Estrogenic control of mitochondrial function and biogenesis

Effects of sex steroids on bones and muscles: Similarities, parallels, and putative interactions in health and disease

Estrogens and androgens influence the growth and maintenance of bones and muscles and are responsible for their sexual dimorphism. A decline in their circulating levels leads to loss of mass and functional integrity in both tissues. In the article, we highlight the similarities of the molecular and cellular mechanisms of action of sex steroids in the two tissues; the commonality of a critical role of mechanical forces on tissue mass and function; emerging evidence for an interplay between mechanical forces and hormonal and growth factor signals in both bones and muscles; as well as the current state of evidence for or against a cross-talk between muscles and bone. In addition, we review evidence for the parallels in the development of osteoporosis and sarcopenia with advancing age and the potential common mechanisms responsible for the age-dependent involution of these two tissues. Lastly, we discuss the striking difference in the availability of several drug therapies for the prevention and treatment of osteoporosis, as compared to none for sarcopenia. This article is part of a Special Issue entitled "Muscle Bone Interactions".

Estrogen receptor-β in mitochondria: implications for mitochondrial bioenergetics and tumorigenesis

Estrogen enhances mitochondrial function by enhancing mitochondrial biogenesis and sustaining mitochondrial energy-transducing capacity. Shifts in mitochondrial bioenergetic pathways from oxidative phosphorylation to glycolysis have been hypothesized to be involved in estrogen-induced tumorigenesis. Studies have shown that mitochondria are an important target of estrogen. Estrogen receptor-β (ERβ) has been shown to localize to mitochondria in a ligand-dependent or -independent manner and can affect mitochondrial bioenergetics and anti-apoptotic signaling. However, the functional role of mitochondrial ERβ in tumorigenesis remains unclear. Clinical studies of ERβ-related tumorigenesis have shown that ERβ stimulates mitochondrial metabolism to meet the high energy demands of processes such as cell proliferation, cell survival, and transformation. Thus, in elucidating the precise role of mitochondrial ERβ in cell transformation and tumorigenesis, it will be particularly valuable to explore new approaches for the development of medical treatments targeting mitochondrial ERβ-mediated mitochondrial function and preventing apoptosis.

Bioenergetic differences between MCF-7 and T47D breast cancer cells and their regulation by oestradiol and tamoxifen

Oestrogen receptor α (ERα+) breast tumours rely on mitochondria (mt) to generate ATP. The goal of the present study was to determine how oestradiol (E2) and 4-hydroxytamoxifen (4-OHT) affect cellular bioenergetic function in MCF-7 and T47D ERα+ breast cancer cells in serum-replete compared with dextran-coated charcoal (DCC)-stripped foetal bovine serum (FBS)-containing medium ('serum-starved'). Serum-starvation reduced oxygen consumption rate (OCR), extracellular acidification rate (ECAR), ATP-linked OCR and maximum mt capacity, reflecting lower ATP demand and mt respiration. Cellular respiratory stateapparent was unchanged by serum deprivation. 4-OHT reduced OCR independent of serum status. Despite having a higher mt DNA/nuclear DNA ratio than MCF-7 cells, T47D cells have a lower OCR and ATP levels and higher proton leak. T47D express higher nuclear respiratory factor-1 (NRF-1) and NRF-1-regulated, nuclear-encoded mitochondrial transcription factor TFAM and cytochrome c, but lower levels of cytochrome c oxidase, subunit IV, isoform 1 (COX4, COX4I1). Mitochondrial reserve capacity, reflecting tolerance to cellular stress, was higher in serum-starved T47D cells and was increased by 4-OHT, but was decreased by 4-OHT in MCF-7 cells. These data demonstrate critical differences in cellular energetics and responses to 4-OHT in these two ERα+ cell lines, likely reflecting cancer cell avoidance of apoptosis.

Mitochondrial and nuclear accumulation of the transcription factor ATFS-1 promotes OXPHOS recovery during the UPR(mt)

Mitochondrial diseases and aging are associated with defects in the oxidative phosphorylation machinery (OXPHOS), which are the only complexes composed of proteins encoded by separate genomes. To better understand genome coordination and OXPHOS recovery during mitochondrial dysfunction, we examined ATFS-1, a transcription factor that regulates mitochondria-to-nuclear communication during the mitochondrial UPR, via ChIP-sequencing. Surprisingly, in addition to regulating mitochondrial chaperone, OXPHOS complex assembly factor, and glycolysis genes, ATFS-1 bound directly to OXPHOS gene promoters in both the nuclear and mitochondrial genomes. Interestingly, atfs-1 was required to limit the accumulation of OXPHOS transcripts during mitochondrial stress, which required accumulation of ATFS-1 in the nucleus and mitochondria. Because balanced ATFS-1 accumulation promoted OXPHOS complex assembly and function, our data suggest that ATFS-1 stimulates respiratory recovery by fine-tuning OXPHOS expression to match the capacity of the suboptimal protein-folding environment in stressed mitochondria, while simultaneously increasing proteostasis capacity.

Sexual dimorphism in the expression of mitochondria-related genes in rat heart at different ages

Cardiovascular disease (CVD) is the leading cause of mortality worldwide. Moreover, sex and age are considered major risk factors in the development of CVDs. Mitochondria are vital for normal cardiac function, and regulation of mitochondrial structure and function may impact susceptibility to CVD. To identify potential role of mitochondria in sex-related differences in susceptibility to CVD, we analyzed the basal expression levels of mitochondria-related genes in the hearts of male and female rats. Whole genome expression profiling was performed in the hearts of young (8-week), adult (21-week), and old (78-week) male and female Fischer 344 rats and the expression of 670 unique genes related to various mitochondrial functions was analyzed. A significant (p<0.05) sexual dimorphism in expression levels of 46, 114, and 41 genes was observed in young, adult and old rats, respectively. Gene Ontology analysis revealed the influence of sex on various biological pathways related to cardiac energy metabolism at different ages. The expression of genes involved in fatty acid metabolism was significantly different between the sexes in young and adult rat hearts. Adult male rats also showed higher expression of genes associated with the pyruvate dehydrogenase complex compared to females. In young and adult hearts, sexual dimorphism was not noted in genes encoding oxidative phosphorylation. In old rats, however, a majority of genes involved in oxidative phosphorylation had higher expression in females compared to males. Such basal differences between the sexes in cardiac expression of genes associated with energy metabolism may indicate a likely involvement of mitochondria in susceptibility to CVDs. In addition, female rats showed lower expression levels of apoptotic genes in hearts compared to males at all ages, which may have implications for better preservation of cardiac mass in females than in males.

Sexual Dimorphism of Doxorubicin-Mediated Cardiotoxicity

Background—

Cardiovascular diseases are the major cause of mortality among both men and women with a lower incidence in women before menopause. The clinical use of doxorubicin, widely used as an antineoplastic agent, is markedly hampered by severe cardiotoxicity. Even if there is a significant sex difference in incidence of cardiovascular disease at the adult stage, it is not known whether a difference in doxorubicin-related cardiotoxicity between men and women also exists. The objective of this work was to explore the cardiac side effects of doxorubicin in adult rats and decipher whether signaling pathways involved in cardiac toxicity differ between sexes.

