Effects of phytoestrogen on mitochondrial structure and function of hippocampal CA1 region of ovariectomized rats

Mitophagy activation by rapamycin enhances mitochondrial function and cognition in 5×FAD mice

Alzheimer's disease (AD) is the most prevalent form of dementia, characterized by severe mitochondrial dysfunction, which is an intracellular process that is significantly compromised in the early stages of AD. Mitophagy, the selective removal of damaged mitochondria, is a potential therapeutic strategy for AD. Rapamycin, a mammalian target of rapamycin (mTOR) inhibitor, augmented autophagy and mitigated cognitive impairment. Our study revealed that rapamycin enhances cognitive function by activating mitophagy, alleviating neuronal loss, and improving mitochondrial dysfunction in 5 ×FAD mice. Interestingly, the neuroprotective effect of rapamycin in AD were negated by treatment with 3-MA, a mitophagy inhibitor. Overall, our findings suggest that rapamycin ameliorates cognitive impairment in 5 ×FAD mice via mitophagy activation and its downstream PINK1-Parkin pathway, which aids in the clearance of amyloid-β (Aβ) and damaged mitochondria. This study reveals a novel mechanism involving mitophagy regulation underlying the therapeutic effect of rapamycin in AD. This study provides new insights and therapeutic targets for rapamycin in the treatment of AD. However, there are still some shortcomings in this topic; if we can further knock out the PINK1/Parkin gene in animals or use siRNA technology, we can further confirm the experimental results.

Genistein improves mitochondrial function and inflammatory in rats with diabetic nephropathy via inhibiting MAPK/NF-κB pathway

Purpose:

To investigate the effect of genistein on inflammation and mitochondrial function of diabetic nephropathy.

Methods:

Diabetic nephropathy model was established in Sprague-Dawley rats. Automatic biochemical analyzer was employed to detect the kidney function index, serum creatinine, serum urea nitrogen, and 24 h-urine protein and blood glucose. Hematoxylin and eosin staining and periodic acid Schiff staining were used to observe renal morphology. Mitochondrial changes and podocyte integrity were monitored by transmission electron microscope. The expression levels of mfn2, NOX4, P53, MAPK, and NF-κB were detected by Western blotting. The changes of mitochondrial membrane potential were measured by JC-1. The level of mfn2 was assessed by immunofluorescence assay.

Results:

Genistein ameliorated the kidney function with reduced Scr and blood glucose. The expressions of NOX4, MAPK, p65 and p53 were downregulated, while the expression of mnf2 was the opposite in genistein-treated kidneys. Further investigations revealed that genistein reduced expansion of mesangial matrix and oxidative stress, protected podocyte integrity and increased mitochondrial membrane potential.

Conclusions:

Genistein could alleviate diabetic nephropathy through inhibiting MAPK/NF-κB pathway, improving mitochondrial function and anti-inflammatory.

Ipriflavone suppresses NLRP3 inflammasome activation in host response to biomaterials and promotes early bone healing

AIM

Emerging studies have shown that immune response to biomaterial implants plays a central role in bone healing. Ipriflavone is clinically used for osteoporosis. However, the mechanism of ipriflavone in immune response to implants in early stages of osseointegration remains unclear. In this study, we aimed to investigate the potential role of ipriflavone in early bone healing process and uncover the underlying mechanism.

MATERIALS AND METHODS

We carried out histological examination as well as analysis of proinflammatory cytokines and NLRP3 inflammasome activation in a tibial implantation mouse model with intra-peritoneal injection of ipriflavone. In addition, we explored the mechanism of ipriflavone in the regulation of NLRP3 inflammasome activation in macrophages.

RESULTS

In vivo, ipriflavone ameliorated host inflammatory response related to NLRP3 inflammasome activation at implantation sites, characterized by reductions of inflammatory cell infiltration and proinflammatory cytokine interleukin-1β levels. Ipriflavone treatment also showed beneficial effects on early osseointegration. Further investigations of the molecular mechanism showed that the suppression of NLRP3 inflammasome acts upstream of NLRP3 oligomerization through abrogating the production of reactive oxygen species.

CONCLUSIONS

These results revealed an anti-inflammatory role of ipriflavone in NLRP3 inflammasome activation through improving mitochondrial function. This study provides a new strategy for the development of immune-regulated biomaterials and treatment options for NLRP3-related diseases.

