Sestrin2 integrates Akt and mTOR signaling to protect cells against energetic stress-induced death

The phosphoinositide-3 kinase/Akt (PI3K/Akt) pathway has a central role in cancer cell metabolism and proliferation. More importantly, it is one of the cardinal pro-survival pathways mediating resistance to apoptosis. The role of Akt in response to an energetic stress is presently unclear. Here, we show that Sestrin2 (Sesn2), also known as Hi95, a p53 target gene that protects cells against oxidative and genotoxic stresses, participates in the protective role of Akt in response to an energetic stress induced by 2-deoxyglucose (2-DG). Sesn2 is upregulated in response to an energetic stress such as 2-DG and metformin, and mediates the inhibition of mammalian target of rapamycin (mTOR), the major cellular regulator of energy metabolism. The increase of Sesn2 is independent of p53 but requires the anti-apoptotic pathway, PI3K/Akt. Inhibition of Akt, as well as loss of Sesn2, sensitizes cells to 2-DG-induced apoptosis. In addition, the rescue of Sesn2 partially reverses the pro-apoptotic effects of 2-DG. In conclusion, we identify Sesn2 as a new energetic stress sensor, which appears to be protective against energetic stress-induced apoptosis that integrates the pro-survival function of Akt and the negative regulation of mTOR.     

Haloperidol and Cerebral Metabolism in the Conscious Rat: Relation to Pharmacokinetics

The time course and distribution of alterations in cerebral metabolic activity after haloperidol administration were evaluated in relation to the pharmacokinetics of haloperidol and the topography of the dopaminergic system in the brain. Local cerebral glucose utilization was measured, using the 2-deoxyglucose technique, in awake rats after i.p. administration of the dopamine antagonist haloperidol (0.5 or 1 mg/kg). Haloperidol significantly reduced glucose utilization in 60% of 59 brain regions examined, but produced a large increase in the lateral habenula. The regional distribution of changes in glucose utilization was not closely related to the known anatomy of the brain dopaminergic system. The time course of the effect of haloperidol on cerebral metabolism was different for the two doses studied (0.5 and 1 mg/kg), and was not simply related to estimated brain concentrations of haloperidol. However, a linear relation between the metabolic effect and the time-integrated brain concentration was demonstrated. These results show that haloperidol has an effect on CNS metabolic activity that is more widespread than would be predicted from the topography of the dopaminergic system; this may be due to indirect propagation of the primary effects of haloperidol. The metabolic response to haloperidol depends on brain concentration and duration of exposure to the drug.     

PET: A biological imaging technique

Like in vivo autoradiography, PET provides a means to image and measure rates of biological processes throughout the distributed and interrelated systems of the entire living brain. In addition, both techniques can track and image the functional interactions of the brain with other systems throughout the entire body. Technological advances are yielding higher image spatial resolution and Electronic generators for automated synthesis of positron labeled compounds. The expanding number of labeled compounds (>500) is providing a growing number of biological assays (i.e., substrate metabolism, pre and post synaptic processes, enzyme activity, interaction of medical and illicit drugs with biological systems of the brain, immune system, membrane processes). Studies of normal cerebral function focus on mapping evoked responses of various components of motor, visual, somatosensory, memory and cognitive functions. Cerebral development, neuronal plasticity, and compensatory reorganization to lesions or surgery are active areas of investigation. Various types of assays have been used to identify specific biological alterations, map progression and determine therapeutic responses in a wide variety of neuropsychiatric disorders and drug abuse.Special issue dedicated to Dr. Louis Sokoloff.     