Methods and Results—

After 7 weeks of doxorubicin (2 mg/kg per week), males developed major signs of cardiomyopathy with cardiac atrophy, reduced left ventricular ejection fraction and 50% mortality. In contrast, no female died and their left ventricular ejection fraction was only moderately affected. Surprisingly, neither global oxidation levels nor the antioxidant response nor the apoptosis signaling pathways were altered by doxorubicin. However, the level of total adenosine monophosphate–activated protein kinase was severely decreased only in males. Moreover, markers of mitochondrial biogenesis and cardiolipin content were strongly reduced only in males. To analyze the onset of the pathology, maximal oxygen consumption rate of left ventricular permeabilized fibers after 4 weeks of treatment was reduced only in doxorubicin-treated males.

Conclusions—

Altogether, these results clearly evidence sex differences in doxorubicin toxicity. Cardiac mitochondrial dysfunction and adenosine monophosphate–activated protein kinase seem as critical sites of sex differences in cardiotoxicity as evidenced by significant statistical interactions between sex and treatment effects.

Sexually-dimorphic targeting of functionally-related genes in COPD

BACKGROUND

There is growing evidence that many diseases develop, progress, and respond to therapy differently in men and women. This variability may manifest as a result of sex-specific structures in gene regulatory networks that influence how those networks operate. However, there are few methods to identify and characterize differences in network structure, slowing progress in understanding mechanisms driving sexual dimorphism.

RESULTS

Here we apply an integrative network inference method, PANDA (Passing Attributes between Networks for Data Assimilation), to model sex-specific networks in blood and sputum samples from subjects with Chronic Obstructive Pulmonary Disease (COPD). We used a jack-knifing approach to build an ensemble of likely networks for each sex. By adapting statistical methods to compare these network ensembles, we were able to identify strong differential-targeting patterns associated with functionally-related sets of genes, including those involved in mitochondrial function and energy metabolism. Network analysis also identified several potential sex- and disease-specific transcriptional regulators of these pathways.

CONCLUSIONS

Network analysis yielded insight into potential mechanisms driving sexual dimorphism in COPD that were not evident from gene expression analysis alone. We believe our ensemble approach to network analysis provides a principled way to capture sex-specific regulatory relationships and could be applied to identify differences in gene regulatory patterns in a wide variety of diseases and contexts.

[Effect of 17β-estradiol on bioenergetic processes in the heart mitochondria of ovariectomized rats with insulin resistance]

Тhe bioenergetic processes in the heart mitochondria of Wistar rats with fructose-induced insulin resistance was investigated in female animals with different estrogen status. Respiration studies on isolated heart mitochondria by the polarographic method revealed that estrogen deficiency reduced complex IV activity, while its combination with high-fructose diet induced additional disturbances in the coupling of respiration and oxidative phosphorylation at the level of complex I of the electron transport chain. Exogenous 17b-estradiol inhibited the development of mitochondrial dysfunction in cardiomyocytes of ovariectomized rats with insulin resistance.

Oestrogen, ocular function and low-level vision: a review

Over the past 10 years, a literature has emerged concerning the sex steroid hormone oestrogen and its role in human vision. Herein, we review evidence that oestrogen (oestradiol) levels may significantly affect ocular function and low-level vision, particularly in older females. In doing so, we have examined a number of vision-related disorders including dry eye, cataract, increased intraocular pressure, glaucoma, age-related macular degeneration and Leber's hereditary optic neuropathy. In each case, we have found oestrogen, or lack thereof, to have a role. We have also included discussion of how oestrogen-related pharmacological treatments for menopause and breast cancer can impact the pathology of the eye and a number of psychophysical aspects of vision. Finally, we have reviewed oestrogen's pharmacology and suggest potential mechanisms underlying its beneficial effects, with particular emphasis on anti-apoptotic and vascular effects.

Expression of mitochondrial regulators PGC1α and TFAM as putative markers of subtype and chemoresistance in epithelial ovarian carcinoma

Epithelial ovarian carcinoma (EOC), the major cause of gynaecological cancer death, is a heterogeneous disease classified into five subtypes. Each subtype has distinct clinical characteristics and is associated with different genetic risk factors and molecular events, but all are treated with surgery and platinum/taxane regimes. Tumour progression and chemoresistance is generally associated with major metabolic alterations, notably altered mitochondrial function(s). Here, we report for the first time that the expression of the mitochondrial regulators PGC1α and TFAM varies between EOC subtypes; furthermore, we have identified a profile in clear-cell carcinoma consisting of undetectability of PGC1α/TFAM, and low ERα/Ki-67. By contrast, high-grade serous carcinomas were characterised by a converse state of PGC1α/TFAM, ERα positivity and a high Ki-67 index. Interestingly, loss of PGC1α/TFAM and ERα was found also in a non-clear cell EOC cell line made highly resistant to platinum in vitro. Similar to clear-cell carcinomas, these resistant cells also showed accumulation of glycogen. Altogether, our data provide mechanistic insights into the chemoresistant nature of ovarian clear-cell carcinomas. Furthermore, these findings corroborate the need to take into account the diversity of EOC and to develop subtype specific treatment strategies.

A genome-wide association study in the genetic analysis of idiopathic thrombophilia project suggests sex-specific regulation of mitochondrial DNA levels

Identifying genes that regulate mitochondrial DNA (mtDNA) levels is of interest due to an increasing number of diseases in humans that are associated with altered mtDNA levels. We searched for nuclear polymorphisms that influence mtDNA levels using a family-based genome-wide association (GWAS) method. Also, our aim was to determine if sex influences the genetic control of mtDNA levels. Two intron-polymorphisms, in the genes PARK2 and MRPL37, showed a tendency toward an association with mtDNA levels only in females and only in males, respectively. Both genes have a role in mitochondrial biogenesis and are potential candidates for the sex-specific control of mtDNA levels.

Phytoestrogens as alternative hormone replacement therapy in menopause: What is real, what is unknown

Menopause is characterized by an altered hormonal status and by a decrease in life quality due to the appearance of uncomfortable symptoms. Nowadays, with increasing life span, women spend one-third of their lifetime under menopause. Understanding menopause-associated pathophysiology and developing new strategies to improve the treatment of menopausal-associated symptoms is an important topic in the clinic. This review describes physiological and hormone alterations observed during menopause and therapeutic strategies used during this period. We critically address the benefits and doubts associated with estrogen/progesterone-based hormone replacement therapy (HRT) and discuss the use of phytoestrogens (PEs) as a possible alternative. These relevant plant-derived compounds have structural similarities to estradiol, interacting with cell proteins and organelles, presenting several advantages and disadvantages versus traditional HRT in the context of menopause. However, a better assessment of PEs safety/efficacy would warrant a possible widespread clinical use.

