Food Selection of Cafeteria Diet Affects Memory Dysfunction Related to Obesity

Neurochemical Research - Cafeteria diet (CAF) mimics human Western diet and has been used in animal models to study obesity. The purpose of this study is to demonstrate that our CAF model induces...     

Characterization of Puma-dependent and Puma-independent neuronal cell death pathways following prolonged proteasomal inhibition

Proteasomal stress and the accumulation of polyubiquitinated proteins are key features of numerous neurodegenerative disorders. Previously we demonstrated that stabilization of p53 and activation of its target gene, puma (p53-upregulated mediator of apoptosis), mediated proteasome inhibitor-induced apoptosis in cancer cells. Here we demonstrated that Puma also contributed to proteasome inhibitor-induced apoptosis in mouse neocortical neurons. Although protection afforded by puma gene deletion was incomplete, we found little evidence indicating contributions from other proapoptotic BH3-only proteins. Attenuation of bax expression did not further reduce Puma-independent apoptosis, suggesting that pathways other than the mitochondrial apoptosis pathway were activated. Real-time imaging experiments in wild-type and puma-deficient neurons using a fluorescence resonance energy transfer (FRET)-based caspase sensor confirmed the involvement of a second cell death pathway characterized by caspase activation prior to mitochondrial permeabilization and, more prominently, a third, caspase-independent and Puma-independent pathway characterized by rapid cell shrinkage and nuclear condensation. This pathway involved lysosomal permeabilization in the absence of autophagy activation and was sensitive to cathepsin but not autophagy inhibition. Our data demonstrate that proteasomal stress activates distinct cell death pathways in neurons, leading to both caspase-dependent and caspase-independent apoptosis, and demonstrate independent roles for Puma and lysosomal permeabilization in this model.     

Synthesis and biological evaluation of biphenylsulfonamide carboxylate aggrecanase-1 inhibitors

Aggrecanases are recently discovered enzymes that cleave aggrecan, a key component of cartilage. Aggrecanase inhibitors may provide a unique means to halt the progression of cartilage destruction in osteoarthritis. The synthesis and evaluation of biphenylsulfonamidocarboxylic acid inhibitors of aggrecanase-1 are reported. Compound 24 demonstrated 89% inhibition of proteoglycan degradation at 10 microg/mL and has an oral bioavailability in rat of 35%.     

Dynamics of intracellular oxygen in PC12 Cells upon stimulation of neurotransmission

Neurotransmission, synaptic plasticity, and maintenance of membrane excitability require high mitochondrial activity in neurosecretory cells. Using a fluorescence-based intracellular O2 sensing technique, we investigated the respiration of differentiated PC12 cells upon depolarization with 100 mm K+. Single cell confocal analysis identified a significant depolarization of the plasma membrane potential and a relatively minor depolarization of the mitochondrial membrane potential following K+ exposure. We observed a two-phase respiratory response: a first intense spike lasting approximately 10 min, during which average intracellular O2 was reduced from 85-90% of air saturation to 55-65%, followed by a second wave of smaller amplitude and longer duration. The fast rise in O2 consumption coincided with a transient increase in cellular ATP by approximately 60%, which was provided largely by oxidative phosphorylation and by glycolysis. The increase of respiration was orchestrated mainly by Ca2+ release from the endoplasmic reticulum, whereas the influx of extracellular Ca2+ contributed approximately 20%. Depletion of Ca2+ stores by ryanodine, thapsigargin, and 4-chloro-m-cresol reduced the amplitude of respiratory spike by 45, 63, and 71%, respectively, whereas chelation of intracellular Ca2+ abolished the response. Uncoupling of the mitochondria with the protonophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone amplified the responses to K+; elevated respiration induced a profound deoxygenation without increasing the cellular ATP levels reduced by carbonyl cyanide p-trifluoromethoxyphenylhydrazone. Cleavage of synaptobrevin 2 by tetanus toxin, known to reduce neurotransmission, did not affect the respiratory response to K+, whereas the general excitability of d PC12 cells increased.     

Ribosome-associated cyclic nucleotide-independent protein kinase of Artemia salina cryptobiotic gastrulae

An extra-ribosomal cAMP-independent protein kinase from cryptobiotic embryos of Artemia salina has been purified to near homogeneity by gel filtration on Bio-Gel A-0.5 m, ion-exchange chromatography on DEAE-cellulose and phosphocellulose P11 and affinity chromatography on casein-Sepharose 4B and ATP-agarose. The enzymatic activity has a broad optimum at pH 7-8. Maximal activity is obtained in the presence of 5-6 mM MgCl2. The activity is inhibited by Mn2+, Ca2+ and K+. The enzyme has an Mr of 127 000, utilizes both ATP and GTP as phosphoryl donors and is completely inhibited by heparin and poly(L-glutamic acid). According to its properties, the enzyme can be classified as a casein kinase type II. Although the enzyme is associated with ribosomes, ribosomal proteins are not among the main substrates. The kinase is able to phosphorylate both the alpha and the beta subunits of initiation factor eIF2 using ATP or GTP as phosphoryl donors. The function of phosphorylation in the initiation of protein synthesis is discussed.     