Proliferation and tissue remodeling in cancer: the hallmarks revisited

Although cancers are highly heterogeneous at the genomic level, they can manifest common patterns of gene expression. Here, we use gene expression signatures to interrogate two major processes in cancer, proliferation and tissue remodeling. We demonstrate that proliferation and remodeling signatures are partially independent and result in four distinctive cancer subtypes. Cancers with the proliferation signature are characterized by signatures of p53 and PTEN inactivation and concomitant Myc activation. In contrast, remodeling correlates with RAS, HIF-1α and NFκB activation. From the metabolic point of view, proliferation is associated with upregulation of glycolysis and serine/glycine metabolism, whereas remodeling is characterized by a downregulation of oxidative phosphorylation. Notably, the proliferation signature correlates with poor outcome in lung, prostate, breast and brain cancer, whereas remodeling increases mortality rates in colorectal and ovarian cancer.     

Kidney glomerular explants in serum-free media: Demonstration of intracellular antioxidant enzymes and active oxygen metabolites

Summary Guinea pig glomeruli were grown for 22 d in a serum-free medium composed of Waymouth's MB 752/1 supplemented with sodium pyruvate, nonessential amino acids, and antibiotics (the basic medium). Intracellular cellular activity of the antioxidant enzymes superoxide dismutase (SOD; both copper-zinc [Cu,Zn] and manganese [Mn] forms) and catalase, and intracellular active oxygen metabolites (hydrogen peroxide [H₂O₂] and superoxide [O_{2 −} ^· ]) were measured with time in culture. The results were compared to results obtained from glomeruli grown in different serum-free media, including the basic medium plus fibronectin (FN), the basic medium plus transferrin and FN, and a complex medium containing insulin, transferrin, selenium (Se), triiodothyronine, and FN (complete medium). In general, although the intracellular activity of antioxidant enzymes and active oxygen metabolites varied over time in culture in all media, there were only a few statistically significant differences among different media. Both CuZn SOD and Mn SOD activity were demonstrated, in isolated glomeruli. The CuZn SOD activity per DNA ratio decreased slightly with time in culture in all media tested except the complete medium, in which CuZn SOD activity per DNA ratio remained more constant. The Mn SOD activity per DNA ratio did not vary significantly over time in culture. Catalaselike activity was very low in isolated glomeruli and declined sharply with time in culture in all media except the complete medium. Both H₂O₂ and O_{2 −} ^· were detected intracellularly in glomerular culture. Our results indicate that intracellular antioxidant enzymes and active oxygen metabolites in glomeruli vary with time in culture and, in some instances, with culture conditions. Supported by grants to Dr. Terry Oberley from the University of Wisconsin Graduate School and by the Veterans Administration. Mr. Steinert was a predoctoral fellow supported by National Institutes of Health training grant 5-T32 ES0715.     

Cerebral ischemia: Changes in monoamines are independent of energy metabolism

The relationship of neurotransmitters and neuroeffectors to the energy state of the brain was examined in the gerbil model of ischemia after 5 and 15 min of bilateral common carotid artery occlusion only or with 1 hr of reperfusion. The gerbil brains were fixed by microwave irradiation and a total of 15 metabolites were measured from a single piece of tissue from either the hippocampus or the striatum. The rapid alterations in energy-related compounds and cyclic nucleotides appeared to be directly related both to the loss of oxygen and glucose during ischemia and the resupply of these nutrients during reflow. Significant reduction in the level of monoamines occurred prinicipally during reflow, at a time when the energy-related metabolites were restored. It is proposed that the changes in monoamines were triggered by other ischemic-induced events unrelated to energy depletion.Presented in part at the Nineteenth Annual Meeting of the American Society for Neurochemistry, 1988     

Local Cerebral Glucose Utilization During Development and Aging of the Fischer-344 Rat

Abstract: Local cerebral glucose utilization was measured in brain regions of awake Fischer-344 rats. Measurements were taken in 15 regions of 1-month-old rats, and 19 regions of 3-, 12-, 24-, and 34-month-old rats. Between 1 and 3 months, glucose utilization tended to increase in all brain regions; statistically significant increases occurred in seven regions. Between the ages of 3 and 12 months, glucose utilization decreased significantly in 12 regions. The greatest reductions (25% or more) occurred in the striatum, inferior colliculus, and pons, but the hypothalamus and thalamus, nucleus accumbens, and septum showed no statistically significant change. Cerebral glucose utilization did not change between 12 and 24 months or between 24 and 34 months of age. The results demonstrate a rise in cerebral glucose utilization with development from 1 to 3 months, a decline between 3 and 12 months, and a constancy in the second and third years that does not reflect reported senescence-associated neurochemical and morphological cerebral changes.     

