Publications by authors named "Michelle M Adams"

35 Publications

Short-term dietary restriction maintains synaptic plasticity whereas short-term overfeeding alters cellular dynamics in the aged brain: evidence from the zebrafish model organism.

Neurobiol Aging 2021 10 19;106:169-182. Epub 2021 Jun 19.

Interdisciplinary Program in Neuroscience, Aysel Sabuncu Brain Research Center, Bilkent University, Ankara, Turkey; National Nanotechnology Research Center (UNAM), Bilkent University, Ankara, Turkey; Department of Molecular Biology and Genetics, Zebrafish Facility, Bilkent University, Ankara, Turkey; Department of Psychology, Bilkent University, Ankara, Turkey. Electronic address:

Increased caloric intake (OF) impairs quality of life causing comorbidities with other diseases and cognitive deficits, whereas dietary restriction (DR) increases healthspan by preventing age-related deteriorations. To understand the effects of these opposing dietary regimens on the cellular and synaptic dynamics during brain aging, the zebrafish model, which shows gradual aging like mammals, was utilized. Global changes in cellular and synaptic markers with respect to age and a 12 week dietary regimen of OF and DR demonstrated that aging reduces the levels of the glutamate receptor subunits, GLUR2/3, inhibitory synaptic clustering protein, GEP, synaptic vesicle protein, SYP, and early-differentiated neuronal marker, HuC. DR significantly elevates levels of glutamate receptor subunits, GLUR2/3, and NMDA clustering protein, PSD95, levels, while OF subtly increases the level of the neuronal protein, DCAMKL1. These data suggest that decreased caloric intake within the context of aging has more robust effects on synapses than cellular proteins, whereas OF alters cellular dynamics. Thus, patterns like these should be taken into account for possible translation to human subjects.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neurobiolaging.2021.06.010DOI Listing
October 2021

Environmental enrichment applied with sensory components prevents age-related decline in synaptic dynamics: Evidence from the zebrafish model organism.

Exp Gerontol 2021 07 8;149:111346. Epub 2021 Apr 8.

Interdisciplinary Program in Neuroscience, Aysel Sabuncu Brain Research Center, Bilkent University, Ankara, Turkey; National Nanotechnology Research Center (UNAM), Bilkent University, Ankara, Turkey; Department of Molecular Biology and Genetics, Zebrafish Facility, Bilkent University, Ankara, Turkey; Department of Psychology, Bilkent University, Ankara, Turkey. Electronic address:

Progression of cognitive decline with or without neurodegeneration varies among elderly subjects. The main aim of the current study was to illuminate the molecular mechanisms that promote and retain successful aging in the context of factors such as environment and gender, both of which alter the resilience of the aging brain. Environmental enrichment (EE) is one intervention that may lead to the maintenance of cognitive processing at older ages in both humans and animal subjects. EE is easily applied to different model organisms, including zebrafish, which show similar age-related molecular and behavioral changes as humans. Global changes in cellular and synaptic markers with respect to age, gender and 4-weeks of EE applied with sensory stimulation were investigated using the zebrafish model organism. Results indicated that EE increases brain weight in an age-dependent manner without affecting general body parameters like body mass index (BMI). Age-related declines in the presynaptic protein synaptophysin, AMPA-type glutamate receptor subunits and a post-mitotic neuronal marker were observed and short-term EE prevents these changes in aged animals, as well as elevates levels of the inhibitory scaffolding protein, gephyrin. Gender-driven alterations were observed in the levels of the glutamate receptor subunits. Oxidative stress markers were significantly increased in the old animals, while exposure to EE did not alter this pattern. These data suggest that EE with sensory stimulation exerts its effects mainly on age-related changes in synaptic dynamics, which likely increase brain resilience through specific cellular mechanisms.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.exger.2021.111346DOI Listing
July 2021

Effects of caloric restriction on the antagonistic and integrative hallmarks of aging.

Ageing Res Rev 2021 03 24;66:101228. Epub 2020 Nov 24.

Interdisciplinary Graduate Program in Neuroscience, Aysel Sabuncu Brain Research Center, Bilkent University, Ankara, Turkey; National Nanotechnology Research Center (UNAM), Bilkent University, Ankara, Turkey; Department of Psychology, Bilkent University, Ankara, Turkey. Electronic address:

Aging is a significant risk factor for cognitive decline associated with neurodegenerative diseases, which makes understanding what promotes 'healthy brain aging' very important. Studies suggest that caloric restriction (CR) is a non-genetic intervention that reliably extends life- and healthspan. Here, we review the CR literature related to both the subject of aging and alterations in cell cycle machinery, especially surrounding the regulation of the E2F/DP1 complex, to elucidate the cellular protection mechanisms in the brain induced via dietary applications. The alterations extending lifespan via CR appear to exert their effects by promoting survival of individual cells, downregulating cell proliferation, and inducing stem cell quiescence, which results in keeping the stem cell reserve for extreme needs. This survival instinct of cells is believed to cause some molecular adaptations for their maintenance of the system. Avoiding energy waste of proliferation machinery promotes the long term survival of the individual cells and this is due to adaptations to the limited nutrient supply in the environment. Such a protective mechanism induced by diet could be promoted via the downregulation of crucial cell cycle-related transcription activators. This review article aims to bring attention to the importance of molecular adaptations induced by diet that promote healthy brain aging. It will provide insights into alternative targets for new treatments or neuroprotective approaches against neurodegenerative pathophysiologies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.arr.2020.101228DOI Listing
March 2021

The optomotor response of aging zebrafish reveals a complex relationship between visual motion characteristics and cholinergic system.

