Sex-specific differences in mitochondria biogenesis, morphology, respiratory function, and ROS homeostasis in young mouse heart and brain

Berry-Derived Polyphenols in Cardiovascular Pathologies: Mechanisms of Disease and the Role of Diet and Sex

Cardiovascular disease (CVD) prevalence, pathogenesis, and manifestation is differentially influenced by biological sex. Berry polyphenols target several signaling pathways pertinent to CVD development, including inflammation, oxidative stress, and cardiac and vascular remodeling, and there are innate differences in these pathways that also vary by sex. There is limited research systematically investigating sex differences in berry polyphenol effects on these pathways, but there are fundamental findings at this time that suggest a sex-specific effect. This review will detail mechanisms within these pathological pathways, how they differ by sex, and how they may be individually targeted by berry polyphenols in a sex-specific manner. Because of the substantial polyphenolic profile of berries, berry consumption represents a promising interventional tool in the treatment and prevention of CVD in both sexes, but the mechanisms in which they function within each sex may vary.

Neuroinflammation, oxidative stress and their interplay in neuropathic pain: Focus on specialized pro-resolving mediators and NADPH oxidase inhibitors as potential therapeutic strategies

Neuropathic pain (NP) is a chronic condition that results from a lesion or disease of the nervous system, greatly impacting patients' quality of life. Current pharmacotherapy options deliver inadequate and/or insufficient responses and thus a significant unmet clinical need remains for alternative treatments in NP. Neuroinflammation, oxidative stress and their reciprocal relationship are critically involved in NP pathophysiology. In this context, new pharmacological approaches, aiming at enhancing the resolution phase of inflammation and/or restoring redox balance by targeting specific reactive oxygen species (ROS) sources, are emerging as potential therapeutic strategies for NP, with improved efficacy and safety profiles. Several reports have demonstrated that administration of exogenous specialized pro-resolving mediators (SPMs) ameliorates NP pathophysiology. Likewise, deletion or inhibition of the ROS-generating enzyme NADPH oxidase (NOX), particularly its isoforms 2 and 4, results in beneficial effects in NP models. Notably, SPMs also modulate oxidative stress and NOX also regulates neuroinflammation. By targeting neuroinflammatory and oxidative pathways, both SPMs analogues and isoform-specific NOX inhibitors are promising therapeutic strategies for NP.

Sex differences in renal mitochondrial function: a hormone-gous opportunity for research

Sex differences (biological distinctions between males and females) present a complex interplay of genetic, developmental, biological, and environmental factors. More and more studies are shedding light on the importance of sex differences in normal physiology and susceptibility to cancer, cardiovascular and renal conditions, and neurodegenerative diseases. This mini-review is devoted to the role of sex dimorphisms in renal function, with a focus on the distinctions between male and female mitochondria. Here, we cover the aspects of renal mitochondrial bioenergetics where sex differences have been reported to date, for instance, biogenesis, reactive oxygen species production, and oxidative stress. Special attention is devoted to the effects of sex hormones, such as estrogen and testosterone, on mitochondrial bioenergetics in the kidney in physiology and pathophysiology.

Maternal Ferritin Levels during Pregnancy and ADHD Symptoms in 4-Year-Old Children: Results from the INMA-INfancia y Medio Ambiente (Environment and Childhood) Prospective Birth Cohort Study

Ferritin status during prenatal brain development may influence the risk of attention deficit and hyperactivity disorder (ADHD) symptoms in childhood. We investigated the association of maternal ferritin in pregnancy and ADHD-like symptoms in offspring. A total of 1095 mother-child pairs from three birth cohorts of the INMA Project (Spain) were studied. Maternal plasma ferritin in pregnancy was measured at 11.57 weeks of gestation. Children′s ADHD-like symptoms at ages 4–5 years were assessed using the ADHD Rating Scale-IV. The count model of the zero-inflated Poisson regression model showed a significant inverse association between ferritin (continuous variable) and inattention, β = −0.19 (−0.32, −0.07), for boys. Comparing ferritin level by tertiles, significant differences were observed between the first tertile ([1.98, 20.92]) and the second ([20.92, 38.79]) and third tertiles ([38.79, 216.5]) (mg/L).The number of symptoms was lower for those in the third tertile, β = −0.3 (−0.55, −0.5), and for those in the second one, β = −0.37 (−0.6, −0.14). The model stratification by sex also showed this inverse association for boys only, β = −0.21 (−0.34, −0.08). No associations were found between ferritin level and hyperactivity or total ADHD symptoms. High ferritin levels during pregnancy show a protective association with child inattentive-type ADHD symptoms.

Susceptibility Factors in Chronic Lung Inflammatory Responses to Engineered Nanomaterials

Engineered nanomaterials (ENMs) are products of the emerging nanotechnology industry and many different types of ENMs have been shown to cause chronic inflammation in the lungs of rodents after inhalation exposure, suggesting a risk to human health. Due to the increasing demand and use of ENMs in a variety of products, a careful evaluation of the risks to human health is urgently needed. An assessment of the immunotoxicity of ENMs should consider susceptibility factors including sex, pre-existing diseases, deficiency of specific genes encoding proteins involved in the innate or adaptive immune response, and co-exposures to other chemicals. This review will address evidence from experimental animal models that highlights some important issues of susceptibility to chronic lung inflammation and systemic immune dysfunction after pulmonary exposure to ENMs.

Age-Related Changes and Sex-Related Differences in Brain Iron Metabolism

Iron is an essential element that participates in numerous cellular processes. Any disruption of iron homeostasis leads to either iron deficiency or iron overload, which can be detrimental for humans' health, especially in elderly. Each of these changes contributes to the faster development of many neurological disorders or stimulates progression of already present diseases. Age-related cellular and molecular alterations in iron metabolism can also lead to iron dyshomeostasis and deposition. Iron deposits can contribute to the development of inflammation, abnormal protein aggregation, and degeneration in the central nervous system (CNS), leading to the progressive decline in cognitive processes, contributing to pathophysiology of stroke and dysfunctions of body metabolism. Besides, since iron plays an important role in both neuroprotection and neurodegeneration, dietary iron homeostasis should be considered with caution. Recently, there has been increased interest in sex-related differences in iron metabolism and iron homeostasis. These differences have not yet been fully elucidated. In this review we will discuss the latest discoveries in iron metabolism, age-related changes, along with the sex differences in iron content in serum and brain, within the healthy aging population and in neurological disorders such as multiple sclerosis, Parkinson's disease, Alzheimer's disease, and stroke.