Administration of miR-195 Inhibitor Enhances Memory Function Through Improving Synaptic Degradation and Mitochondrial Dysfunction of the Hippocampal Neurons in SAMP8 Mice

BACKGROUND

Mitochondrial dysfunction is an early feature of Alzheimer's disease (AD) and miR-195 is involved in mitochondrial disorder through targeting MFN-2 protein in hippocampal neurons of AD.

OBJECTIVE

To clarify if administration of miR-195 inhibitor could enhance the memory deficits through improving hippocampal neuron mitochondrial dysfunction in SAMP8 mice.

METHODS

The expression of miR-195 was detected by RT-qPCR in primary hippocampal neurons and HT-22 cells treated with Aβ 1-42. Morris water maze (MWM) was used to assess the learning and memory function in SAMP8 mice administrated with antagomir-195. Transmission electron microscopy was employed to determine the morphological changes of synapses and mitochondria of hippocampus in SAMP8 mice. Mitochondrial respiration was measured using a high-resolution oxygraph.

RESULTS

The expression of miR-195 were upregulated in the primary hippocampal neurons and HT-22 cells induced by Aβ 1-42. Inhibition of miR-195 ameliorated the mitochondrial dysfunction in HT-22 cells induced by Aβ 1-42, including mitochondrial morphologic damages, mitochondrial membrane potential, respiration function, and ATP production. Administration of antagomir-195 by the third ventricle injection markedly ameliorated the cognitive function, postsynaptic density thickness, length of synaptic active area, mitochondrial aspect ratio, and area in hippocampus of SAMP8 mice. Finally, antagomir-195 was able to promote an increase in the activity of respiratory chain complex CI and II in SAMP8 mice.

CONCLUSION

This study demonstrated that miR-195 inhibitor ameliorated the cognitive impairment of AD mice by improving mitochondrial structure damages and dysfunction in the hippocampal neurons, which provide an experimental basis for further exploring the treatment strategy of AD.

Ginsenoside Rg1 can restore hematopoietic function by inhibiting Bax translocation-mediated mitochondrial apoptosis in aplastic anemia

The present study investigated, the anti-apoptotic activity of Ginsenoside Rg1 (Rg1) via inhibition of Bax translocation and the subsequent recovery of hematopoietic function. Mitochondrial apoptosis in bone marrow mononuclear cells (BMNCs) was observed in aplastic anemia (AA) patients. To establish a mouse model of AA, BALB/c mice were transplanted with lymph node cells from DBA/2 donor mice via vein injection after treatment with Co60 γ-radiation. After treatment with Rg1 for 14 days, the peripheral blood and Lin–Sca-1 + c-Kit + (LSK) cell counts of the treated group were increased compared with those of the untreated model mice. In in vivo and in vitro tests of LSKs, Rg1 was found to increase mitochondrial number and the ratio of Bcl-2/Bax and to decrease damage to the mitochondrial inner and outer membranes, the mitochondrial Bax level and the protein levels of mitochondrial apoptosis-related proteins AIF and Cyt-C by decreasing the ROS level. Rg1 also improved the concentration–time curve of MAO and COX and levels of ATP, ADP and AMP in an in vitro test. In addition, high levels of Bax mitochondrial translocation could be corrected by Rg1 treatment. Levels of markers of mitochondrial apoptosis in the Rg1-treated group were significantly better than those in the AA model group, implying that Rg1 might improve hematopoietic stem cells and thereby restore hematopoietic function in AA by suppressing the mitochondrial apoptosis mediated by Bax translocation.

A review on protective role of genistein against oxidative stress in diabetes and related complications

Diabetes mellitus (DM) is metabolism related problems that share the phenotype of hyperglycemia, which is triggered by a complicated interaction of hereditary and environmental elements. It is the main reason for end-stage renal disease (ESRD), amputations of the traumatic lower extremity, and grown-up visual impairment. It additionally inclines to neurodegenerative and cardiovascular sicknesses. With an expanding rate around the world, DM may be the main motive of morbidity and mortality within the foreseeable future. The objective of treatment for DM is to inhibit mortality and difficulties through normalizing blood glucose stage. Genistein, a naturally available soy isoflavone, is accounted for to have various medical advantages credited to numerous natural capacities. In the course of recent years, various examinations have shown that genistein has hostile to diabetic impacts, specifically, direct consequences for β-cell expansion, glucose-triggered insulin discharge, and safety towards apoptosis, unbiased of its functions as an estrogen receptor agonist, cancer prevention agent, or tyrosine kinase inhibitor. The present evaluation emphases on the promising molecular and biochemical paths associated with DM complications and, specifically, the multi-target method of genistein in diminishing diabetic neuropathy, nephropathy, and retinopathy.