Neurobiol Aging 2021 02 23;98:21-32. Epub 2020 Oct 23.

National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey; Interdisciplinary Neuroscience Program, Aysel Sabuncu Brain Research Center, Bilkent University, Ankara, Turkey; Department of Molecular Biology and Genetics Zebrafish Facility, Bilkent University, Ankara, Turkey; National Nanotechnology Research Center (UNAM), Bilkent University, Ankara, Turkey. Electronic address:

Understanding the principles underlying age-related changes in motion perception is paramount for improving the quality of life and health of older adults. However, the mechanisms underlying age-related alterations in this aspect of vision, which is essential for survival in a dynamic world, still remain unclear. Using optomotor responses to drifting gratings, we investigated age-related changes in motion detection of adult zebrafish (wild-type/AB-strain and ache mutants with decreased levels of acetylcholinesterase). Our results pointed out negative optomotor responses that significantly depend on the spatial frequency and contrast level of stimulation, providing supporting evidence for the visual motion-driven aspect of this behavior mainly exhibited by adult zebrafish. Although there were no significant main effects of age and genotype, we found a significant three-way interaction between contrast level, age, and genotype. In the contrast domain, the changes in optomotor responses and thus in the detection of motion direction were age- and genotype-specific. Accordingly, these behavioral findings suggest a strong but complicated relationship between visual motion characteristics and the cholinergic system during neural aging.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neurobiolaging.2020.10.018DOI Listing
February 2021

Zebrafish brain RNA sequencing reveals that cell adhesion molecules are critical in brain aging.

Neurobiol Aging 2020 10 12;94:164-175. Epub 2020 May 12.

Stem Cell Research and Application Center, Hacettepe University, Ankara, Turkey. Electronic address:

Brain aging is a complex process, which involves multiple pathways including various components from cellular to molecular. This study aimed to investigate the gene expression changes in zebrafish brains through young-adult to adult, and adult to old age. RNA sequencing was performed on isolated neuronal cells from zebrafish brains. The cells were enriched in progenitor cell markers, which are known to diminish throughout the aging process. We found 176 statistically significant, differentially expressed genes among the groups, and identified a group of genes based on gene ontology descriptions, which were classified as cell adhesion molecules. The relevance of these genes was further tested in another set of zebrafish brains, human healthy, and Alzheimer's disease brain samples, as well as in Allen Brain Atlas data. We observed that the expression change of 2 genes, GJC2 and ALCAM, during the aging process was consistent in all experimental sets. Our findings provide a new set of markers for healthy brain aging and suggest new targets for therapeutic approaches to neurodegenerative diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neurobiolaging.2020.04.017DOI Listing
October 2020

Dietary and Pharmacological Interventions That Inhibit Mammalian Target of Rapamycin Activity Alter the Brain Expression Levels of Neurogenic and Glial Markers in an Age-and Treatment-Dependent Manner.

Rejuvenation Res 2020 Dec 19;23(6):485-497. Epub 2020 May 19.

Interdisciplinary Graduate Program in Neuroscience, Aysel Sabuncu Brain Research Center, Bilkent University, Ankara, Turkey.

Intermittent fasting (IF) and its mimetic, rapamycin extend lifespan and healthspan through mechanisms that are not fully understood. We investigated different short-term durations of IF and rapamycin on cellular and molecular changes in the brains of young (6-10 months) and old (26-31 months) zebrafish. Interestingly, our results showed that IF significantly lowered glucose levels while increasing DCAMKL1 in both young and old animals. This proliferative effect of IF was supported by the upregulation of transcript in old animals. Rapamycin did not change glucose levels in young and old animals but had differential effects depending on age. In young zebrafish, proliferating cell nuclear antigen and the LC3-II/LC3-I ratio was decreased, whereas glial fibrillary acidic protein and gephyrin were decreased in old animals. The changes in proliferative markers and a marker of autophagic flux suggest an age-dependent interplay between autophagy and cell proliferation. Additionally, changes in glia and inhibitory tone suggest a suppressive effect on neuroinflammation but may push the brain toward a more excitable state. Mammalian target of rapamycin (mTOR) activity in the brain following the IF and rapamycin treatment was differentially regulated by age. Interestingly, rapamycin inhibited mTOR more potently in young animals than IF. Principal component analysis supported our conclusion that the regulatory effects of IF and rapamycin were age-specific, since we observed different patterns in the expression levels and clustering of young and old animals. Taken together, our results suggest that even a short-term duration of IF and rapamycin have significant effects in the brain at young and old ages, and that these are age and treatment dependent.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1089/rej.2019.2297DOI Listing
December 2020

Expression Levels of SMAD Specific E3 Ubiquitin Protein Ligase 2 (Smurf2) and its Interacting Partners Show Region-specific Alterations During Brain Aging.

Neuroscience 2020 06 8;436:46-73. Epub 2020 Apr 8.