Traumatic stress history interacts with sex and chronic peripheral inflammation to alter mitochondrial function of synaptosomes

BACKGROUND

Repeated exposures to chronic stress can lead to long lasting negative behavioral and metabolic outcomes. Here, we aim to determine the impact of chronic stress and chronic low-level inflammation on behavior and synaptosomal metabolism.

METHODS

Male (n = 31) and female (n = 32) C57Bl/6 mice underwent chronic repeated predation stress or daily handling for two rounds of 15 consecutive days of exposure during the adolescent and early adult timeframes. Subsequently, mice were exposed to repeated lipopolysaccharide (LPS; 7.5 × 10⁵ EU/kg) or saline injections every third day for eight weeks. Exploratory and social behaviors were assessed in the open field and social interaction tests prior to examination of learning and memory with the Barnes Maze. Mitochondrial function and morphology were assessed in synaptosomes post-mortem using the Cell Mito Stress test and Seahorse XFe24 analyzer, TEM, and western analysis, respectively. In addition, expression of TNF-α, IL-1ß, and ROMO1 were examined in the hippocampus and prefrontal cortex with Taqman qPCR. Circulating pro- and anti-inflammatory cytokines in the periphery were assessed using the MSD V-plex Proinflammatory Panel 1 following the first and last LPS injection as well as at the time of tissue collection. Circulating ROMO1 was assessed in terminal samples via ELISA.

RESULTS

Exposure to repeated predatory stress increased time spent in the corners of the open field, suggestive of anxiety-like behavior, in both males and females. There were no significant group differences in the social interaction test and minimal effects were evident in the Barnes maze. A history of chronic stress interacted with chronic LPS in male mice to lead to a deficit in synaptosomal respiration. Female mice were more sensitive to both chronic stress and chronic LPS such that either a history of chronic stress or chronic LPS exposure was sufficient to disrupt synaptosomal respiration in females. Both stress and chronic LPS were sufficient to increase inflammation and reactive oxygen in males centrally and peripherally. Females had increased markers of peripheral inflammation following acute LPS but no evidence of peripheral or central increases in inflammatory factors or reactive oxygen following chronic exposures.

CONCLUSION

Collectively, these data suggest that while metrics of inflammation and reactive oxygen are disrupted in males following chronic stress and chronic LPS, only the combined condition is sufficient to alter synaptosomal respiration. Conversely, although evidence of chronic inflammation or chronic elevation in reactive oxygen is absent, females demonstrate profound shifts in synaptosomal mitochondrial function with either a history of chronic stress or a history of chronic inflammation. These data highlight that different mechanisms are likely in play between the sexes and that sex differences in neural outcomes may be precipitated by sex-specific effects of life experiences on mitochondrial function in the synapse.

ATR-IR and EPR spectroscopy for following the membrane restoration of isolated cortical synaptosomes in aluminium-induced Alzheimer's disease - Like rat model

Synaptosomal membrane peroxidation and alteration in its biophysical properties are associated with Aluminium (Al) toxicity that may lead to cognitive dysfunction and Alzheimer's disease (AD) like pathogenesis. Here we investigated the therapeutic potential of Lepedium sativum (LS) as a natural anti-inflammatory, antioxidant and as acetyl cholinesterase inhibitor in treating Al induced AD-like in rat model. We utilized ATR-IR spectroscopy to follow the restoration in the damaged membrane structure of isolated rat cortical synaptosomes and its biophysical properties, electron paramagnetic resonance (EPR) spin trapping to follow NADPH oxidase activity (NOX), and EPR spin labelling in response to LS treatment after Al intoxication. We measured the concentration of Ca²⁺ ions in rat cortical tissue by inductively coupled plasma (ICP), the brain atrophy/curing and hydrocephalus by magnetic resonance imaging (MRI) besides light microscope histopathology. Our results revealed significant increase in synaptosomal membrane rgidification, order, lipid packing, reactive oxygen species (ROS) production and Ca²⁺ ion concentration as a result of Al intoxication. The dramatic increase in Ca²⁺ ion concentration detected in AD group associated with the increase in synaptic membrane polarity and EPR-detected order S-parameter suggest that release of synaptic vesicles into synaptic cleft might be hindered. LS treatment reversed these changes in synaptic membranes, and rescued an observed deficit in the exploratory behaviour of AD group. Our results also strongly suggest that the synaptosomal membrane phospholipids that underwent free radical attacks mediated by AlCl3, due to greater NOX activity, was prevented in the LS group. The results of ATR-IR and EPR spectroscopic techniques recommend LS as a promising therapeutic agent against synaptic membrane alterations opening a new window for AD drug developers.

Sex-specific differences in transcriptomic profiles and cellular characteristics of oligodendrocyte precursor cells

The susceptibility to neurological and psychiatric disorders reveals sexual dimorphism in the structure and function of human brains. Recent evidence has also demonstrated the sex-related differences in cellular components of the brain, including neurons, microglia, astrocytes, and endothelial cells. Oligodendrocyte precursor cells (OPCs) regulate the neuronal system in various ways and play crucial roles in brain homeostasis beyond their well-known role as a reservoir for mature oligodendrocytes. Although recent studies have shown regional diversities and heterogeneities of OPCs, sex-related differences in OPCs are largely unknown. Here, we revealed transcriptomic differences in OPCs isolated from male and female neonatal rat brains. Furthermore, we demonstrated sex-dependent differences in OPCs regarding proliferation, migration, differentiation, tolerance against ischemic stress, energy metabolism, and the ability to regulate the blood-brain barrier integrity.

Improving translational research in sex-specific effects of comorbidities and risk factors in ischaemic heart disease and cardioprotection: position paper and recommendations of the ESC Working Group on Cellular Biology of the Heart

Ischaemic heart disease (IHD) is a complex disorder and a leading cause of death and morbidity in both men and women. Sex, however, affects several aspects of IHD, including pathophysiology, incidence, clinical presentation, diagnosis as well as treatment and outcome. Several diseases or risk factors frequently associated with IHD can modify cellular signalling cascades, thus affecting ischaemia/reperfusion injury as well as responses to cardioprotective interventions. Importantly, the prevalence and impact of risk factors and several comorbidities differ between males and females, and their effects on IHD development and prognosis might differ according to sex. The cellular and molecular mechanisms underlying these differences are still poorly understood, and their identification might have important translational implications in the prediction or prevention of risk of IHD in men and women. Despite this, most experimental studies on IHD are still undertaken in animal models in the absence of risk factors and comorbidities, and assessment of potential sex-specific differences are largely missing. This ESC WG Position Paper will discuss: (i) the importance of sex as a biological variable in cardiovascular research, (ii) major biological mechanisms underlying sex-related differences relevant to IHD risk factors and comorbidities, (iii) prospects and pitfalls of preclinical models to investigate these associations, and finally (iv) will provide recommendations to guide future research. Although gender differences also affect IHD risk in the clinical setting, they will not be discussed in detail here.

