Mechanisms of Longevity Regulation and Extension in Yeast and Mechanisms Underlying the Anti-Tumor Effect of Lithocholic Acid in Human Neuroblastoma Cells

Aging of multicellular and unicellular eukaryotic organisms is a multifactorial biological phenomenon that has various causes and affects a plethora of cellular activities. I employ the yeast Saccharomyces cerevisiae as a model to study the basic biology and molecular mechanisms of cellular aging in multicellular eukaryotes. The use of this budding yeast as an advantageous model organism in aging research greatly contributed to the current understanding of the molecular and cellular mechanisms underlying longevity regulation in evolutionarily distant eukaryotic organisms, thereby convincingly demonstrating that longevity signaling pathways and mechanisms of their modulation by dietary and pharmacological interventions are conserved across phyla. To address the inherent complexity of aging from a systems perspective and to build an integrative spatiotemporal model of aging process, I investigated the effect of caloric restriction (CR), a low-calorie dietary regimen, on the metabolic history of chronologically aging yeast. CR has been shown not only to exhibit a robust longevity-extending effect in evolutionarily distant organisms ranging from yeast to rhesus monkeys, but also to improve health by attenuating age-related pathologies and delaying the onset of age-related diseases across phyla. I examined how CR influences the age-related dynamics of changes in the intracellular levels of numerous proteins and metabolites, carbohydrate metabolism, interorganellar metabolic flow, concentration of reactive oxygen species (ROS), mitochondrial morphology, essential oxidation-reduction processes in mitochondria, mitochondrial proteome, frequency of mitochondrial DNA mutations, dynamics of mitochondrial nucleoid, susceptibility to mitochondria-controlled apoptosis, and stress resistance. Based on my comparison of the metabolic histories of long-lived CR yeast and short-lived non-CR yeast, I concluded that yeast define their long-term viability by designing a diet-specific pattern of metabolism and organelle dynamics prior to reproductive maturation. My data imply that longevity in chronologically aging yeast is programmed by the level of metabolic capacity and organelle organization they developed, in a diet-specific fashion, prior to entry into a non-proliferative state. Therefore, chronological aging in yeast is the final step of a developmental program progressing through a series of checkpoints. I designed a chemical genetic screen for small molecules that increase the chronological life span (CLS) of yeast under CR by targeting lipid metabolism and modulating housekeeping longevity pathways that regulate longevity irrespective of the number of available calories. My screen identifies lithocholic acid (LCA) as one of such molecules. My evaluation of the life-extending efficacy of LCA in wild-type (WT) strain on a high- or low-calorie diet revealed that this compound extends yeast CLS irrespective of the number of available calories. I found that the extent to which LCA extends longevity is highest under CR conditions, when the pro-aging processes modulated by the adaptable target of rapamycin (TOR) and cAMP/protein kinase A (cAMP/PKA) signaling pathways are suppressed and the anti-aging processes are activated. Furthermore, the life-extending efficacy of LCA in CR yeast significantly exceeded that in yeast on a high-calorie diet, in which the adaptable TOR and cAMP/PKA pathways greatly activate the pro-aging processes and suppress the anti-aging processes. Altogether, my findings suggest that, consistent with its sought-after effect on a longevity signaling network, LCA mostly targets certain housekeeping longevity assurance pathways that do not overlap (or only partially overlap) with the adaptable TOR and cAMP/PKA pathways modulated by calorie availability. Consistent with my assumption that LCA extends longevity not by modulating the adaptable TOR pathway, I found that lack of Tor1p does not impair the life-extending efficacy of LCA under CR. I also revealed that, LCA extends longevity of the tor1 mutant strain to a very similar degree under CR and non-CR conditions. Thus, by eliminating a master regulator of this key adaptable pathway that shortens the CLS of yeast on a high-calorie diet, the tor1 mutation abolished the dependence of the anti-aging efficacy of LCA on the number of available calories. My findings revealed two mechanisms underlying the life-extending effect of LCA in chronologically aging yeast. One mechanism operates in a calorie availability-independent