Interdisciplinary Program in Neuroscience, Aysel Sabuncu Brain Research Center, Bilkent University, Ankara, Turkey; National Nanotechnology Research Center (UNAM), Bilkent University, Ankara, Turkey; Department of Molecular Biology and Genetics, Zebrafish Facility, Bilkent University, Ankara, Turkey; Department of Psychology, Bilkent University, Ankara, Turkey. Electronic address:

Aging occurs due to a combination of several factors, such as telomere attrition, cellular senescence, and stem cell exhaustion. The telomere attrition-dependent cellular senescence is regulated by increased levels of SMAD specific E3 ubiquitin protein ligase 2 (smurf2). With age smurf2 expression increases and Smurf2 protein interacts with several regulatory proteins including, Smad7, Ep300, Yy1, Sirt1, Mdm2, and Tp53, likely affecting its function related to cellular aging. The current study aimed at analyzing smurf2 expression in the aged brain because of its potential regulatory roles in the cellular aging process. Zebrafish were used because like humans they age gradually and their genome has 70% similarity. In the current study, we demonstrated that smurf2 gene and protein expression levels altered in a region-specific manner during the aging process. Also, in both young and old brains, Smurf2 protein was enriched in the cytosol. These results imply that during aging Smurf2 is regulated by several mechanisms including post-translational modifications (PTMs) and complex formation. Also, the expression levels of its interacting partners defined by the STRING database, tp53, mdm2, ep300a, yy1a, smad7, and sirt1, were analyzed. Multivariate analysis indicated that smurf2, ep300a, and sirt1, whose proteins regulate ubiquitination, acetylation, and deacetylation of target proteins including Smad7 and Tp53, showed age- and brain region-dependent patterns. Our data suggest a likely balance between Smurf2- and Mdm2-mediated ubiquitination, and Ep300a-mediated acetylation/Sirt1-mediated deacetylation, which most possibly affects the functionality of other interacting partners in regulating cellular and synaptic aging and ultimately cognitive dysfunction.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuroscience.2020.04.003DOI Listing
June 2020

Zebrafish-A Model Organism for Studying the Neurobiological Mechanisms Underlying Cognitive Brain Aging and Use of Potential Interventions.

Front Cell Dev Biol 2018 1;6:135. Epub 2018 Nov 1.

Interdisciplinary Neuroscience Program, Aysel Sabuncu Brain Research Center, Bilkent University, Ankara, Turkey.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fcell.2018.00135DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6221905PMC
November 2018

Development of a novel zebrafish xenograft model in ache mutants using liver cancer cell lines.

Sci Rep 2018 01 25;8(1):1570. Epub 2018 Jan 25.

Department of Molecular Biology and Genetics, Bilkent University, 06800, Ankara, Turkey.

Acetylcholinesterase (AChE), an enzyme responsible for degradation of acetylcholine, has been identified as a prognostic marker in liver cancer. Although in vivo Ache tumorigenicity assays in mouse are present, no established liver cancer xenograft model in zebrafish using an ache mutant background exists. Herein, we developed an embryonic zebrafish xenograft model using epithelial (Hep3B) and mesenchymal (SKHep1) liver cancer cell lines in wild-type and ache sibling mutant larvae after characterization of cholinesterase expression and activity in cell lines and zebrafish larvae. The comparison of fluorescent signal reflecting tumor size at 3-days post-injection (dpi) revealed an enhanced tumorigenic potential and a reduced migration capacity in cancer cells injected into homozygous ache mutants when compared with the wild-type. Increased tumor load was confirmed using an ALU based tumor DNA quantification method modified for use in genotyped xenotransplanted zebrafish embryos. Confocal microscopy using the Huh7 cells stably expressing GFP helped identify the distribution of tumor cells in larvae. Our results imply that acetylcholine accumulation in the microenvironment directly or indirectly supports tumor growth in liver cancer. Use of this model system for drug screening studies holds potential in discovering new cholinergic targets for treatment of liver cancers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-018-19817-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5785479PMC
January 2018

A Novel, Low-Cost Anesthesia and Injection System for Zebrafish Researchers.

Zebrafish 2018 04 20;15(2):85-95. Epub 2017 Dec 20.

2 Interdisciplinary Graduate Program in Neuroscience, Aysel Sabuncu Brain Research Center, Bilkent University , Ankara, Turkey .

In this study, we designed and developed a novel low-cost system for anesthetizing and injecting adult zebrafish. The system utilizes a gradual cooling method for the anesthesia and maintains the fish in a stable anesthetic plane, as well as stabilizes the animal so that intraperitoneal injections can be consistently performed. It is a system that any laboratory with access to a workshop can build for their group. Moreover, it is a safe system for researchers, as well as a reliable one for repeated experiments since multiple fish can be injected quickly and there is little physical contact necessary between the investigator and the animal. This will likely reduce any unnecessary stress in the fish, as compared with manual methods of injection. Finally, the system is adaptable so that as the investigators' procedural needs change due to different research questions, that is, gradual rewarming or something of that nature, it could be modified.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1089/zeb.2017.1513DOI Listing
April 2018

Aging alters the molecular dynamics of synapses in a sexually dimorphic pattern in zebrafish (Danio rerio).

Neurobiol Aging 2017 06 20;54:10-21. Epub 2017 Feb 20.

