPDH, but no other glycolytic enzymes tested, when overexpressed could bind to active Akt and limit its dephosphorylation. Active Akt prevents FoxO nuclear localization, which precludes Bcl-6 expression and leads to Bcl-xL overexpression. The GAPDH-dependent Bcl-xL overexpression is able to protect a subset of mitochondria from permeabilization that are required for cellular survival from CICD. Thus, our work suggests that GAPDH overexpression could induce Bcl-xL overexpression and protect cells from CICD-induced chemotherapy through preservation of intact mitochondria that may facilitate tumor survival and chemotherapeutic resistance.

Cancer metabolism: current perspectives and future directions.

Cellular metabolism influences life and death decisions. An emerging theme in cancer biology is that metabolic regulation is intricately linked to cancer progression. In part, this is due to the fact that proliferation is tightly regulated by availability of nutrients. Mitogenic signals promote nutrient uptake and synthesis of DNA, RNA, proteins and lipids. Therefore, it seems straight-forward that oncogenes, that often promote proliferation, also promote metabolic changes. In this review we summarize our current understanding of how 'metabolic transformation' is linked to oncogenic transformation, and why inhibition of metabolism may prove a cancer's 'Achilles' heel'. On one hand, mutation of metabolic enzymes and metabolic stress sensors confers synthetic lethality with inhibitors of metabolism. On the other hand, hyperactivation of oncogenic pathways makes tumors more susceptible to metabolic inhibition. Conversely, an adequate nutrient supply and active metabolism regulates Bcl-2 family proteins and inhibits susceptibility to apoptosis. Here, we provide an overview of the metabolic pathways that represent anti-cancer targets and the cell death pathways engaged by metabolic inhibitors. Additionally, we will detail the similarities between metabolism of cancer cells and metabolism of proliferating cells.

miR-210 is overexpressed in late stages of lung cancer and mediates mitochondrial alterations associated with modulation of HIF-1 activity.

Following the identification of a set of hypoxia-regulated microRNAs (miRNAs), recent studies have highlighted the importance of miR-210 and of its transcriptional regulation by the transcription factor hypoxia-inducible factor-1 (HIF-1). We report here that miR-210 is overexpressed at late stages of non-small cell lung cancer. Expression of miR-210 in lung adenocarcinoma A549 cells caused an alteration of cell viability associated with induction of caspase-3/7 activity. miR-210 induced a loss of mitochondrial membrane potential and the apparition of an aberrant mitochondrial phenotype. The expression profiling of cells overexpressing miR-210 revealed a specific signature characterized by enrichment for transcripts related to 'cell death' and 'mitochondrial dysfunction', including several subunits of the electron transport chain (ETC) complexes I and II. The transcript coding for one of these ETC components, SDHD, subunit D of succinate dehydrogenase complex (SDH), was validated as a bona fide miR-210 target. Moreover, SDHD knockdown mimicked miR-210-mediated mitochondrial alterations. Finally, miR-210-dependent targeting of SDHD was able to activate HIF-1, in line with previous studies linking loss-of-function SDH mutations to HIF-1 activation. miR-210 can thus regulate mitochondrial function by targeting key ETC component genes with important consequences on cell metabolism, survival and modulation of HIF-1 activity. These observations help explain contradictory data regarding miR-210 expression and its putative function in solid tumors.

Glucose deprivation induces an atypical form of apoptosis mediated by caspase-8 in Bax-, Bak-deficient cells.

Apoptosis induced by most stimuli proceeds through the mitochondrial pathway. One such stimulus is nutrient deprivation. In this study we studied death induced by glucose deprivation in cells deficient in Bax and Bak. These cells cannot undergo mitochondrial outer membrane permeabilization (MOMP) during apoptosis, but they undergo necrosis when treated with MOMP-dependent apoptotic stimuli. We find in these cells that glucose deprivation, rather than inducing necrosis, triggered apoptosis. Cell death required caspase activation as inhibition of caspases with peptidic inhibitors prevented death. Glucose deprivation-induced death displayed many hallmarks of apoptosis, such as caspase cleavage and activity, phosphatidyl-serine exposure and cleavage of caspase substrates. Neither overexpression of Bcl-xL nor knockdown of caspase-9 prevented death. However, transient or stable knockdown of caspase-8 or overexpression of CrmA inhibited apoptosis. Cell death was not inhibited by preventing death receptor-ligand interactions, by overexpression of c-FLIP or by knockdown of RIPK1. Glucose deprivation induced apoptosis in the human tumor cell line HeLa, which was prevented by knockdown of caspase-8. Thus, we have found that glucose deprivation can induce a death receptor-independent, caspase-8-driven apoptosis, which is engaged to kill cells that cannot undergo MOMP.