An energetic view of stress: Focus on mitochondria

Autophagy Dysfunction: The Kernel of Hair Loss?

Autophagy is recognized as a crucial regulatory process, instrumental in the removal of senescent, dysfunctional, and damaged cells. Within the autophagic process, lysosomal digestion plays a critical role in the elimination of impaired organelles, thus preserving fundamental cellular metabolic functions and various biological processes. Mitophagy, a targeted autophagic process that specifically focuses on mitochondria, is essential for sustaining cellular health and energy balance. Therefore, a deep comprehension of the operational mechanisms and implications of autophagy and mitophagy is vital for disease prevention and treatment. In this context, we examine the role of autophagy and mitophagy during hair follicle cycles, closely scrutinizing their potential association with hair loss. We also conduct a thorough review of the regulatory mechanisms behind autophagy and mitophagy, highlighting their interaction with hair follicle stem cells and dermal papilla cells. In conclusion, we investigate the potential of manipulating autophagy and mitophagy pathways to develop innovative therapeutic strategies for hair loss.

Hepatic mitochondrial bioenergetics and metabolism across lactation and in response to heat stress in dairy cows

Lactation is energetically demanding for the dairy cow. Numerous morphological and metabolic changes orchestrated across different tissues in the body partition nutrients for milk synthesis. The liver is a key organ coordinating modifications in metabolism that increase substrate availability for the mammary gland. Impaired capacity to make the needed physiological adjustments for lactation, such as occurs with heat stress, can result in metabolic disease and poor lactation performance. At the cellular level, increases in mitochondrial density and bioenergetic and biosynthetic capacity are critical adaptations for successful lactation, providing energy and substrates for milk synthesis. Mitochondria are also involved in coordinating adaptation to a variety of stressors by providing the metabolic foundation to enlist a stress response. Heat stress can damage mitochondrial structures and impair mitochondrial function, with implications for pathogenesis and production. This systematic review focuses on the hepatic mitochondrial adaptations to lactation and the mitochondrial responses to heat stress. Future research directions are also discussed that may lead to improvements in managing the metabolic needs of the lactating cow and diminishing the adverse production and health consequences from environmental stress.

Synergistic Regulation of Targeted Organelles in Tumor Cells to Promote Photothermal-Immunotherapy Using Intelligent Core-Satellite-Like Nanoparticles for Effective Treatment of Breast Cancer

The normal operation of organelles is critical for tumor growth and metastasis. Herein, an intelligent nanoplatform (BMAEF) is fabricated to perform on-demand destruction of mitochondria and golgi apparatus, which also generates the enhanced photothermal-immunotherapy, resulting in the effective inhibition of primary and metastasis tumor. The BMAEF has a core of mesoporous silica nanoparticles loaded with brefeldin A (BM), which is connected to ethylenebis(oxyethylenenitrilo)tetraacetic acid (EGTA) and folic acid co-modified gold nanoparticles (AEF). During therapy, the BMAEF first accumulates in tumor cells via folic acid-induced targeting. Subsequently, the schiff base/ester bond cleaves in lysosome to release brefeldin A and AEF with exposed EGTA. The EGTA further captures Ca2+ to block ion transfer among mitochondria, endoplasmic reticulum, and golgi apparatus, which not only induced dysfunction of mitochondria and golgi apparatus assisted by brefeldin A to suppress both energy and material metabolism against tumor growth and metastasis, but causes AEF aggregation for tumor-specific photothermal therapy and photothermal assisted immunotherapy. Moreover, the dysfunction of these organelles also stops the production of BMI1 and heat shock protein 70 to further enhance the metastasis inhibition and photothermal therapy, which meanwhile triggers the escape of cytochrome C to cytoplasm, leading to additional apoptosis of tumor cells.

Differential mitochondrial bioenergetics and cellular resilience in astrocytes, hepatocytes, and fibroblasts from aging baboons

Biological resilience, broadly defined as the ability to recover from an acute challenge and return to homeostasis, is of growing importance to the biology of aging. At the cellular level, there is variability across tissue types in resilience and these differences are likely to contribute to tissue aging rate disparities. However, there are challenges in addressing these cell-type differences at regional, tissue, and subject level. To address this question, we established primary cells from aged male and female baboons between 13.3 and 17.8 years spanning across different tissues, tissue regions, and cell types including (1) fibroblasts from skin and from the heart separated into the left ventricle (LV), right ventricle (RV), left atrium (LA), and right atrium (RA); (2) astrocytes from the prefrontal cortex and hippocampus; and (3) hepatocytes. Primary cells were characterized by their cell surface markers and their cellular respiration was assessed with Seahorse XFe96. Cellular resilience was assessed by modifying a live-cell imaging approach; we previously reported that monitors proliferation of dividing cells following response and recovery to oxidative (50 µM-H2O2), metabolic (1 mM-glucose), and proteostasis (0.1 µM-thapsigargin) stress. We noted significant differences even among similar cell types that are dependent on tissue source and the diversity in cellular response is stressor-specific. For example, astrocytes had a higher oxygen consumption rate and exhibited greater resilience to oxidative stress (OS) than both fibroblasts and hepatocytes. RV and RA fibroblasts were less resilient to OS compared with LV and LA, respectively. Skin fibroblasts were less impacted by proteostasis stress compared to astrocytes and cardiac fibroblasts. Future studies will test the functional relationship of these outcomes to the age and developmental status of donors as potential predictive markers.

Telomeres and telomerase: active but complex players in life-history decisions

Studies on human telomeres have established that telomeres exert a significant influence on lifespan and health of organisms. However, recent research has indicated that the original idea that telomeres affect lifespan in a universal and central manner across all eukaryotic species is an oversimplification. Indeed, findings from a variety of animal species revealed that the role of telomere biology in aging is more subtle and intricate than previously recognized. Here, we show how telomere biology varies depending on the taxon. We also show how telomere biology corresponds to basic life history traits and affects the life table of a species and investments in growth, body size, reproduction, and lifespan; telomeres are hypothesized to shape evolutionary perspectives for species in an active but complex manner. Our evaluation is based on telomere biology data from many examples from throughout the animal kingdom that vary according to the degree of organismal complexity and life history strategies.

Myalgic encephalomyelitis/chronic fatigue syndrome from current evidence to new diagnostic perspectives through skeletal muscle and metabolic disturbances

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a demanding medical condition for patients and society. It has raised much more public awareness after the COVID-19 pandemic since ME/CFS and long-COVID patients share many clinical symptoms such as debilitating chronic fatigue. However, unlike long COVID, the etiopathology of ME/CFS remains a mystery despite several decades' research. This review moves from pathophysiology of ME/CFS through the compelling evidence and most interesting hypotheses. It focuses on the pathophysiology of skeletal muscle by proposing the hypothesis that skeletal muscle tissue offers novel opportunities for diagnosis and treatment of this syndrome and that new evidence can help resolve the long-standing debate on terminology.

Adolescent Stress-Induced Ventral Hippocampus Redox Dysregulation Underlies Behavioral Deficits and Excitatory/Inhibitory Imbalance Related to Schizophrenia

BACKGROUND AND HYPOTHESIS

Redox dysregulation has been proposed as a convergent point of childhood trauma and the emergence of psychiatric disorders, such as schizophrenia (SCZ). A critical region particularly vulnerable to environmental insults during adolescence is the ventral hippocampus (vHip). However, the impact of severe stress on vHip redox states and their functional consequences, including behavioral and electrophysiological changes related to SCZ, are not entirely understood.

STUDY DESIGN

After exposing adolescent animals to physical stress (postnatal day, PND31-40), we explored social and cognitive behaviors (PND47-49), the basal activity of pyramidal glutamate neurons, the number of parvalbumin (PV) interneurons, and the transcriptomic signature of the vHip (PND51). We also evaluated the impact of stress on the redox system, including mitochondrial respiratory function, reactive oxygen species (ROS) production, and glutathione (GSH) levels in the vHip and serum.

STUDY RESULTS

Adolescent-stressed animals exhibited loss of sociability, cognitive impairment, and vHip excitatory/inhibitory (E/I) imbalance. Genome-wide transcriptional profiling unveiled the impact of stress on redox system- and synaptic-related genes. Stress impacted mitochondrial respiratory function and changes in ROS levels in the vHip. GSH and glutathione disulfide (GSSG) levels were elevated in the serum of stressed animals, while GSSG was also increased in the vHip and negatively correlated with sociability. Additionally, PV interneuron deficits in the vHip caused by adolescent stress were associated with oxidative stress.