Endogenous NO upon estradiol-17β stimulation and NO donor differentially regulate mitochondrial S-nitrosylation in endothelial cells

Adduction of a nitric oxide (NO) moiety (NO(•)) to cysteines termed as S-nitrosylation (SNO) has emerged as a crucial mechanism for NO signaling crucial for mediating the vascular effects of estrogens. Mitochondrion is a known vascular risk factor; however, the effects of estrogens on mitochondrial SNO are incompletely understood. In this study we determined the effects of estradiol-17β (E2β) on mitochondrial protein SNO in primary human umbilical vein endothelial cells and compared the mitochondrial nitroso-proteomes in E2β- and a NO donor S-nitrosoglutathione (GSNO)-treated cells using a proteomics approach. Treatment with 10 nM E2β and 1 mM GSNO for 30 minutes significantly increased the levels of mitochondrial SNO-proteins. Subcellular localization of SNO-proteins showed mitochondria as the major cellular organelle for protein SNO in response to E2β and GSNO. E2β stimulated mitochondrial endothelial nitric oxide synthase (eNOS) phosphorylation and mitochondrial protein SNO that was enhanced by overexpression of mitochondrion or Golgi, but not membrane targeting eNOS constructs. We identified 11, 32, and 54 SNO-proteins in the mitochondria from the untreated, E2β-, and GSNO-treated human umbilical vein endothelial cells, respectively. Comparisons of the nitroso-proteomes revealed that common and different mitochondrial SNO-proteins were affected by endogenous NO on E2β stimulation and exogenous NO from donor. These SNO-proteins were associated with various mitochondrial functions, including energy and redox regulation, transport, iron homeostasis, translation, mitochondrial morphology, and apoptosis, etc. Collectively, we conclude that estrogens rapidly stimulate protein SNO in endothelial mitochondria via mitochondrial eNOS, providing a mechanism for mediating the vascular effects of estrogens.

Estradiol stimulates mitochondrial biogenesis and adiponectin expression in skeletal muscle

Sexual dimorphism has been found in mitochondrial features of skeletal muscle, with female rats showing greater mitochondrial mass and function compared with males. Adiponectin is an insulin-sensitizing adipokine whose expression has been related to mitochondrial function and that is also expressed in skeletal muscle, where it exerts local metabolic effects. The aim of this research was to elucidate the role of sex hormones in modulation of mitochondrial function, as well as its relationship with adiponectin production in rat skeletal muscle. An in vivo study with ovariectomized Wistar rats receiving or not receiving 17β-estradiol (E2) (10 μg/kg per 48 h for 4 weeks) was carried out, in parallel with an assay of cultured myotubes (L6E9) treated with E2 (10 nM), progesterone (Pg; 1 μM), or testosterone (1 μM). E2 upregulated the markers of mitochondrial biogenesis and dynamics, and also of mitochondrial function in skeletal muscle and L6E9. Although in vivo E2 supplementation only partially restored the decreased adiponectin expression levels induced by ovariectomy, these were enhanced by E2 and Pg treatment in cultured myotubes, whereas testosterone showed no effects. Adiponectin receptor 1 expression was increased by E2 treatment, both in vivo and in vitro, but testosterone decreased it. In conclusion, our results are in agreement with the sexual dimorphism previously reported in skeletal muscle mitochondrial function and indicate E2 to be its main effector, as it enhances mitochondrial function and diminishes oxidative stress. Moreover, our data support the idea of the existence of a link between mitochondrial function and adiponectin expression in skeletal muscle, which could be modulated by sex hormones.

Downregulation of nuclear respiratory factor-1 contributes to mitochondrial events induced by benzo(a)pyrene

Environmental carcinogen benzo(a)pyrene (BaP) has been shown to be a genotoxicant that affects both nuclear DNA (nDNA) and mitochondrial DNA (mtDNA). Nuclear respiratory factor 1 (NRF-1) is a transcriptional activator of nuclear genes that encode a range of mitochondrial proteins including mitochondrial transcription factor A (mtTFA). However, the role of NRF-1 in BaP-induced mitochondrial event is not clear. We investigated the change of NRF-1 and mtTFA in human bronchial epithelial cells (16HBE) elicited by BaP. The results indicated that BaP induced cell apoptosis, total mitochondrial enzymes activities and ATP levels decrease in dose- and time-dependent manners, respectively. The transcription and protein levels of NRF-1 and mtTFA decreased at 48 h after 16 μM BaP treatment. Our results indicated downregulation of NRF-1 and mtTFA is involved in BaP-induced mitochondrial events.

Rap1 ameliorates renal tubular injury in diabetic nephropathy

Rap1b ameliorates high glucose (HG)-induced mitochondrial dysfunction in tubular cells. However, its role and precise mechanism in diabetic nephropathy (DN) in vivo remain unclear. We hypothesize that Rap1 plays a protective role in tubular damage of DN by modulating primarily the mitochondria-derived oxidative stress. The role and precise mechanisms of Rap1b on mitochondrial dysfunction and of tubular cells in DN were examined in rats with streptozotocin (STZ)-induced diabetes that have Rap1b gene transfer using an ultrasound microbubble-mediated technique as well as in renal proximal epithelial tubular cell line (HK-2) exposed to HG ambiance. The results showed that Rap1b expression decreased significantly in tubules of renal biopsies from patients with DN. Overexpression of a constitutively active Rap1b G12V notably ameliorated renal tubular mitochondrial dysfunction, oxidative stress, and apoptosis in the kidneys of STZ-induced rats, which was accompanied with increased expression of transcription factor C/EBP-β and PGC-1α. Furthermore, Rap1b G12V also decreased phosphorylation of Drp-1, a key mitochondrial fission protein, while boosting the expression of genes related to mitochondrial biogenesis and antioxidants in HK-2 cells induced by HG. These effects were imitated by transfection with C/EBP-β or PGC-1α short interfering RNA. In addition, Rap1b could modulate C/EBP-β binding to the endogenous PGC-1α promoter and the interaction between PGC-1α and catalase or mitochondrial superoxide dismutase, indicating that Rap1b ameliorates tubular injury and slows the progression of DN by modulation of mitochondrial dysfunction via C/EBP-β-PGC-1α signaling.

Role of estrogen on skeletal muscle mitochondrial function in ovariectomized rats: a time course study in different fiber types

Postmenopausal women are prone to develop obesity and insulin resistance, which might be related to skeletal muscle mitochondrial dysfunction. In a rat model of ovariectomy (OVX), skeletal muscle mitochondrial function was examined at short- and long-term periods after castration. Mitochondrial parameters in the soleus and white gastrocnemius muscle fibers were analyzed. Three weeks after surgery, there were no differences in coupled mitochondrial respiration (ATP synthesis) with pyruvate, malate, and succinate; proton leak respiration; or mitochondrial reactive oxygen species production. However, after 3 wk of OVX, the soleus and white gastrocnemius muscles of the OVX animals showed a lower use of palmitoyl-carnitine and glycerol-phosphate substrates, respectively, and decreased peroxisome proliferator-activated receptor-γ coactivator-1α expression. Estrogen replacement reverted all of these phenotypes. Eight weeks after OVX, ATP synthesis was lower in the soleus and white gastrocnemius muscles of the OVX animals than in the sham-operated and estrogen-treated animals; however, when normalized by citrate synthase activity, these differences disappeared, indicating a lower muscle mitochondria content. No differences were observed in the proton leak parameter. Mitochondrial alterations did not impair the treadmill exercise capacity of the OVX animals. However, blood lactate levels in the OVX animals were higher after the physical test, indicating a compensatory extramitochondrial ATP synthesis system, but this phenotype was reverted by estrogen replacement. These results suggest early mitochondrial dysfunction related to lipid substrate use, which could be associated with the development of the overweight phenotype of ovariectomized animals.

