Design, synthesis, crystallographic studies, and preliminary biological appraisal of new substituted triazolo[4,3-b]pyridazin-8-amine derivatives as tankyrase inhibitors.

Searching for selective tankyrases (TNKSs) inhibitors, a new small series of 6,8-disubstituted triazolo[4,3-b]piridazines has been synthesized and characterized biologically. Structure-based optimization of the starting hit compound NNL (3) prompted us to the discovery of 4-(2-(6-methyl-[1,2,4]triazolo[4,3-b]pyridazin-8-ylamino)ethyl)phenol (12), a low nanomolar selective TNKSs inhibitor working as NAD isostere as ascertained by crystallographic analysis. Preliminary biological data candidate this new class of derivatives as a powerful pharmacological tools in the unraveling of TNKS implications in physiopathological conditions.

Parp-2 is required to maintain hematopoiesis following sublethal γ-irradiation in mice.

Hematopoietic stem cells self-renew for life to guarantee the continuous supply of all blood cell lineages. Here we show that Poly(ADP-ribose) polymerase-2 (Parp-2) plays an essential role in hematopoietic stem/progenitor cells (HSPC) survival under steady-state conditions and in response to stress. Increased levels of cell death were observed in HSPC from untreated Parp-2-/- mice, but this deficit was compensated by increased rates of self-renewal, associated with impaired reconstitution of hematopoiesis upon serial bone marrow transplantation.

PARP-1 and PARP-2: New players in tumour development.

Poly(ADP-ribose) polymerase-1 (PARP-1) and PARP-2 belong to a family of enzymes that, using NAD(+) as a substrate, catalyze poly(ADP-ribosyl)ation of proteins. PARP-1 and PARP-2 catalytic activity is stimulated by DNA-strand breaks targeting mainly proteins involved in chromatin structure and DNA metabolism, providing strong support for a dual role of both PARP-1 and PARP-2 in the DNA damage response as DNA damage sensors and signal transducers to downstream effectors. The DNA damage response has important consequences for genomic stability and tumour development.

Probiotic sonicates selectively induce mucosal immune cells apoptosis through ceramide generation via neutral sphingomyelinase.

Background: Probiotics appear to be beneficial in inflammatory bowel disease, but their mechanism of action is incompletely understood. We investigated whether probiotic-derived sphingomyelinase mediates this beneficial effect.

Methodology/principal Findings: Neutral sphingomyelinase (NSMase) activity was measured in sonicates of the probiotic L.

Targeting cholesterol at different levels in the mevalonate pathway protects fatty liver against ischemia-reperfusion injury.

Background & Aims: Liver steatosis enhances ischemia/reperfusion (I/R) injury and is considered a primary factor in graft failure after liver transplantation. Although previous reports have shown a role for qualitative steatosis (macrovesicular vs. microvesicular) in hepatic I/R injury, no studies have compared side by side the specific contribution of individual lipids accumulating in fatty liver to I/R damage.

Growth arrest-specific protein 6 is hepatoprotective against murine ischemia/reperfusion injury.

Unlabelled: Growth arrest-specific gene 6 (GAS6) promotes growth and cell survival during tissue repair and development in different organs, including the liver. However, the specific role of GAS6 in liver ischemia/reperfusion (I/R) injury has not been previously addressed. Here we report an early increase in serum GAS6 levels after I/R exposure.

GD3 synthase overexpression sensitizes hepatocarcinoma cells to hypoxia and reduces tumor growth by suppressing the cSrc/NF-kappaB survival pathway.

Background: Hypoxia-mediated HIF-1alpha stabilization and NF-kappaB activation play a key role in carcinogenesis by fostering cancer cell survival, angiogenesis and tumor invasion. Gangliosides are integral components of biological membranes with an increasingly recognized role as signaling intermediates. In particular, ganglioside GD3 has been characterized as a proapoptotic lipid effector by promoting cell death signaling and suppression of survival pathways.

Mitochondrial cholesterol loading exacerbates amyloid beta peptide-induced inflammation and neurotoxicity.

The role of cholesterol in Alzheimer's disease (AD) has been linked to the generation of toxic amyloid beta peptides (Abeta). Using genetic mouse models of cholesterol loading, we examined whether mitochondrial cholesterol regulates Abeta neurotoxicity and AD pathology. Isolated mitochondria from brain or cortical neurons of transgenic mice overexpressing SREBP-2 (sterol regulatory element binding protein 2) or NPC1 (Niemann-Pick type C1) knock-out mice exhibited mitochondrial cholesterol accumulation, mitochondrial glutathione (mGSH) depletion and increased susceptibility to Abeta1-42-induced oxidative stress and release of apoptogenic proteins.

Reactive oxygen species mediate liver injury through parenchymal nuclear factor-kappaB inactivation in prolonged ischemia/reperfusion.

Nuclear factor (NF)-kappaB participates in ischemia/reperfusion (I/R) hepatic signaling, stimulating both protective mechanisms and the generation of inflammatory cytokines. After analyzing NF-kappaB activation during increasing times of ischemia in murine I/R, we observed that the nuclear translocation of p65 paralleled Src and IkappaB tyrosine phosphorylation, which peaked after 60 minutes of ischemia. After extended ischemic periods (90 to 120 minutes) however, nuclear p65 levels were inversely correlated with the progressive induction of oxidative stress.

Mitochondrial cholesterol contributes to chemotherapy resistance in hepatocellular carcinoma.

Cholesterol metabolism is deregulated in carcinogenesis, and cancer cells exhibit enhanced mitochondrial cholesterol content whose role in cell death susceptibility and cancer therapy has not been investigated. Here, we describe that mitochondria from rat or human hepatocellular carcinoma (HC) cells (HCC) or primary tumors from patients with HC exhibit increased mitochondrial cholesterol levels. HCC sensitivity to chemotherapy acting via mitochondria is enhanced upon cholesterol depletion by inhibition of hydroxymethylglutaryl-CoA reductase or squalene synthase (SS), which catalyzes the first committed step in cholesterol biosynthesis.

Critical role of acidic sphingomyelinase in murine hepatic ischemia-reperfusion injury.

The molecular mechanisms of hepatic ischemia/reperfusion (I/R) damage are incompletely understood. We investigated the role of ceramide in a murine model of warm hepatic I/R injury. This sphingolipid induces cell death and participates in tumor necrosis factor (TNF) signaling.