CONCLUSIONS

Our results highlight the negative impact of adolescent stress on vHip redox regulation and mitochondrial function, which are partially associated with E/I imbalance and behavioral abnormalities related to SCZ.

Childhood adverse life events and skeletal muscle mitochondrial function

Social stress experienced in childhood is associated with adverse health later in life. Mitochondrial function has been implicated as a mechanism for how stressful life events "get under the skin" to influence physical well-being. Using data from the Study of Muscle, Mobility, and Aging (n = 879, 59% women), linear models examined whether adverse childhood events (i.e., physical abuse) were associated with two measures of skeletal muscle mitochondrial energetics in older adults: (i) maximal adenosine triphosphate production (ATPmax) and (ii) maximal state 3 respiration (Max OXPHOS). Forty-five percent of the sample reported experiencing one or more adverse childhood events. After adjustment, each additional event was associated with -0.08 SD (95% confidence interval = -0.13, -0.02) lower ATPmax. No association was observed with Max OXPHOS. Adverse childhood events are associated with lower ATP production in later life. Findings indicate that mitochondrial function may be a mechanism for understanding how early social stress influences health in later life.

Physical activity as a promoter of stress resilience: An analysis of behavioral effects and brain connectivity with cytochrome c-oxidase activity in adult male Wistar rats

Physical activity (PA) is very beneficial for physical and mental health. This study aims to examine the resilience-inducting effect of PA in adult male Wistar rats exposed to unpredictable chronic mild stress (UCMS). Furthermore, we analyzed the influence of PA on behavioral tasks and functional brain connectivity with cytochrome c oxidase technique. The cytochrome c oxidase (CCO) is a mitochondrial enzyme involved in oxidative phosphorylation and ATP generation. For this analysis, we included five groups: Basal (n = 10, to determine the basal level of brain activity), Behav (n = 15, subjected exclusively to behavioral tests), PA (n = 10, exposed to physical activity), UCMS (n = 15, subjected to a stress protocol) and PA + UCMS (n = 15, exposed to PA prior to stress). The UCMS protocol consisted of randomly presenting several different stressors over four consecutive weeks. We evaluated several behaviors of the Behav, UCMS, and PA + UCMS groups. This assessment includes the hedonic responses using the sucrose consumption task, unconditioned anxiety with the zero maze, and coping strategies assessed with the cat odor test. The UCMS group showed an anhedonia profile and increased anxiety compared with the other groups. Although in the exposure to cat odor test, the PA + UCMS remained for the same time in the cat odor compartment as the other groups, it did not approach the odor, showing that it detected the risk. This response is more adaptive than the responses of the UCMS and Behav groups. An exploratory analysis of the cerebral connections showed an increase in CCO activity in the UCMS group compared to the other groups. This overactivity was reduced in dorsal Cornu Ammonis 3(dCA3) by prior PA. In this region, PA + UCMS showed similar activity as the groups not subjected to chronic stress. Therefore, PA can prevent the harmful effects of chronic stress on dCA3.

Differential mitochondrial bioenergetics and cellular resilience in astrocytes, hepatocytes, and fibroblasts from aging baboons

Biological resilience, broadly defined as ability to recover from acute challenge and return to homeostasis, is of growing importance to the biology of aging. At the cellular level, there is variability across tissue types in resilience and these differences likely to contribute to tissue aging rate disparities. However, there are challenges in addressing these cell-type differences at regional, tissue and subject level. To address this question, we established primary cells from aged male and female baboons between 13.3-17.8 years spanning across different tissues, tissue regions, and cell types including: (1) fibroblasts from skin and from heart separated into left ventricle (LV), right ventricle (RV), left atrium (LA) and right atrium (RA), (2) astrocytes from the prefrontal cortex and hippocampus and (3) hepatocytes. Primary cells were characterized by their cell surface markers and their cellular respiration assessed with Seahorse XFe96. Cellular resilience was assessed by modifying a live-cell imaging approach we previously reported that monitors proliferation of dividing cells following response and recovery to oxidative (50µM-H2O2), metabolic (1mM-glucose) and proteostasis (0.1µM-thapsigargin) stress. We noted significant differences even among similar cell types that are dependent on tissue source and the diversity in cellular response is stressor specific. For example, astrocytes were more energetic and exhibited greater resilience to oxidative stress (OS) than both fibroblasts and hepatocytes. RV and RA fibroblasts were less resilient to OS compared with LV and LA respectively. Skin fibroblasts were less impacted by proteostasis stress compared to astrocytes and cardiac fibroblasts. Future studies will test the functional relationship of these outcomes to age and developmental status of donors as potential predictive markers.

The brain's go-getter circuit: Anterior cingulate cortex to nucleus accumbens and its disruption by stress

In this issue of Neuron, Fetcho, Parekh, et al.1 show that neurons in the anterior cingulate cortex (ACC) projecting to the nucleus accumbens (NAc) are essential for integrating reward and effort evaluation in mice, and that this circuit is sensitive to exposure to stress hormones.

A mitochondrial nexus in major depressive disorder: Integration with the psycho-immune-neuroendocrine network

Nervous system processes, including cognition and affective state, fundamentally rely on mitochondria. Impaired mitochondrial function is evident in major depressive disorder (MDD), reflecting cumulative detrimental influences of both extrinsic and intrinsic stressors, genetic predisposition, and mutation. Glucocorticoid 'stress' pathways converge on mitochondria; oxidative and nitrosative stresses in MDD are largely mitochondrial in origin; both initiate cascades promoting mitochondrial DNA (mtDNA) damage with disruptions to mitochondrial biogenesis and tryptophan catabolism. Mitochondrial dysfunction facilitates proinflammatory dysbiosis while directly triggering immuno-inflammatory activation via released mtDNA, mitochondrial lipids and mitochondria associated membranes (MAMs), further disrupting mitochondrial function and mitochondrial quality control, promoting the accumulation of abnormal mitochondria (confirmed in autopsy studies). Established and putative mechanisms highlight a mitochondrial nexus within the psycho-immune neuroendocrine (PINE) network implicated in MDD. Whether lowering neuronal resilience and thresholds for disease, or linking mechanistic nodes within the MDD pathogenic network, impaired mitochondrial function emerges as an important risk, a functional biomarker, providing a therapeutic target in MDD. Several treatment modalities have been demonstrated to reset mitochondrial function, which could benefit those with MDD.

Cortisol enhances aerobic metabolism and locomotor performance during the transition to land in an amphibious fish

Amphibious fishes on land encounter higher oxygen (O2) availability and novel energetic demands, which impacts metabolism. Previous work on the amphibious mangrove killifish (Kryptolebias marmoratus) has shown that cortisol becomes elevated in response to air exposure, suggesting a possible role in regulating metabolism as fish move into terrestrial environments. We tested the hypothesis that cortisol is the mechanism by which oxidative processes are upregulated during the transition to land in amphibious fishes. We used two groups of fish, treated fish (+metyrapone, a cortisol synthesis inhibitor) and control (-metyrapone), to determine the impact of cortisol during air exposure (0 and 1 h, 7 days) on O2 consumption, terrestrial locomotion, the phenotype of red skeletal muscle, and muscle lipid concentration. Metyrapone-treated fish had an attenuated elevation in O2 consumption rate during the water to air transition and an immediate reduction in terrestrial exercise performance relative to control fish. In contrast, we found no short- (0 h) or long-term (7 days) differences between treatments in the oxidative phenotype of red muscles, nor in muscle lipid concentrations. Our results suggest that cortisol stimulates the necessary increase in aerobic metabolism needed to fuel the physiological changes that amphibious fishes undergo during the acclimation to air, although further studies are required to determine specific mechanisms of cortisol regulation.

Glucocorticoid and Adrenergic Receptor Distribution Across Human Organs and Tissues: A Map for Stress Transduction

OBJECTIVE

Psychosocial stress is transduced into disease risk through energy-dependent release of hormones from the hypothalamic-pituitary-adrenal and sympathetic-adrenal-medullary axes. The levels of glucocorticoid and adrenergic hormones, together with the sensitivity of tissues to their signaling, define stress responses. To understand existing pathways responsible for the psychobiological transduction of stressful experiences, we provide a quantitative whole-body map of glucocorticoid and adrenergic receptor (AR) expression.