fashion and involves the LCA-governed modulation of housekeeping longevity assurance pathways that do not overlap with the adaptable TOR and cAMP/PKA pathways. The other mechanism extends yeast longevity under non-CR conditions and consists in LCA-driven unmasking of the previously unknown anti-aging potential of PKA. I provide evidence that LCA modulates housekeeping longevity assurance pathways by 1) attenuating mitochondrial fragmentation, a hallmark event of age-related cell death; 2) altering oxidation-reduction processes in mitochondria, including oxygen consumption, the maintenance of membrane potential, and reactive oxygen species production; 3) enhancing resistance to oxidative and thermal stresses; 4) suppressing mitochondria-controlled apoptosis; and 5) enhancing stability of nuclear and mitochondrial DNA. Yeast do not synthesize LCA or any other bile acids produced by mammals. Therefore, I propose that bile acids released into the environment by mammals may act as interspecies chemical signals providing longevity benefits to yeast and, perhaps, other species within an ecosystem. I hypothesize that, because bile acids are known to be mildly toxic compounds, they may create selective pressure for the evolution of yeast species that can respond to the bile acids-induced mild cellular damage by developing the most efficient stress protective mechanisms. It is likely that such mechanisms may provide effective protection of yeast against molecular and cellular damage accumulated with age. Thus, I propose that yeast species that have been selected for the most effective mechanisms providing protection against bile acids may evolve the most effective anti-aging mechanisms that are sensitive to regulation by bile acids. I extend my hypothesis on longevity regulation by bile acids by suggesting a hypothesis of the xenohormetic, hormetic and cytostatic selective forces driving the evolution of longevity regulation mechanisms at the ecosystemic level. To verify my hypothesis empirically, I carried out the LCA-driven multistep selection of long-lived yeast species under laboratory conditions. I found that a lasting exposure of wild-type yeast to LCA results in selection of yeast species that live longer in the absence of this bile acid than their ancestor. My data enabled to rank different concentrations of LCA with respect to the efficiency with which they cause the appearance of long-lived yeast species. Aging is one of the major risk factors in the onset and incidence of cancer, and cancer is considered as one of the numerous age-associated diseases whose onset can be delayed and incidence reduced by anti-aging interventions. The interplay between aging and cancer is intricate as these two complex and dynamic biological phenomena have both convergent and divergent underlying mechanisms. One of the major objectives of my thesis was to examine if LCA, a novel anti-aging compound that I identified in a high-throughput chemical genetic screen, also exhibits an anti-tumor effect in cultured human cancer cells by activating certain anti-cancer processes that may (or may not) play an essential role in cellular aging. As a model system for addressing this important question (and if LCA indeed displays an anti-tumor effect, for establishing the mechanism underlying such effect), I choose several cell lines of the human neuroblastoma (NB) tumor. My findings provide strong evidence that LCA exhibits a potent anti-tumor effect in cultured human NB cells by: 1) activating both intrinsic (mitochondrial) and extrinsic (death receptor) pathways of apoptotic death in these cells; 2) sensitizing them to hydrogen peroxide-induced apoptotic death; and 3) preventing growth and proliferation of their neighbouring NB cells in the culture. Importantly, my findings also imply that LCA does not display any of these deleterious effects in human neurons and, therefore, is a selective anti-tumor compound. Moreover, my mass spectrometry-based measurement of intracellular and extracellular levels of exogenously added LCA revealed that this bile acid does not enter cultured NB cells. Thus, LCA prevents proliferation of human NB cells and selectively kills these cancer cells by binding to their surface and then initiating intracellular signaling cascades that not only impair their growth and division, but also cause their apoptotic death. The demonstrated inability of LCA to enter cultured human NB cells suggests that this potent and selective anti-cancer compound is unlikely to display undesirable side effects in non-cancerous human neurons. My findings suggest a mechanism underlying a potent and selective anti-tumor effect of LCA in human NB cancer cells

