OBJECTIVE

Results from animal and human studies suggest that disregulations of the hypothalamus-pituitary-adrenal (HPA) axis are involved in several behavioral, circulatory, endocrine, and immune disorders with clear-cut gender differences in disease prevalence. The aim of the present study was to investigate sex-specific HPA response patterns with a focus on the contribution of gonadal steroids as possible mediators.

METHODS

A total of 81 healthy adults were investigated in the present study. Twenty men, 19 women in the follicular phase of the menstrual cycle, 21 women in the luteal phase, and 21 women using oral contraceptives (OC) were exposed to a brief psychosocial stress test (Trier Social Stress Test; TSST) and injected with 0.25 mg ACTH1-24 on consecutive days. Basal HPA activity was investigated by repeatedly measuring cortisol levels immediately after awakening, as well as in 30-minute intervals from 9:00 AM to 9:00 PM. Additionally, questionnaires were used to assess psychological state and trait parameters.

RESULTS

Results show that the TSST induced significant increases in ACTH, salivary-free cortisol, total plasma cortisol, and heart rates, as well as increased wakefulness and reduced calmness in the total group. Significant group differences emerged for ACTH and salivary-free cortisol stress responses: Although men showed higher ACTH responses to the TSST compared with each of the three groups of women, salivary cortisol responses showed the following response pattern: Luteal = Men>> Follicular = OC. The salivary cortisol responses to ACTH1-24 showed a similar response pattern: Luteal>> Men>> Follicular>> OC. In contrast, total blood cortisol levels did not reveal any group difference between sexes or follicular versus luteal phase in either test. Although a similar salivary-free cortisol increase after awakening was found in the four groups, the circadian cortisol profile was significantly different throughout the first 4 hours of sampling. Questionnaire-derived psychological variables, as measured in the present study, could not explain the observed results.

CONCLUSIONS

We conclude that gender, menstrual cycle phase, and OC use exert important effects on HPA responsiveness to psychosocial stress in healthy subjects. Although men seem to have a stronger hypothalamic drive in response to stressful stimulation than women, differences in salivary-free cortisol levels, at least in part, may be explained by estradiol-induced changes in corticosteroid-binding protein levels. ACTH and cortisol secretion is not affected by OC use per se but the amount of bioavailable unbound cortisol ("free") is greatly reduced in this group of women after stimulation. Inasmuch as none of these differences between the study groups emerged in total blood cortisol levels, we strongly advocate for the simultaneous measurement of free and total cortisol levels in future studies on HPA functioning.

Nanomaterials (NM) exhibit novel physicochemical properties that determine their interaction with biological substrates and processes. Three metal oxide nanoparticles that are currently being produced in high tonnage, TiO(2), ZnO, and CeO(2), were synthesized by flame spray pyrolysis process and compared in a mechanistic study to elucidate the physicochemical characteristics that determine cellular uptake, subcellular localization, and toxic effects based on a test paradigm that was originally developed for oxidative stress and cytotoxicity in RAW 264.7 and BEAS-2B cell lines. ZnO induced toxicity in both cells, leading to the generation of reactive oxygen species (ROS), oxidant injury, excitation of inflammation, and cell death. Using ICP-MS and fluorescent-labeled ZnO, it is found that ZnO dissolution could happen in culture medium and endosomes. Nondissolved ZnO nanoparticles enter caveolae in BEAS-2B but enter lysosomes in RAW 264.7 cells in which smaller particle remnants dissolve. In contrast, fluorescent-labeled CeO(2) nanoparticles were taken up intact into caveolin-1 and LAMP-1 positive endosomal compartments, respectively, in BEAS-2B and RAW 264.7 cells, without inflammation or cytotoxicity. Instead, CeO(2) suppressed ROS production and induced cellular resistance to an exogenous source of oxidative stress. Fluorescent-labeled TiO(2) was processed by the same uptake pathways as CeO(2) but did not elicit any adverse or protective effects. These results demonstrate that metal oxide nanoparticles induce a range of biological responses that vary from cytotoxic to cytoprotective and can only be properly understood by using a tiered test strategy such as we developed for oxidative stress and adapted to study other aspects of nanoparticle toxicity.