METHODS

We systematically examined gene expression levels for the glucocorticoid receptor (GR), α- and β-ARs (AR-α1B, AR-α2B AR-β2, and AR-β3), across 55 different organs using the Human Protein Atlas and Human Proteome Map datasets. Given that mitochondria produce the energy required to respond to stress, we leveraged the Human Protein Atlas and MitoCarta3.0 data to examine the link between stress hormone receptor density and mitochondrial gene expression. Finally, we tested the functional interplay between GR activation and AR expression in human fibroblast cells.

RESULTS

The GR was expressed ubiquitously across all investigated organ systems, whereas AR subtypes showed lower and more localized expression patterns. Receptor co-regulation, meaning the correlated gene expression of multiple stress hormone receptors, was found between GR and AR-α1B, as well as between AR-α1B and AR-α2B. In cultured human fibroblasts, activating the GR selectively increased AR-β2 and AR-α1B expression. Consistent with the known energetic cost of stress responses, GR and AR expressions were positively associated with the expression of specific mitochondrial pathways.

CONCLUSIONS

Our results provide a cartography of GR and AR expression across the human body. Because stress-induced GR and AR signaling triggers energetically expensive cellular pathways involving energy-transforming mitochondria, the tissue-specific expression and co-expression patterns of hormone receptor subtypes may in part determine the resilience or vulnerability of different organ systems.

Mitochondrial function and sexual selection: can physiology resolve the 'lek paradox'?

Across many taxa, males use elaborate ornaments or complex displays to attract potential mates. Such sexually selected traits are thought to signal important aspects of male 'quality'. Female mating preferences based on sexual traits are thought to have evolved because choosy females gain direct benefits that enhance their lifetime reproductive success (e.g. greater access to food) and/or indirect benefits because high-quality males contribute genes that increase offspring fitness. However, it is difficult to explain the persistence of female preferences when males only provide genetic benefits, because female preferences should erode the heritable genetic variation in fitness that sexually selected traits signal. This 'paradox of the lek' has puzzled evolutionary biologists for decades, and inspired many hypotheses to explain how heritable variation in sexually selected traits is maintained. Here, we discuss how factors that affect mitochondrial function can maintain variation in sexually selected traits despite strong female preferences. We discuss how mitochondrial function can influence the expression of sexually selected traits, and we describe empirical studies that link the expression of sexually selected traits to mitochondrial function. We explain how mothers can affect mitochondrial function in their offspring by (a) influencing their developmental environment through maternal effects and (b) choosing a mate to increase the compatibility of mitochondrial and nuclear genes (i.e. the 'mitonuclear compatibility model of sexual selection'). Finally, we discuss how incorporating mitochondrial function into models of sexual selection might help to resolve the paradox of the lek, and we suggest avenues for future research.

Circulating cell-free mitochondrial DNA levels and glucocorticoid sensitivity in a cohort of male veterans with and without combat-related PTSD

Circulating cell-free mitochondrial DNA (ccf-mtDNA) is a biomarker of cellular injury or cellular stress and is a potential novel biomarker of psychological stress and of various brain, somatic, and psychiatric disorders. No studies have yet analyzed ccf-mtDNA levels in post-traumatic stress disorder (PTSD), despite evidence of mitochondrial dysfunction in this condition. In the current study, we compared plasma ccf-mtDNA levels in combat trauma-exposed male veterans with PTSD (n = 111) with those who did not develop PTSD (n = 121) and also investigated the relationship between ccf mt-DNA levels and glucocorticoid sensitivity. In unadjusted analyses, ccf-mtDNA levels did not differ significantly between the PTSD and non-PTSD groups (t = 1.312, p = 0.191, Cohen's d = 0.172). In a sensitivity analysis excluding participants with diabetes and those using antidepressant medication and controlling for age, the PTSD group had lower ccf-mtDNA levels than did the non-PTSD group (F(1, 179) = 5.971, p = 0.016, partial η2 = 0.033). Across the entire sample, ccf-mtDNA levels were negatively correlated with post-dexamethasone adrenocorticotropic hormone (ACTH) decline (r = -0.171, p = 0.020) and cortisol decline (r = -0.149, p = 0.034) (viz., greater ACTH and cortisol suppression was associated with lower ccf-mtDNA levels) both with and without controlling for age, antidepressant status and diabetes status. Ccf-mtDNA levels were also significantly positively associated with IC50-DEX (the concentration of dexamethasone at which 50% of lysozyme activity is inhibited), a measure of lymphocyte glucocorticoid sensitivity, after controlling for age, antidepressant status, and diabetes status (β = 0.142, p = 0.038), suggesting that increased lymphocyte glucocorticoid sensitivity is associated with lower ccf-mtDNA levels. Although no overall group differences were found in unadjusted analyses, excluding subjects with diabetes and those taking antidepressants, which may affect ccf-mtDNA levels, as well as controlling for age, revealed decreased ccf-mtDNA levels in PTSD. In both adjusted and unadjusted analyses, low ccf-mtDNA levels were associated with relatively increased glucocorticoid sensitivity, often reported in PTSD, suggesting a link between mitochondrial and glucocorticoid-related abnormalities in PTSD.

Deep rest: An integrative model of how contemplative practices combat stress and enhance the body's restorative capacity

Engaging in contemplative practice like meditation, yoga, and prayer, is beneficial for psychological and physical well-being. Recent research has identified several underlying psychological and biological pathways that explain these benefits. However, there is not yet consensus on the underlying overlapping physiological mechanisms of contemplative practice benefits. In this article, we integrate divergent scientific literatures on contemplative practice interventions, stress science, and mitochondrial biology, presenting a unified biopsychosocial model of how contemplative practices reduce stress and promote physical health. We argue that engaging in contemplative practice facilitates a restorative state termed "deep rest," largely through safety signaling, during which energetic resources are directed toward cellular optimization and away from energy-demanding stress states. Our model thus presents a framework for how contemplative practices enhance positive psychological and physiological functioning by optimizing cellular energy consumption. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Mitochondria as a sensor, a central hub and a biological clock in psychological stress-accelerated aging

The theory that oxidative damage caused by mitochondrial free radicals leads to aging has brought mitochondria into the forefront of aging research. Psychological stress that encompasses many different experiences and exposures across the lifespan has been identified as a catalyst for accelerated aging. Mitochondria, known for their dynamic nature and adaptability, function as a highly sensitive stress sensor and central hub in the process of accelerated aging. In this review, we explore how mitochondria as sensors respond to psychological stress and contribute to the molecular processes in accelerated aging by viewing mitochondria as hormonal, mechanosensitive and immune suborganelles. This understanding of the key role played by mitochondria and their close association with accelerated aging helps us to distinguish normal aging from accelerated aging, correct misconceptions in aging studies, and develop strategies such as exercise and mitochondria-targeted nutrients and drugs for slowing down accelerated aging, and also hold promise for prevention and treatment of age-related diseases.

Whole blood mitochondrial copy number in clinical populations with mood disorders: A meta-analysis: Blood mitochondrial copy number and mood disorders

Major depressive disorder (MDD) and bipolar disorder (BD), are globally prevalent, contributing to significant disease burden and adverse health outcomes. These mood disorders are associated with changes in many aspects of brain reward pathways, yet cellular and molecular changes in the brain are not readily available in clinical populations. Therefore, the use of biomarkers as proxies for changes in the brain are necessary. The proliferation of mitochondria in blood has emerged as a potentially useful biomarker, yet a clear consensus on how these mood disorders impact mitochondrial DNA copy number (mtDNAcn) has not been reached. To determine the current available consensus on the relationship of mood disorder diagnosis and blood mtDNcn, we performed a meta-analysis of available literature measuring this biomarker. Following PRISMA guidelines for a systematic search, 22 papers met inclusion criteria for meta-analysis (10 MDD, 10 BD, 2 both MDD and BD). We extracted demographic, disorder, and methodological information with mtDNAcn. Using the metafor package for R, calculated effect sizes were used in random effects or meta regression models for MDD and BD. Overall, our data suggest blood mtDNAcn may be a useful biomarker for mood disorders, with MDD and BD Type II associated with higher mtDNAcn, and BD Type I associated with lower mtDNAcn. Initially, we observed a trending increase in mtDNAcn in patients with MDD, which reached significance when one study with outlying demographic characteristics was excluded. Subgroup and meta-regression analysis indicated the relationship between mtDNAcn and diagnosis in patients with BD is dependent on BD type, while no relationship is detectable when BD types are mixed. Further study of blood mtDNAcn could predict downstream health outcomes or treatment responsivity in individuals with mood disorders.