Sexual and parental antagonism shape genomic architecture

Populations with two sexes are vulnerable to a pair of genetic conflicts: sexual antagonism that can arise when alleles have opposing fitness effects on females and males; and parental antagonism that arises when alleles have opposing fitness effects when maternally and paternally inherited. This paper extends previous theoretical work that found stable linkage disequilibrium (LD) between sexually antagonistic loci. We find that LD is also generated between parentally antagonistic loci, and between sexually and parentally antagonistic loci, without any requirement of epistasis. We contend that the LD in these models arises from the admixture of gene pools subject to different selective histories. We also find that polymorphism maintained by parental antagonism at one locus expands the opportunity for polymorphism at a linked locus experiencing parental or sexual antagonism. Taken together, our results predict the chromosomal clustering of loci that segregate for sexually and parentally antagonistic alleles. Thus, genetic conflict may play a role in the evolution of genomic architecture.     

Chrysanthemum expressing a linalool synthase gene ‘smells good’, but ‘tastes bad’ to western flower thrips

Herbivore‐induced plant volatiles are often involved in direct and indirect plant defence against herbivores. Linalool is a common floral scent and found to be released from leaves by many plants after herbivore attack. In this study, a linalool/nerolidol synthase, FaNES1, was overexpressed in the plastids of chrysanthemum plants (Chrysanthemum morifolium). The volatiles of FaNES1 chrysanthemum leaves were strongly dominated by linalool, but they also emitted small amount of the C11‐homoterpene, (3E)‐4,8‐dimethyl‐1,3,7‐nonatriene, a derivative of nerolidol. Four nonvolatile linalool glycosides in methanolic extracts were found to be significantly increased in the leaves of FaNES1 plants compared to wild‐type plants. They were putatively identified by LC‐MS‐MS as two linalool–malonyl–hexoses, a linalool–pentose–hexose and a glycoside of hydroxy–linalool. A leaf‐disc dual‐choice assay with western flower thrips (WFT, Frankliniella occidentalis) showed, initially during the first 15 min of WFT release, that FaNES1 plants were significantly preferred. This gradually reversed into significant preference for the control, however, at 20–28 h after WFT release. The initial preference was shown to be based on the linalool odour of FaNES1 plants by olfactory dual‐choice assays using paper discs emitting pure linalool at similar rates as leaf discs. The reversal of preference into deterrence could be explained by the initial nonvolatile composition of the FaNES1 plants, as methanolic extracts were less preferred by WFT. Considering the common occurrence of linalool and its glycosides in plant tissues, it suggests that plants may balance attractive fragrance with ‘poor taste’ using the same precursor compound.     

Autophagy: a new player in hepatic stellate cell activation

Hepatic stellate cell (HSC) activation, the transition from a resident quiescent HSC to a myofibroblastic collagen-producing HSC, is a fundamental feature of liver fibrosis. Autophagy has been implicated in major liver pathologies, such as HCV infection and hepatocarcinoma. However, its role in HSC biology is largely unknown. Recently, we were able to demonstrate that HSC activation is followed by an increased autophagic flux and that its inhibition can partially inhibit the HSC myofibroblastic transition. These results point to autophagy as a possible target in the prevention of HSC activation.     

Cellular and subcellular calcium accumulation during glutamate-induced injury in cerebellar granule neurons

Abstract We have investigated the role of Ca2+ accumulation and neuronal injury in cerebellar granule neurons after glutamate receptor overactivation. After the removal of the free cytosolic Ca2+ we identified an extensive second Ca2+ fraction (SCF) that is retained within the neurons after glutamate receptor overactivation. The SCF reaches a plateau within 10 min with the magnitude of this SCF accumulation reflecting the extent of the neuronal injury that occurs within the neurons. The existence of this SCF is sensitive to both NMDA receptor antagonists and mitochondrial inhibitors but is unaffected by agents that deplete endoplasmic reticulum Ca2+, indicating that this Ca2+ fraction may be located within the mitochondria. Through the isolation of mitochondria from cerebellar granule neurons treated with glutamate we have shown that the majority of the SCF is mitochondrial in location. On the removal of the glutamate stimulus the SCF recovers at a slower rate than the free Ca2+ concentration within the neuron. This is intriguing, as it implies a capacity to remember previous excitatory events. Most significantly we have shown that a short pre-application of subthreshold glutamate or kainate blocks both SCF Ca2+ accumulation and extensive neuronal injury in response to high concentrations of glutamate. These findings may be relevant to the observations of pre-conditioning in the brain and heart.