BACKGROUND

The relationship between the amount of inducible ischemia present on stress myocardial perfusion single photon emission computed tomography (myocardial perfusion stress [MPS]) and the presence of a short-term survival benefit with early revascularization versus medical therapy is not clearly defined.

RESULTS

A total of 10 627 consecutive patients who underwent exercise or adenosine MPS and had no prior myocardial infarction or revascularization were followed up (90.6% complete; mean: 1.9+/-0.6 years). Cardiac death occurred in 146 patients (1.4%). Treatment received within 60 days after MPS defined subgroups undergoing revascularization (671 patients, 2.8% mortality) or medical therapy (MT) (9956 patients, 1.3% mortality; P=0.0004). To adjust for nonrandomization of treatment, a propensity score was developed using logistic regression to model the decision to refer to revascularization. This model (chi2=1822, c index=0.94, P<10-7) identified inducible ischemia and anginal symptoms as the most powerful predictors (83%, 6% of overall chi2) and was incorporated into survival models. On the basis of the Cox proportional hazards model predicting cardiac death (chi2=539, P<0.0001), patients undergoing MT demonstrated a survival advantage over patients undergoing revascularization in the setting of no or mild ischemia, whereas patients undergoing revascularization had an increasing survival benefit over patients undergoing MT when moderate to severe ischemia was present. Furthermore, increasing survival benefit for revascularization over MT was noted in higher risk patients (elderly, adenosine stress, and women, especially those with diabetes).

CONCLUSIONS

Revascularization compared with MT had greater survival benefit (absolute and relative) in patients with moderate to large amounts of inducible ischemia. These findings have significant consequences for future approaches to post-single photon emission computed tomography patient management if confirmed by prospective evaluations.

Healthy cells use autophagy as a general 'housekeeping' mechanism and to survive stress, including stress induced by nutrient deprivation. Autophagy is initiated at the isolation membrane (originally termed the phagophore), and the coordinated action of ATG (autophagy-related) proteins results in the expansion of this membrane to form the autophagosome. Although the biogenesis of the isolation membrane and the autophagosome is complex and incompletely understood, insight has been gained into the molecular processes involved in initiating the isolation membrane, the source from which this originates (for example, it was recently proposed that the isolation membrane forms from the mitochondria-associated endoplasmic reticulum (ER) membrane (MAM)) and the role of ATG proteins and the vesicular trafficking machinery in autophagosome formation.

Cellular senescence is a program activated by normal cells in response to various types of stress. These include telomere uncapping, DNA damage, oxidative stress, oncogene activity and others. Senescence can occur following a period of cellular proliferation or in a rapid manner in response to acute stress. Once cells have entered senescence, they cease to divide and undergo a series of dramatic morphologic and metabolic changes. Cellular senescence is thought to play an important role in tumor suppression and to contribute to organismal aging, but a detailed description of its physiologic occurrence in vivo is lacking. Recent studies have provided important insights regarding the manner by which different stresses and stimuli activate the signaling pathways leading to senescence. These studies reveal that a population of growing cells may suffer from a combination of different physiologic stresses acting simultaneously. The signaling pathways activated by these stresses are funneled to the p53 and Rb proteins, whose combined levels of activity determine whether cells enter senescence. Here we review recent advances in our understanding of the stimuli that trigger senescence, the molecular pathways activated by these stimuli, and the manner by which these signals determine the entry of a population of cells into senescence.