Interdisciplinary Graduate Program in Neuroscience, Aysel Sabuncu Brain Research Center, Bilkent University, Ankara, Turkey; UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara, Turkey; Department of Molecular Biology and Genetics Zebrafish Facility, Bilkent University, Ankara, Turkey; Department of Psychology, Bilkent University, Ankara, Turkey. Electronic address:

The zebrafish has become a popular model for studying normal brain aging due to its large fecundity, conserved genome, and available genetic tools; but little data exists about neurobiological age-related alterations. The current study tested the hypothesis of an association between brain aging and synaptic protein loss across males and females. Western blot analysis of synaptophysin (SYP), a presynaptic vesicle protein, and postsynaptic density-95 (PSD-95) and gephyrin (GEP), excitatory and inhibitory postsynaptic receptor-clustering proteins, respectively, was performed in young, middle-aged, and old male and female zebrafish (Danio rerio) brains. Univariate and multivariate analyses demonstrated that PSD-95 significantly increased in aged females and SYP significantly decreased in males, but GEP was stable. Thus, these key synaptic proteins vary across age in a sexually dimorphic manner, which has been observed in other species, and these consequences may represent selective vulnerabilities for aged males and females. These data expand our knowledge of normal aging in zebrafish, as well as further establish this model as an appropriate one for examining human brain aging.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neurobiolaging.2017.02.007DOI Listing
June 2017

Short-term dietary restriction in old zebrafish changes cell senescence mechanisms.

Neuroscience 2016 Oct 28;334:64-75. Epub 2016 Jul 28.

Bilkent University, Interdisciplinary Neuroscience Program, Ankara, Turkey; Bilkent University, Molecular Biology and Genetics Department Zebrafish Facility, Ankara, Turkey; Bilkent University, UNAM-Institute of Materials Science and Nanotechnology, Ankara, Turkey; Bilkent University, Department of Psychology, Ankara, Turkey; Bilkent University, Aysel Sabuncu Brain Research Center, Ankara, Turkey. Electronic address:

Brain aging is marked by a decline in cognitive abilities and associated with neurodegenerative disorders. Recent studies have shown, neurogenesis continues into adulthood but is known to be decreasing during advancing age and these changes may contribute to cognitive alterations. Advances, which aim to promote better aging are of paramount importance. Dietary restriction (DR) is the only non-genetic intervention that reliably extends life- and health-span. Mechanisms of how and why DR and age affect neurogenesis are not well-understood, and have not been utilized much in the zebrafish, which has become a popular model to study brain aging and neurodegenerative disease due to widely available genetic tools. In this study we used young (8-8.5months) and old (26-32.5months) zebrafish as the model to investigate the effects of a short-term DR on actively proliferating cells. We successfully applied a 10-week DR to young and old fish, which resulted in a significant loss of body weight in both groups with no effect on normal age-related changes in body growth. We found that age decreased cell proliferation and increased senescence associated β-galactosidase, as well as shortened telomere lengths. In contrast, DR shortened telomere lengths only in young animals. Neither age nor DR changed the differentiation patterns of glial cells. Our results suggest that the potential effects of DR could be mediated by telomere regulation and whether these are beneficial or negative remains to be determined.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuroscience.2016.07.033DOI Listing
October 2016

Characterization of a novel zebrafish (Danio rerio) gene, wdr81, associated with cerebellar ataxia, mental retardation and dysequilibrium syndrome (CAMRQ).

BMC Neurosci 2015 12 23;16(1):96. Epub 2015 Dec 23.

UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara, Turkey.

Background: WDR81 (WD repeat-containing protein 81) is associated with cerebellar ataxia, mental retardation and disequilibrium syndrome (CAMRQ2, [MIM 610185]). Human and mouse studies suggest that it might be a gene of importance during neurodevelopment. This study aimed at fully characterizing the structure of the wdr81 transcript, detecting the possible transcript variants and revealing its expression profile in zebrafish, a powerful model organism for studying development and disease.

Results: As expected in human and mouse orthologous proteins, zebrafish wdr81 is predicted to possess a BEACH (Beige and Chediak-Higashi) domain, a major facilitator superfamily domain and WD40-repeats, which indicates a conserved function in these species. We observed that zebrafish wdr81 encodes one open reading frame while the transcript has one 5' untranslated region (UTR) and the prediction of the 3' UTR was mainly confirmed along with a detected insertion site in the embryo and adult brain. This insertion site was also found in testis, heart, liver, eye, tail and muscle, however, there was no amplicon in kidney, intestine and gills, which might be the result of possible alternative polyadenylation processes among tissues. The 5 and 18 hpf were critical timepoints of development regarding wdr81 expression. Furthermore, the signal of the RNA probe was stronger in the eye and brain at 18 and 48 hpf, then decreased at 72 hpf. Finally, expression of wdr81 was detected in the adult brain and eye tissues, including but not restricted to photoreceptors of the retina, presumptive Purkinje cells and some neurogenic brains regions.

Conclusions: Taken together these data emphasize the importance of this gene during neurodevelopment and a possible role for neuronal proliferation. Our data provide a basis for further studies to fully understand the function of wdr81.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s12868-015-0229-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4690267PMC
December 2015

Gene expression changes in aging zebrafish (Danio rerio) brains are sexually dimorphic.

BMC Neurosci 2014 Feb 18;15:29. Epub 2014 Feb 18.