Observation-assisted optimal control of quantum dynamics

This paper explores the utility of instantaneous and continuous observations in the optimal control of quantum dynamics. Simulations of the processes are performed on several multilevel quantum systems with the goal of population transfer. Optimal control fields are shown to be capable of cooperating or fighting with observations to achieve a good yield, and the nature of the observations may be optimized to more effectively control the quantum dynamics. Quantum observations also can break dynamical symmetries to increase the controllability of a quantum system. The quantum Zeno and anti-Zeno effects induced by observations are the key operating principles in these processes. The results indicate that quantum observations can be effective tools in the control of quantum dynamics

Xenohormetic, hormetic and cytostatic selective forces driving longevity at the ecosystemic level

We recently found that lithocholic acid (LCA), a bile acid, extends yeast longevity. Unlike mammals, yeast do not synthesize bile acids. We therefore propose that bile acids released into the environment by mammals may act as interspecies chemical signals providing longevity benefits to yeast and, perhaps, other species within an ecosystem

Cosmic Neutrino Pevatrons: A Brand New Pathway to Astronomy, Astrophysics, and Particle Physics

The announcement by the IceCube Collaboration of the observation of 28 cosmic neutrino candidates has been greeted with a great deal of justified excitement. The data reported so far depart by 4.3\sigma from the expected atmospheric neutrino background, which raises the obvious question: "Where in the Cosmos are these neutrinos coming from?" We review the many possibilities which have been explored in the literature to address this question, including origins at either Galactic or extragalactic celestial objects. For completeness, we also briefly discuss new physics processes which may either explain or be constrained by IceCube data.Comment: This is a review article solicited for the inaugural edition of Journal of High Energy Astrophysics (JHEAp). Matching version accepted for publicatio

Stereoselective Lewis Acid Mediated (3+2) Cycloadditions of N-H- and N-Sulfonylaziridines with Heterocumulenes

Alkyl and aryl isothiocyanates and carbodiimides are effective substrates in (3+2) cycloadditions with N-sulfonyl-2-substituted aziridines and 2-phenylaziridine for the synthesis of iminothiazolidines and iminoimidazolidines. Additionally, the stereoselective (3+2) cycloaddition of N-H- and N-sulfonylaziridines with isothiocyanates can be accomplished, allowing for the synthesis of highly enantioenriched iminothiazolidines. Evidence for an intimate ion-pair mechanism is presented herein in the context of these chemo-, regio-, and diastereoselective transformations. The demonstrated ability to remove the sulfonyl group from the heterocyclic products displays the utility of these compounds for further derivatization and application

Lithocholic bile acid selectively kills neuroblastoma cells, while sparing normal neuronal cells

Aging is one of the major risk factors of cancer. The onset of cancer can be postponed by pharmacological and dietary anti-aging interventions. We recently found in yeast cellular models of aging that lithocholic acid (LCA) extends longevity. Here we show that, at concentrations that are not cytotoxic to primary cultures of human neurons, LCA kills the neuroblastoma (NB) cell lines BE(2)-m17, SK-n-SH, SK-n-MCIXC and Lan-1. In BE(2)-m17, SK-n-SH and SK-n-MCIXC cells, the LCA anti-tumor effect is due to apoptotic cell death. In contrast, the LCA-triggered death of Lan-1 cells is not caused by apoptosis. While low concentrations of LCA sensitize BE(2)-m17 and SK-n-MCIXC cells to hydrogen peroxide-induced apoptotic cell death controlled by mitochondria, these LCA concentrations make primary cultures of human neurons resistant to such a form of cell death. LCA kills BE(2)-m17 and SK-n-MCIXC cell lines by triggering not only the intrinsic (mitochondrial) apoptotic cell death pathway driven by mitochondrial outer membrane permeabilization and initiator caspase-9 activation, but also the extrinsic (death receptor) pathway of apoptosis involving activation of the initiator caspase-8. Based on these data, we propose a mechanism underlying a potent and selective anti-tumor effect of LCA in cultured human NB cells. Moreover, our finding that LCA kills cultured human breast cancer and rat glioma cells implies that it has a broad anti-tumor effect on cancer cells derived from different tissues and organisms