Gonadal hormones impart male-biased behavioral vulnerabilities to immune activation via microglial mitochondrial function

There is a strong male bias in the prevalence of many neurodevelopmental disorders such as autism spectrum disorder. However, the mechanisms underlying this sex bias remain elusive. Infection during the perinatal period is associated with an increased risk of neurodevelopmental disorder development. Here, we used a mouse model of early-life immune activation that reliably induces deficits in social behaviors only in males. We demonstrate that male-biased alterations in social behavior are dependent upon microglial immune signaling and are coupled to alterations in mitochondrial morphology, gene expression, and function specifically within microglia, the innate immune cells of the brain. Additionally, we show that this behavioral and microglial mitochondrial vulnerability to early-life immune activation is programmed by the male-typical perinatal gonadal hormone surge. These findings demonstrate that social behavior in males over the lifespan are regulated by microglia-specific mechanisms that are shaped by events that occur in early development.

The cortisol switch between vulnerability and resilience

In concert with neuropeptides and transmitters, the end products of the hypothalamus-pituitary-adrenal (HPA) axis, the glucocorticoid hormones cortisol and corticosterone (CORT), promote resilience: i.e., the ability to cope with threats, adversity, and trauma. To exert this protective action, CORT activates mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) that operate in a complementary manner -as an on/off switch- to coordinate circadian events, stress-coping, and adaptation. The evolutionary older limbic MR facilitates contextual memory retrieval and supports an on-switch in the selection of stress-coping styles at a low cost. The rise in circulating CORT concentration after stress subsequently activates a GR-mediated off-switch underlying recovery of homeostasis by providing the energy for restraining the primary stress reactions and promoting cognitive control over emotional reactivity. GR activation facilitates contextual memory storage of the experience to enable future stress-coping. Such complementary MR-GR-mediated actions involve rapid non-genomic and slower gene-mediated mechanisms; they are time-dependent, conditional, and sexually dimorphic, and depend on genetic background and prior experience. If coping fails, GR activation impairs cognitive control and promotes emotional arousal which eventually may compromise resilience. Such breakdown of resilience involves a transition to a chronic stress construct, where information processing is crashed; it leads to an imbalanced MR-GR switch and hence increased vulnerability. Novel MR-GR modulators are becoming available that may reset a dysregulated stress response system to reinstate the cognitive flexibility required for resilience.

Mitochondrial might: powering the peripartum for risk and resilience

The peripartum period, characterized by dynamic hormonal shifts and physiological adaptations, has been recognized as a potentially vulnerable period for the development of mood disorders such as postpartum depression (PPD). Stress is a well-established risk factor for developing PPD and is known to modulate mitochondrial function. While primarily known for their role in energy production, mitochondria also influence processes such as stress regulation, steroid hormone synthesis, glucocorticoid response, GABA metabolism, and immune modulation - all of which are crucial for healthy pregnancy and relevant to PPD pathology. While mitochondrial function has been implicated in other psychiatric illnesses, its role in peripartum stress and mental health remains largely unexplored, especially in relation to the brain. In this review, we first provide an overview of mitochondrial involvement in processes implicated in peripartum mood disorders, underscoring their potential role in mediating pathology. We then discuss clinical and preclinical studies of mitochondria in the context of peripartum stress and mental health, emphasizing the need for better understanding of this relationship. Finally, we propose mitochondria as biological mediators of resilience to peripartum mood disorders.

Effects of Indoor Dust Exposure on Lung Cells: Association of Chemical Composition with Phenotypic and Lipid Changes in a 3D Lung Cancer Cell Model

Indoor dust is a key contributor to the global human exposome in urban areas since the population develops most of its activities in private and public buildings. To gain insight into the health risks associated with this chronic exposure, it is necessary to characterize the chemical composition of dust and understand its biological impacts using reliable physiological models. The present study investigated the biological effects of chemically characterized indoor dust extracts using three-dimensional (3D) lung cancer cell cultures combining phenotypic and lipidomic analyses. Apart from the assessment of cell viability, reactive oxygen species (ROS) induction, and interleukin-8 release, lipidomics was applied to capture the main lipid changes induced as a cellular response to the extracted dust compounds. The application of chemometric tools enabled the finding of associations between chemical compounds present in dust and lipidic and phenotypic profiles in the cells. This study contributes to a better understanding of the toxicity mechanisms associated with exposure to chemical pollutants present in indoor dust.

In vitro evaluation of p-coumaric acid and naringin combination in human epidermoid carcinoma cell line (A431)

Cancer is considered most detrimental due to high mortality worldwide. Among them, skin cancers play a major part by affecting one in three cancer patients globally. About 2-3 million cancer cases were reported to be non-melanoma and melanoma skin cancers, respectively. Although chemotherapeutic drugs act on cancer cells but results in long-lasting morbidities which affects one's quality of life and also works only in the initial stage of the cancer. Hence, an idea of traditional medicine to cure the disease efficiently with less side effects was pursued by the researchers. We have assessed the combination effect of p-coumaric acid and naringin in exerting anticancer activity using A431 (epidermoid carcinoma) cells. The MTT analysis of the combination on A431 cells showed the least IC50 concentration of 41 µg/ml which is effective than the standard drug imiquimod with IC50 concentration of 52 µg/ml. Further, flow cytometric analysis was carried out to identify the molecular mechanism behind the anticancer effects of the combination. The results revealed that the combination arrested the A431 cell cycle at S phase, induced apoptosis as indicated by more early and late apoptotic cells when compared with the control, and further altered reactive oxygen species (ROS) and mitochondrial membrane potential in A431 cells. Hence, the results suggest the potential anticancer effects of p-coumaric acid and naringin combination against the skin cancer (A431) cell line. The observed effects may be additive or synergistic effects in inducing ROS generation and apoptosis, and reducing the viability of A431 cells.

Transcriptomic analysis reveals mitochondrial pathways associated with distinct adolescent behavioral phenotypes and stress response

Adolescent individuals exhibit great variability in cortical dynamics and behavioral outcomes. The developing adolescent brain is highly sensitive to social experiences and environmental insults, influencing how personality traits emerge. A distinct pattern of mitochondrial gene expression in the prefrontal cortex (PFC) during adolescence underscores the essential role of mitochondria in brain maturation and the development of mental illnesses. Mitochondrial features in certain brain regions account for behavioral differences in adulthood. However, it remains unclear whether distinct adolescent behavioral phenotypes and the behavioral consequences of early adolescent stress exposure in rats are accompanied by changes in PFC mitochondria-related genes and mitochondria respiratory chain capacity. We performed a behavioral characterization during late adolescence (postnatal day, PND 47-50), including naïve animals and a group exposed to stress from PND 31-40 (10 days of footshock and 3 restraint sessions) by z-normalized data from three behavioral domains: anxiety (light-dark box tests), sociability (social interaction test) and cognition (novel-object recognition test). Employing principal component analysis, we identified three clusters: naïve with higher-behavioral z-score (HBZ), naïve with lower-behavioral z-score (LBZ), and stressed animals. Genome-wide transcriptional profiling unveiled differences in the expression of mitochondria-related genes in both naïve LBZ and stressed animals compared to naïve HBZ. Genes encoding subunits of oxidative phosphorylation complexes were significantly down-regulated in both naïve LBZ and stressed animals and positively correlated with behavioral z-score of phenotypes. Our network topology analysis of mitochondria-associated genes found Ndufa10 and Cox6a1 genes as central identifiers for naïve LBZ and stressed animals, respectively. Through high-resolution respirometry analysis, we found that both naïve LBZ and stressed animals exhibited a reduced prefrontal phosphorylation capacity and redox dysregulation. Our findings identify an association between mitochondrial features and distinct adolescent behavioral phenotypes while also underscoring the detrimental functional consequences of adolescent stress on the PFC.