The serine/threonine kinase Akt has been implicated in the control of cell survival and metabolism. Here we report the disruption of the most ubiquitously expressed member of the akt family of genes, akt1, in the mouse. Akt1(-/-) mice are viable but smaller when compared to wild-type littermates. In addition, the life span of Akt1(-/-) mice, upon exposure to genotoxic stress, is shorter. However, Akt1(-/-) mice do not display a diabetic phenotype. Increased spontaneous apoptosis in testes, and attenuation of spermatogenesis is observed in Akt1(-/-) male mice. Increased spontaneous apoptosis is also observed in the thymi of Akt1(-/-) mice, and Akt1(-/-) thymocytes are more sensitive to apoptosis induced by gamma-irradiation and dexamethasone. Finally, Akt1(-/-) mouse embryo fibroblasts (MEFs) are more susceptible to apoptosis induced by TNF, anti-Fas, UV irradiation, and serum withdrawal.

S. typhimurium become resistant to killing by hydrogen peroxide and other oxidants when pretreated with nonlethal levels of hydrogen peroxide. During adaptation to hydrogen peroxide, 30 proteins are induced. Nine are constitutively overexpressed in dominant hydrogen peroxide-resistant oxyR mutants. Mutant oxyR1 is resistant to a variety of oxidizing agents and overexpresses at least five enzyme activities involved in defenses against oxidative damage. Deletions of oxyR are recessive and uninducible by hydrogen peroxide for the nine proteins overexpressed in oxyR1, demonstrating that oxyR is a positive regulatory element. The oxyR1 mutant is also more resistant than the wild-type parent to killing by heat, and it constitutively overexpresses three heat-shock proteins. The oxyR regulatory network is a previously uncharacterized global regulatory system in enteric bacteria.

Maintenance of endoplasmic reticulum (ER) function is achieved in part through Ire1 (inositol-requiring enzyme 1), a transmembrane protein activated by protein misfolding in the ER. The cytoplasmic nuclease domain of Ire1 cleaves the messenger RNA (mRNA) encoding XBP-1 (X-box-binding protein 1), enabling splicing and production of this active transcription factor. We recently showed that Ire1 activation independently induces the rapid turnover of mRNAs encoding membrane and secreted proteins in Drosophila melanogaster cells through a pathway we call regulated Ire1-dependent decay (RIDD). In this study, we show that mouse fibroblasts expressing wild-type Ire1 but not an Ire1 variant lacking nuclease activity also degrade mRNAs in response to ER stress. Using a second variant of Ire1 that is activated by a small adenosine triphosphate analogue, we show that although XBP-1 splicing can be artificially induced in the absence of ER stress, RIDD appears to require both Ire1 activity and ER stress. Our data suggest that cells use a multitiered mechanism by which different conditions in the ER lead to distinct outputs from Ire1.

Jasmonates are a family of plant hormones that regulate plant growth, development and responses to stress. The F-box protein CORONATINE INSENSITIVE 1 (COI1) mediates jasmonate signalling by promoting hormone-dependent ubiquitylation and degradation of transcriptional repressor JAZ proteins. Despite its importance, the mechanism of jasmonate perception remains unclear. Here we present structural and pharmacological data to show that the true Arabidopsis jasmonate receptor is a complex of both COI1 and JAZ. COI1 contains an open pocket that recognizes the bioactive hormone (3R,7S)-jasmonoyl-l-isoleucine (JA-Ile) with high specificity. High-affinity hormone binding requires a bipartite JAZ degron sequence consisting of a conserved α-helix for COI1 docking and a loop region to trap the hormone in its binding pocket. In addition, we identify a third critical component of the jasmonate co-receptor complex, inositol pentakisphosphate, which interacts with both COI1 and JAZ adjacent to the ligand. Our results unravel the mechanism of jasmonate perception and highlight the ability of F-box proteins to evolve as multi-component signalling hubs.