BilGen Genetics and Biotechnology Center, Bilkent University, Ankara, Turkey.

Background: Brain aging is a multi-factorial process due to both genetic and environmental factors. The zebrafish has recently become a popular model organism for examining aging and age-related diseases because as in humans they age gradually and exhibit cognitive decline. Few studies have examined the biological changes in the aging brain that may contribute to these declines and none have examined them within individuals with respect to gender. Our aim was to identify the main genetic pathways associated with zebrafish brain aging across gender. We chose males and females from specific age groups (young, 7.5-8.5 months and old, 31-36 months) based on the progression of cognitive decline in zebrafish. RNA was isolated from individual brains and subjected to microarray and qPCR analysis. Statistical analyses were performed using a two-way ANOVA and the relevant post-hoc tests.

Results: Our results demonstrated that in the brains of young and old male and female zebrafish there were over 500 differentially expressed genes associated with multiple pathways but most notably were those related to neurogenesis and cell differentiation, as well as brain and nervous system development.

Conclusions: The gene expression of multiple pathways is altered with age and differentially expressed in males and females. Future studies will be aimed at determining the causal relationships of age-related changes in gene expression in individual male and female brains, as well as possible interventions that counteract these alterations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/1471-2202-15-29DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3937001PMC
February 2014

Aging, neurogenesis, and caloric restriction in different model organisms.

Aging Dis 2013 Aug 17;4(4):221-32. Epub 2013 Jun 17.

BilGen Genetics and Biotechnology Center, Bilkent University, Ankara, 06800 Turkey ; Department of Molecular Biology and Genetics, Bilkent University, Ankara, 06800 Turkey ; Department of Psychology, Bilkent University, Ankara, 06800 Turkey.

Brain aging is a multifactorial process that is occurring across multiple cognitive domains. A significant complaint that occurs in the elderly is a decrement in learning and memory ability. Both rodents and zebrafish exhibit a similar problem with memory during aging. The neurobiological changes that underlie this cognitive decline are complex and undoubtedly influenced by many factors. Alterations in the birth of new neurons and neuron turnover may contribute to age-related cognitive problems. Caloric restriction is the only non-genetic intervention that reliably increases life span and healthspan across multiple organisms although the molecular mechanisms are not well-understood. Recently the zebrafish has become a popular model organism for understanding the neurobiological consequences but to date very little work has been performed. Similarly, few studies have examined the effects of dietary restriction in zebrafish. Here we review the literature related to memory decline, neurogenesis, and caloric restriction across model organisms and suggest that zebrafish has the potential to be an important animal model for understanding the complex interactions between age, neurobiological changes in the brain, and dietary regimens or their mimetics as interventions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3733585PMC
August 2013

Synthesis and preclinical evaluation of QS-21 variants leading to simplified vaccine adjuvants and mechanistic probes.

J Am Chem Soc 2012 Aug 6;134(32):13448-57. Epub 2012 Aug 6.

Pharmacology Program, Weill Cornell Graduate School of Medical Sciences, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York 10065, USA.

QS-21 is a potent immunostimulatory saponin that is currently under clinical investigation as an adjuvant in various vaccines to treat infectious diseases, cancers, and cognitive disorders. Herein, we report the design, synthesis, and preclinical evaluation of simplified QS-21 congeners to define key structural features that are critical for adjuvant activity. Truncation of the linear tetrasaccharide domain revealed that a trisaccharide variant is equipotent to QS-21, while the corresponding disaccharide and monosaccharide congeners are more toxic and less potent, respectively. Modification of the acyl chain domain in the trisaccharide series revealed that a terminal carboxylic acid is well-tolerated while a terminal amine results in reduced adjuvant activity. Acylation of the terminal amine can, in some cases, restore adjuvant activity and enables the synthesis of fluorescently labeled QS-21 variants. Cellular studies with these probes revealed that, contrary to conventional wisdom, the most highly adjuvant active of these fluorescently labeled saponins does not simply associate with the plasma membrane, but rather is internalized by dendritic cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ja305121qDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3436428PMC
August 2012

Growth hormone and insulin-like growth factor-I alter hippocampal excitatory synaptic transmission in young and old rats.

Age (Dordr) 2013 Oct 1;35(5):1575-87. Epub 2012 Aug 1.

Departments of Neurobiology and Anatomy, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC, 27157-1010, USA.

In rats, as in humans, normal aging is characterized by a decline in hippocampal-dependent learning and memory, as well as in glutamatergic function. Both growth hormone (GH) and insulin-like growth factor-I (IGF-I) levels have been reported to decrease with age, and treatment with either GH or IGF-I can ameliorate age-related cognitive decline. Interestingly, acute GH and IGF-I treatments enhance glutamatergic synaptic transmission in the rat hippocampus of juvenile animals. However, whether this enhancement also occurs in old rats, when cognitive impairment is ameliorated by GH and IGF-I (des-IGF-I), remains to be determined. To address this issue, we used an in vitro CA1 hippocampal slice preparation and extracellular recording techniques to study the effects of acute application of GH and IGF-I on compound field excitatory postsynaptic potentials (fEPSPs), as well as AMPA- and NMDA-dependent fEPSPs, in young adult (10 months) and old (28 months) rats. The results indicated that both GH and IGF-I increased compound-, AMPA-, and NMDA-dependent fEPSPs to a similar extent in slices from both age groups and that this augmentation was likely mediated via a postsynaptic mechanism. Initial characterization of the signaling cascades underlying these effects revealed that the GH-induced enhancement was not mediated by the JAK2 signaling element in either young adult or old rats but that the IGF-I-induced enhancement involved a PI3K-mediated mechanism in old, but not young adults. The present findings are consistent with a role for a GH- or IGF-I-induced enhancement of glutamatergic transmission in mitigating age-related cognitive impairment in old rats.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11357-012-9460-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3776110PMC
October 2013

Growth hormone modulates hippocampal excitatory synaptic transmission and plasticity in old rats.