Childhood adverse life events and skeletal muscle mitochondrial function

Social stress experienced in childhood is associated with adverse health later in life. Mitochondrial function has been implicated as a mechanism for how stressful life events "get under the skin" to influence physical wellbeing. Using data from the Study of Muscle, Mobility and Aging (n=879, 59% women), linear models examined whether adverse childhood events (i.e., physical abuse) were associated with two measures of skeletal muscle mitochondrial energetics in older adults: (1) maximal adenosine triphosphate production (ATP max ) and (2) maximal state 3 respiration (Max OXPHOS). Forty-five percent of the sample reported experiencing 1+ adverse childhood event. After adjustment, each additional event was associated with -0.07 SD (95% CI= - 0.12, -0.01) lower ATP max . No association was observed with Max OXPHOS. Adverse childhood events are associated with lower ATP production in later life. Findings indicate that mitochondrial function may be a mechanism in understanding how early social stress influences health in later life.

The effect of vitrification on blastocyst mitochondrial DNA dynamics and gene expression profiles

PURPOSE

Does vitrification/warming affect the mitochondrial DNA (mtDNA) content and the gene expression profile of blastocysts?

METHODS

Prospective cohort study in which 89 blastocysts were obtained from 50 patients between July 2017 and August 2018. mtDNA was measured in a total of 71 aneuploid blastocysts by means of real-time polymerase chain reaction (RT-PCR). Transcriptomic analysis was performed by RNA sequencing (RNA-seq) in an additional 8 aneuploid blastocysts cultured for 0 h after warming, and 10 aneuploid blastocysts cultured for 4-5 h after warming.

RESULTS

A significant decrease in mtDNA content just during the first hour after the warming process in blastocysts was found (P < 0.05). However, mtDNA content experimented a significantly increased along the later culture hours achieving the original mtDNA levels before vitrification after 4-5 h of culture (P < 0.05). Gene expression analysis and functional enrichment analysis revealed that such recovery was accompanied by upregulation of pathways associated with embryo developmental capacity and uterine embryo development. Interestingly, the significant increase in mtDNA content observed in blastocysts just after warming also coincided with the differential expression of several cellular stress response-related pathways, such as apoptosis, DNA damage, humoral immune responses, and cancer.

CONCLUSION

To our knowledge, this is the first study demonstrating in humans, a modulation in blastocysts mtDNA content in response to vitrification and warming. These results will be useful in understanding which pathways and mechanisms may be activated in human blastocysts following vitrification and warming before a transfer.

Glucocorticoid feedback paradox: a homage to Mary Dallman

As the end product of the hypothalamus-pituitary-adrenal (HPA) axis, the glucocorticoid hormones cortisol and corticosterone coordinate circadian activities, stress-coping, and adaptation to change. For this purpose, the hormone promotes energy metabolism and controls defense reactions in the body and brain. This life-sustaining action exerted by glucocorticoids occurs in concert with the autonomic nervous and immune systems, transmitters, growth factors/cytokines, and neuropeptides. The current contribution will focus on the glucocorticoid feedback paradox in the HPA-axis: the phenomenon that stress responsivity remains resilient if preceded by stress-induced secretion of glucocorticoid hormone, but not if this hormone is previously administered. Furthermore, in animal studies, the mixed progesterone/glucocorticoid antagonist RU486 or mifepristone switches to an apparent partial agonist upon repeated administration. To address these enigmas several interesting phenomena are highlighted. These include the conditional nature of the excitation/inhibition balance in feedback regulation, the role of glucose as a determinant of stress responsivity, and the potential of glucocorticoids in resetting the stress response system. The analysis of the feedback paradox provides also a golden opportunity to review the progress in understanding the role of glucocorticoid hormone in resilience and vulnerability during stress, the science that was burned deeply in Mary Dallman's emotions.

Glyphosate is Harmful to Early Life Stages of the Viviparous Fish Jenynsia Multidentata: Biochemical and Locomotor Effects

Glyphosate is the most widely used herbicide worldwide due to its efficacy in weed control in agriculture. This herbicide has been consistently detected in the aquatic environment, causing harmful consequences to nontarget organisms residing in agricultural regions. In this study, we assessed the effects of environmentally relevant concentrations of glyphosate (30-100 µg/L) on the early life stages of the viviparous fish Jenynsia multidentata through biochemical and locomotor endpoints. At 96 h of exposure, 30 and 65 µg/L glyphosate caused an increase in acetylcholinesterase (AChE) activity, and 65 µg/L glyphosate also augmented the levels of lipid peroxidation. Glyphosate at 100 µg/L did not alter the activity of acetylcholinesterase or the levels of lipid peroxidation, but it stimulated the activity of the cellular detoxification enzyme glutathione S-transferase. In addition, all concentrations affected the swimming of the fish. Under light conditions, glyphosate caused hypolocomotion at all concentrations tested, whereas under dark conditions, this was observed at 30 and 100 µg/L. Hyperlocomotion was observed at 65 µg/L glyphosate. These findings are alarming for the health of fish, such as J. multidentata that inhabit streams that pass through agricultural areas, especially for the early life stages of these fish. Research studying the effects of pollutants on native species is relevant to improve regulation that protects aquatic ecosystems.

Mitochondrial health index correlates with plasma circulating cell-free mitochondrial DNA in bipolar disorder

Although mitochondrial dysfunction is known to play an essential role in the pathophysiology of bipolar disorder (BD), there is a glaring gap in our understanding of how mitochondrial dysfunction can modulate clinical phenotypes. An emerging paradigm suggests mitochondria play an important non-energetic role in adaptation to stress, impacting cellular resilience and acting as a source of systemic allostatic load. Known as mitochondrial allostatic load, this (phenomenon) occurs when mitochondria are unable to recalibrate and maintain cell homeostasis. This study aimed to evaluate the composite mitochondrial health index (MHI) in BD subjects and non-psychiatry controls. We will also explore whether lower MIH will be related to higher cell-free mtDNA (ccf-mtDNA) levels and poor clinical outcomes. In this study, 14 BD-I patients and 16 age- and sex-matched non-psychiatry controls were enrolled. Peripheral blood mononuclear cells (PBMCs) were used to measure the enzymatic activities of citrate synthase and complexes I, II, and IV and mtDNA copy number. Ccf-mtDNA was evaluated by qPCR in plasma. Mitochondrial quality control (MQC) proteins were evaluated by western blotting. After adjusting for confounding variables, such as age, sex, body mass index (BMI), and smoking status, patients with BD presented lower MHI compared to non-psychiatry controls, as well as higher ccf-mtDNA levels that negatively correlated with MHI. Because the MQC network is essential to maintain mitochondrial health, MHI and ccf-mtDNA were also examined in relation to several MQC-related proteins, such as Fis-1, Opa-1, and LC3. Our results showed that MHI correlated negatively with Fis-1 and positively with Opa-1 and LC3. Accordingly, ccf-mtDNA had a positive correlation with Fis-1 and a negative correlation with Opa-1 and LC3. Furthermore, we found a noteworthy inverse correlation between illness severity and MHI, with lower MHI and higher ccf-mtDNA levels in subjects with a longer illness duration, worse functional status, and higher depressive symptoms. Our findings indicate that mitochondrial allostatic load contributes to BD, suggesting mitochondria represent a potential biological intersection point that could contribute to impaired cellular resilience and increased vulnerability to stress and mood episodes. Ultimately, by linking mitochondrial dysfunction to disease progression and poor outcomes, we might be able to build a predictive marker that explains how mitochondrial function and its regulation contribute to BD development and that may eventually serve as a treatment guide for both old and new therapeutic targets.

Mitochondrial dysfunction as a possible trigger of neuroinflammation at post-traumatic stress disorder (PTSD)

Post-traumatic stress disorder (PTSD) is a neuropsychiatric disorder that occurs in approximately 15% of people as a result of some traumatic events. The main symptoms are re-experiencing and avoidance of everything related to this event and hyperarousal. The main component of the pathophysiology of PTSD is an imbalance in the functioning of the hypothalamic-pituitary-adrenal axis (HPA) and development of neuroinflammation. In parallel with this, mitochondrial dysfunction is observed, as in many other diseases. In this review, we focus on the question how mitochondria may be involved in the development of neuroinflammation and its maintaining at PTSD. First, we describe the differences in the operation of the neuro-endocrine system during stress versus PTSD. We then show changes in the activity/expression of mitochondrial proteins in PTSD and how they can affect the levels of hormones involved in PTSD development, as well as how mitochondrial damage/pathogen-associated molecule patterns (DAMPs/PAMPs) trigger development of inflammation. In addition, we examine the possibility of treating PTSD-related inflammation using mitochondria as a target.