Oxidative/nitrosative stress, a pervasive condition of increased amounts of reactive oxygen/nitrogen species, is now recognized to be a prominent feature of many acute and chronic diseases and even of the normal aging process. However, definitive evidence for this association has often been lacking because of recognized shortcomings with biomarkers and/or methods available to assess oxidative stress status in humans. Emphasis is now being placed on biomarkers of oxidative stress, which are objectively measured and evaluated as indicators of normal biological processes, pathogenic processes, or pharmacologic responses to therapeutic intervention. To be a predictor of disease, a biomarker must be validated. Validation criteria include intrinsic qualities such as specificity, sensitivity, degree of inter- and intraindividual variability, and knowledge of the confounding and modifying factors. In addition, characteristics of the sampling and analytical procedures are of relevance, including constraints and noninvasiveness of sampling, stability of potential biomarkers, and the simplicity, sensitivity, specificity, and speed of the analytical method. Here we discuss some of the more commonly used biomarkers of oxidative/nitrosative damage and include selected examples of human studies.

The hormones and other physiological agents that mediate the effects of stress on the body have protective and adaptive effects in the short run and yet can accelerate pathophysiology when they are over-produced or mismanaged. Here we consider the protective and damaging effects of these mediators as they relate to the immune system and brain. 'Stress' is a principle focus, but this term is rather imprecise. Therefore, the article begins by noting two new terms, allostasis and allostatic load that are intended to supplement and clarify the meanings of 'stress' and 'homeostasis'. For the immune system, acute stress enhances immune function whereas chronic stress suppresses it. These effects can be beneficial for some types of immune responses and deleterious for others. A key mechanism involves the stress-hormone dependent translocation of immune cells in the blood to tissues and organs where an immune defense is needed. For the brain, acute stress enhances the memory of events that are potentially threatening to the organism. Chronic stress, on the other hand, causes adaptive plasticity in the brain, in which local neurotransmitters as well as systemic hormones interact to produce structural as well as functional changes, involving the suppression of ongoing neurogenesis in the dentate gyrus and remodelling of dendrites in the Ammon's horn. Under extreme conditions only does permanent damage ensue. Adrenal steroids tell only part of the story as far as how the brain adapts, or shows damage, and local tissue modulators - cytokines for the immune response and excitatory amino acid neurotransmitters for the hippocampus. Moreover, comparison of the effects of experimenter-applied stressors and psychosocial stressors show that what animals do to each other is often more potent than what experimenters do to them. And yet, even then, the brain is resilient and capable of adaptive plasticity. Stress-induced structural changes in brain regions such as the hippocampus have clinical ramifications for disorders such as depression, post-traumatic stress disorder and individual differences in the aging process.

Overproduction of IL-6, a proinflammatory cytokine, is associated with a spectrum of age-related conditions including cardiovascular disease, osteoporosis, arthritis, type 2 diabetes, certain cancers, periodontal disease, frailty, and functional decline. To describe the pattern of change in IL-6 over 6 years among older adults undergoing a chronic stressor, this longitudinal community study assessed the relationship between chronic stress and IL-6 production in 119 men and women who were caregiving for a spouse with dementia and 106 noncaregivers, with a mean age at study entry of 70.58 (SD = 8.03) for the full sample. On entry into this portion of the longitudinal study, 28 of the caregivers' spouses had already died, and an additional 50 of the 119 spouses died during the 6 years of this study. Levels of IL-6 and health behaviors associated with IL-6 were measured across 6 years. Caregivers' average rate of increase in IL-6 was about four times as large as that of noncaregivers. Moreover, the mean annual changes in IL-6 among former caregivers did not differ from that of current caregivers even several years after the death of the impaired spouse. There were no systematic group differences in chronic health problems, medications, or health-relevant behaviors that might have accounted for caregivers' steeper IL-6 slope. These data provide evidence of a key mechanism through which chronic stressors may accelerate risk of a host of age-related diseases by prematurely aging the immune response.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme defect, being present in more than 400 million people worldwide. The global distribution of this disorder is remarkably similar to that of malaria, lending support to the so-called malaria protection hypothesis. G6PD deficiency is an X-linked, hereditary genetic defect due to mutations in the G6PD gene, which cause functional variants with many biochemical and clinical phenotypes. About 140 mutations have been described: most are single base changes, leading to aminoacid substitutions. The most frequent clinical manifestations of G6PD deficiency are neonatal jaundice, and acute haemolytic anaemia, which is usually triggered by an exogenous agent. Some G6PD variants cause chronic haemolysis, leading to congenital non-spherocytic haemolytic anaemia. The most effective management of G6PD deficiency is to prevent haemolysis by avoiding oxidative stress. Screening programmes for the disorder are undertaken, depending on the prevalence of G6PD deficiency in a particular community.

