Nancy J. Linford

17β-Estradiol and the phytoestrogen genistein attenuate neuronal apoptosis induced by the endoplasmic reticulum calcium-ATPase inhibitor thapsigargin

Estrogenic compounds have been shown to protect neurons from a variety of toxic stimuli in vitro and in vivo and depletion of estrogen at menopause has been associated with increased risk of neurodegenerative diseases. Genistein is an isoflavone soy derivative that binds to estrogen receptors with selective estrogen receptor modulator (SERM) properties. Recent FDA recommendations of soy intake for cholesterol reduction have prompted investigation into the potentially estrogenic role of dietary soy phytochemicals in the brain. In this study, we have shown that 50nM genistein significantly reduces neuronal apoptosis in an estrogen receptor-dependent manner. The importance of apoptosis in the brain has been recognized with regard to organization of the developing brain as well as degeneration in response to disease or stroke; however, the effects of estrogenic compounds on neuronal apoptosis have not been thoroughly examined. We developed a model of apoptotic toxicity in primary cortical neurons by using the endoplasmic reticulum (ER) calcium-ATPase inhibitor, thapsigargin, to test potential anti-apoptotic effects of 17beta-estradiol and genistein. Estrogen receptor beta, but not estrogen receptor alpha, was detected in our primary neuron cultures. Thapsigargin-induced apoptosis was confirmed by loss of mitochondrial function, DNA laddering, nuclear condensation and fragmentation, and caspase activation. Both 17beta-estradiol and genistein reduced the number of apoptotic neurons and reduced the number of neurons containing active caspase-3. This effect was blocked by co-addition of ICI 182780. Our results demonstrate that genistein and 17beta-estradiol have comparable anti-apoptotic properties in primary cortical neurons and that these properties are mediated through estrogen receptors.

Transcriptional response to aging and caloric restriction in heart and adipose tissue

Sustained caloric restriction (CR) extends lifespan in animal models but the mechanism and primary tissue target(s) have not been identified. Gene expression changes with aging and CR were examined in both heart and white adipose tissue (WAT) of Fischer 344 (F344) male rats using Affymetrix® RAE 230 arrays and validated by quantitative reverse transcriptase–polymerase chain reaction (qRT‐PCR) on 18 genes. As expected, age had a substantial effect on transcription on both tissues, although only 21% of cardiac age‐associated genes were also altered in WAT. Gene set enrichment analysis revealed coordinated small magnitude changes in ribosomal, proteasomal, and mitochondrial genes with similarities in aging between heart and WAT. CR had very different effects on these two tissues at the transcriptional level. In heart, very few age‐associated expression changes were affected by CR, while in WAT, CR suppressed a substantial subset of the age‐associated changes. Genes unaltered by aging but altered by CR were identified in WAT but not heart. Most interestingly, we identified a gene expression signature associated with mammalian target of rapamycin (mTOR) activity that was down‐regulated with age but preserved by CR in both WAT and heart. In addition, lipid metabolism genes, particularly those associated with peroxisome proliferator‐activated receptor γ (PPARγ)‐mediated adipogenesis were reduced with age but preserved with CR in WAT. These results highlight tissue‐specific differences in the gene expression response to CR and support a role for CR‐mediated preservation of mTOR activity and adipogenesis in aging WAT.

Oxidative Damage and Aging: Spotlight on Mitochondria

Whereas free radical damage has been proposed as a key component in the tissue degeneration associated with aging, there has been little evidence that free radical damage limits life span in mammals. The current research shows that overexpression of the antioxidant enzyme catalase in mitochondria can extend mouse life span. These results highlight the importance of mitochondrial damage in aging and suggest that when targeted appropriately, boosting antioxidant defenses can increase mammalian life span.

The rapid effects of estrogen are implicated in estrogen-mediated neuroprotection

A review of the literature reveals an impressively broad spectrum of effects of the hormone estrogen in the CNS. One of the more recently documented is the ability of estrogen to protect neurons from cell death associated with a variety of insults. While some of these actions can be attributed to nuclear effects of the hormone, mediated by the estrogen receptors alpha and/or beta, an increasing number of these effects appear to result from actions of the hormone mediated by signal transduction pathways traditionally associated with activation of membrane receptors. Here, we review current findings on actions of estrogen mediated by two pathways: those dependent on cAMP and Protein Kinase A, and those related to activation of the Mitogen Acivated Protein Kinase cascade. The evidence that estrogen can rapidly activate either pathway, and the potential involvement of the estrogen receptors alpha or beta acting in the vicinity of the cell membrane will be discussed. The possible role of MAP-Kinase activation and BCL-2 induction in the phenomenon of estrogen-neuroprotection will also be addressed.