Expression and subcellular localization of estrogen receptors α and β in human fetal brown adipose tissue

CONTEXT

Brown adipose tissue (BAT) has the unique ability of generating heat due to the expression of mitochondrial uncoupling protein 1 (UCP1). A recent discovery regarding functional BAT in adult humans has increased interest in the molecular pathways of BAT development and functionality. An important role for estrogen in white adipose tissue was shown, but the possible role of estrogen in human fetal BAT (fBAT) is unclear.

OBJECTIVE

The objective of this study was to determine whether human fBAT expresses estrogen receptor α (ERα) and ERβ. In addition, we examined their localization as well as their correlation with crucial proteins involved in BAT differentiation, proliferation, mitochondriogenesis and thermogenesis including peroxisome proliferator-activated receptor γ (PPARγ), proliferating cell nuclear antigen (PCNA), PPARγ-coactivator-1α (PGC-1α), and UCP1.

DESIGN

The fBAT was obtained from 4 human male fetuses aged 15, 17, 20, and 23 weeks gestation. ERα and ERβ expression was assessed using Western blotting, immunohistochemistry, and immunocytochemistry. Possible correlations with PPARγ, PCNA, PGC-1α, and UCP1 were examined by double immunofluorescence.

RESULTS

Both ERα and ERβ were expressed in human fBAT, with ERα being dominant. Unlike ERβ, which was present only in mature brown adipocytes, we detected ERα in mature adipocytes, preadipocytes, mesenchymal and endothelial cells. In addition, double immunofluorescence supported the notion that differentiation in fBAT probably involves ERα. Immunocytochemical analysis revealed mitochondrial localization of both receptors.

CONCLUSION

The expression of both ERα and ERβ in human fBAT suggests a role for estrogen in its development, primarily via ERα. In addition, our results indicate that fBAT mitochondria could be targeted by estrogens and pointed out the possible role of both ERs in mitochondriogenesis.

Estrogen and mitochondria function in cardiorenal metabolic syndrome

The cardiorenal metabolic syndrome (CRS) consists of a constellation of cardiac, renal, and metabolic disorders including insulin resistance (IR), obesity, metabolic dyslipidemia, high-blood pressure, and evidence of early cardiac and renal disease. Mitochondria dysfunction often occurs in the CRS, and this dysfunction is promoted by excess reactive oxygen species, genetic factors, IR, aging, and altered mitochondrial biogenesis. Recently, it has been shown that there are important sex-related differences in mitochondria function and metabolic, cardiovascular, and renal components. Sex differences in the CRS have mainly been attributed to the estrogen's effects that are mainly mediated by estrogen receptor (ER) α, ERβ, and G-protein coupled receptor 30. In this review, we discuss the effects of estrogen on the mitochondrial function, insulin metabolic signaling, glucose transport, lipid metabolism, and inflammatory responses from liver, pancreatic β cells, adipocytes, skeletal muscle, and cardiovascular tissue.

Estrogen in the fetus

Estradiol and other estrogens are important modulators of fetal and maternal physiology in pregnancy. Much is known about the biosynthesis of estrogens in fetus and mother, and much is known about the role that estrogen plays in labor and delivery. However, much less is known about the regulation of estrogen biosynthesis throughout the latter half of gestation, and the role that estrogen plays in homeostatic and neuroendocrine control in the fetus. This review focuses on the biosynthesis and actions of estrogen in the fetal circulation, the role that it plays in the development of the fetus in the latter half of gestation, and the role that is played by the estrogen milieu in the control of the timing of birth. Estrogen circulates in fetal blood in both unconjugated and conjugated molecular forms, with the conjugated steroids far more abundant than the unconjugated steroids. This review therefore also addresses the biological significance of the variety of molecular forms of estrogen circulating in fetal and maternal blood.

Alterations in sensitivity to estrogen, dihydrotestosterone, and xenogens in B-lymphocytes from children with autism spectrum disorder and their unaffected twins/siblings

It has been postulated that androgen overexposure in a susceptible person leads to excessive brain masculinization and the autism spectrum disorder (ASD) phenotype. In this study, the responses to estradiol (E2), dihydrotestosterone (DHT), and dichlorodiphenyldichloroethylene (DDE) on B-lymphocytes from ASD subjects and controls are compared. B cells were obtained from 11 ASD subjects, their unaffected fraternal twins, and nontwin siblings. Controls were obtained from a different cell bank. Lactate dehydrogenase (LDH) and sodium 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction levels were measured after incubation with different concentrations of E2, DHT, and DDE. XTT/LDH ratio, representative of mitochondria number per cell, was calculated. E2, DHT, and DDE all cause “U”-shaped growth curves, as measured by LDH levels. ASD B cells show less growth depression compared to siblings and controls (P < 0.01). They also have reduced XTT/LDH ratios (P < 0.01) when compared to external controls, whereas siblings had values of XTT/LDH between ASD and external controls. B-lymphocytes from people with ASD exhibit a differential response to E2, DHT, and hormone disruptors in regard to cell growth and mitochondrial upregulation when compared to non-ASD siblings and external controls. Specifically, ASD B-lymphocytes show significantly less growth depression and less mitochondrial upregulation when exposed to these effectors. A mitochondrial deficit in ASD individuals is implied.

Tumor suppressor p53 and estrogen receptors in nuclear-mitochondrial communication

Several gene transcription regulators considered solely localized within the nuclear compartment are being reported to be present in the mitochondria as well. There is growing interest in the role of mitochondria in regulating cellular metabolism in normal and disease states. Various findings demonstrate the importance of crosstalk between nuclear and mitochondrial genomes, transcriptomes, and proteomes in regulating cellular functions. Both tumor suppressor p53 and estrogen receptor (ER) were originally characterized as nuclear transcription factors. In addition to their individual roles as regulators of various genes, these two proteins interact resulting in major cellular consequences. In addition to its nuclear role, p53 has been localized to the mitochondria where it executes various transcription-independent functions. Likewise, ERs are reported to be present in mitochondria; however their functional roles remain to be clearly defined. In this review, we provide an integrated view of the current knowledge of nuclear and mitochondrial p53 and ERs and how it relates to normal and pathological physiology.

