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Background: Emerging evidence indicates that impaired mitophagy-mediated clearance of defective mitochondria is a critical event in Alzheimer’s disease (AD) pathogenesis. Amyloid-beta (Aβ) metabolism and the microtubule-associated protein tau have been reported to regulate key components of the mitophagy machinery. However, the mechanisms that lead to mitophagy dysfunction in AD are not fully deciphered. We have previously shown that intraneuronal cholesterol accumulation can disrupt the autophagy flux, resulting in low Aβ clearance. In this study, we examine the impact of neuronal cholesterol changes on mitochondrial removal by autophagy. Methods: Regulation of PINK1-parkin-mediated mitophagy was investigated in conditions of acute (in vitro) and chronic (in vivo) high cholesterol loading using cholesterol-enriched SH-SY5Y cells, cultured primary neurons from transgenic mice overexpressing active SREBF2 (sterol regulatory element binding factor 2), and mice of increasing age that express the amyloid precursor protein with the familial Alzheimer Swedish mutation (Mo/HuAPP695swe) and mutant presenilin 1 (PS1-dE9) together with active SREBF2. Results: In cholesterol-enriched SH-SY5Y cells and cultured primary neurons, high intracellular cholesterol levels stimulated mitochondrial PINK1 accumulation and mitophagosomes formation triggered by Aβ while impairing lysosomal-mediated clearance. Antioxidant recovery of cholesterol-induced mitochondrial glutathione (GSH) depletion prevented mitophagosomes formation indicating mitochondrial ROS involvement. Interestingly, when brain cholesterol accumulated chronically in aged APP-PSEN1-SREBF2 mice the mitophagy flux was affected at the early steps of the pathway, with defective recruitment of the key autophagy receptor optineurin (OPTN). Sustained cholesterol-induced alterations in APP-PSEN1-SREBF2 mice promoted an age-dependent accumulation of OPTN into HDAC6-positive aggresomes, which disappeared after in vivo treatment with GSH ethyl ester (GSHee). The analyses in post-mortem brain tissues from individuals with AD confirmed these findings, showing OPTN in aggresome-like structures that correlated with high mitochondrial cholesterol levels in late AD stages. Conclusions: Our data demonstrate that accumulation of intracellular cholesterol reduces the clearance of defective mitochondria and suggest recovery of the cholesterol homeostasis and the mitochondrial scavenging of ROS as potential therapeutic targets for AD., This work was supported by the Ministerio de Ciencia, Innovación y Universidades (MCIU), Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) under grants: RTI2018–095572-B-100 to A.C., RTI2018–095672-B-I00 to A.M., SAF2017–89791-R to R.T.; Fundació La Marató de TV3 (2014–0930 to A.C.); the Instituto de Salud Carlos III under grant PI19/01410 to M.M.; the Agencia de Gestió d’Ajuts Universitaris i de Recerca, Spain (2017_SGR_177); and the CERCA Programme from the Generalitat de Catalunya, Spain. C.dD. has a FPU fellowship from Ministerio de Ciencia, Innovación y Universidades, Spain. We acknowledge support of the publication fee by the CSIC Open Acess Publication Support Initiative through its Unit of Information Resource for Research (URICI).