Oxidative Stress and BPA Toxicity: An Antioxidant Approach for Male and Female Reproductive Dysfunction

Bisphenol A (BPA) is a non-persistent anthropic and environmentally ubiquitous compound widely employed and detected in many consumer products and food items; thus, human exposure is prolonged. Over the last ten years, many studies have examined the underlying molecular mechanisms of BPA toxicity and revealed links among BPA-induced oxidative stress, male and female reproductive defects, and human disease. Because of its hormone-like feature, BPA shows tissue effects on specific hormone receptors in target cells, triggering noxious cellular responses associated with oxidative stress and inflammation. As a metabolic and endocrine disruptor, BPA impairs redox homeostasis via the increase of oxidative mediators and the reduction of antioxidant enzymes, causing mitochondrial dysfunction, alteration in cell signaling pathways, and induction of apoptosis. This review aims to examine the scenery of the current BPA literature on understanding how the induction of oxidative stress can be considered the "fil rouge" of BPA's toxic mechanisms of action with pleiotropic outcomes on reproduction. Here, we focus on the protective effects of five classes of antioxidants-vitamins and co-factors, natural products (herbals and phytochemicals), melatonin, selenium, and methyl donors (used alone or in combination)-that have been found useful to counteract BPA toxicity in male and female reproductive functions.

Sex differences in cancer mechanisms

We now know that cancer is many different diseases, with great variation even within a single histological subtype. With the current emphasis on developing personalized approaches to cancer treatment, it is astonishing that we have not yet systematically incorporated the biology of sex differences into our paradigms for laboratory and clinical cancer research. While some sex differences in cancer arise through the actions of circulating sex hormones, other sex differences are independent of estrogen, testosterone, or progesterone levels. Instead, these differences are the result of sexual differentiation, a process that involves genetic and epigenetic mechanisms, in addition to acute sex hormone actions. Sexual differentiation begins with fertilization and continues beyond menopause. It affects virtually every body system, resulting in marked sex differences in such areas as growth, lifespan, metabolism, and immunity, all of which can impact on cancer progression, treatment response, and survival. These organismal level differences have correlates at the cellular level, and thus, males and females can fundamentally differ in their protections and vulnerabilities to cancer, from cellular transformation through all stages of progression, spread, and response to treatment. Our goal in this review is to cover some of the robust sex differences that exist in core cancer pathways and to make the case for inclusion of sex as a biological variable in all laboratory and clinical cancer research. We finish with a discussion of lab- and clinic-based experimental design that should be used when testing whether sex matters and the appropriate statistical models to apply in data analysis for rigorous evaluations of potential sex effects. It is our goal to facilitate the evaluation of sex differences in cancer in order to improve outcomes for all patients.

Sex differences in inflammation, redox biology, mitochondria and autoimmunity

Autoimmune diseases are characterized by circulating antibodies and immune complexes directed against self-tissues that result in both systemic and organ-specific inflammation and pathology. Most autoimmune diseases occur more often in women than men. One exception is myocarditis, which is an inflammation of the myocardium that is typically caused by viral infections. Sex differences in the immune response and the role of the sex hormones estrogen and testosterone are well established based on animal models of autoimmune viral myocarditis as well as in mitochondrial function leading to reactive oxygen species production. RNA viruses like coxsackievirus B3, the primary cause of myocarditis in the US, activate the inflammasome through mitochondrial antiviral signaling protein located on the mitochondrial outer membrane. Toll-like receptor 4 and the inflammasome are the primary signaling pathways that increase inflammation during myocarditis, which is increased by testosterone. This review describes what is known about sex differences in inflammation, redox biology and mitochondrial function in the male-dominant autoimmune disease myocarditis and highlights gaps in the literature and future directions.

Sexual hormones regulate the redox status and mitochondrial function in the brain. Pathological implications

Compared to other organs, the brain is especially exposed to oxidative stress. In general, brains from young females tend to present lower oxidative damage in comparison to their male counterparts. This has been attributed to higher antioxidant defenses and a better mitochondrial function in females, which has been linked to neuroprotection in this group. However, these differences usually disappear with aging, and the incidence of brain pathologies increases in aged females. Sexual hormones, which suffer a decrease with normal aging, have been proposed as the key factors involved in these gender differences. Here, we provide an overview of redox status and mitochondrial function regulation by sexual hormones and their influence in normal brain aging. Furthermore, we discuss how sexual hormones, as well as phytoestrogens, may play an important role in the development and progression of several brain pathologies, including neurodegenerative diseases such as Alzheimer's and Parkinson's diseases, stroke or brain cancer.

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Sex hormones are reduced with aging, especially in females, affecting redox balance.

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Normal aging is associated to a worse redox homeostasis in the brain.

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Young females show better mitochondrial function and higher antioxidant defenses.

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Development of brain pathologies is influenced by sex hormones and phytoestrogens.

Transgenerational Effects of Periconception Heavy Metal Administration on Adipose Weight and Glucose Homeostasis in Mice at Maturity

We previously demonstrated that periconception maternal administration (2 mg/kg body weight each) of cadmium chloride (CdCl2) plus methylmercury (II) chloride (CH3HgCl) impaired glucose homeostasis and increased body weights and abdominal adipose tissue weight of male offspring in the F1 generation. However, transgenerational effects of this exposure have not been studied. Therefore, the effects of periconception Cd+Hg administration on indices of chronic diseases at adulthood in F2-F4 generations were examined. Male and female progeny of Cd+Hg periconceptionally treated females, and offspring of vehicle control females were bred with naïve CD1 mice to obtain F2 offspring, with additional crosses as above to the F4 generation (F1-F4 animals were not administered Cd+Hg). Birth weights and litter size were similar in all generations. Indices of impaired glucose homeostasis were observed in matrilineally descended F2 male offspring, including reduced glucose tolerance, along with increased basal phosphorylation of insulin receptor substrate 1 (IRS1) at serine 307 suggesting altered insulin signaling. Reduced glucose tolerance was also seen in F4 males. Increased body weight and/or abdominal adiposity were observed through the F4 generation in males descended matrilineally from the treated female progenitors. Patrilineally derived F2 females displayed reduced glucose tolerance. Females (F2) patrilineally and matrilineally derived displayed significant kidney enlargement. Periconception administration of cadmium and mercury caused persistent transgenerational effects in offspring through the F4 generation in the absence of continued toxicant exposure, with persistent transgenerational effects inherited specifically through the matrilineal germline.