Mining Markov Network Surrogates for Value-Added Optimisation

Surrogate fitness functions are a popular technique for speeding up metaheuristics, replacing calls to a costly fitness function with calls to a cheap model. However, surrogates also represent an explicit model of the fitness function, which can be exploited beyond approximating the fitness of solutions. This paper proposes that mining surrogate fitness models can yield useful additional information on the problem to the decision maker, adding value to the optimisation process. An existing fitness model based on Markov networks is presented and applied to the optimisation of glazing on a building facade. Analysis of the model reveals how its parameters point towards the global optima of the problem after only part of the optimisation run, and reveals useful properties like the relative sensitivities of the problem variables

Inter-Hemispheric Coupling During Recent North Polar Summer Periods as Predicted by MaCWAVE/MIDAS Rocket Data and Traced by TIMED/SABER Measurements

In July, 2002, the MaCWAVE-MIDAS Rocket Program was launched from And0ya Rocket Range (ARR) in Norway. Data from these flights demonstrated that the polar summer mesosphere during this period was unusual, at least above ARR. Theoretical studies have since been published that imply that the abnormal characteristics of this polar summer were generated by dynamical processes occurring in the southern polar winter hemisphere. We have used data from the SABER instrument aboard the NASA TIMED Satellite to study these characteristics and compare them with the features observed in the ensuing eight years. For background, the TIMED Satellite was launched on December 7, 2001 to study the dynamics and energy of the mesosphere and lower thermosphere. The SABER instrument is a limb scanning infrared radiometer designed to measure temperature of the region as well as a large number of minor constituents. In this study, we review the MaCWAVE rocket results. Next, we investigate the temperature characteristics of the polar mesosphere as a function of spatial and temporal considerations. We have used the most recent SABER dataset (1.07). Weekly averages are used to make comparisons between the winter and summer hemispheres. Furthermore, the data analysis agrees with recent theoretical studies showing that this behavior is a result of anomalous dynamical events in the southern hemisphere. The findings discussed here clearly show the value of scientific rocket flights used in a discovery mode

3,3'-Diindolylmethane (DIM) and its ring-substituted halogenated analogs (ring-DIMs) induce differential mechanisms of survival and death in androgen-dependent and -independent prostate cancer cells.

International audienceWe recently reported that novel ring-substituted analogs of 3,3'-diindolylmethane (ring-DIMs) induce apoptosis and necrosis in androgen-dependent and -independent prostate cancer cells. In this paper, we have focused on the mechanism(s) associated with ring-DIM-mediated cell death, and on identifying the specific intracellular target(s) of these compounds. The 4,4'- and 7,7'-dichloroDIMs and 4,4'- and 7,7'-dibromoDIMs induced the death of LNCaP, C42B and DU145 prostate cancer cells, but not that of immortalized normal human prostate epithelial (RWPE-1) cells. Ring-DIMs caused the early loss of mitochondrial membrane potential (MMP) and decreased mitochondrial ATP generation in prostate cancer cells. Cyclosporin A, an inhibitor of the mitochondrial permeability transition pore, inhibited ring-DIM-mediated cell death, and salubrinal, an inhibitor of ER stress, inhibited cell death mediated only by 4,4'-dihaloDIMs. We found that although salubrinal did not inhibit the onset of ER stress, it prevented 4,4'-dibromoDIM mediated loss of MMP. Salubrinal potentiated cell death in response to 7,7'-dihaloDIMs and DIM, and this effect concurred with increased loss of MMP. Using in silico 3-D docking affinity analysis, we identified Ca2+/calmodulin-dependent kinase II (CaMKII) as a potential direct target for the most toxic ring-DIM, 4,4'-dibromoDIM. An inhibitor of CaMKII, KN93, but not its inactive analog KN92, abrogated cell death mediated by 4,4'-dibromoDIM. The ring-DIMs induced ER stress and autophagy, but these processes were not necessary for ring-DIM-mediated cell death. Inhibition of autophagy with bafilomycin A1, 3-methyladenine or by LC3B gene silencing sensitized LNCaP and C42B, but not ATG5-deficient DU145 cells to ring-DIM- and DIM-mediated cell death. We propose that autophagy induced by the ring-DIMs and DIM has a cytoprotective function in prostate cancer cells