Estradiol and tamoxifen regulate NRF-1 and mitochondrial function in mouse mammary gland and uterus

Nuclear respiratory factor-1 (NRF-1) stimulates the transcription of nuclear-encoded genes that regulate mitochondrial (mt) genome transcription and biogenesis. We reported that estradiol (E2) and 4-hydroxytamoxifen (4-OHT) stimulate NRF-1 transcription in an estrogen receptor α (ERα)- and ERβ-dependent manner in human breast cancer cells. The aim of this study was to determine whether E2 and 4-OHT increase NRF-1 in vivo. Here, we report that E2 and 4-OHT increase NRF-1 expression in mammary gland (MG) and uterus of ovariectomized C57BL/6 mice in a time-dependent manner. E2 increased NRF-1 protein in the uterus and MG; however, in MG, 4-OHT increased Nrf1 mRNA but not protein. Chromatin immunoprecipitation assays revealed increased in vivo recruitment of ERα to the Nrf1 promoter and intron 3 in MG and uterus 6 h after E2 and 4-OHT treatment, commensurate with increased NRF-1 expression. E2- and 4-OHT-induced increases in NRF-1 and its target genes Tfam, Tfb1m, and Tfb2m were coordinated in MG but not in uterus due to uterine-selective inhibition of the expression of the NRF-1 coactivators Ppargc1a and Ppargc1b by E2 and 4-OHT. E2 transiently increased NRF-1 and PGC-1α nuclear staining while reducing PGC-1α in uterus. E2, not 4-OHT, activates mt biogenesis in MG and uterus in a time-dependent manner. E2 increased mt outer membrane Tomm40 protein levels in MG and uterus whereas 4-OHT increased Tomm40 only in uterus. These data support the hypothesis of tissue-selective regulation of NRF-1 and its downstream targets by E2 and 4-OHT in vivo.

Moderate to high levels of exercise are associated with higher resting energy expenditure in community-dwelling postmenopausal women

Postmenopausal women experience an age-related decline in resting energy expenditure (REE), which is a risk factor for energy imbalance and metabolic disease. Exercise, because of its association with greater lean tissue mass and other factors, has the potential to mediate REE decline, but the relation between exercise and REE in postmenopausal women is not well characterized. This study tests the hypothesis that exercise energy expenditure (EEE) is positively associated with REE and can counter the effects of age and menopause. It involves a cross-sectional sample of 31 healthy postmenopausal women (aged 49-72 years) with habitual exercise volumes at or above levels consistent with current clinical recommendations. Subjects kept exercise diaries for 4 weeks that quantified exercise activity and were measured for body composition, maximal oxygen uptake, and REE. Multiple regression analysis was used to test for associations between EEE, age, body composition, and REE. There was a significant positive relation between EEE and lean tissue mass (fat-free mass and fat-free mass index). The relation between REE and EEE remained significant even after controlling for lean tissue mass. These results support the hypothesis that exercise is positively associated with REE and can counter the negative effects of age and menopause. They also indicate a continuous relation between exercise and REE across ranges of exercise, from moderate to high. Exercise at levels that are at or above current clinical guidelines might, in part, ameliorate the risk for energy imbalance and metabolic disease because of its positive relation with REE.

Actions of 17β-estradiol and testosterone in the mitochondria and their implications in aging

A decline in the mitochondrial functions and aging are two closely related processes. The presence of estrogen and androgen receptors and hormone-responsive elements in the mitochondria represents the starting point for the investigation of the effects of 17β-estradiol and testosterone on the mitochondrial functions and their relationships with aging. Both steroids trigger a complex molecular mechanism that involves crosstalk between the mitochondria, nucleus, and plasma membrane, and the cytoskeleton plays a key role in these interactions. The result of this signaling is mitochondrial protection. Therefore, the molecular components of the pathways activated by the sexual steroids could represent targets for anti-aging therapies. In this review, we discuss previous studies that describe the estrogen- and testosterone-dependent actions on the mitochondrial processes implicated in aging.

Mitochondrial dysfunction in psychiatric and neurological diseases: cause(s), consequence(s), and implications of antioxidant therapy

Mitochondrial dysfunction is at the base of development and progression of several psychiatric and neurologic diseases with different etiologies. MtDNA/nDNA mutational damage, failure of endogenous antioxidant defenses, hormonal malfunction, altered membrane permeability, metabolic dysregulation, disruption of calcium buffering capacity and ageing have been found to be the root causes of mitochondrial dysfunction in psychatric and neurodegenerative diseases. However, the overall consequences of mitochondrial dysfunction are only limited to increase in oxidative/nitrosative stress and cellular energy crises. Thus far, extensive efforts have been made to improve mitochondrial function through specific cause-dependent antioxidant therapy. However, owing to complex genetic and interlinked causes of mitochondrial dysfunction, it has not been possible to achieve any common, unique supportive antioxidant therapeutic strategy for the treatment of psychiatric and neurologic diseases. Hence, we propose an antioxidant therapeutic strategy for management of consequences of mitochondrial dysfunction in psychiatric and neurologic diseases. It is expected that this will not only reduces oxidative stress, but also promote anaerobic energy production.

Regulation of physiological and metabolic function of muscle by female sex steroids

The ability of female sex steroids to regulate tissue function has long been appreciated; however, their role in the regulation of striated muscle function has received considerably less attention. The purpose of this symposium review was to document recent evidence indicating the role female sex steroids have in defining the functional characteristics of striated muscle. The presentations provide substantial evidence indicating that estrogens are critical to the physiological and metabolic regulations of striated muscle; thus, when considering women's health issues, striated muscle must included as an important target tissue along with other classically thought of estrogen-sensitive tissues.

Characterization of the role of distinct plasma cell-free DNA species in age-associated inflammation and frailty

Plasma cell-free DNA (cf-DNA) has recently emerged as a potential biomarker of aging, reflecting systemic inflammation, and cell death. In addition, it has been suggested that cf-DNA could promote autoinflammation. Because the total cf-DNA pool comprises different cf-DNA species, we quantified the plasma levels of gene-coding cf-DNA, Alu repeat cf-DNA, mitochondrial DNA (mtDNA) copy number, and the amounts of unmethylated and total cf-DNAs. We identified the relationships between these cf-DNA species and age-associated inflammation, immunosenescence, and frailty. Additionally, we determined the cf-DNA species-specific transcriptomic signatures in blood mononuclear cells to elucidate the age-linked leukocyte responses to cf-DNA. The study population consisted of n = 144 nonagenarian participants of the Vitality 90+ Study and n = 30 young controls. In the nonagenarians, higher levels of total and unmethylated cf-DNAs were associated with systemic inflammation and increased frailty. The mtDNA copy number was also directly correlated with increased frailty but not with inflammation. None of the cf-DNA species were associated with immunosenescence. The transcriptomic pathway analysis revealed that higher levels of total and unmethylated cf-DNAs were associated with immunoinflammatory activation in the nonagenarians but not in the young controls. The plasma mtDNA appeared to be inert in terms of inflammatory activation in both the nonagenarians and young controls. These data demonstrate that the plasma levels of total and unmethylated cf-DNA and the mtDNA copy number could serve as biomarkers of frailty. In addition, we suggest that circulating self-DNA, assessed as total or unmethylated cf-DNA, might aggravate immunoinflammatory reactivity in very old individuals.