Sex differences in redox homeostasis in renal disease

Sex differences in redox signaling in the kidney present new challenges and opportunities for understanding the physiology and pathophysiology of the kidney. This review will focus on reactive oxygen species, immune-related signaling pathways and endothelin-1 as potential mediators of sex-differences in redox homeostasis in the kidney. Additionally, this review will highlight male-female differences in redox signaling in several major cardiovascular and renal disorders namely acute kidney injury, diabetic nephropathy, kidney stone disease and salt-sensitive hypertension. Furthermore, we will discuss the contribution of redox signaling in the pathogenesis of postmenopausal hypertension and preeclampsia.

The mTOR Inhibitor Rapamycin Prevents General Anesthesia-Induced Changes in Synaptic Transmission and Mitochondrial Respiration in Late Postnatal Mice

Preclinical animal studies have continuously reported the possibility of long-lasting neurotoxic effects after general anesthesia in young animals. Such studies also show that the neurological changes induced by anesthesia in young animals differ by their neurodevelopmental stage. Exposure to anesthetic agents increase dendritic spines and induce sex-dependent changes of excitatory/inhibitory synaptic transmission in late postnatal mice, a critical synaptogenic period. However, the mechanisms underlying these changes remain unclear. Abnormal activation of the mammalian target of rapamycin (mTOR) signaling pathway, an important regulator of neurodevelopment, has also been shown to induce similar changes during neurodevelopment. Interestingly, previous studies show that exposure to general anesthetics during neurodevelopment can activate the mTOR signaling pathway. This study, therefore, evaluated the role of mTOR signaling after exposing postnatal day (PND) 16/17 mice to sevoflurane, a widely used inhalation agent in pediatric patients. We first confirmed that a 2-h exposure of 2.5% sevoflurane could induce widespread mTOR phosphorylation in both male and female mice. Pretreatment with the mTOR inhibitor rapamycin not only prevented anesthesia-induced mTOR phosphorylation, but also the increase in mitochondrial respiration and male-dependent enhancement of excitatory synaptic transmission. However, the changes in inhibitory synaptic transmission that appear after anesthesia in female mice were not affected by rapamycin pretreatment. Our results suggest that mTOR inhibitors may act as potential therapeutic agents for anesthesia-induced changes in the developing brain.

Exploring mechanisms of increased cardiovascular disease risk with antipsychotic medications: Risperidone alters the cardiac proteomic signature in mice

Atypical antipsychotic (AA) medications including risperidone (RIS) and olanzapine (OLAN) are FDA approved for the treatment of psychiatric disorders including schizophrenia, bipolar disorder and depression. Clinical side effects of AA medications include obesity, insulin resistance, dyslipidemia, hypertension and increased cardiovascular disease risk. Despite the known pharmacology of these AA medications, the mechanisms contributing to adverse metabolic side-effects are not well understood. To evaluate drug-associated effects on the heart, we assessed changes in the cardiac proteomic signature in mice administered for 4 weeks with clinically relevant exposure of RIS or OLAN. Using proteomic and gene enrichment analysis, we identified differentially expressed (DE) proteins in both RIS- and OLAN-treated mouse hearts (p < 0.05), including proteins comprising mitochondrial respiratory complex I and pathways involved in mitochondrial function and oxidative phosphorylation. A subset of DE proteins identified were further validated by both western blotting and quantitative real-time PCR. Histological evaluation of hearts indicated that AA-associated aberrant cardiac gene expression occurs prior to the onset of gross pathomorphological changes. Additionally, RIS treatment altered cardiac mitochondrial oxygen consumption and whole body energy expenditure. Our study provides insight into the mechanisms underlying increased patient risk for adverse cardiac outcomes with chronic treatment of AA medications.

Dimorphic effect of 17β-oestradiol on pathology and oxidative stress in experimental malaria

Malaria is the parasitic disease with the highest mortality worldwide; males exhibit higher mortality and more severe symptomatology than females, suggesting the participation of sexual hormones in protection and pathology. We have documented that gonadectomy modifies oxidative stress in Plasmodium berghei ANKA-infected mice in a dimorphic manner. However, gonadectomy decreases all sexual steroids levels, making it difficult to determine the contribution of each hormone to the results. This study aimed to explore the participation of 17β-oestradiol (E2) in oxidative stress in the blood, spleen, liver and brain of P. berghei-infected female and male mice. E2 was administered to intact or gonadectomized (GX) male and female mice to assess their effects on parasitaemia, body weight loss and hypothermia. We also measured the effect of E2 on the specific activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) and on malondialdehyde (MDA) levels in the blood, spleen, liver and brain of CBA/Ca male and female mice infected with P. berghei ANKA. We detected the effects of E2 and sexual dimorphism on all tissues and variables analysed. Administration of E2 increased parasitaemia in intact mice. However, reconstitution of GX female mice with E2 decreased parasitaemia. E2 decreased body weight and differentially modulated oxidative stress depending on the sex, infection and tissue analysed. Low antioxidant activity was detected in the brain, suggesting additional protective antioxidant mechanisms in the brain independent of antioxidant enzymes. Our results explained, at least in part, the sexual dimorphism in this experimental model of malaria.