This review provides a neuroadaptive perspective regarding the role of the hormonal and brain stress systems in drug addiction with a focus on the changes that occur during the transition from limited access to drugs to long-term compulsive use of drugs. A dramatic escalation in drug intake with extended access to drug self-administration is characterized by a dysregulation of brain reward pathways. Hormonal studies using an experimenter-administered cocaine binge model and an escalation self-administration model have revealed large increases in ACTH and corticosterone in rats during an acute binge with attenuation during the chronic binge stage and a reactivation of the hypothalamic-pituitary-adrenal axis during acute withdrawal. The activation of the hypothalamic-pituitary-adrenal axis with cocaine appears to depend on feed-forward activation of the mesolimbic dopamine system. At the same time, escalation in drug intake with either extended access or dependence-induction produces an activation of the brain stress system's corticotropin-releasing factor outside of the hypothalamus in the extended amygdala, which is particularly evident during acute withdrawal. A model of the role of different levels of hormonal/brain stress activation in addiction is presented that has heuristic value for understanding individual vulnerability to drug dependence and novel treatments for the disorder.

The OxyR transcription factor is sensitive to oxidation and activates the expression of antioxidant genes in response to hydrogen peroxide in Escherichia coli. Genetic and biochemical studies revealed that OxyR is activated through the formation of a disulfide bond and is deactivated by enzymatic reduction with glutaredoxin 1 (Grx1). The gene encoding Grx1 is regulated by OxyR, thus providing a mechanism for autoregulation. The redox potential of OxyR was determined to be -185 millivolts, ensuring that OxyR is reduced in the absence of stress. These results represent an example of redox signaling through disulfide bond formation and reduction.

Mitochondria are remarkably dynamic organelles that migrate, divide and fuse. Cycles of mitochondrial fission and fusion ensure metabolite and mitochondrial DNA mixing and dictate organelle shape, number and bioenergetic functionality. There is mounting evidence that mitochondrial dysfunction is an early and causal event in neurodegeneration. Mutations in the mitochondrial fusion GTPases mitofusin 2 and optic atrophy 1, neurotoxins and oxidative stress all disrupt the cable-like morphology of functional mitochondria. This results in impaired bioenergetics and mitochondrial migration, and can trigger neurodegeneration. These findings suggest potential new treatment avenues for neurodegenerative diseases.

As sessile organisms, plants must cope with abiotic stress such as soil salinity, drought, and extreme temperatures. Core stress-signaling pathways involve protein kinases related to the yeast SNF1 and mammalian AMPK, suggesting that stress signaling in plants evolved from energy sensing. Stress signaling regulates proteins critical for ion and water transport and for metabolic and gene-expression reprogramming to bring about ionic and water homeostasis and cellular stability under stress conditions. Understanding stress signaling and responses will increase our ability to improve stress resistance in crops to achieve agricultural sustainability and food security for a growing world population.

Neurodegenerative disorders such as Parkinson and Alzheimer disease cause motor and cognitive dysfunction and belong to a heterogeneous group of common and disabling disorders. Although the complex molecular pathophysiology of neurodegeneration is largely unknown, major advances have been achieved by elucidating the genetic defects underlying mendelian forms of these diseases. This has led to the discovery of common pathophysiological pathways such as enhanced oxidative stress, protein misfolding and aggregation and dysfunction of the ubiquitin-proteasome system. Here, we describe loss-of-function mutations in a previously uncharacterized, predominantly neuronal P-type ATPase gene, ATP13A2, underlying an autosomal recessive form of early-onset parkinsonism with pyramidal degeneration and dementia (PARK9, Kufor-Rakeb syndrome). Whereas the wild-type protein was located in the lysosome of transiently transfected cells, the unstable truncated mutants were retained in the endoplasmic reticulum and degraded by the proteasome. Our findings link a class of proteins with unknown function and substrate specificity to the protein networks implicated in neurodegeneration and parkinsonism.