Feeling your way in Java: An essay on society and emotion

This article reconsiders the place of emotion in society. With the example of Java, I argue for an expanded understanding of social sentiments that would recognize a structuring role for emotion beyond the family and the shaping, through emotional practices, of a fluid but crucial level of ‘community’. Using Balinese ethnology as a foil, I contrast the uses of emotion in Java and Bali, drawing, toward the end, upon Bateson's concept of schismogenesis.     

课堂教学随笔:谷氨酰胺的氨基

氨基代谢是《生物化学》中"氨基酸代谢"教学的重要内容,谷氨酰胺氨基的去向和利用是其中的重点之一。谷氨酰胺既有α-氨基又有酰胺基,其代谢由不同的酶分别催化,涉及转氨酶、酰胺基转移酶、谷氨酰胺酶、转谷氨酰胺酶等。不同代谢酶作用的基团和机理不同,学生容易混淆它们的作用。本文拟通过讨论几种谷氨酰胺氨基相关代谢酶的作用特点,指导学生掌握谷氨酰胺氨基的代谢。     

CO2 and plants: revisited

The decade-long USA research program on the direct effects of CO₂ enrichment on vegetation has achieved important milestones and has produced a number of interesting and exciting findings. Research beginning in 1980 focused on field experiments to determine whether phenomena observed in the laboratory indeed occurred in natural environments. The answer is yes. Data obtained from numerous field studies show mixed response of crop and native species to CO₂ enrichment however. Nearly all experiments demonstrate that plants exhibit positive gain when grown at elevated CO₂; although the magnitude varies greatly. Most crop responses range from 30 to 50 % increase in yield. Results from long-term experiments with woody species and ecosystems are even more variable. Huge growth responses (100 to nearly 300 % increase relative to controls) are reported from several tree experiments and the salt-marsh ecosystem experiment. Other results from experiments with woody species and the tundra ecosystem suggest little no effect of CO₂ on physiology, growth or productivity. Numerous studies of the physiology of the CO₂ effect are continuing in attempts to understand controlling mechanisms and to explain the variable growth responses. Particular emphasis needs to be given to physiological measures of interactions involving the CO₂ effect and other environmental influences, and to the wide-ranging observations of photosynthesis acclimation to CO₂. Prospects for future research are identified.     

Locating lipids in the CNS: An historical perspective

Localization of lipids in the CNS is considered from an historical perspective. General consideration is given to the identification and separation of different parts of the CNS and to the recognition and detection of lipids. Problems associated with each of these aspects are noted. More treatment is given to the localization of gangliosides and the contributions of Leon Wolfe are highlighted.Special issue dedicated to Dr. Leon S. Wolfe.     

An essay on the evolution of cognition: Constructing a theoretical conceptual framework

In this essay we provide an interdisciplinary approach to the problem of the evolution of human cognition and suggest the theoretical framework of genetic system theory (GST) for organizing the relevant content of several disciplines. This bio-social-cultural theory is based on the assumption that organisms are dynamic systems which interact with one another and their environment and are themselves composed of dynamic internal relations at several levels. Special emphasis will be placed upon these internal cellular and molecular mechanisms underlying the physiological mechanisms of learning and memory. The human individual organism is emphasized because in its experiential activity over time it is the site of integration for social, and cultural stimuli and because of its unique properties among living things. The primary disciplines for our discussion are drawn from the biological, social, and humanistic sciences and several concrete examples are given from each science.     