A big picture of the mitochondria-mediated signals: From mitochondria to organism

Mitochondria, well-known for years as the powerhouse and biosynthetic center of the cell, are dynamic signaling organelles beyond their energy production and biosynthesis functions. The metabolic functions of mitochondria, playing an important role in various biological events both in physiological and stress conditions, transform them into important cellular stress sensors. Mitochondria constantly communicate with the rest of the cell and even from other cells to the organism, transmitting stress signals including oxidative and reductive stress or adaptive signals such as mitohormesis. Mitochondrial signal transduction has a vital function in regulating integrity of human genome, organelles, cells, and ultimately organism.

Sexually dimorphic mechanisms of VGLUT-mediated protection from dopaminergic neurodegeneration

Parkinson's disease (PD) targets some dopamine (DA) neurons more than others. Sex differences offer insights, with females more protected from DA neurodegeneration. The mammalian vesicular glutamate transporter VGLUT2 and Drosophila ortholog dVGLUT have been implicated as modulators of DA neuron resilience. However, the mechanisms by which VGLUT2/dVGLUT protects DA neurons remain unknown. We discovered DA neuron dVGLUT knockdown increased mitochondrial reactive oxygen species in a sexually dimorphic manner in response to depolarization or paraquat-induced stress, males being especially affected. DA neuron dVGLUT also reduced ATP biosynthetic burden during depolarization. RNA sequencing of VGLUT+ DA neurons in mice and flies identified candidate genes that we functionally screened to further dissect VGLUT-mediated DA neuron resilience across PD models. We discovered transcription factors modulating dVGLUT-dependent DA neuroprotection and identified dj-1β as a regulator of sex-specific DA neuron dVGLUT expression. Overall, VGLUT protects DA neurons from PD-associated degeneration by maintaining mitochondrial health.

Glucocorticoid-driven mitochondrial damage stimulates Tau pathology

Prolonged exposure to glucocorticoids, the main stress hormones, damages the brain and is a risk factor for depression and Alzheimer's disease. Two major drivers of glucocorticoid-related neurotoxicity are mitochondrial dysfunction and Tau pathology; however, the molecular/cellular mechanisms precipitating these events, and their causal relationship, remain unclear. Using cultured murine hippocampal neurons and 4-5-month-old mice treated with the synthetic glucocorticoid dexamethasone, we investigate the mechanisms underlying glucocorticoid-induced mitochondrial damage and Tau pathology. We find that glucocorticoids stimulate opening of the mitochondrial permeability transition pore via transcriptional upregulation of its activating component, cyclophilin D. Inhibition of cyclophilin D is protective against glucocorticoid-induced mitochondrial damage as well as Tau phosphorylation and oligomerization in cultured neurons. We further identify the mitochondrially-targeted compound mito-apocynin as an inhibitor of glucocorticoid-induced permeability transition pore opening, and show that this compound protects against mitochondrial dysfunction, Tau pathology, synaptic loss, and behavioural deficits induced by glucocorticoids in vivo. Finally, we demonstrate that mito-apocynin and the glucocorticoid receptor antagonist mifepristone rescue Tau pathology in cytoplasmic hybrid cells, an ex vivo Alzheimer's disease model wherein endogenous mitochondria are replaced with mitochondria from Alzheimer's subjects. These findings show that mitochondrial permeability transition pore opening is a precipitating factor in glucocorticoid-induced mitochondrial dysfunction, and that this event stimulates Tau pathogenesis. Our data also link glucocorticoids to mitochondrial dysfunction and Tau pathology in the context of Alzheimer's disease and suggest that mitochondria are promising therapeutic targets for mitigating stress- and Tau-related brain damage.

Randomized controlled trial investigating potential effects of relaxation on mitochondrial function in immune cells: A pilot experiment

This study aimed to investigate the effect of a relaxation response induced by hypnosis on the mitochondrial energy production of immune cells compared to an everyday relaxing situation. Chronically stressed individuals (88% women) with at least moderate suggestibility were randomized to a hypnosis (20 min relaxation hypnosis; n = 20) or a control condition (20 min documentary; n = 22). Before and after intervention, peripheral blood was collected. The primary outcomes were mitochondrial respiration and density in immune cells measured by high-resolution respirometry and citrate synthase activity assays. As secondary outcome, perceived stress, anxiety, and depressive mood were assessed. The intervention led to no significant Group × Time effects on mitochondrial bioenergetic parameters but a significant Time effect (ηp2 = .09 -.10). Thus, there were no differences in the experimental conditions concerning the measured parameters of mitochondrial bioenergetics. Exploratory subanalyses indicated that stress, anxiety, and depressive mood were linked to lower mitochondrial respiration. Individuals with higher anxiety had less decrease in routine respiration over time than those with lower anxiety (ηp2 = .09). This study explores the effects of relaxation in the form of hypnosis compared to watching a video on the energy metabolism of immune cells. Relaxation, whether in targeted (hypnosis) or untargeted (documentary) form, affected mitochondrial respiration. Further research should focus on the long-term effects of relaxation on bioenergetics. The trial was retrospectively registered on 07/12/2021, DRKS00027356, https://drks.de/search/de/trial/DRKS00027356.

Dietary nucleotides can prevent glucocorticoid-induced telomere attrition in a fast-growing wild vertebrate

Telomeres are chromosome protectors that shorten during eukaryotic cell replication and in stressful conditions. Developing individuals are susceptible to telomere erosion when their growth is fast and resources are limited. This is critical because the rate of telomere attrition in early life is linked to health and life span of adults. The metabolic telomere attrition hypothesis (MeTA) suggests that telomere dynamics can respond to biochemical signals conveying information about the organism's energetic state. Among these signals are glucocorticoids, hormones that promote catabolic processes, potentially impairing costly telomere maintenance, and nucleotides, which activate anabolic pathways through the cellular enzyme target of rapamycin (TOR), thus preventing telomere attrition. During the energetically demanding growth phase, the regulation of telomeres in response to two contrasting signals - one promoting telomere maintenance and the other attrition - provides an ideal experimental setting to test the MeTA. We studied nestlings of a rapidly developing free-living passerine, the great tit (Parus major), that either received glucocorticoids (Cort-chicks), nucleotides (Nuc-chicks) or a combination of both (NucCort-chicks), comparing these with controls (Cnt-chicks). As expected, Cort-chicks showed telomere attrition, while NucCort- and Nuc-chicks did not. NucCort-chicks was the only group showing increased expression of a proxy for TOR activation (the gene TELO2), of mitochondrial enzymes linked to ATP production (cytochrome oxidase and ATP-synthase) and a higher efficiency in aerobically producing ATP. NucCort-chicks had also a higher expression of telomere maintenance genes (shelterin protein TERF2 and telomerase TERT) and of enzymatic antioxidant genes (glutathione peroxidase and superoxide dismutase). The findings show that nucleotide availability is crucial for preventing telomere erosion during fast growth in stressful environments.

Single-Nucleus Transcriptome Profiling of Dorsolateral Prefrontal Cortex: Mechanistic Roles for Neuronal Gene Expression, Including the 17q21.31 Locus, in PTSD Stress Response

OBJECTIVE

Multidisciplinary studies of posttraumatic stress disorder (PTSD) and major depressive disorder (MDD) implicate the dorsolateral prefrontal cortex (DLPFC) in disease risk and pathophysiology. Postmortem brain studies have relied on bulk-tissue RNA sequencing (RNA-seq), but single-cell RNA-seq is needed to dissect cell-type-specific mechanisms. The authors conducted the first single-nucleus RNA-seq postmortem brain study in PTSD to elucidate disease transcriptomic pathology with cell-type-specific resolution.

METHOD

Profiling of 32 DLPFC samples from 11 individuals with PTSD, 10 with MDD, and 11 control subjects was conducted (∼415K nuclei; >13K cells per sample). A replication sample included 15 DLPFC samples (∼160K nuclei; >11K cells per sample).