Neurobiol Aging 2012 Sep 19;33(9):1938-49. Epub 2011 Oct 19.

Department of Neurobiology, Wake Forest University School of Medicine, Winston-Salem, NC, USA.

Alterations in the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor (AMPA-R) and N-methyl-D-aspartate receptor (NMDA-R) have been documented in aged animals and may contribute to changes in hippocampal-dependent memory. Growth hormone (GH) regulates AMPA-R and NMDA-R-dependent excitatory transmission and decreases with age. Chronic GH treatment mitigates age-related cognitive decline. An in vitro CA1 hippocampal slice preparation was used to compare hippocampal excitatory transmission and plasticity in old animals treated for 6-8 months with either saline or GH. Our findings indicate that GH treatment restores NMDA-R-dependent basal synaptic transmission in old rats to young adult levels and enhances both AMPA-R-dependent basal synaptic transmission and long-term potentiation. These alterations in synaptic function occurred in the absence of changes in presynaptic function, as measured by paired-pulse ratios, the total protein levels of AMPA-R and NMDA-R subunits or in plasma or hippocampal levels of insulin-like growth factor-I. These data suggest a direct role for GH in altering age-related changes in excitatory transmission and provide a possible cellular mechanism through which GH changes the course of cognitive decline.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neurobiolaging.2011.09.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3266474PMC
September 2012

Serum albumins as differential receptors for the discrimination of fatty acids and oils.

Org Lett 2010 Nov;12(21):4780-3

Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A5300, Austin, Texas 78712, United States.

Using fluorescent indicators and several serum albumins, a sensing system for fatty acids was developed. Fatty acids were able to be differentiated based on their carbon chain length and degree of unsaturation. A sensing ensemble was then applied to study complex mixtures of triglycerides, namely, edible oils. The oils, with different fatty acid compositions, were successfully differentiated using principal component analysis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ol101906gDOI Listing
November 2010

A highly selective low-background fluorescent imaging agent for nitric oxide.

J Am Chem Soc 2010 Sep;132(38):13114-6

Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA.

We introduce a novel sensing mechanism for nitric oxide (NO) detection with a particular easily synthesized embodiment (NO(550)), which displays a rapid and linear response to NO with a red-shifted 1500-fold turn-on signal from a dark background. Excellent selectivity was observed against other reactive oxygen/nitrogen species, pH, and various substances that interfere with existing probes. NO(550) crosses cell membranes but not nuclear membranes and is suitable for both intra- and extracellular NO quantifications. Good cytocompatibility was found during in vitro studies with two different cell lines. The high specificity, dark background, facile synthesis, and low pH dependence make NO(550) a superior probe for NO detection when used as an imaging agent.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ja1040013DOI Listing
September 2010

Preclinical evaluation of the synthetic adjuvant SQS-21 and its constituent isomeric saponins.

Vaccine 2010 Jun 5;28(26):4260-7. Epub 2010 May 5.

Laboratory of Tumor Vaccinology, Melanoma and Sarcoma Service, Department of Medicine, 1275 York Avenue, New York, NY 10065, USA.

The saponin fraction QS-21 from Quillaja saponaria has been demonstrated to be a potent immunological adjuvant when mixed with keyhole limpet hemocyanin conjugate vaccines, as well as with other classes of subunit antigen vaccines. QS-21 adjuvant is composed of two isomers that include the apiose and xylose forms in a ratio of 65:35, respectively. The chemical syntheses of these two isomers in pure form have recently been disclosed. Herein we describe detailed in vivo immunological evaluations of these synthetic QS-21 isomeric constituents, employing the GD3-KLH melanoma antigen. With this vaccine construct, high antibody titers against GD3 ganglioside and KLH were elicited when GD3-KLH was co-administered with adjuvant, either as the individual separate synthetic QS-21 isomers (SQS-21-Api or SQS-21-Xyl), or as its reconstituted 65:35 isomeric mixture (SQS-21). These antibody titer levels were comparable to that elicited by vaccinations employing naturally derived QS-21 (PQS-21). Moreover, toxicities of the synthetic saponin adjuvants were also found to be comparable to that of naturally derived PQS-21. These findings demonstrate unequivocally that the adjuvant activity of QS-21 resides in these two principal isomeric forms, and not in trace contaminants within the natural extracts. This lays the foundation for future exploration of structure-function correlations to enable the discovery of novel saponins with increased potency, enhanced stability, and attenuated toxicity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.vaccine.2010.04.034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2882175PMC
June 2010

Design and synthesis of potent Quillaja saponin vaccine adjuvants.