Mitochondrial connexin 43 in sex-dependent myocardial responses and estrogen-mediated cardiac protection following acute ischemia/reperfusion injury

Preserving mitochondrial activity is crucial in rescuing cardiac function following acute myocardial ischemia/reperfusion (I/R). The sex difference in myocardial functional recovery has been observed after I/R. Given the key role of mitochondrial connexin43 (Cx43) in cardiac protection initiated by ischemic preconditioning, we aimed to determine the implication of mitochondrial Cx43 in sex-related myocardial responses and to examine the effect of estrogen (17β-estradiol, E2) on Cx43, particularly mitochondrial Cx43-involved cardiac protection following I/R. Mouse primary cardiomyocytes and isolated mouse hearts (from males, females, ovariectomized females, and doxycycline-inducible Tnnt2-controlled Cx43 knockout without or with acute post-ischemic E2 treatment) were subjected to simulated I/R in culture or Langendorff I/R (25-min warm ischemia/40-min reperfusion), respectively. Mitochondrial membrane potential and mitochondrial superoxide production were measured in cardiomyocytes. Myocardial function and infarct size were determined. Cx43 and its isoform, Gja1-20k, were assessed in mitochondria. Immunoelectron microscopy and co-immunoprecipitation were also used to examine mitochondrial Cx43 and its interaction with estrogen receptor-α by E2 in mitochondria, respectively. There were sex disparities in stress-induced cardiomyocyte mitochondrial function. E2 partially restored mitochondrial activity in cardiomyocytes following acute injury. Post-ischemia infusion of E2 improved functional recovery and reduced infarct size with increased Cx43 content and phosphorylation in mitochondria. Ablation of cardiac Cx43 aggravated mitochondrial damage and abolished E2-mediated cardiac protection during I/R. Female mice were more resistant to myocardial I/R than age-matched males with greater protective role of mitochondrial Cx43 in female hearts. Post-ischemic E2 usage augmented mitochondrial Cx43 content and phosphorylation, increased mitochondrial Gja1-20k, and showed cardiac protection.

Diabetic Pregnancy and Maternal High-Fat Diet Impair Mitochondrial Dynamism in the Developing Fetal Rat Heart by Sex-Specific Mechanisms

Infants born to diabetic or obese mothers are at greater risk of heart disease at birth and throughout life, but prevention is hindered because underlying mechanisms remain poorly understood. Using a rat model, we showed that prenatal exposure to maternal diabetes and a high-fat diet caused diastolic and systolic dysfunction, myocardial lipid accumulation, decreased respiratory capacity, and oxidative stress in newborn offspring hearts. This study aimed to determine whether mitochondrial dynamism played a role. Using confocal live-cell imaging, we examined mitochondrial dynamics in neonatal rat cardiomyocytes (NRCM) from four prenatally exposed groups: controls, diabetes, high-fat diet, and combination exposed. Cardiac expression of dynamism-related genes and proteins were compared, and gender-specific differences were evaluated. Findings show that normal NRCM have highly dynamic mitochondria with a well-balanced number of fusion and fission events. Prenatal exposure to diabetes or a high-fat diet impaired dynamism resulting in shorter, wider mitochondria. Mechanisms of impaired dynamism were gender-specific and protein regulated. Females had higher expression of fusion proteins which may confer a cardioprotective effect. Prenatally exposed male hearts had post-translational modifications known to impair dynamism and influence mitophagy-mediated cell death. This study identifies mitochondrial fusion and fission proteins as targetable, pathogenic regulators of heart health in offspring exposed to excess circulating maternal fuels.

Fetal Programming and Sexual Dimorphism of Mitochondrial Protein Expression and Activity of Hearts of Prenatally Hypoxic Guinea Pig Offspring

Chronic intrauterine hypoxia is a programming stimulus of cardiovascular dysfunction. While the fetal heart adapts to the reduced oxygenation, the offspring heart becomes vulnerable to subsequent metabolic challenges as an adult. Cardiac mitochondria are key organelles responsible for an efficient energy supply but are subject to damage under hypoxic conditions. We propose that intrauterine hypoxia alters mitochondrial function as an underlying programming mechanism of contractile dysfunction in the offspring. Indices of mitochondrial function such as mitochondrial DNA content, Complex (C) I-V expression, and CI/CIV enzyme activity were measured in hearts of male and female offspring at 90 days old exposed to prenatal hypoxia (10.5% O2) for 14 d prior to term (65 d). Both left ventricular tissue and cardiomyocytes exhibited decreased mitochondrial DNA content, expression of CIV, and CI/CIV activity in male hearts. In female cardiomyocytes, hypoxia had no effect on protein expression of CI-CV nor on CI/CIV activity. This study suggests that chronic intrauterine hypoxia alters the intrinsic properties of select respiratory complexes as a programming mechanism of cardiac dysfunction in the offspring. Sex differences in mitochondrial function may underlie the increased vulnerability of age-matched males compared to females in cardiovascular disease and heart failure.

Effects of Cardiac Hypertrophy, Diabetes, Aging, and Pregnancy on the Cardioprotective Effects of Postconditioning in Male and Female Rats

Background

Aging, left ventricular hypertrophy (LVH), diabetes mellitus, and pregnancy are well-recognized risk factors that increase the prevalence of cardio-ischemic events and are linked to poor clinical recovery following acute myocardial infarction. The coexistence of these risk factors with ischemic heart disease (IHD) deteriorates disease prognosis and could potentially lead to fatal arrhythmias and heart failure. The objective of this study was to investigate the vulnerability of hearts with aging, LVH, diabetes, and pregnancy to ischemic insult and their response to pacing postconditioning- (PPC-) induced heart protection.

Methods

Hearts isolated from aged, spontaneously hypertensive and diabetic male and female rats and hearts from pregnant female rats (n=8 per group) were subjected to coronary occlusion followed by reperfusion using a modified Langendorff system. Hemodynamics data were computed digitally, and cardiac damage was accessed by measurements of infarct size and cardiac enzyme release.

Results

There were no significant differences in the vulnerability of all hearts to ischemic insult compared to their respective controls. PPC improved cardiac hemodynamics and reduced infarct size and cardiac enzyme release in hearts isolated from aged and spontaneously hypertensive female rats and female rats with hypertrophied hearts subjected to PPC (P < 0.001). Aged or hypertrophied male hearts were not protected by PPC maneuver. Moreover, the protective effects of PPC were lost in diabetic male and female hearts although retained in hearts from pregnant rats.

Conclusions

We demonstrate that aging, LVH, diabetes mellitus, and pregnancy do not affect cardiac vulnerability to ischemic insult. Moreover, PPC mediates cardioprotection in a gender-specific manner in aged and spontaneously hypertensive rats. Diabetes mellitus provokes the protective effects of PPC on both genders equally. Finally, we demonstrate that PPC is a new cardioprotective maneuver in hearts from pregnant female rats.

Genes involved in mitochondrial biogenesis and function may not show synchronised responses to mitochondria in shell gland of laying chickens under infectious bronchitis virus challenge

BACKGROUND

Egg formation takes place in the oviduct of laying hens over a 24 h period. Infectious bronchitis virus (IBV) causes pathological lesions in the chicken oviduct. In the current study, mitochondrial counts were determined in three different segments of the oviduct during egg formation in laying chickens challenged with IBV T strain. Nuclear DNA encoded genes that are involved in mitochondrial biogenesis, fission and function were studied in the shell gland of the oviduct undergoing virus multiplication.