RESULTS

Differential gene expression analyses identified significant single-nucleus RNA-seq differentially expressed genes (snDEGs) in excitatory (EX) and inhibitory (IN) neurons and astrocytes, but not in other cell types or bulk tissue. MDD samples had more false discovery rate-corrected significant snDEGs, and PTSD samples had a greater replication rate. In EX and IN neurons, biological pathways that were differentially enriched in PTSD compared with MDD included glucocorticoid signaling. Furthermore, glucocorticoid signaling in induced pluripotent stem cell (iPSC)-derived cortical neurons demonstrated greater relevance in PTSD and opposite direction of regulation compared with MDD, especially in EX neurons. Many snDEGs were from the 17q21.31 locus and are particularly interesting given causal roles in disease pathogenesis and DLPFC-based neuroimaging (PTSD: ARL17B, LINC02210-CRHR1, and LRRC37A2; MDD: LRRC37A and LRP4), while others were regulated by glucocorticoids in iPSC-derived neurons (PTSD: SLC16A6, TAF1C; MDD: CDH3).

CONCLUSIONS

The study findings point to cell-type-specific mechanisms of brain stress response in PTSD and MDD, highlighting the importance of examining cell-type-specific gene expression and indicating promising novel biomarkers and therapeutic targets.

Graduate Student Literature Review: Mitochondrial response to heat stress and its implications on dairy cattle bioenergetics, metabolism, and production

The dairy industry depends upon the cow's successful lactation for economic profitability. Heat stress compromises the economic sustainability of the dairy industry by reducing milk production and increasing the risk of metabolic and pathogenic disease. Heat stress alters metabolic adaptations, such as nutrient mobilization and partitioning, that support the energetic demands of lactation. Metabolically inflexible cows are unable to enlist the necessary homeorhetic shifts that provide the needed nutrients and energy for milk synthesis, thereby impairing lactation performance. Mitochondria provide the energetic foundation that enable a myriad of metabolically demanding processes, such as lactation. Changes in an animal's energy requirements are met at the cellular level through alterations in mitochondrial density and bioenergetic capacity. Mitochondria also act as central stress modulators and coordinate tissues' energetic responses to stress by integrating endocrine signals, through mito-nuclear communication, into the cellular stress response. In vitro heat insults affect mitochondria through a compromise in mitochondrial integrity, which is linked to a decrease in mitochondrial function. However, limited evidence exists linking the in vivo metabolic effects of heat stress with parameters of mitochondrial behavior and function in lactating animals. This review summarizes the literature describing the cellular and subcellular effects of heat stress, with a focus on the effect of heat stress on mitochondrial bioenergetics and cellular dysfunction in livestock. Implications for lactation performance and metabolic health are also discussed.

A functional account of stimulation-based aerobic glycolysis and its role in interpreting BOLD signal intensity increases in neuroimaging experiments

In aerobic glycolysis, oxygen is abundant, and yet cells metabolize glucose without using it, decreasing their ATP per glucose yield by 15-fold. During task-based stimulation, aerobic glycolysis occurs in localized brain regions, presenting a puzzle: why produce ATP inefficiently when, all else being equal, evolution should favor the efficient use of metabolic resources? The answer is that all else is not equal. We propose that a tradeoff exists between efficient ATP production and the efficiency with which ATP is spent to transmit information. Aerobic glycolysis, despite yielding little ATP per glucose, may support neuronal signaling in thin (< 0.5 µm), information-efficient axons. We call this the efficiency tradeoff hypothesis. This tradeoff has potential implications for interpretations of task-related BOLD "activation" observed in fMRI. We hypothesize that BOLD "activation" may index local increases in aerobic glycolysis, which support signaling in thin axons carrying "bottom-up" information, or "prediction error"-i.e., the BIAPEM (BOLD increases approximate prediction error metabolism) hypothesis. Finally, we explore implications of our hypotheses for human brain evolution, social behavior, and mental disorders.

A ribosome-bound tRNA half stimulates mitochondrial translation during stress recovery in Trypanosoma brucei

The protozoan parasite Trypanosoma brucei and its disease-causing relatives are among the few organisms that barely regulate the transcription of protein-coding genes. Yet, alterations in its gene expression are essential to survive in different host environments. Recently, tRNA-derived RNAs have been implicated as regulators of many cellular processes within and beyond translation. Previously, we identified the tRNAThr-3'-half (AGU) as a ribosome-associated non-coding RNA able to enhance global translation. Here we report that the tRNAThr-3'-half is generated upon starvation inside the mitochondria. The tRNAThr-3'-half associates with mitochondrial ribosomes and stimulates translation during stress recovery, positively affecting mitochondrial activity and, consequently, cellular energy production capacity. Our results describe an organelle ribosome-associated ncRNA involved in translation regulation to boost the central hub of energy metabolism as an immediate stress recovery response.

Chronic Stress Decreases Lactation Performance

The ability to provision offspring with milk is a significant adaptive feature of mammals that allows for considerable maternal regulation of offspring beyond gestation, as milk provides complete nutrition for developing neonates. For mothers, lactation is a period of marked increases in energetic and nutritive demands to support milk synthesis; because of this considerable increase in demand imposed on multiple physiological systems, lactation is particularly susceptible to the effects of chronic stress. Here, we present work that explores the impact of chronic stress during lactation on maternal lactation performance (i.e., milk quality and quantity) and the expression of key milk synthesis genes in mammary tissue using a Sprague-Dawley rat model. We induced chronic stress using a well-established, ethologically relevant novel male intruder paradigm for 10 consecutive days during the postpartum period. We hypothesized that the increased energetic burden of mounting a chronic stress response during lactation would decrease lactation performance. Specifically, we predicted that chronic exposure to this social stressor would decrease either milk quality (i.e., composition of proximate components and energy density) or quantity. We also predicted that changes in proximate composition (i.e., lipid, lactose, and protein concentrations) would be associated with changes in gene expression levels of milk synthesis genes. Our results supported our hypothesis that chronic stress impairs lactation performance. Relative to the controls, chronically stressed rats had lower milk yields. We also found that milk quality was decreased; milk from chronically stressed mothers had lower lipid concentration and lower energy density, though protein and lactose concentrations were not different between treatment groups. Although there was a change in proximate composition, chronic stress did not impact mammary gland expression of key milk synthesis genes. Together, this work demonstrates that exposure to a chronic stressor impacts lactation performance, which in turn has the potential to impact offspring development via maternal effects.

Whole blood mitochondrial copy number in clinical populations with mood disorders: a meta-analysis

Background

Major depressive disorder (MDD) and bipolar disorder (BD), are globally prevalent, contributing to significant disease burden and adverse health outcomes. These mood disorders are associated with changes in many aspects of brain reward pathways, yet cellular and molecular changes in the brain are not readily available in clinical populations. Therefore, the use of biomarkers as proxies for changes in the brain are necessary. The proliferation of mitochondria in blood has emerged as a potentially useful biomarker, yet a clear consensus on how these mood disorders impact mitochondrial DNA copy number (mtDNAcn) has not been reached.

Methods

Following PRISMA guidelines for a systematic search, 22 papers met inclusion criteria for meta-analysis (10 MDD, 10 BD, 2 both MDD and BD). We extracted demographic, disorder, and methodological information with mtDNAcn. Using the metafor package for R, calculated effect sizes were used in random effects or meta regression models for MDD and BD.

Results

Our results show a trending increase in mtDNAcn in patients with MDD, which reaches significance when one study with outlying demographic characteristics is excluded. Overall, there was no effect of BD on mtDNAcn, however, further subgroup and meta-regression analysis indicated the effects on mtDNAcn are dependent on BD type.

Conclusions

Together our data suggest whole blood/leukocyte mtDNAcn may be a useful biomarker for mood disorders, with MDD and BD Type II associated with higher mtDNAcn, and BD Type I associated with lower mtDNAcn. Further study of blood mtDNAcn could predict downstream health outcomes or treatment responsivity in individuals with mood disorders.