J Am Chem Soc 2010 Feb;132(6):1939-45

Molecular Pharmacology and Chemistry Program, and the Melanoma and Sarcoma Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York 10065, USA.

The success of antitumor and antiviral vaccines often requires the use of an adjuvant, a substance that significantly enhances the immune response to a coadministered antigen. Only a handful of adjuvants have both sufficient potency and acceptable toxicity for clinical investigation. One promising adjuvant is QS-21, a saponin natural product that is the immunopotentiator of choice in many cancer and infectious disease vaccine clinical trials. However, the therapeutic promise of QS-21 adjuvant is curtailed by several factors, including its scarcity, difficulty in purification to homogeneity, dose-limiting toxicity, and chemical instability. Here, we report the design, synthesis, and evaluation of chemically stable synthetic saponins. These novel, amide-modified, non-natural substances exhibit immunopotentiating effects in vivo that rival or exceed that of QS-21 in evaluations with the GD3-KLH melanoma conjugate vaccine. The highly convergent synthetic preparation of these novel saponins establishes new avenues for discovering improved molecular adjuvants for specifically tailored vaccine therapies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ja9082842DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2820154PMC
February 2010

Differential sensing using proteins: exploiting the cross-reactivity of serum albumin to pattern individual terpenes and terpenes in perfume.

J Am Chem Soc 2009 Dec;131(47):17068-9

Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712, USA.

There has been a growing interest in the use of differential sensing for analyte classification. In an effort to mimic the mammalian senses of taste and smell, which utilize protein-based receptors, we have introduced serum albumins as nonselective receptors for recognition of small hydrophobic molecules. Herein, we employ a sensing ensemble consisting of serum albumins, a hydrophobic fluorescent indicator (PRODAN), and a hydrophobic additive (deoxycholate) to detect terpenes. With the aid of linear discriminant analysis, we successfully applied our system to differentiate five terpenes. We then extended our terpene analysis and utilized our sensing ensemble for terpene discrimination within the complex mixtures found in perfume.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ja908319mDOI Listing
December 2009

Stability of local brain levels of insulin-like growth factor-I in two well-characterized models of decreased plasma IGF-I.

Growth Factors 2009 Jun;27(3):181-8

Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1010, USA.

Insulin-like growth factor-I (IGF-I), a functionally important neurotrophic factor, impacts tissues throughout the body including the central nervous system. In addition to the significant proportion of IGF-I that is synthesized in the liver and released into the plasma, IGF-I is expressed locally in tissues. The present study investigated the relationship between plasma and local brain levels of IGF-I in two well-characterized models of decreased IGF-I. The first is an adult-onset growth hormone deficiency (AOGHD) model, and the second is a caloric restriction (CR) model. In the first cohort of animals from both models, the hippocampus was removed from the brain immediately following decapitation, and in the second cohort, the animals were perfused transcardially with phosphate buffered saline to remove cerebral blood prior to harvesting the hippocampus. Our results demonstrated that although the plasma IGF-I levels were decreased in the CR and AOGHD rats compared to controls, the hippocampal IGF-I levels did not differ among the groups. These data suggest that local brain IGF-I levels are regulated in a different manner than plasma IGF-I levels.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/08977190902863639DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3085503PMC
June 2009

Synthesis and structure verification of the vaccine adjuvant QS-7-Api. Synthetic access to homogeneous Quillaja saponaria immunostimulants.

J Am Chem Soc 2008 May 15;130(18):5860-1. Epub 2008 Apr 15.

Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York 10065, USA.

QS-7-Api is an exceedingly potent immuno-adjuvant isolated from the bark of Quillaja saponaria. It is significantly less toxic than QS-21, a related saponin that is currently the favored adjuvant in anticancer and antiviral vaccine clinical trials. Tedious isolation/purification protocols and uncertainty in its structural constitution have hindered the clinical development of QS-7. A chemical synthesis of QS-7-Api is described, providing structural verification of the adjuvant. A novel semisynthetic sequence to QS-7-Api has also been established, greatly facilitating access to QS-7 for preclinical and clinical evaluation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ja801008mDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2610460PMC
May 2008

Caloric restriction and age affect synaptic proteins in hippocampal CA3 and spatial learning ability.

Exp Neurol 2008 May 8;211(1):141-9. Epub 2008 Feb 8.

Department of Neurobiology and Anatomy, Wake Forest University Health Sciences, Winston-Salem, NC 27157, USA.

Caloric restriction (CR) is a daily reduction of total caloric intake without a decrease in micronutrients or disproportionate reduction of any one dietary component. CR can increase lifespan reliably in a wide range of species and appears to counteract some aspects of the aging process throughout the body. The effects on the brain are less clear, but moderate CR seems to attenuate age-related cognitive decline. Thus, we determined the effects of age and CR on key synaptic proteins in the CA3 region of the hippocampus and whether these changes were correlated with differences in behavior on a hippocampal-dependent learning and memory task. We observed an overall, age-related decline in the NR1, N2A and N2B subunits of the N-methyl-d-aspartate (NMDA)-type and the GluR1 and GluR2 subunits of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (AMPA)-type ionotropic glutamate receptors. Interestingly, we found that CR initially lowers the glutamate receptor subunit levels as compared to young AL animals, and then stabilizes the levels across lifespan. Synaptophysin, a presynaptic vesicle protein, showed a similar pattern. We also found that both CR and ad libitum (AL) fed animals exhibited age-related cognitive decline on the Morris water maze task. However, AL animals declined between young and middle age, and between middle age and old, whereas CR rats only declined between young and middle age. Thus, the decrease in key synaptic proteins in CA3 and cognitive decline occurring across lifespan are stabilized by CR. This age-related decrease and CR-induced stabilization are likely to affect CA3 synaptic plasticity and, as a result, hippocampal function.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.expneurol.2008.01.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2805131PMC
May 2008

Caloric restriction eliminates the aging-related decline in NMDA and AMPA receptor subunits in the rat hippocampus and induces homeostasis.