RESULTS

In the shell gland, the mitochondrial count was significantly lower (P < 0.05) in the challenged group, compared with the control group. However, it did not vary in response to IBV challenge in the isthmus and magnum regions of the oviduct. The gene succinate dehydrogenase complex, subunit A, flavoprotein variant (SDHA) was down-regulated in the shell gland by IBV challenge (P < 0.05), while other genes being studied did not show responses to the challenge (P > 0.05). Differential expression of the genes was observed at different time-points of egg-shell formation. The expression levels of citrate synthase (CS), cytochrome C, somatic (CYC, S) and sodium-potassium adenosine triphosphatase (Na+-K+ATPase) genes were significantly higher, while those of SDHA and dynamin related protein 1 (Drp1) genes were significantly lower, at 15 h compared with 5 h following oviposition of the previous egg. The expression level of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) did not show significant change at different time-points.

CONCLUSIONS

It was concluded that IBV T strain infection in laying hens reduced mitochondrial counts only in the shell gland region of the oviduct. The genes involved in mitochondrial biogenesis or function may not show synchronised responses to that of mitochondria in the shell gland of chickens under T strain of IBV challenge.

Mitochondrial dysfunction in acute kidney injury and sex-specific implications

The kidney is one of the most energy-demanding organs in the human body, and the maintenance of mitochondrial homeostasis is central to kidney function. Recent advances have led to a greater appreciation of how mitochondrial dysfunction contributes to the pathogenesis of AKI, from decreased ATP production, to enhanced mitochondrial oxidative stress, cell necrosis and apoptosis. Accumulating evidence suggests sexual dimorphism in the response to AKI with males demonstrating greater risk for developing ischemia-reperfusion and sepsis-induced kidney injury. In contrast, females may be more susceptible to nephrotoxic-AKI. There are important sex-related differences in mitochondrial respiration, biogenesis and dynamics that likely contribute to the observed sexual dimorphism in AKI. Sex hormones mediate many of these differences with multiple preclinical studies demonstrating the renoprotective actions of estrogen in many rodent models of AKI. Estrogenic control of mitochondrial biogenesis, function and reactive oxygen species (ROS) generation is discussed. Furthermore, the potential role for sex chromosomes in mediating sex differences in AKI is examined. Novel animal models such as the "four core genotypes" (FCG) mouse model provide us with important tools to study sex chromosome effects in kidney health and disease. By understanding the influences of sexual dimorphism or sex hormones on mitochondrial homeostasis and disease manifestations, we may be able to identify novel therapeutic targets and improve existing treatment options for AKI.

Prohibitin: A hypothetical target for sex-based new therapeutics for metabolic and immune diseases

IMPACT STATEMENT

Traditional sex-related biases in research are now obsolete, and it is important to identify the sex of humans, animals, and even cells in research protocols, due to the role of sex as a fundamental facet of biology, predisposition to disease, and response to therapy. Genetic sex, epigenetics and hormonal regulations, generate sex-dimorphisms. Recent investigations acknowledge sex differences in metabolic and immune health as well as chronic diseases. Prohibitin, an evolutionarily conserved molecule, has pleotropic functions in mitochondrial housekeeping, plasma membrane signaling, and nuclear genetic transcription. Studies in adipocytes, macrophages, and transgenic mice indicate that prohibitin interacts with sex steroids and plays a role in mediating sex differences in adipose tissues and immune cell types. Prohibitin may, depending on context, modulate predisposition to chronic metabolic diseases and malignancy and, because of these attributes, could be a target for sex-based therapies of metabolic and immune-related diseases as well as cancer.

Estrogens, Estrogen Receptors Effects on Cardiac and Skeletal Muscle Mitochondria

Mitochondria are unique organelles present in almost all cell types. They are involved not only in the supply of energy to the host cell, but also in multiple biochemical and biological processes like calcium homeostasis, production, and regulation of reactive oxygen species (ROS), pH control, or cell death. The importance of mitochondria in cell biology and pathology is increasingly recognized. Being maternally inherited, mitochondria exhibit a tissue-specificity, because most of the mitochondrial proteins are encoded by the nuclear genome. This renders them exquisitely well-adapted to the physiology of the host cell. It is thus not surprising that mitochondria show a sexual dimorphism and that they are also prone to the influence of sex chromosomes and sex hormones. Estrogens affect mitochondria through multiple processes involving membrane and nuclear estrogen receptors (ERs) as well as more direct effects. Moreover, estrogen receptors have been identified within mitochondria. The effects of estrogens on mitochondria comprise protein content and specific activity of mitochondrial proteins, phospholipid content of membranes, oxidant and anti-oxidant capacities, oxidative phosphorylation, and calcium retention capacities. Herein we will briefly review the life cycle and functions of mitochondria, the importance of estrogen receptors and the effects of estrogens on heart and skeletal muscle mitochondria.

Prenatal hypoxia impairs cardiac mitochondrial and ventricular function in guinea pig offspring in a sex-related manner

Adverse intrauterine conditions cause fetal growth restriction and increase the risk of adult cardiovascular disease. We hypothesize that intrauterine hypoxia impairs fetal heart function, is sustained after birth, and manifests as both cardiac and mitochondrial dysfunction in offspring guinea pigs (GPs). Pregnant GPs were exposed to 10.5% O₂ (HPX) at 50 days of gestation (full term = 65 days) or normoxia (NMX) for the duration of the pregnancy. Pups were allowed to deliver vaginally and raised in a NMX environment. At 90 days of age, mean arterial pressure (MAP) was measured in anesthetized GPs. NMX and prenatally HPX offspring underwent echocardiographic imaging for in vivo measurement of left ventricular cardiac morphology and function, and O₂ consumption rates and complex IV enzyme activity were measured from isolated cardiomyocytes and mitochondria, respectively. Prenatal HPX increased ( P < 0.01) MAP (52.3 ± 1.3 and 58.4 ± 1.1 mmHg in NMX and HPX, respectively) and decreased ( P < 0.05) stroke volume (439.8 ± 54.5 and 289.4 ± 15.8 μl in NMX and HPX, respectively), cardiac output (94.4 ± 11.2 and 67.3 ± 3.8 ml/min in NMX and HPX, respectively), ejection fraction, and fractional shortening in male, but not female, GPs. HPX had no effect on left ventricular wall thickness or end-diastolic volume in either sex. HPX reduced mitochondrial maximal respiration and respiratory reserve capacity and complex IV activity rates in hearts of male, but not female, GPs. Prenatal HPX is a programming stimulus that increases MAP and decreases cardiac and mitochondrial function in male offspring. Sex-related differences in the contractile and mitochondrial responses suggest that female GPs are protected from cardiovascular programming of prenatal HPX.