Recurrent nonsevere hypoglycemia exacerbates imbalance of mitochondrial homeostasis leading to synapse injury and cognitive deficit in diabetes

Recurrent nonsevere hypoglycemia (RH) can lead to cognitive dysfunction in patients with diabetes, although the involved mechanisms remain unclear. Here, we aimed to investigate the mechanism underlying RH-induced cognitive deficits with a focus on mitochondrial homeostasis. To establish a model that mimicked RH in patients with type 1 diabetes (T1DM) receiving insulin therapy, streptozotocin-induced mice with T1DM were subjected to recurrent, twice-weekly insulin injections over 4 wk. We found that RH disrupted the mitochondrial fine structure, reduced the number of mitochondria, and upregulated the expression of mitochondrial dynamics and mitophagy markers, including dynamin-related protein 1 (Drp1), Bcl-2/adenovirus E1B 19-kDa-interacting protein-3 (BNIP3), and microtubule-associated protein 1 light-chain 3 (LC3) in the hippocampus of T1DM mice. Moreover, RH and chronic hyperglycemia synergistically promoted the production of reactive oxygen species, impaired mitochondrial membrane potential, and suppressed mitochondrial energy metabolism. Under diabetic conditions, RH also altered the synaptic morphology and reduced the expression of synaptic marker proteins. Long-term recognition memory and spatial memory, assessed with the Morris water maze test, were also impaired. However, these effects were largely prevented by mitochondrial division inhibitor 1, a potent and selective Drp1 inhibitor. Thus, it appears that RH exacerbates the imbalance of mitochondrial homeostasis, leading to synapse injury and cognitive deficits in diabetes. The adjustment of mitochondrial homeostasis could serve as an effective neuroprotective approach when addressing low blood sugar conditions.

Genistein: mechanisms of action for a pleiotropic neuroprotective agent in stroke

Genistein is a plant estrogen promoted as an alternative to post-menopausal hormone therapy because of a good safety profile and its promotion as a natural product. Several preclinical studies of cerebral ischemia and other models of brain injury support a beneficial role for genistein in protecting the brain from injury whether administered chronically or acutely. Like estrogen, genistein is a pleiotropic molecule that engages several different mechanisms to enhance brain health, including reduction of oxidative stress, promotion of growth factor signaling, and immune suppression. These actions occur in endothelial, glial, and neuronal cells to provide a coordinated beneficial action to ischemic challenge. Though many of these protective actions are associated with estrogen-like actions of genistein, additional activities on other receptors and intracellular targets suggest that genistein is more than a mere estrogen-mimic. Importantly, genistein lacks some of the detrimental effects associated with post-menopausal estrogen treatment and may provide an alternative to hormone therapy in those patients at risk for ischemic events.

Neuroprotective effect of ipriflavone against scopolamine-induced memory impairment in rats

BACKGROUND

Alzheimer's disease is an age-related neurodegenerative disorder characterized clinically by a progressive loss of memory and cognitive functions resulting in severe dementia. Ipriflavone (IPRI) is a non-hormonal, semi-synthetic isoflavone, clinically used in some countries for the treatment and prevention of postmenopausal osteoporosis. Moreover, ipriflavone is a non-peptidomimetic small molecule AChE inhibitor with an improved bioavailability after systemic administration, due to its efficient blood-brain barrier permeability in comparison with peptidomimetic inhibitors.

OBJECTIVE

The present study aimed to evaluate the possible enhancing effects of IPRI on memory impairments caused by scopolamine administration.

METHODS

Male rats were administered IPRI (50 mg/kg, oral) 2 h before scopolamine injection (2 mg/kg, intraperitoneally injected) daily for 4 weeks. Effects of IPRI on acetylcholinesterase activity, amyloid-β precursor processing, and neuroplasticity in the rats' hippocampus were investigated.

RESULTS

Daily administration of IPRI reverted memory impairment caused by scopolamine as measured by the reduction of the escape latency. IPRI significantly alleviated the oxidative stress and restored the mRNA expression of both cAMP-response element-binding protein and brain-derived neurotrophic factor in the hippocampus. Furthermore, it significantly increased the expression of ADAM10 and ADAM17 (two putative α-secretase enzymes) and phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2) that associated with decreased expression of β-secretase (BACE) in the hippocampus. Finally, both the amyloid-β (Aβ) and Tau pathologies were reduced.

