Phytosphingosine-phosphate is a signal for AtMPK6 activation and Arabidopsis response to chilling

Long-chain bases (LCBs) are pleiotropic sphingolipidic signals in eukaryotes. We investigated the source and function of phytosphingosine-1-phosphate (PHS-P), a phospho-LCB rapidly and transiently formed in Arabidopsis thaliana on chilling.PHS-P was analysed by thin-layer chromatography following in vivo metabolic radiolabelling. Pharmacological and genetic approaches were used to identify the sphingosine kinase isoforms involved in cold-responsive PHS-P synthesis. Gene expression, mitogen-activated protein kinase activation and growth phenotypes of three LCB kinase mutants (lcbk1, sphk1 and lcbk2) were studied following cold exposure. Chilling provoked the rapid and transient formation of PHS-P in Arabidopsis cultured cells and plantlets. Cold-evoked PHS-P synthesis was reduced by LCB kinase inhibitors and abolished in the LCB kinase lcbk2 mutant, but not in lcbk1 and sphk1 mutants. lcbk2 presented a constitutive AtMPK6 activation at 22°C. AtMPK6 activation was also triggered by PHS-P treatment independently of PHS/PHS-P balance. lcbk2 mutants grew comparably with wild-type plants at 22 and 4°C, but exhibited a higher root growth at 12°C, correlated with an altered expression of the cold-responsive DELLA gene RGL3. Together, our data indicate a function for LCBK2 in planta. Furthermore, they connect PHS-P formation with plant response to cold, expanding the field of LCB signalling in plants

CD95-mediated calcium signaling promotes T helper 17 trafficking to inflamed organs in lupus-prone mice

CD95 ligand (CD95L) is expressed by immune cells and triggers apoptotic death. Metalloprotease-cleaved CD95L (cl-CD95L) is released into the bloodstream but does not trigger apoptotic signaling. Hence, the pathophysiological role of cl-CD95L remains unclear. We observed that skin-derived endothelial cells from systemic lupus erythematosus (SLE) patients expressed CD95L and that after cleavage, cl-CD95L promoted T helper 17 (Th17) lymphocyte transmigration across the endothelial barrier at the expense of T regulatory cells. T cell migration relied on a direct interaction between the CD95 domain called calcium-inducing domain (CID) and the Src homology 3 domain of phospholipase Cγ1. Th17 cells stimulated with cl-CD95L produced sphingosine-1-phosphate (S1P), which promoted endothelial transmigration by activating the S1P receptor 3. We generated a cell-penetrating CID peptide that prevented Th17 cell transmigration and alleviated clinical symptoms in lupus mice. Therefore, neutralizing the CD95 non-apoptotic signaling pathway could be an attractive therapeutic approach for SLE treatment

Voies de signalisation de l’apoptose médiées par les sphingolipides

Divers sphingolipides sont aujourd’hui reconnus comme étant doués de propriétés biologiques et/ou agissant comme seconds messagers. Parmi eux, le céra- mide (ou N-acylsphingosine) et la sphingosine se comportent comme des médiateurs généralement proapoptotiques. Ainsi, le céramide relaie le signal cytotoxique d’un certain nombre d’agents de stress qui, soit, stimulent sa biosynthèse de novo, soit, activent l’hydrolyse de sphingomyéline par des sphingomyélinases. Par exemple, la génération précoce de céramide induite par le TNF est médiée par une sphingomyélinase neutre dont l’activité est sous la dépendance de la protéine adaptatrice FAN, contrôlant ainsi l’activation des caspases et le processus apoptotique. De plus, l’activité de cette sphingomyélinase neutre semble être modulée négativement par la cavéoline, un constituant essentiel de certains microdomaines membranaires. Par ailleurs, la sphingosine kinase est une enzyme-clé du métabolisme des sphingolipides car elle contrôle les taux intracellulaires de deux molécules aux effets antagonistes, la sphingosine, pro-apoptotique, et la sphingosine 1-phosphate, anti-apoptotique. Le métabolisme du céramide et de la sphingosine est donc considéré actuellement comme au cœur d'un ensemble de voies de signalisation régulant le devenir de la cellule

Oxidative stress-dependent sphingosine kinase-1 inhibition mediates monoamine oxidase A-associated cardiac cell apoptosis