Background: Emerging evidence indicates that impaired mitophagy-mediated clearance of defective mitochondria is a critical event in Alzheimer’s disease (AD) pathogenesis. Amyloid-beta (A) metabolism and the microtubule-associated protein tau have been reported to regulate key components of the mitophagy machinery. However, the mechanisms that lead to mitophagy dysfunction in AD are not fully deciphered. We have previously shown that intraneuronal cholesterol accumulation can disrupt the autophagy flux, resulting in low A clearance. In this study, we examine the impact of neuronal cholesterol changes on mitochondrial removal by autophagy.Methods: Regulation of PINK1-parkin-mediated mitophagy was investigated in conditions of acute (in vitro) and chronic (in vivo) high cholesterol loading using cholesterol-enriched SH-SY5Y cells, cultured primary neurons from transgenic mice overexpressing active SREBF2 (sterol regulatory element binding factor 2), and mice of increasing age that express the amyloid precursor protein with the familial Alzheimer Swedish mutation (Mo/HuAPP695swe) and mutant presenilin 1 (PS1-dE9) together with active SREBF2.Results: In cholesterol-enriched SH-SY5Y cells and cultured primary neurons, high intracellular cholesterol levels stimulated mitochondrial PINK1 accumulation and mitophagosomes formation triggered by A while impairing lysosomal-mediated clearance. Antioxidant recovery of cholesterol-induced mitochondrial glutathione (GSH) depletion prevented mitophagosomes formation indicating mitochondrial ROS involvement. Interestingly, when brain cholesterol accumulated chronically in aged APP-PSEN1-SREBF2 mice the mitophagy flux was affected at the early steps of the pathway, with defective recruitment of the key autophagy receptor optineurin (OPTN). Sustained cholesterol-induced alterations in APP-PSEN1-SREBF2 mice promoted an age-dependent accumulation of OPTN into HDAC6-positive aggresomes, which disappeared after in vivo treatment with GSH ethyl ester (GSHee). The analyses in post-mortem brain tissues from individuals with AD confirmed these findings, showing OPTN in aggresome-like structures that correlated with high mitochondrial cholesterol levels in late AD stages. Conclusions: Our data demonstrate that accumulation of intracellular cholesterol reduces the clearance of defective mitochondria and suggest recovery of the cholesterol homeostasis and the mitochondrial scavenging of ROS as potential therapeutic targets for AD.

Evasive mechanisms triggered by the tyrosine kinase inhibitor sorafenib reduce its efficacy in hepatocellular carcinoma (HCC) treatment. Drug-resistant cancer cells frequently exhibit sphingolipid dysregulation, reducing chemotherapeutic cytotoxicity via the induction of ceramide-degrading enzymes. However, the role of ceramide in sorafenib therapy and resistance in HCC has not been clearly established. Our data reveals that ceramide-modifying enzymes, particularly glucosylceramide synthase (GCS), are upregulated during sorafenib treatment in hepatoma cells (HepG2 and Hep3B), and more importantly, in sorafenib-resistant cell lines. GCS silencing or pharmacological GCS inhibition sensitized hepatoma cells to sorafenib exposure. GCS inhibition, combined with sorafenib, triggered cytochrome c release and ATP depletion in sorafenib-treated hepatoma cells, leading to mitochondrial cell death after energetic collapse. Conversely, genetic GCS overexpression increased sorafenib resistance. Of interest, GCS inhibition improved sorafenib effectiveness in a xenograft mouse model, recovering drug sensitivity of sorafenib-resistant tumors in mice. In conclusion, our results reveal GCS induction as a mechanism of sorafenib resistance, suggesting that GCS targeting may be a novel strategy to increase sorafenib efficacy in HCC management, and point to target the mitochondria as the subcellular location where sorafenib therapy could be potentiated., This study was funded by grants from the Instituto de Salud Carlos III (FIS PI12/00110, PI09/00056 to A.M., PI13/00374 to M.M, PI13/01339 to A.V., and SAF2015-69944-R and PI11/0325 to J.F.C.), Ministerio de Economía y Competitividad (SAF2012/34831 to J.F.C., SAF2014-57674-R to C.G.R. and SAF2013-47246-R to A.C.) and co-funded by FEDER (Fondo Europeo de Desarrollo Regional, Unión Europea. “Una manera de hacer Europa”); center grant P50-AA-11999 from Research Center for Liver and Pancreatic Diseases, US NIAAA to J.F.C.); Fundació la Marató de TV3 to J.F.C. and A.C., Mutua Madrileña (AP103502012) to C.G.R., and by CIBEREHD from the Instituto de Salud Carlos III. We also want to thank the support of the AGAUR (2014SGR785) from the Generalitat de Catalunya.