Sex and gender differences in developmental programming of metabolism

BACKGROUND

The early life environment experienced by an individual in utero and during the neonatal period is a major factor in shaping later life disease risk-including susceptibility to develop obesity, diabetes, and cardiovascular disease. The incidence of metabolic disease is different between males and females. How the early life environment may underlie these sex differences is an area of active investigation.

SCOPE OF REVIEW

The purpose of this review is to summarize our current understanding of how the early life environment influences metabolic disease risk in a sex specific manner. We also discuss the possible mechanisms responsible for mediating these sexually dimorphic effects and highlight the results of recent intervention studies in animal models.

MAJOR CONCLUSIONS

Exposure to states of both under- and over-nutrition during early life predisposes both sexes to develop metabolic disease. Females seem particularly susceptible to develop increased adiposity and disrupted glucose homeostasis as a result of exposure to in utero undernutrition or high sugar environments, respectively. The male placenta is particularly vulnerable to damage by adverse nutritional states and this may underlie some of the metabolic phenotypes observed in adulthood. More studies investigating both sexes are needed to understand how changes to the early life environment impact differently on the long-term health of male and female individuals.

Neuroactive steroids, neurosteroidogenesis and sex

The nervous system is a target and a source of steroids. Neuroactive steroids are steroids that target neurons and glial cells. They include hormonal steroids originated in the peripheral glands, steroids locally synthesized by the neurons and glial cells (neurosteroids) and synthetic steroids, some of them used in clinical practice. Here we review the mechanisms of synthesis, metabolism and action of neuroactive steroids, including the role of epigenetic modifications and the mitochondria in their sex specific actions. We examine sex differences in neuroactive steroid levels under physiological conditions and their role in the establishment of sex dimorphic structures in the nervous system and sex differences in its function. In addition, particular attention is paid to neuroactive steroids under pathological conditions, analyzing how pathology alters their levels and their role as neuroprotective factors, considering the influence of sex in both cases.

Sex Differences in Neurotoxicogenetics

A major development in biomedical research is the recognition that the sex of an individual plays a key role in susceptibility, treatment, and outcomes of most diseases. In this contribution, we present evidence that sex is also important in the toxicity of many environmental toxicants and contributes to the effect of genetics. Thus, individual differences in response to toxicants includes genetic makeup, the environment and sex; in fact, sex differences may be considered a part of genetic constitution. In this review, we present evidence for sex contribution to susceptibility for a number of toxicants.

Sex-related differences in oxidative stress and neurodegeneration

Oxidative stress has been implicated in a number of neurodegenerative diseases spanning various fields of research. Reactive oxygen species can be beneficial or harmful, depending on their concentration. High levels of reactive oxygen species can lead to oxidative stress, which is an imbalance between free radicals and antioxidants. Increased oxidative stress can result in cell loss. Interestingly, sex differences have been observed in oxidative stress generation, which may underlie sex differences observed in neurodegenerative disorders. An enhanced knowledge of the role of sex hormones on oxidative stress signaling and cell loss can yield valuable information, leading to sex-based mechanistic approaches to neurodegeneration.

Prenatal particulate matter exposure and mitochondrial dysfunction at the maternal-fetal interface: Effect modification by maternal lifetime trauma and child sex

BACKGROUND

Prenatal ambient fine particulate matter (PM_2.5) and maternal chronic psychosocial stress have independently been linked to changes in mithochondrial DNA copy number (mtDNAcn), a marker of mitochondrial response and dysfunction. Further, overlapping research shows sex-specific effects of PM_2.5 and stress on developmental outcomes. Interactions among PM_2.5, maternal stress, and child sex have not been examined in this context.

METHODS

We examined associations among exposure to prenatal PM_2.5, maternal lifetime traumatic stressors, and mtDNAcn at birth in a sociodemographically diverse pregnancy cohort (N=167). Mothers' daily exposure to PM_2.5 over gestation was estimated using a satellite-based spatio-temporally resolved prediction model. Lifetime exposure to traumatic stressors was ascertained using the Life Stressor Checklist-Revised; exposure was categorized as high vs. low based on a median split. Quantitative real-time polymerase chain reaction (qPCR) was used to determine mtDNAcn in placenta and cord blood leukocytes. Bayesian Distributed Lag Interaction regression models (BDLIMs) were used to statistically model and visualize the PM_2.5 timing-dependent pattern of associations with mtDNAcn and explore effect modification by maternal lifetime trauma and child sex.

RESULTS

Increased PM_2.5 exposure across pregnancy was associated with decreased mtDNAcn in cord blood (cumulative effect estimate=-0.78; 95%CI -1.41, -0.16). Higher maternal lifetime trauma was associated with reduced mtDNAcn in placenta (β=-0.33; 95%CI -0.63, -0.02). Among women reporting low trauma, increased PM_2.5 exposure late in pregnancy (30-38weeks gestation) was significantly associated with decreased mtDNAcn in placenta; no significant association was found in the high trauma group. BDLIMs identified a significant 3-way interaction between PM_2.5, maternal trauma, and child sex. Specifically, PM_2.5 exposure between 25 and 40weeks gestation was significantly associated with increased placental mtDNAcn among boys of mothers reporting high trauma. In contrast, PM_2.5 exposure in this same window was significantly associated with decreased placental mtDNAcn among girls of mothers reporting low trauma. Similar 3-way interactive effects were observed in cord blood.

CONCLUSIONS

These results indicate that joint exposure to PM_2.5 in late pregnancy and maternal lifetime trauma influence mtDNAcn at the maternal-fetal interface in a sex-specific manner. Additional studies will assist in understanding if the sex-specific patterns reflect distinct pathophysiological processes in addition to mitochondrial dysfunction.