The mitochondrial enzyme monoamine oxidase (MAO), its isoform MAO-A, plays a major role in reactive oxygen species-dependent cardiomyocyte apoptosis and postischemic cardiac damage. In the current study, we investigated whether sphingolipid metabolism can account for mediating MAO-A- and reactive oxygen species-dependent cardiomyocyte apoptosis. In H9c2 cardiomyoblasts, MAO-A-dependent reactive oxygen species generation led to mitochondria-mediated apoptosis, along with sphingosine kinase-1 (SphK1) inhibition. These phenomena were associated with generation of proapoptotic ceramide and decrease in prosurvival sphingosine 1-phosphate. These events were mimicked by inhibition of SphK1 with either pharmacological inhibitor or small interfering RNA, as well as by extracellular addition of C(2)-ceramide or H(2)O(2). In contrast, enforced expression of SphK1 protected H9c2 cells from serotonin- or H(2)O(2)-induced apoptosis. Analysis of cardiac tissues from wild-type mice subjected to ischemia/reperfusion revealed significant upregulation of ceramide and inhibition of SphK1. It is noteworthy that SphK1 inhibition, ceramide accumulation, and concomitantly infarct size and cardiomyocyte apoptosis were significantly decreased in MAO-A-deficient animals. In conclusion, we show for the first time that the upregulation of ceramide/sphingosine 1-phosphate ratio is a critical event in MAO-A-mediated cardiac cell apoptosis. In addition, we provide the first evidence linking generation of reactive oxygen species with SphK1 inhibition. Finally, we propose sphingolipid metabolites as key mediators of postischemic/reperfusion cardiac injury

" Vieillir séropositif(ve) aujourd'hui dans la région Rhône-Alpes (France). Une recherche interdisciplinaire en sciences humaines et sociales ": Communication au VIè Congrès Brésilien de Sciences Sociales et Humaines en Santé, Université de l'Etat de Rio de Janeiro

International audienc

Targeting the sphingolipid metabolism to defeat pancreatic cancer cell resistance to the chemotherapeutic gemcitabine drug

Defeating pancreatic cancer resistance to the chemotherapeutic drug gemcitabine remains a challenge to treat this deadly cancer. Targeting the sphingolipid metabolism for improving tumor chemosensitivity has recently emerged as a promising strategy. The fine balance between intracellular levels of the prosurvival sphingosine-1-phosphate (S1P) and the proapoptotic ceramide sphingolipids determines cell fate. Among enzymes that control this metabolism, sphingosine kinase-1 (SphK1), a tumor-associated protein overexpressed in many cancers, favors survival through S1P production, and inhibitors of SphK1 are used in ongoing clinical trials to sensitize epithelial ovarian and prostate cancer cells to various chemotherapeutic drugs. We here report that the cellular ceramide/S1P ratio is a critical biosensor for predicting pancreatic cancer cell sensitivity to gemcitabine. A low level of the ceramide/S1P ratio, associated with a high SphK1 activity, correlates with a robust intrinsic pancreatic cancer cell chemoresistance toward gemcitabine. Strikingly, increasing the ceramide/S1P ratio, by using pharmacologic (SphK1 inhibitor or ceramide analogue) or small interfering RNA-based approaches to up-regulate intracellular ceramide levels or reduce SphK1 activity, sensitized pancreatic cancer cells to gemcitabine. Conversely, decreasing the ceramide/S1P ratio, by up-regulating SphK1 activity, promoted gemcitabine resistance in these cells. Development of novel pharmacologic strategies targeting the sphingolipid metabolism might therefore represent an interesting promising approach, when combined with gemcitabine, to defeat pancreatic cancer chemoresistance to this drug

: Congrès Brésilien sur les Sciences Humaines et Sociales et la Santé.

Seropositivity e envelhecimento na França, na Espanha e em Portugal. Congrès Brésilien sur les Sciences Humaines et Sociales et la Santé. Rio de Janeiro 2012 Conférence invitée au IV Congrès international en promotion à la santé : promotion de la santé - avancements et défis, organisé par l'Université de Fortaleza, l'Université de l'Etat du Ceara et Université Fédérale du Ceara. Université de Fortaleza (Fortaleza, Ceara, Brésil)(présentée par Mendes-Leite, R.

: Congrès Brésilien sur les Sciences Humaines et Sociales et la Santé.

Seropositivity e envelhecimento na França, na Espanha e em Portugal. Congrès Brésilien sur les Sciences Humaines et Sociales et la Santé. Rio de Janeiro 2012 Conférence invitée au IV Congrès international en promotion à la santé : promotion de la santé - avancements et défis, organisé par l'Université de Fortaleza, l'Université de l'Etat du Ceara et Université Fédérale du Ceara. Université de Fortaleza (Fortaleza, Ceara, Brésil)(présentée par Mendes-Leite, R.