Micro-evolution in a wine cellar population: An historical perspective

The population ofDrosophila melanogaster inside the wine cellar of Chateau Tahbilk of Victoria, Australia was found by McKenzie and Parsons (1974) to have undergone microevolution for greater alcohol tolerance when compared to the neighboring population outside the cellar. This triggered additional studies at Tahbilk, and at other wine cellars throughout the world. The contributions and interactions of researchers and the development of ideas on the ecology and genetics of this unique experimental system are traced. Although the ADH-F/ADH-S polymorphism was found to be maintained by selection in the Tahbilk populations, the selection is not significantly associated with alcohol tolerance. The environment inside the Tahbilk wine cellar is not as rich in ethanol as was originally anticipated, and selection that affects the alcohol dehydrogenase polymorphism may be more concerned with the relative efficiency with which ethanol is used as a nutrient byD. melanogaster. The synthesis and modification of lipids, particularly in membranes, appears to be important to alcohol tolerance. The studies of the Tahbilk population are at a crossroad. New experimental approaches promise to provide the keys to the selection that maintains the alcohol dehydrogenase polymorphism, and to factors that are important to alcohol tolerance and stress adaptation. From these research foundations at Tahbilk very significant contributions to our future understanding of the genetic processes of evolution can be made.     

Neuronal Glutamine Utilization: Pathways of Nitrogen Transfer tudied with [15N]Glutamine

Gas chromatography-mass spectrometry was used to evaluate the metabolism of [15N]glutamine in isolated rat brain synaptosomes. In the presence of 0.5 mM glutamine, synaptosomes accumulated this amino acid to a level of 25-35 nmol/mg protein at an initial rate greater than 9 nmol/min/mg of protein. The metabolism of [15N]glutamine generated 15N-labelled glutamate, aspartate, and gamma-aminobutyric acid (GABA). An efflux of both [15N]glutamate and [15N]aspartate from synaptosomes to the medium was observed. Enrichment of 15N in alanine could not be detected because of a limited pool size. Elimination of glucose from the incubation medium substantially increased the rate and amount of [15N]aspartate formed. It is concluded that: (1) With 0.5 mM external glutamine, the glutaminase reaction, and not glutamine transport, determines the rate of metabolism of this amino acid. (2) The primary route of glutamine catabolism involves aspartate aminotransferase which generates 2-oxoglutarate, a substrate for the tricarboxylic acid cycle. This reaction is greatly accelerated by the omission of glucose. (3) Glutamine has preferred access to a population of synaptosomes or to a synaptosomal compartment that generates GABA. (4) Synaptosomes maintain a constant internal level of glutamate plus aspartate of about 70-80 nmol/mg protein. As these amino acids are produced from glutamine in excess of this value, they are released into the medium. Hence synaptosomal glutamine and glutamate metabolism are tightly regulated in an interrelated manner.     

Metabolic Consequences of Inhibition of Cerebral Adenosylmethionine Decarboxylase by Methylglyoxal bis(Guanylhydrazone)

Abstract: Effects of intracerebroventricularly injected methylglyoxal bis(guanylhydrazone) on polyamine metabolism in mouse brain were recorded during 180 h after a single dose of 3.4 μmol/kg body weight. Cerebral concentrations of 31 other amino compounds were also asayed during the experiment. The drug caused a significant inhibition of adenosylmethionine decarboxylase that lasted for 50 h, with the maximal decrease, about 70%, occurring between 5 and 10 h after injection. Significant decreases of brain spermidine and spermine concentrations were observed in three phases. Two transient decreases occurred at 10 and at 35 h, and a longer-lasting one between 60 and 100 h. Ornithine decarboxylase was stimulated within 5 h after the injection, reaching a maximal level about 30-fold above normal at 60 h, and returned to control level at 140 h. This stimulation was accompanied by significant accumulation of the reaction product, putrescine, in the brain. It was maximally > 10-fold above normal at 160 h, and was still significantly above control at the end of the observation period. The time course of changes in the parameters of polyamine metabolism was regarded as support of a previously presented hypothesis that limiting putrescine concentration may play a role in the regulation of cerebral polyamine metabolism. In addition, the present results emphasize the possibility that changes in the activities of catabolic reactions may also contribute to the regulation of cerebral polyamine concentrations. Of the 31 amino compounds analyzed, only the concentrations of ornithine, urea, glutamine, and glutamate showed significant changes from normal. Ornithine concentration first was significantly increased at 25 h, whereafter it decreased and was somewhat below normal for most of the period between 60 and 180 h. The urea concentration showed a tendency to increase throughout the experiment, being significantly elevated at the end. These changes were regarded as suggesting that the increased need for ornithine in putrescine synthesis is satisfied mainly by increased arginine uptake and degradation. The magnitude of urea accumulation suggested that metabolism of ornithine to glutamate was also accelerated. An unexpected shift toward glutamine in the glutamine/glutamate relationship was observed during the first 100 h. However, the total concentration of these two compounds was quite constant throughout the experiment. Inhibition of ornithine decarboxylase by intraventricular injection of 2-difluoromethylornithine was tried during the study, but sufficient doses could not be used without induction of acute side effects.     