CONCLUSIONS

IPRI showed promising neuroprotective effects against scopolamine-induced memory dysfunction in rats. These findings contributed to the stimulation of α-secretase enzymes, the activation of MAPK/ERK1/2, and the alleviation of oxidative stress.

Development of Therapeutics That Induce Mitochondrial Biogenesis for the Treatment of Acute and Chronic Degenerative Diseases

Mitochondria have various roles in cellular metabolism and homeostasis. Because mitochondrial dysfunction is associated with many acute and chronic degenerative diseases, mitochondrial biogenesis (MB) is a therapeutic target for treating such diseases. Here, we review the role of mitochondrial dysfunction in acute and chronic degenerative diseases and the cellular signaling pathways by which MB is induced. We then review existing work describing the development and application of drugs that induce MB in vitro and in vivo. In particular, we discuss natural products and modulators of transcription factors, kinases, cyclic nucleotides, and G protein-coupled receptors.

Combined high-fat-resveratrol diet and RIP140 knockout mice reveal a novel relationship between elevated bone mitochondrial content and compromised bone microarchitecture, bone mineral mass, and bone strength in the tibia

SCOPE

While resveratrol (RSV) is associated with the prevention of high-fat (HF) diet-induced insulin resistance, the effects on bone health combined with an HF-diet is unknown. Therefore, we determined the effect of RSV on bone microarchitecture in the presence of an HF-diet, while also elucidating molecular adaptations within bone that could contribute to bone health status.

METHODS AND RESULTS

Male C57BL6 mice were provided control (10% fat) or HF-diet (60% fat) in the presence or absence of RSV for 12 weeks. While RSV prevented HF diet-induced glucose intolerance, HF-RSV compromised tibial microarchitecture, mineral mass, and strength. The compromised outcomes following HF-RSV corresponded with higher markers of osteoclast-activation and bone-resorption (decreased OPG/RANKL ratio; increased cathepsin K), as well as higher markers of tibial mitochondrial content. A molecular model of elevated mitochondrial content (RIP140 knock out (KO) mice) was utilized to determine proof-of-principle that increasing mitochondrial content coincides with decrements in bone health. RIP140 KO mice displayed higher markers of mitochondrial content, and similar to HF-RSV, had compromised bone microarchitecture, lower BMD/strength, and higher markers of osteoclast-activation/bone-resorption.

CONCLUSION

These data show that in the presence of an HF-diet, RSV negatively alters bone health, a process associated with increased mitochondrial content and markers of bone resorption.

Neuroprotective activity of hydroponic Teucrium polium following bilateral ovariectomy

Ovariectomy is known as "surgical menopause" with decreased levels of estrogen in female rodents. Its reported risks and adverse effects include cognitive impairment. The action of hydroponic Teucrium polium on nucleus basalis of Meynert (bnM) neurons following 6 weeks of ovariectomy was carried out. The analysis of spike activity was observed by on-line selection and the use of a software package. Early and late tetanic, - posttetanic potentiation and depression of neurons to high frequency stimulation of hippocampus were studied. The complex averaged peri-event time and frequency histograms were constructed. The histochemical study of the activity of Са(2+)-dependent acid phosphatase was observed. In conditions of hydroponic Teucrium polium administration, positive changes in neurons and gain of metabolism leading to cellular survival were revealed. The administration of Teucrium polium elicited neurodegenerative changes in bnM.

Bufei Jianpi granules improve skeletal muscle and mitochondrial dysfunction in rats with chronic obstructive pulmonary disease

Background

Bufei Jianpi granules has been confirmed effective in improving pulmonary function, alleviating acute exacerbations, improving six-minute walk distance and quality of life, and benefited in 12-month follow-up in chronic obstructive pulmonary disease (COPD) patients with syndrome of lung-spleen qi deficiency. Skeletal muscle dysfunction (SMD), an important extrapulmonary complication, occurs in the very initiation of COPD and is closely related to morbidity and mortality. To evaluate the efficacy of Bufei Jianpi granules on SMD, we observed skeletal muscular function and histomorphology, mitochondrial morphormetry and proteins in COPD rats induced by cigarette-smoke and Klebsiella pneumoniae.