Extension of mouse lifespan by overexpression of catalase

The free radical theory of aging was originally proposed 50 years ago, and is arguably the most popular mechanism explaining the aging process. According to this theory, aging results from the progressive decline in organ function due to the damage generated by reactive oxygen species (ROS). These chemical species are a normal part of metabolism, and a group of enzymes exists to protect cells against their toxic effects. One of these species is hydrogen peroxide (H2O2), which can be degraded by catalase. To determine the role of hydrogen peroxide in aging and its importance in different subcellular compartments, transgenic mice were developed with increased catalase activities localized to the peroxisome (PCAT), nucleus (NCAT), or mitochondrion (MCAT). The largest effect on lifespan was found in MCAT animals, with a 20% increase in median lifespan and a 10% increase in the maximum lifespan. A more modest effect was seen in PCAT animals, and no significant change was found in NCAT animals. Upon further examination of the MCAT mice, it was found that H2O2 production and H2O2-induced aconitase inactivation were attenuated, oxidative damage and the development of mitochondrial deletions were reduced, and cardiac pathology and cataract development were delayed. These results are consistent with a role of H2O2 in the development of pathology and in the limitation of mouse lifespan. They also demonstrate the importance of mitochondria as a source, and possible target, of ROS.

Chromosomal instability in pancreatic ductal cells from patients with chronic pancreatitis and pancreatic adenocarcinoma

Pancreatic adenocarcinoma is a disease with high mortality for which chronic pancreatitis confers a markedly increased risk. We hypothesize that chromosome instability and genomic damage occur in pre‐neoplastic pancreatic ductal epithelium, and that this damage may be related to oxidative stress. We used dual‐color fluorescence in situ hybridization with centromere probes and locus‐specific arm probes for chromosome arms 11q, 17p, and 18q to identify genomic instability in cultures of normal‐appearing human pancreatic ductal epithelium from normal organ donor controls compared to patients with chronic pancreatitis or pancreatic adenocarcinoma. To examine early pancreatic tumorigenesis, we studied only normal‐appearing pancreatic ductal cells adjacent to pancreatitis or carcinoma. We found that, compared to the finding in normal controls, chromosomal abnormalities are present in normal‐appearing human pancreatic ductal epithelia obtained from patients with chronic pancreatitis or pancreatic adenocarcinoma. Furthermore, these chromosomal abnormalities could be induced in cultured pancreatic ductal epithelium from normal organ donors by chronic exposure to dilute hydrogen peroxide, suggesting that oxidative stress may contribute to the development of chromosomal instability in the pancreas. These results elucidate a potential mechanism linking chronic pancreatitis to pancreatic cancer and suggest that chromosomal instability may be an early event in the pathogenesis of pancreatic cancer.

Gustatory and metabolic perception of nutrient stress in Drosophila

Significance Starvation induces a suite of costly behavioral and metabolic responses to maximize the possibility of finding a new nutrient source. It is therefore advantageous for an organism to switch out of the starvation state when food is encountered. How does an animal know when a food source is found and ultimate starvation is unlikely? This new work addresses this fundamental question, which is essential for broadening our understanding of how organisms interpret information from their environment to enact changes in complex behaviors and physiology. We describe an intriguing mechanism that combines information from both sensory and metabolic perception depending on the nutrient density in the food source. Sleep loss is an adaptive response to nutrient deprivation that alters behavior to maximize the chances of feeding before imminent death. Organisms must maintain systems for detecting the quality of the food source to resume healthy levels of sleep when the stress is alleviated. We determined that gustatory perception of sweetness is both necessary and sufficient to suppress starvation-induced sleep loss when animals encounter nutrient-poor food sources. We further find that blocking specific dopaminergic neurons phenocopies the absence of gustatory stimulation, suggesting a specific role for these neurons in transducing taste information to sleep centers in the brain. Finally, we show that gustatory perception is required for survival, specifically in a low nutrient environment. Overall, these results demonstrate an important role for gustatory perception when environmental food availability approaches zero and illustrate the interplay between sensory and metabolic perception of nutrient availability in regulating behavioral state.

Microarray Analysis of Gene Expression Changes in Aging

Publisher Summary The most common application of microarray technology to the research of aging is the search for gene expression changes that correlates with organismal age. Microarrays can also be used to compare individuals or populations of similar age but with different aging potentials. In several research, these two types of experimental design have been combined in such a way that the microarray analysis is carried out on control and long-lived animals at two or more ages. Microarray analysis of tissues or cells derived from short-lived mutants offers the opportunity to identify gene expression changes correlated with short life span and, potentially, accelerated aging. Microarrays offer the opportunity to detect a group of gene expression biomarkers that more accurately reflect biological age than currently possible. Several potential biomarkers can be assayed simultaneously in a single array experiment. Appropriate experimental design for the identification of individual biomarkers of longevity using microarrays, however, is nontrivial. While considering the design of a microarray experiment, the sources of biological and technical variability must be considered as they affect the ability to detect true gene expression changes.