O2 replenishment to fish nests: males adjust brood care to ambient conditions and brood development

Parental care through nest defense and maintenance enhancesoffspring success. In nature, obligate anemone-dwelling fishesand their nests of benthic eggs are protected against most predatorsby their host anemone; thus, parental care generally consistsof nest tending through fanning and mouthing. Tending in fishesis believed to oxygenate the eggs; however, a real-time linkbetween fanning and oxygenation is tenuous. This study investigatedwhether tending modified the oxygen microenvironment of theembryos and, subsequently, whether tending was modified accordingto ambient dissolved oxygen (DO), increasing metabolic demandsof developing embryos, and water temperature. There was a timelag of approximately 1 s between tending and increases in theamount of oxygen within the nest, demonstrating that DO is directlyaffected by parental tending. While there was evidence of biparentalcare, males invested more time tending embryos (40% initially)than did females (20–30%), and male investment increasedto 70% as embryo development progressed and embryonic metabolicdemands increased. Additionally, male fish adjusted tendingeffort on a diel cycle as ambient DO fluctuated: time spenttending was lowest between 1000 and 1400 h (35%), when ambientDO was highest, and increased throughout the day, reaching apeak of 70% between 2200 and 0200 h, when ambient DO was lowest.Increased water temperature reduced the number of tending boutsper minute throughout the day but did not influence any otheraspect of tending behavior. These results suggest that fishadjust tending behavior coincident to changing conditions inthe nest, both on a daily basis and throughout development ofthe embryos.     

Cerebral metabolism of plasma [14C]palmitate in awake,adult rat: Subcellular localization

Following intravenous injection of [U-¹⁴C]palmitate in awake adult rats, whole brain radioactivity reached a broad maximum between 15–60 min, then declined rapidly to reach a relatively stable level between 4 hr and 20 hr. At 44 hr total radioactivity was 57% of the 4 hr value (p<0.05). About 50% of palmitate which entered the brain from the blood was oxidized rapidly, producing¹⁴C-labeled water-soluble components which later left the cytosol. Radioactivity in the cytosolic fraction peaked at 45 min and then declined, coincident with the decline in total brain radioactivity. Membrane fractions were rapidly labeled to levels which remained relatively stable from 1 to 44 hr. Increases in the relative distributions of radioactivity were seen between 1 and 4 hr for the microsomal and mitochondrial fractions, and beyond 4 hr for the synaptic and myelin membrane fractions (p<0.05). Radioactivity in membrane fractions was 80–90% lipid, 5–13% water-soluble components and 3–17% protein. The proportion of label in membrane-associated protein increased with time. Proportions of radioactivity in the combined membrane fractions increased from 65% to 76% to 80% at 4, 20 and 44 hr, respectively. The results show that plasma-derived palmitate enters oxidative and synthetic pathways to an equal extent, immediately after entry into the brain. At and after 4 hr, the radiolabel resides predominantly in stable membrane lipids and protein. Brain radioactivity at 4 hr can be used therefore, to examine incorporation of palmitate into lipids in vivo, in different experimental conditions.