Macroautophagy/autophagy failure with the accumulation of autophagosomes is an early neuropathological feature of Alzheimer disease (AD) that directly affects amyloid beta (Ab) metabolism. Although loss of presenilin 1 function has been reported to impair lysosomal function and prevent autophagy flux, the detailed mechanism leading to autophagy dysfunction in AD remains to be elucidated. The resemblance between pathological hallmarks of AD and Niemann-Pick Type C disease, including endosome-lysosome abnormalities and impaired autophagy, suggests cholesterol accumulation as a common link. Using a mouse model of AD (APP-PSEN1-SREBF2 mice), expressing chimeric mousehuman amyloid precursor protein with the familial Alzheimer Swedish mutation (APP695swe) and mutant presenilin 1 (PSEN1-dE9), together with a dominant-positive, truncated and active form of SREBF2/SREBP2 (sterol regulatory element binding factor 2), we demonstrated that high brain cholesterol enhanced autophagosome formation, but disrupted its fusion with endosomal-lysosomal vesicles. The combination of these alterations resulted in impaired degradation of Ab and endogenous MAPT (microtubule associated protein tau), and stimulated autophagy-dependent Ab secretion. Exacerbated Ab-induced oxidative stress in APP-PSEN1-SREBF2 mice, due to cholesterol-mediated depletion of mitochondrial glutathione/mGSH, is critical for autophagy induction. In agreement, in vivo mitochondrial GSH recovery with GSH ethyl ester, inhibited autophagosome synthesis by preventing the oxidative inhibition of ATG4B deconjugation activity exerted by Ab. Moreover, cholesterol-enrichment within the endosomes-lysosomes modified the levels and membrane distribution of RAB7A and SNAP receptors (SNAREs), which affected its fusogenic ability. Accordingly, in vivo treatment with 2-hydroxypropyl-b-cyclodextrin completely rescued these alterations, making it a potential therapeutic tool for AD., This work was supported by Ministerio de Economía y Competitividad under Grant: SAF2013-47246-R to A.C., SAF2015-66515-R to A.M., SAF2015-69944-R to J.F-C.); FEDER (Fondo Europeo de Desarrollo Regional, Unión Europea. “Una manera de hacer Europa”); Fundació La Marató de TV3 (2014-0930); Instituto de Salud Carlos III under Grant PI13/00374 and PI16/00930 to M.M., US NIAAA under Center grant P50- AA-11999 from Research Center for Liver and Pancreatic Diseases to J.F. C. We also want to thank the support of the AGAUR (2014-SGR785) and CERCA Programme from the Generalitat de Catalunya. C.dD. has a FPU fellowship from Ministerio de Economía y Competitividad. This work was developed (in part) at the Centre Esther Koplowitz.

A qui no li agradaria coneixer els indrets mes bells i geologicament interessants de la Terra? En aquesta sequencia didactica us proposo treballar la dinamica interna i externa de la Terra a partir d’un context de viatges figurats pel mon per quinze destinacions diferents. La sequencia, d’un total de nou sessions, esta organitzada d’acord amb la metodologia 5E (Enganxa, Explora, Explica, Elabora i Avalua) incloent aprenentatge basat en projectes (ABP) i coavaluacio. L’estructura senzilla que segueix vol animar a treballar per projectes a docents que encara no hi tinguin amplia experiencia previa, aixi com ajudar a coneixer el model de programacio en 5E.

International audience; Background: Reduced uteroplacental perfusion, the initiating event in preeclampsia, is associated with enhanced endothelin-1 (ET-1) production which feeds the vasoconstriction of uterine artery. Whether the treatments of preeclampsia were effective on ET-1 induced contraction and could reverse placental ischemia is the question addressed in this study. We investigated the effect of antihypertensive drugs used in preeclampsia and of ET receptor antagonists on the contractile response to ET-1 on human uterine arteries.Methodology/Principal Findings: Experiments were performed, ex vivo, on human uterine artery samples obtained after hysterectomy. We studied variations in isometric tension of arterial rings in response to the vasoconstrictor ET-1 and evaluated the effects of various vasodilators and ET-receptor antagonists on this response. Among antihypertensive drugs, only dihydropyridines were effective in blocking and reversing the ET-1 contractile response. Their efficiency, independent of the concentration of ET-1, was only partial. Hydralazine, alpha-methyldopa and labetalol had no effect on ET-1 induced contraction which is mediated by both ETA and ETB receptors in uterine artery. ET receptors antagonists, BQ-123 and BQ-788, slightly reduced the amplitude of the response to ET-1. Combination of both antagonists was more efficient, but it was not possible to reverse the maximal ET-1-induced contraction with antagonists used alone or in combination.Conclusion: Pharmacological drugs currently used in the context of preeclampsia, do not reverse ET-1 induced contraction. Only dihydropyridines, which partially relax uterine artery previously contracted with ET-1, might offer interesting perspectives to improve placental perfusion.