Oxidative status interactome map: towards novel approaches in experiment planning, data analysis, diagnostics and therapy

Experimental evidence suggests an immense variety of processes associated with and aimed at producing reactive oxygen and/or nitrogen species. Clinical studies implicate an enormous range of pathologies associated with reactive oxygen/nitrogen species metabolism deregulation, particularly oxidative stress. Recent advances in biochemistry, proteomics and molecular biology/biophysics of cells suggest oxidative stress to be an endpoint of complex dysregulation events of conjugated pathways consolidated under the term, proposed here, "oxidative status". The oxidative status concept, in order to allow for novel diagnostic and therapeutic approaches, requires elaboration of a new logic system comprehending all the features, versatility and complexity of cellular pro- and antioxidative components of different nature. We have developed a curated and regularly updated interactive interactome map of human cellular-level oxidative status allowing for systematization of the related most up-to-date experimental data. A total of more than 600 papers were selected for the initial creation of the map. The map comprises more than 300 individual factors with respective interactions, all subdivided hierarchically for logical analysis purposes. The pilot application of the interactome map suggested several points for further development of oxidative status-based technologies.

Effect of estrogens on base excision repair in brain and liver mitochondria of aged female rats

Changes in the endocrine system have been suggested to act as signaling factors in the regulation of age-related events. Among the different hormones that have been linked to the aging process, estrogens have been widely investigated. They have been associated with inflammatory and oxidative processes and several investigations have established a relationship between the protective effects of estrogens and the mitochondrial function. Mitochondrial DNA is subjected to continuous oxidative attack by free radicals, and the base excision repair (BER) pathway is the main DNA repair route present in mitochondria. We have investigated the effect of estrogen levels on some of the key enzymes of BER in brain and liver mitochondria. In both tissues, depletion of estrogens led to an increased mitochondrial AP endonuclease (mtAPE1) activity, while restoration of estrogen levels by exogenous supplementation resulted in restitution of control APE1 activity only in liver. Moreover, in hepatic mitochondria, changes in estrogen levels affected the processing of oxidative lesions but not deaminations. Our results suggest that changes in mtAPE1 activity are related to specific translocation of the enzyme from the cytosol into the mitochondria probably due to oxidative stress changes as a consequence of changes in estrogen levels.

Periodic 17β-estradiol pretreatment protects rat brain from cerebral ischemic damage via estrogen receptor-β

Although chronic 17β-estradiol (E2) has been shown to be a cognition-preserving and neuroprotective agent in animal brain injury models, concern regarding its safety was raised by the failed translation of this phenomenon to the clinic. Previously, we demonstrated that a single bolus of E2 48 hr prior to ischemia protected the hippocampus from damage in ovariectomized rats via phosphorylation of cyclic-AMP response element binding protein, which requires activation of estrogen receptor subtype beta (ER-β). The current study tests the hypothesis that long-term periodic E2-treatment improves cognition and reduces post-ischemic hippocampal injury by means of ER-β activation. Ovariectomized rats were given ten injections of E2 at 48 hr intervals for 21 days. Hippocampal-dependent learning, memory and ischemic neuronal loss were monitored. Results demonstrated that periodic E2 treatments improved spatial learning, memory and ischemic neuronal survival in ovariectomized rats. Additionally, periodic ER-β agonist treatments every 48 hr improved post-ischemic cognition. Silencing of hippocampal ER-β attenuated E2-mediated ischemic protection suggesting that ER-β plays a key role in mediating the beneficial effects of periodic E2 treatments. This study emphasizes the need to investigate a periodic estrogen replacement regimen to reduce cognitive decline and cerebral ischemia incidents/impact in post-menopausal women.

17β-Estradiol and genistein acute treatments improve some cerebral cortex homeostasis aspects deteriorated by aging in female rats

Aging is associated with decreased insulin sensitivity and impaired cerebral glucose homeostasis. These changes increase neural sensitivity to metabolic damage contributing to cognitive decline, being the decrease in plasma estrogen following menopause one of the main factors involved in aged females. Phytoestrogens as genistein are structurally similar to 17β-estradiol, bind to estrogen receptors, and can evoke both estrogenic and anti-estrogenic effects. Estrogens and phytoestrogens have neuroprotective potential, but the physiological mechanisms are not fully understood. Young and aged female Wistar rats were ovariectomized and treated acutely with 17β-estradiol (1.4μg/kg body weight), genistein (10 or 40 mg/kg body weight), or vehicle. Cortical expression of glucose transporter-3 (GLUT-3) and -4 (GLUT-4), cytochrome c oxidase (CO), estrogen receptor-α (ERα) and -β (ERβ) was measured by Western blotting. There was an age-related decline in GLUT-4, CO and ERβ levels. Both drugs, estradiol and genistein, were able to reverse GLUT-3 downregulation in the cortex following late ovariectomy. However, genistein was the only treatment able to restore completely GLUT-4 levels in aged rats. In contrast, estradiol was more potent than genistein at increasing CO, a marker of cerebral oxidative metabolism. As regards ER levels, estradiol increased the ERα67 quantity diminished by late ovariectomy, while genistein did the same with the other ERα isoform, ERα46, highlighting drug-specific differences in expression changes for both isoforms. On the other hand, no treatment-related differences were found regarding ERβ levels. Therefore, genistein like estradiol could be suitable treatments against cortical metabolic dysfunction caused by aging. These treatments may hold promise as neuroprotective strategies against diabetes and age-related neurodegenerative diseases.

Oral contraceptives and nicotine synergistically exacerbate cerebral ischemic injury in the female brain

Oral contraceptives (OC) and smoking-derived nicotine (N) are known to synergistically increase the risk and severity of cerebral ischemia in women. Although it has been known for some time that long-term use of OC and nicotine will have an increased risk of peripheral thrombus formation, little is known about how the combination of OC and nicotine increases severity of brain ischemia. Recent laboratory studies simulating the conditions of nicotine exposure produced by cigarette smoking and OC regimen of women in female rats confirms that the severity of ischemic hippocampal damage is far greater in female rats simultaneously exposed to OC than to nicotine alone. These studies also demonstrated that the concurrent exposure of OC and nicotine reduces endogenous 17β-estradiol levels and inhibits estrogen signaling in the brain of female rats. The endogenous 17β-estradiol plays a key role in cerebrovascular protection in women during their pre-menopausal life and loss of circulating estrogen at reproductive senescence increases both the incidence and severity of cerebrovascular diseases. Therefore, OC and nicotine induced severe post-ischemic damage might be a consequence of lack of estrogen signaling in the brain. In the present review we highlight possible mechanisms by which OC and nicotine inhibits estrogen signaling that could be responsible for severe ischemic damage in females.

Pleiotropic actions of estrogen: a mitochondrial matter

Estrogen provides many beneficial effects early in life by regulating normal tissue development and several physiological functions. While estrogen replacement therapy (ERT) in women was expected to reduce the health risks associated with the age-related decline in estrogen levels during menopause, ERT also resulted in increased progression to other types of diseases. Hence, distinguishing the signaling pathways that regulate the beneficial and detrimental effects of estrogen is important for developing interventions that selectively harness the hormone's beneficial effects, while minimizing its side effects. Estrogen can minimize mitochondrial dysfunction, which is thought to contribute to aging phenotypes. Decline in estrogen levels during menopause may lead to progressive mitochondrial dysfunction and may permanently alter cellular response, including that of estrogen (i.e., ERT). This review discusses the interplay between estrogen and mitochondrial function during the aging process and suggests a potential role of mitochondria in influencing the pleiotropic action of estrogen.