Gestational stress decreases postpartum mitochondrial respiration in the prefrontal cortex of female rats

Postpartum depression (PPD) is a major psychiatric complication of childbirth, affecting up to 20% of mothers, yet remains understudied. Mitochondria, dynamic organelles crucial for cell homeostasis and energy production, share links with many of the proposed mechanisms underlying PPD pathology. Brain mitochondrial function is affected by stress, a major risk factor for development of PPD, and is linked to anxiety-like and social behaviors. Considering the importance of mitochondria in regulating brain function and behavior, we hypothesized that mitochondrial dysfunction is associated with behavioral alterations in a chronic stress-induced rat model of PPD. Using a validated and translationally relevant chronic mild unpredictable stress paradigm during late gestation, we induced PPD-relevant behaviors in adult postpartum Wistar rats. In the mid-postpartum, we measured mitochondrial function in the prefrontal cortex (PFC) and nucleus accumbens (NAc) using high-resolution respirometry. We then measured protein expression of mitochondrial complex proteins and 4-hydroxynonenal (a marker of oxidative stress), and Th1/Th2 cytokine levels in PFC and plasma. We report novel findings that gestational stress decreased mitochondrial function in the PFC, but not the NAc of postpartum dams. However, in groups controlling for the effects of either stress or parity alone, no differences in mitochondrial respiration measured in either brain regions were observed compared to nulliparous controls. This decrease in PFC mitochondrial function in stressed dams was accompanied by negative behavioral consequences in the postpartum, complex-I specific deficits in protein expression, and increased Tumor Necrosis Factor alpha cytokine levels in plasma and PFC. Overall, we report an association between PFC mitochondrial respiration, PPD-relevant behaviors, and inflammation following gestational stress, highlighting a potential role for mitochondrial function in postpartum health.

Activation of cell-free mtDNA-TLR9 signaling mediates chronic stress-induced social behavior deficits

Inflammation and social behavior deficits are associated with a number of neuropsychiatric disorders. Chronic stress, a major risk factor for depression and other mental health conditions is known to increase inflammatory responses and social behavior impairments. Disturbances in mitochondria function have been found in chronic stress conditions, however the mechanisms that link mitochondrial dysfunction to stress-induced social behavior deficits are not well understood. In this study, we found that chronic restraint stress (RS) induces significant increases in serum cell-free mitochondrial DNA (cf-mtDNA) levels in mice, and systemic Deoxyribonuclease I (DNase I) treatment attenuated RS-induced social behavioral deficits. Our findings revealed potential roles of mitophagy and Mitochondrial antiviral-signaling protein (MAVS) in mediating chronic stress-induced changes in cf-mtDNA levels and social behavior. Furthermore, we showed that inhibition of Toll-like receptor 9 (TLR9) attenuates mtDNA-induced social behavior deficits. Together, these findings show that cf-mtDNA-TLR9 signaling is critical in mediating stress-induced social behavior deficits.

Cellular allostatic load is linked to increased energy expenditure and accelerated biological aging

Stress triggers anticipatory physiological responses that promote survival, a phenomenon termed allostasis. However, the chronic activation of energy-dependent allostatic responses results in allostatic load, a dysregulated state that predicts functional decline, accelerates aging, and increases mortality in humans. The energetic cost and cellular basis for the damaging effects of allostatic load have not been defined. Here, by longitudinally profiling three unrelated primary human fibroblast lines across their lifespan, we find that chronic glucocorticoid exposure increases cellular energy expenditure by ∼60%, along with a metabolic shift from glycolysis to mitochondrial oxidative phosphorylation (OxPhos). This state of stress-induced hypermetabolism is linked to mtDNA instability, non-linearly affects age-related cytokines secretion, and accelerates cellular aging based on DNA methylation clocks, telomere shortening rate, and reduced lifespan. Pharmacologically normalizing OxPhos activity while further increasing energy expenditure exacerbates the accelerated aging phenotype, pointing to total energy expenditure as a potential driver of aging dynamics. Together, our findings define bioenergetic and multi-omic recalibrations of stress adaptation, underscoring increased energy expenditure and accelerated cellular aging as interrelated features of cellular allostatic load.

Single Cell Transcriptome of Stress Vulnerability Network in mouse Prefrontal Cortex

Increased vulnerability to stress is a major risk factor for the manifestation of several mood disorders, including major depressive disorder (MDD). Despite the status of MDD as a significant donor to global disability, the complex integration of genetic and environmental factors that contribute to the behavioral display of such disorders has made a thorough understanding of related etiology elusive. Recent developments suggest that a brain-wide network approach is needed, taking into account the complex interplay of cell types spanning multiple brain regions. Single cell RNA-sequencing technologies can provide transcriptomic profiling at the single-cell level across heterogenous samples. Furthermore, we have previously used local field potential oscillations and machine learning to identify an electrical brain network that is indicative of a predisposed vulnerability state. Thus, this study combined single cell RNA-sequencing (scRNA-Seq) with electrical brain network measures of the stress-vulnerable state, providing a unique opportunity to access the relationship between stress network activity and transcriptomic changes within individual cell types. We found especially high numbers of differentially expressed genes between animals with high and low stress vulnerability brain network activity in astrocytes and glutamatergic neurons but we estimated that vulnerability network activity depends most on GABAergic neurons. High vulnerability network activity included upregulation of microglia and mitochondrial and metabolic pathways, while lower vulnerability involved synaptic regulation. Genes that were differentially regulated with vulnerability network activity significantly overlapped with genes identified as having significant SNPs by human GWAS for depression. Taken together, these data provide the gene expression architecture of a previously uncharacterized stress vulnerability brain state, enabling new understanding and intervention of predisposition to stress susceptibility.

Local coordination of mRNA storage and degradation near mitochondria modulates C. elegans ageing

Mitochondria are central regulators of healthspan and lifespan, yet the intricate choreography of multiple, tightly controlled steps regulating mitochondrial biogenesis remains poorly understood. Here, we uncover a pivotal role for specific elements of the 5'-3' mRNA degradation pathway in the regulation of mitochondrial abundance and function. We find that the mRNA degradation and the poly-A tail deadenylase CCR4-NOT complexes form distinct foci in somatic Caenorhabditis elegans cells that physically and functionally associate with mitochondria. Components of these two multi-subunit complexes bind transcripts of nuclear-encoded mitochondria-targeted proteins to regulate mitochondrial biogenesis during ageing in an opposite manner. In addition, we show that balanced degradation and storage of mitochondria-targeted protein mRNAs are critical for mitochondrial homeostasis, stress resistance and longevity. Our findings reveal a multifaceted role of mRNA metabolism in mitochondrial biogenesis and show that fine-tuning of mRNA turnover and local translation control mitochondrial abundance and promote longevity in response to stress and during ageing.

Brain mitochondrial diversity and network organization predict anxiety-like behavior in male mice

The brain and behavior are under energetic constraints, limited by mitochondrial energy transformation capacity. However, the mitochondria-behavior relationship has not been systematically studied at a brain-wide scale. Here we examined the association between multiple features of mitochondrial respiratory chain capacity and stress-related behaviors in male mice with diverse behavioral phenotypes. Miniaturized assays of mitochondrial respiratory chain enzyme activities and mitochondrial DNA (mtDNA) content were deployed on 571 samples across 17 brain areas, defining specific patterns of mito-behavior associations. By applying multi-slice network analysis to our brain-wide mitochondrial dataset, we identified three large-scale networks of brain areas with shared mitochondrial signatures. A major network composed of cortico-striatal areas exhibited the strongest mitochondria-behavior correlations, accounting for up to 50% of animal-to-animal behavioral differences, suggesting that this mito-based network is functionally significant. The mito-based brain networks also overlapped with regional gene expression and structural connectivity, and exhibited distinct molecular mitochondrial phenotype signatures. This work provides convergent multimodal evidence anchored in enzyme activities, gene expression, and animal behavior that distinct, behaviorally-relevant mitochondrial phenotypes exist across the male mouse brain.

The role and risks of selective adaptation in extreme coral habitats

The alarming rate of climate change demands new management strategies to protect coral reefs. Environments such as mangrove lagoons, characterized by extreme variations in multiple abiotic factors, are viewed as potential sources of stress-tolerant corals for strategies such as assisted evolution and coral propagation. However, biological trade-offs for adaptation to such extremes are poorly known. Here, we investigate the reef-building coral Porites lutea thriving in both mangrove and reef sites and show that stress-tolerance comes with compromises in genetic and energetic mechanisms and skeletal characteristics. We observe reduced genetic diversity and gene expression variability in mangrove corals, a disadvantage under future harsher selective pressure. We find reduced density, thickness and higher porosity in coral skeletons from mangroves, symptoms of metabolic energy redirection to stress response functions. These findings demonstrate the need for caution when utilizing stress-tolerant corals in human interventions, as current survival in extremes may compromise future competitive fitness.