Mitochondria and Sex-Specific Cardiac Function

The focus of this chapter is the gender differences in mitochondria in cardiovascular disease. There is broad evidence suggesting that some of the gender differences in cardiovascular outcome may be partially related to differences in mitochondrial biology (Ventura-Clapier R, Moulin M, Piquereau J, Lemaire C, Mericskay M, Veksler V, Garnier A, Clin Sci (Lond) 131(9):803-822, 2017)). Mitochondrial disorders are causally affected by mutations in either nuclear or mitochondrial genes involved in the synthesis of respiratory chain subunits or in their posttranslational control. This can be due to mutations of the mtDNA which are transmitted by the mother or mutations in the nuclear DNA. Because natural selection on mitochondria operates only in females, mutations may have had more deleterious effects in males than in females (Ventura-Clapier R, Moulin M, Piquereau J, Lemaire C, Mericskay M, Veksler V, Garnier A, Clin Sci (Lond) 131(9):803-822, 2017; Camara AK, Lesnefsky EJ, Stowe DF. Antioxid Redox Signal 13(3):279-347, 2010). As mitochondrial mutations can affect all tissues, they are responsible for a large panel of pathologies including neuromuscular disorders, encephalopathies, metabolic disorders, cardiomyopathies, neuropathies, renal dysfunction, etc. Many of these pathologies present sex/gender specificity. Thus, alleviating or preventing mitochondrial dysfunction will contribute to mitigating the severity or progression of the development of diseases. Here, we present evidence for the involvement of mitochondria in the sex specificity of cardiovascular disorders.

Concussion: pathophysiology and clinical translation

The majority of the 3.8 million estimated annual traumatic brain injuries (TBI) in the United States are mild TBIs, or concussions, and they occur primarily in adolescents and young adults. A concussion is a brain injury associated with rapid brain movement and characteristic clinical symptoms, with no associated objective biomarkers or overt pathologic brain changes, thereby making it difficult to diagnose by neuroimaging or other objective diagnostic tests. Most concussion symptoms are transient and resolve within 1-2 weeks. Concussions share similar acute pathophysiologic perturbations to more severe TBI: there is a rapid release of neurotransmitters, which causes ionic disequilibrium across neuronal membranes. Re-establishing ionic homeostasis consumes energy and leads to dynamic changes in cerebral glucose uptake. The magnitude and duration of these changes are related to injury severity, with milder injuries showing faster normalization. Cerebral sex differences add further variation to concussion manifestation. Relative to the male brain, the female brain has higher overall cerebral blood flow, and demonstrates regional differences in glucose metabolism, inflammatory responses, and connectivity. Understanding the pathophysiology and clinical translation of concussion can move research towards management paradigms that will minimize the risk for prolonged recovery and repeat injury.

Survival kinase-dependent pathways contribute to gender difference in the response to myocardial ischemia-reperfusion and ischemic post-conditioning

The response to ischemia/reperfusion and the effects of ischemic post-conditioning (IPC) are sex-dependent, but the mechanisms have not been clarified. Male (M) and female (F) rat hearts isolated and perfused using the Langendorff technique were subject to 30 min of global ischemia (GI) and 60 min reperfusion (R). In IPC hearts, three cycles of 30-sec GI/30-sec R were applied at the beginning of R. Infarct size and myocardial function were assessed. Superoxide production, antioxidant systems, and expressions of phosphorylated forms of serine/threonine kinase (Akt), glycogen synthase kinase 3β (GSK-3β), protein kinase C ε (PKCε), endothelial nitric oxide synthase (eNOS), and apoptosis were measured. In the basal state, superoxide production and apoptosis were lower, and antioxidant systems and phospho-kinase expressions were higher in F rather than in M hearts. After ischemia-reperfusion, infarct size was less in F hearts, and post-ischemic recovery of myocardial function was higher in F rather than in M hearts. Superoxide production, phospho-kinase activity, phospho-eNOS, and apoptosis increased in both sexes while antioxidants decreased in both sexes. After IPC, infarct size, superoxide production, and apoptosis decreased and phospho-eNOS increased in F and M hearts but phospho-kinase expressions and post-ischemic recovery of myocardial function improved only in M hearts. These results show that Akt/GSK-3β/PKCε/eNOS-dependent pathways-mediated superoxide production and apoptosis appear as important factors involved in the observed gender differences.

Role of Sex Hormones on Brain Mitochondrial Function, with Special Reference to Aging and Neurodegenerative Diseases

The mitochondria have a fundamental role in both cellular energy supply and oxidative stress regulation and are target of the effects of sex steroids, particularly the neuroprotective ones. Aging is associated with a decline in the levels of different steroid hormones, and this decrease may underline some neural dysfunctions. Besides, modifications in mitochondrial functions associated with aging processes are also well documented. In this review, we will discuss studies that describe the modifications of brain mitochondrial function and of steroid levels associated with physiological aging and with neurodegenerative diseases. A special emphasis will be placed on describing and discussing our recent findings concerning the concomitant study of mitochondrial function (oxidative phosphorylation, oxidative stress) and brain steroid levels in both young (3-month-old) and aged (20-month-old) male and female mice.

Sex-specific differences in mitochondria biogenesis, morphology, respiratory function, and ROS homeostasis in young mouse heart and brain

Sex-specific differences in mitochondrial function and free radical homeostasis are reported in the context of aging but not well-established in pathogeneses occurring early in life. Here, we examine if sex disparity in mitochondria function, morphology, and redox status starts early and hence can be implicated in sexual dimorphism in cardiac as well as neurological disorders prevalent at young age. Although mitochondrial activity in the heart did not significantly vary between sexes, female brain exhibited enhanced respiration and higher reserve capacity. This was associated with lower H₂O₂ production in female cardiac and brain tissues. Using transmission electron microscopy, we found that the number of female cardiac mitochondria is moderately greater (117 ± 3%, P = 0.049, N = 4) than male's, which increased significantly for cortical mitochondria (134 ± 4%, P = 0.001, N = 4). However, male's cardiac mitochondria exhibited fragmented, circular, and smaller mitochondria relative to female's mitochondria, while no morphologic sex-dependent differences were observed in cortical mitochondria. No sex differences were detected in Nox2 and Nox4 proteins or O₂-consuming/H₂O₂-producing activities in brain homogenate or synaptosomes. However, a strong trend of increased EPR-detected NOX superoxide in male synaptosomes hinted at higher superoxide dismutase activity in female brains, which was confirmed by two independent protocols. We also provide direct evidence that respiring mitochondria generally produce an order-of-magnitude lower reactive oxygen species (ROS) proportions than currently estimated. Our results indicate that sex differences in mitochondrial biogenesis, bioenergetics, and morphology may start at young age and that sex-dependent SOD capacity may be responsible for differences in ROS homeostasis in heart and brain.