Long-term exercise treatment reduces oxidative stress in the hippocampus of aging rats

Exercise can exert beneficial effects on cognitive functions of older subjects and it can also play an important role in the prevention of neurodegenerative diseases. At the same time it is perceivable that limited information is available on the nature of molecular pathways supporting the antioxidant effects of exercise in the brain. In this study 12-month old, middle-aged female Wistar rats were subjected to daily moderate intensity exercise on a rodent treadmill for a period of 15weeks which covered the early aging period unmasking already some aging-related molecular disturbances. The levels of reactive oxygen species (ROS), the amount of protein carbonyls, the levels of antioxidant intracellular enzymes superoxide dismutases (SOD-1, SOD-2) and glutathione peroxidase (GPx) were determined in the hippocampus. In addition, to identify the molecular pathways that may be involved in ROS metabolism and mitochondrial biogenesis, the activation of 5'-AMP-activated protein kinase (AMPK), the protein level of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), nuclear respiratory factor 1 (NRF-1) and mitochondrial transcription factor A (mtTFA) were measured. Our results revealed a lower level of ROS associated with a reduced amount of protein carbonyls in the hippocampus of physically trained rats compared to sedentary controls. Furthermore, exercise induced an up-regulation of SOD-1 and GPx enzymes, p-AMPK and PGC-1α, that can be related to an improved redox balance in the hippocampus. These results suggest that long-term physical exercise can comprises antioxidant properties and by this way protect neurons against oxidative stress at the early stage of aging.

Cytochrome c oxidase and its role in neurodegeneration and neuroprotection

A hallmark of neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases, and stroke is a malfunction of mitochondria including cytochrome c oxidase (COX), the terminal enzyme complex of the respiratory chain. COX is ascribed a key role based on mainly two regulatory mechanisms. These are the expression of isoforms and the binding of specific allosteric factors to nucleus--encoded subunits. These characteristics represent a unique feature of COX compared with the other respiratory chain complexes. Additional regulatory mechanisms, such as posttranslational modification, substrate availability, and allosteric feedback inhibition by products of the COX reaction, control the enzyme activity in a complex way. In many tissues and cell types, COX represents the rate-limiting enzyme of the respiratory chain which further emphasizes the impact of the regulation of COX as a central site for regulating energy metabolism and oxidative stress. Two of the best-analyzed regulatory mechanisms of COX to date are the allosteric feedback inhibition of the enzyme by its indirect product ATP and the expression of COX subunit IV isoforms. This ATP feedback inhibition of COX requires the expression of COX isoform IV-1. At high ATP/ADP ratios, ADP is exchanged for ATP at the matrix side of COX IV-1 leading to an inhibition of COX activity, thus enabling COX to sense the energy level and to adjust ATP synthesis to energy demand. However, under hypoxic, toxic, and degenerative conditions, COX isoform IV-2 expression is up-regulated and exchanged for COX IV-1 in the enzyme complex. This COX IV isoform switch causes an abolition of the allosteric ATP feedback inhibition of COX and consequently the loss of sensing the energy level. Thus, COX activity is increased leading to higher levels of ATP in neural cells independently of the cellular energy level. Concomitantly, ROS production is increased. Thus, under pathological conditions, neural cells are provided with ATP to meet the energy demand, but at the expense of elevated oxidative stress. This mechanism explains the functional relevance of COX subunit IV isoform expression for cellular energy sensing, ATP production, and oxidative stress levels. This, in turn, affects neural cell function, signaling, and -survival. Thus, COX is a crucial factor in etiology, progression, and prevalence of numerous human neurodegenerative diseases and represents an important target for developing diagnostic and therapeutic tools against those diseases.

Sex-specific regulation of mitochondrial DNA levels: genome-wide linkage analysis to identify quantitative trait loci

Altered mitochondrial DNA (mtDNA) levels have been associated with common diseases in humans. We investigated the genetic mechanism that controls mtDNA levels using genome-wide linkage analyses in families from the Genetic Analysis of Idiopathic Thrombophilia Project (GAIT). We measure mtDNA levels by quantitative real-time PCR in 386 subjects from 21 extended Spanish families. A variance component linkage method using 485 microsatellites was conducted to evaluate linkage and to detect quantitative trait loci (QTLs) involved in the control of mtDNA levels. The heritalibility of mtDNA levels was 0.33 (p=1.82e-05). We identified a QTL on Chromosome 2 (LOD=2.21) using all of the subjects, independently on their sex. When females and males were analysed separately, three QTLs were identified. Females showed the same QTL on Chromosome 2 (LOD=3.09), indicating that the QTL identified in the analysis using all of the subjects was a strong female QTL, and another one on Chromosome 3 (LOD=2.67), whereas in males a QTL was identified on Chromosome 1 (LOD=2.81). These QTLs were fine-mapped to find associations with mtDNA levels. The most significant SNP association was for the rs10888838 on Chromosome 1 in males. This SNP mapped to the gene MRPL37, involved in mitochondrial protein translation. The rs2140855 on Chromosome 2 showed association in the analysis using all of the subjects. It was near the gene CMPK2, which encodes a mitochondrial enzyme of the salvage pathway of deoxyribonucleotide synthesis. Our results provide evidence of a sex-specific genetic mechanism for the control of mtDNA levels and provide a framework to identify new genes that influence mtDNA levels.

The influence of gender and sexual hormones on incidence and outcome of chronic kidney disease

It has long been known that the female sex is associated with a better clinical outcome in chronic renal diseases. Although many experimental, clinical, and epidemiological studies in adults have attempted to explain the difference in disease progression between females and males, a definitive understanding of the underlying mechanisms is still lacking. Hormone-modulating therapies are being increasingly used for various indications (such as post-menopausal hormone replacement, estrogen- or androgen-receptor antagonists for cancer therapy). Therefore, a deeper knowledge of the interaction between sexual hormones and progression of kidney disease is important, as hormone-modulating therapy for non-renal indication may influence both kidney structure and function. In addition, specific modulation of the sexual hormone system, such as the use of selective estrogen receptor modulators, may represent a therapeutic option for patients with renal diseases. Although conclusive data on this topic in the pediatric population are still lacking, the aim of this review is to familiarize pediatric nephrologists with gender-specific differences in renal physiology, pathophysiology, and the progression of kidney diseases. Experimental models that analyze the effects of sexual hormones on renal structure and function are discussed. It is hoped that this review will stimulate researchers to focus on pediatric studies that will provide a deeper insight into the interaction of gender hormones and the kidney both before and during puberty.