Methods

Seventy-two Sprague–Dawley rats were randomized into Control + Saline, Control + Bufei Jianpi, Control + Aminophylline, COPD + Saline, COPD + Bufei Jianpi and COPD + Aminophylline groups. From week 9 to 20, rats were administrated intragastricly by normal saline, Bufei Jianpi granules and aminophylline, respectively. Muscular tension and fatigue index of intercostal muscle, quadriceps, biceps and soleus were detected by using electrophysiological technology. Pathological and ultrastructural changes and expressions of mitochondrial Bcl-2 nineteen-kilodalton interacting protein 3 (Bnip3) and cytoplasm cytochrome C (Cyto C) in the four skeletal muscles were observed by using optical and electron microscope and western blotting.

Results

There was no statistical difference among the control rats treated with saline, Bufei Jianpi granules or aminophylline in above-mentioned parameters. Muscular tension, mitochondria volume density (Vv) and compared membrane surface (δm) of the four muscles were significantly lower in COPD + Saline group compared to Control + Saline group, while fatigue index, mitochondria surface area (δ), Bnip3 and Cyto C were higher (P < 0.05). COPD rats showed more morphological changes in muscle tissues than controls, such as atrophy, degeneration, necrosis and matrix hyperplasia. Utrastructurally, mitochondria populations decreased significantly in the four muscles, and were shrunken and even cavitation changed. The up-mentioned parameters were improved in Bufei Jianpi group (P < 0.05) in the four muscles.

Conclusions

Bufei Jianpi granules can improve skeletal muscle function via improving mitochondria population and function, reducing apoptotic factors such as Bnip3 and Cyto C, and is more effective than aminophylline.

Effect of physical exercise on changes in activities of creatine kinase, cytochrome c oxidase and ATP levels caused by ovariectomy

The reduction in the secretion of ovarian hormones, principally estrogen, is a consequence of menopause. Estrogens act primarily as female sex hormones, but also exert effects on different physiological systems including the central nervous system. The treatment normally used to reduce the symptoms of menopause is the hormone therapy, which seems to be effective in treating symptoms, but it may be responsible for adverse effects. Based on this, there is an increasing demand for alternative therapies that minimize signs and symptoms of menopause. In the present study we investigated the effect of ovariectomy and/or physical exercise on the activities of energy metabolism enzymes, such as creatine kinase (cytosolic and mitochondrial fractions), pyruvate kinase, succinate dehydrogenase, complex II, cytochrome c oxidase, as well as on ATP levels in the hippocampus of adult rats. Adult female Wistar rats with 90 days of age were subjected to ovariectomy (an animal model widely used to mimic the postmenopausal changes). Thirty days after the procedure, the rats were submitted to the exercise protocol, which was performed three times a week for 30 days. Twelve hours after the last training session, the rats were decapitated for subsequent biochemical analyzes. Results showed that ovariectomy did not affect the activities of pyruvate kinase, succinate dehydrogenase and complex II, but decreased the activities of creatine kinase (cytosolic and mitochondrial fractions) and cytochrome c oxidase. ATP levels were also reduced. Exercise did not produce the expected results since it was only able to partially reverse the activity of creatine kinase cytosolic fraction. The results of this study suggest that estrogen deficiency, which occurs as a result of ovariectomy, affects generation systems and energy homeostasis, reducing ATP levels in hippocampus of adult female rats.

The effects of soy isoflavone on bone density in north region of climacteric Chinese women

Only a few investigations were based on limb bone density. This study evaluated the efficacy of soy isoflavone in the treatment of the principal menopausal disorders, limb bone density and the role of pathway. The research protocol involved the random subdivision of the enrolled sample into two groups of 40 women, who were to receive treatment for 6 months with isoflavone (90 mg/day) and with placebo. All of the patients were asked to fill in a questionnaire concerning their complaints. BMD of the radius and tibia were measured using quantitative ultrasound. Bone metabolism indexes calcium, phosphorus and alkaline phosphatase (ALP) were examined regularly. Serum cytokines interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) examined by ELISA. The results of the score of Kupperman table showed that the isoflavone can lead to a significant reduction in some of the disorders. Compared with placebo, the tibia bone density in isoflavone group increased obviously against the base value before trail. Isoflavone led to a stronger descent of the concentration of ALP and a decrease of IL-6 and TNF-α level than placebo. For climacteric women, soy isoflavone in the dose of 90 mg/day could improve some menopausal syndromes and was effective on increasing limb bone density, which maybe had the relationship with the levels of IL-6, TNF-α and ALP in serum.