Exp Neurol 2007 Jul 4;206(1):70-9. Epub 2007 Apr 4.

Department of Neurobiology and Anatomy, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157-1010, USA.

Caloric restriction (CR) extends life span and ameliorates the aging-related decline in hippocampal-dependent cognitive function. In the present study, we compared subunit levels of NMDA and AMPA types of the glutamate receptor and quantified total synapses and multiple spine bouton (MSB) synapses in hippocampal CA1 from young (10 months), middle-aged (18 months), and old (29 months) Fischer 344xBrown Norway rats that were ad libitum (AL) fed or caloric restricted (CR) from 4 months of age. Each of these parameters has been reported to be a potential contributor to hippocampal function. Western blot analysis revealed that NMDA and AMPA receptor subunits in AL animals decrease between young and middle age to levels that are present at old age. Interestingly, young CR animals have significantly lower levels of glutamate receptor subunits than young AL animals and those lower levels are maintained across life span. In contrast, stereological quantification indicated that total synapses and MSB synapses are stable across life span in both AL and CR rats. These results indicate significant aging-related losses of hippocampal glutamate receptor subunits in AL rats that are consistent with altered synaptic function. CR eliminates that aging-related decline by inducing stable NMDA and AMPA receptor subunit levels.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.expneurol.2007.03.026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2805133PMC
July 2007

Spatial learning and memory deficits after whole-brain irradiation are associated with changes in NMDA receptor subunits in the hippocampus.

Radiat Res 2006 Dec;166(6):892-9

Department of Neurobiology and Anatomy, Wake Forest University Health Sciences, Winston-Salem, North Carolina 27157, USA.

Whole-brain irradiation is used for the treatment of brain tumors, but can it also induce neural changes, with progressive dementia occurring in 20-50% of long-term survivors. The present study investigated whether 45 Gy of whole-brain irradiation delivered to 12-month-old Fischer 344 x Brown Norway rats as nine fractions over 4.5 weeks leads to impaired Morris water maze (MWM) performance 12 months later. Compared to sham-irradiated rats, the irradiated rats demonstrated impaired MWM performance. The relative levels of the NR1 and NR2A but not the NR2B subunits of the NMDA receptor were significantly higher in hippocampal CA1 of irradiated rats compared to control rats. No significant differences were detected for these NMDA subunits in CA3 or dentate gyrus. Further analysis of CA1 revealed that the relative levels of the GluR1 and GluR2 subunits of the AMPA receptor and synaptophysin were not altered by whole-brain irradiation. In summary, a clinically relevant regimen of fractionated whole-brain irradiation led to significant impairments in spatial learning and reference memory and alterations in the relative levels of subunits of the NMDA, but not the AMPA, receptors in hippocampal CA1. These findings suggest for the first time that radiation-induced cognitive impairments may be associated with alterations in glutamate receptor composition.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1667/RR0588.1DOI Listing
December 2006

Functional characterization of des-IGF-1 action at excitatory synapses in the CA1 region of rat hippocampus.

J Neurophysiol 2005 Jul;94(1):247-54

Department of Physiology, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, North Carolina 27157-1083, USA.

Insulin-like growth factor-1 (IGF-1) and growth hormone play a major role in the growth and development of tissues throughout the mammalian body. Plasma IGF-1 concentrations peak during puberty and decline with age. We have determined that chronic treatments to restore plasma IGF-1 concentrations to adult levels attenuate spatial learning deficits in aged rats, but little is known of the acute actions of IGF-1 in the brain. To this end, we utilized hippocampal slices from young Sprague-Dawley rats to characterize the acute effects of des-IGF-1 on excitatory synaptic transmission in the CA1 region. We observed a 40% increase in field excitatory postsynaptic potential (fEPSP) slope with application of des-IGF-1 (40 ng/ml) and used whole cell patch-clamp recordings to determine that this enhancement was due to a postsynaptic mechanism involving alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate (AMPA) but not N-methyl-D-aspartate receptors. Furthermore, the enhancement was completely blocked by the broad-spectrum tyrosine kinase inhibitor, genistein (220 microM), and significantly reduced by the PI3K blockers wortmannin (1 microM) and 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (10 microM), suggesting that the effect was predominantly dependent on PI3K activation. This characterization of the acute actions of des-IGF-1 at hippocampal excitatory synapses may provide insight into the mechanism by which long-term increases in plasma IGF-1 impart cognitive benefits in aged rats. Increases in AMPA receptor-mediated synaptic transmission may contribute directly to cognitive improvement or initiate long-term changes in synthesis of proteins such as brain-derived neurotrophic factor that are important to learning and memory.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/jn.00768.2004DOI Listing
July 2005
-->