Mitochondrial dynamics is affected by 17β-estradiol in the MCF-7 breast cancer cell line. Effects on fusion and fission related genes

Mitochondrial dynamics, specifically fusion and fission processes, maintain mitochondria integrity and function, yet at this time, effect of estrogens on fusion and fission in breast cancer cell lines has not been studied. The aim of this study was to characterize the effect of 17β-estradiol on fusion and fission-related genes, as well as on mitochondria proliferation and function. We used MCF-7 breast cancer cell line, which is estrogen sensitive (estrogen receptor positive). Cells were grown in Dulbecco's modified Eagle medium charcoal-stripped fetal bovine serum and treated with 1nM of 17β-estradiol and with/without 100nM of ICI 182,780, a drug that caused rapid degradation of estrogen receptor. mRNA levels of fusion (mfn1, mfn2, opa1) and fission-related genes (drp1 and fis1) were examined by RT-PCR, cardiolipin content by N-acridyl-orange fluorescence and oxidative phosphorylation protein levels, as well as, the major fusion and fission related protein levels, by Western blot. mRNA expression of fusion-related genes increased after 17β-estradiol-treatment for 4h; however fis1 fission-related gene expression decreased. All these effects were not found in cells pre-treated with ICI 182,780, save for the changes in mfn-1, conferring them the effects of 17β-estradiol to estrogen receptor. The changes in protein levels were less prominent, but in the same way, than in mRNA levels, showing an increase in Mfn1 and Mfn2, as well as in Drp1, but there was no change in Fis1 protein levels. Mitochondrial biogenesis was also affected by 17β-estradiol, showing an increase in mtDNA but with no change in N-acridyl-orange fluorescence. On the whole, our results suggest an imbalance in the fusion/fission ratio, with a high fusion by 17β-estradiol-estrogen receptor action, which can affect to mitochondrial biogenesis, concretely in mitochondria proliferation. According to this information, 17β-estradiol would modify mitochondrial dynamics, biogenesis and metabolism, and thus compromise the normal development and function of mitochondria in cancer affected tissues.

Multi-tasking: nuclear transcription factors with novel roles in the mitochondria

Coordinated responses between the nucleus and mitochondria are essential for the maintenance of homeostasis. For over 15 years, pools of nuclear transcription factors (TFs), such as p53 and nuclear hormone receptors, have been observed in the mitochondria. The contribution of the mitochondrial pool of these TFs to their well-defined biological actions is in some cases clear and in others not well understood. Recently, a small mitochondrial pool of the TF signal transducer and activator of transcription factor 3 (STAT3) was shown to modulate the activity of the electron transport chain (ETC). The mitochondrial function of STAT3 encompasses both its biological actions in the heart as well as its oncogenic effects. This review highlights advances in our understanding of how mitochondrial pools of nuclear TFs may influence the function of this organelle.

27-hydroxycholesterol and the expression of three estrogen-sensitive proteins in MCF7 cells

The principal aim of this study was to analyze in estrogen receptor-positive MCF7 cells the response of three estrogen-dependent proteins to 27-hydroxycholesterol (27OHC), a major circulating cholesterol metabolite. Immunofluorescence, immunoblotting and immunogold labelling analyses of MCF7 cells exposed for up to 72 h to 2 nM estradiol (E2) or to 2 µM 27OHC demonstrated similar responses in the expression of MnSOD and ERβ compared to the non-stimulated cells. Thus, the results confirm 27OHC's function as a novel selective estrogen receptor modulator (SERM). The epithelial to mesenchymal transition (EMT), observed in MCF7 cells stimulated for longer than 48 h with 2 µM 27OHC, was accompanied by lower immunoreactive levels of nuclear FOXM1 in comparison to E2-treated cells. The results presented in this study are discussed taking into consideration the relationship of hypercholesterolemia, 27OHC production, ROS synthesis and macrophage infiltration, potentially occurring in obese patients with ERα-positive, infiltrated mammary tumors.

Inhibition of the Mitochondrial Permeability Transition for Cytoprotection: Direct versus Indirect Mechanisms

Mitochondria are fascinating organelles, which fulfill multiple cellular functions, as diverse as energy production, fatty acid β oxidation, reactive oxygen species (ROS) production and detoxification, and cell death regulation. The coordination of these functions relies on autonomous mitochondrial processes as well as on sustained cross-talk with other organelles and/or the cytosol. Therefore, this implies a tight regulation of mitochondrial functions to ensure cell homeostasis. In many diseases (e.g., cancer, cardiopathies, nonalcoholic fatty liver diseases, and neurodegenerative diseases), mitochondria can receive harmful signals, dysfunction and then, participate to pathogenesis. They can undergo either a decrease of their bioenergetic function or a process called mitochondrial permeability transition (MPT) that can coordinate cell death execution. Many studies present evidence that protection of mitochondria limits disease progression and severity. Here, we will review recent strategies to preserve mitochondrial functions via direct or indirect mechanisms of MPT inhibition. Thus, several mitochondrial proteins may be considered for cytoprotective-targeted therapies.

Signaling the mitochondrial unfolded protein response

Mitochondria are compartmentalized organelles essential for numerous cellular functions including ATP generation, iron-sulfur cluster biogenesis, nucleotide and amino acid metabolism as well as apoptosis. To promote biogenesis and proper function, mitochondria have a dedicated repertoire of molecular chaperones to facilitate protein folding and quality control proteases to degrade those proteins that fail to fold correctly. Mitochondrial protein folding is challenged by the complex organelle architecture, the deleterious effects of electron transport chain-generated reactive oxygen species and the mitochondrial genome's susceptibility to acquiring mutations. In response to the accumulation of unfolded or misfolded proteins beyond the organelle's chaperone capacity, cells mount a mitochondrial unfolded protein response (UPR(mt)). The UPR(mt) is a mitochondria-to-nuclear signal transduction pathway resulting in the induction of mitochondrial protective genes including mitochondrial molecular chaperones and proteases to re-establish protein homeostasis within the mitochondrial protein-folding environment. Here, we review the current understanding of UPR(mt) signal transduction and the impact of the UPR(mt) on diseased cells. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.

Activation of GPR30 attenuates diastolic dysfunction and left ventricle remodelling in oophorectomized mRen2.Lewis rats

AIMS

GPR30 is a novel oestrogen receptor expressed in various tissues, including the heart. We determined the role of GPR30 in the maintenance of left ventricular (LV) structure and diastolic function after the surgical loss of ovarian hormones in the female mRen2.Lewis rat, a model emulating the cardiac phenotype of the post-menopausal woman.

METHODS AND RESULTS

Bilateral oophorectomy (OVX) or sham surgery was performed in study rats; the selective GPR30 agonist, G-1 (50 µg/kg/day), or vehicle was given subcutaneously to OVX rats from 13-15 weeks of age. Similar to the cardiac phenotype of sham rats, G-1 preserved diastolic function and structure relative to vehicle-treated OVX littermates independent of changes in blood pressure. G-1 limited the OVX-induced increase in LV filling pressure, LV mass, wall thickness, interstitial collagen deposition, atrial natriuretic factor and brain natriuretic peptide mRNA levels, and cardiac NAD(P)H oxidase 4 (NOX4) expression. In vitro studies showed that G-1 inhibited angiotensin II-induced hypertrophy in H9c2 cardiomyocytes, evidenced by reductions in cell size, protein content per cell, and atrial natriuretic factor mRNA levels. The GPR30 antagonist, G15, inhibited the protective effects of both oestradiol and G-1 on this hypertrophy.

CONCLUSION

These data show that the GPR30 agonist G-1 mitigates the adverse effects of oestrogen loss on LV remodelling and the development of diastolic dysfunction in the study rats. This expands our knowledge of the sex-specific mechanisms underlying diastolic dysfunction and provides a potential therapeutic target for reducing the progression of this cardiovascular disease process in post-menopausal women.