The composition of cytoplasmic messenger ribonucleoproteins (mRNPs) is determined by their nuclear and cytoplasmic histories and reflects past functions and future fates. The protein components of selected mRNP complexes promote their assembly into microscopically visible cytoplasmic RNA granules, including stress granules, processing bodies and germ cell (or polar) granules. We propose that RNA granules can be both a cause and a consequence of altered mRNA translation, decay or editing. In this capacity, RNA granules serve as key modulators of post-transcriptional and epigenetic gene expression.

The MSN2 and MSN4 genes encode homologous and functionally redundant Cys2His2 zinc finger proteins. A disruption of both MSN2 and MSN4 genes results in a higher sensitivity to different stresses, including carbon source starvation, heat shock and severe osmotic and oxidative stresses. We show that MSN2 and MSN4 are required for activation of several yeast genes such as CTT1, DDR2 and HSP12, whose induction is mediated through stress-response elements (STREs). Msn2p and Msn4p are important factors for the stress-induced activation of STRE dependent promoters and bind specifically to STRE-containing oligonucleotides. Our results suggest that MSN2 and MSN4 encode a DNA-binding component of the stress responsive system and it is likely that they act as positive transcription factors.

Loss-of-function mutations in parkin are the predominant cause of familial Parkinson's disease. We previously reported that parkin-/- mice exhibit nigrostriatal deficits in the absence of nigral degeneration. Parkin has been shown to function as an E3 ubiquitin ligase. Loss of parkin function, therefore, has been hypothesized to cause nigral degeneration via an aberrant accumulation of its substrates. Here we employed a proteomic approach to determine whether loss of parkin function results in alterations in abundance and/or modification of proteins in the ventral midbrain of parkin-/- mice. Two-dimensional gel electrophoresis followed by mass spectrometry revealed decreased abundance of a number of proteins involved in mitochondrial function or oxidative stress. Consistent with reductions in several subunits of complexes I and IV, functional assays showed reductions in respiratory capacity of striatal mitochondria isolated from parkin-/- mice. Electron microscopic analysis revealed no gross morphological abnormalities in striatal mitochondria of parkin-/- mice. In addition, parkin-/- mice showed a delayed rate of weight gain, suggesting broader metabolic abnormalities. Accompanying these deficits in mitochondrial function, parkin-/- mice also exhibited decreased levels of proteins involved in protection from oxidative stress. Consistent with these findings, parkin-/- mice showed decreased serum antioxidant capacity and increased protein and lipid peroxidation. The combination of proteomic, genetic, and physiological analyses reveal an essential role for parkin in the regulation of mitochondrial function and provide the first direct evidence of mitochondrial dysfunction and oxidative damage in the absence of nigral degeneration in a genetic mouse model of Parkinson's disease.

A protective mechanism used by cells to adapt to stress of the endoplasmic reticulum (ER) is the induction of members of the glucose-regulated protein (Grp) family. The induction of mammalian Grp proteins in response to ER stress involves a complex network of regulators and novel mechanisms. The elucidation of Grp function and regulation opens up new therapeutic approaches to diseases associated with ER stress and cancer.

Commensal and pathogenic microorganisms must resist the deleterious actions of bile in order to survive in the human gastrointestinal tract. Herein we review the current knowledge on the mechanisms by which Gram-positive and Gram-negative bacteria contend with bile stress. We describe the antimicrobial actions of bile, assess the variations in bile tolerance between bacterial genera and examine the interplay between bile stress and other stresses. The molecular mechanisms underlying bile tolerance are investigated and the relationship between bile and virulence is examined. Finally, the potential benefits of bile research are briefly discussed.