17β-estradiol modulates mitochondrial Ca²⁺ flux in rat caudate nucleus and brain stem

The aim of this study was to examine the rapid non-genomic effect of 17β-estradiol (E2) on Ca(2+) transport in mitochondria isolated from the nerve terminals (synaptosomes) of caudate nuclei (NC) and brain stems (BS) of ovariectomised female rats. In physiological conditions no effect of E2 on Ca(2+) influx into synaptosomal mitochondria through ruthenium red (RR)-sensitive uniporter was observed. However, in the presence of uncoupling agent carbonyl cyanide4-(trifluoromethoxy)phenylhydrazone (FCCP) (1μmol/l), pre-treatment with 0.5nmol/l E2 protected mitochondrial membrane potential and consequently increased Ca(2+) influx (2.3-fold in NC and 3.1-fold in BS). At the same time, 0.5nmol/l E2 by increasing the affinity of mitochondrial Na(+)/Ca(2+) exchanger for Na(+) inhibited mitochondrial Ca(2+) efflux in NC and BS by about 40%. Also, the specific binding of physiological E2 concentrations (0.1-10nmol/l) to isolated synaptosomal mitochondria was detected. Using membrane impermeable E2 bound to bovine serum albumin and selective inhibitor of mitochondrial Na(+)/Ca(2+) exchanger, we obtained that E2's action on mitochondrial Ca(2+) efflux at least partially is due to the direct effects on the mitochondrial membrane and/or Na(+)/Ca(2+) exchanger located in inner mitochondrial membrane. Our results implicate E2 as a modulator of Ca(2+) concentration in mitochondrial matrix, and ultimately in the cytosol. Given the vital role of Ca(2+) in regulation of total nerve cells activity, especially energy metabolism, neurotransmission and directing the cells toward survival or cell death, the effects on mitochondrial Ca(2+) transport could be one of the important modes of E2 neuromodulatory action independent of the genome.

Inhibition of mitochondrial Na+-dependent Ca²+ efflux by 17β-estradiol in the rat hippocampus

Our results, as well as those of others, have indicated that 17β-estradiol (E2) exerts its nongenomic effects in neuronal cells by affecting plasma membrane Ca(2+) flux. In neuronal cells mitochondria possess Ca(2+) buffering properties as they both sequester and release Ca(2+). The goal of this study was to examine the rapid non-genomic effect of E2 on mitochondrial Ca(2+) transport in hippocampal synaptosomes from ovariectomised rats. In addition, we aimed to determine if, and to what extent, E2 receptors participated in mitochondrial Ca(2+) transport modulation by E2 in vitro. E2-specific binding and Ca(2+) transport was monitored. At physiological E2 concentrations (0.1-1.5 nmol/L), specific E2 binding to mitochondria isolated from hippocampal synaptosomes was detected with a B(max.) and K(m) of 37.6±2.6 fmol/mg protein and 0.69±0.14 nmol/L of free E2, respectively. The main mitochondrial Ca(2+) influx mechanism is the Ruthenium Red-sensitive uniporter driven by mitochondrial membrane potential. Despite no effect of E2 on Ca(2+) influx, a physiological E2 concentration (0.5 nmol/L) protected mitochondrial membrane potential and consequently Ca(2+) influx from the uncoupling agent carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (1 μmol/L). In neuronal cells the predominant mitochondrial Ca(2+) efflux mechanism is the Na(+)/Ca(2+) exchanger. E2 caused Ca(2+) efflux inhibition (by 46%) coupled with increased affinity of the Na(+)/Ca(2+) exchanger for Na(+). Using E2 receptor (ERα and ERβ) antagonists and agonists, we confirmed ERβ's involvement in E2-induced mitochondrial membrane potential protection as well as Ca(2+) efflux inhibition. In summary, our results indicate that the non-genomic neuromodulatory role of E2 in rat hippocampus is achieved by affecting mitochondrial Ca(2+) transport via, in part, mitochondrial ERβ.

Ovariectomy alters energy metabolism in rat striatum: effect of supplementation with soy diet rich in isoflavones

In the present study we investigated the effect of ovariectomy on some parameters of energy metabolism, namely Na(+),K(+)-ATPase and pyruvate kinase activities, as well as the mitochondrial respiratory chain enzymes activities succinate dehydrogenase, complex II and cytochrome c oxidase in rat striatum. The influence of soy diet rich in isoflavones on the effects elicited by ovariectomy on enzyme activities was also evaluated. Female adult Wistar rats were assigned to one of the following groups: sham (submitted to surgery without removal of the ovaries) and ovariectomized. Seven days after surgery animals were fed for 30 days on a special diet with soy protein or a standard diet with casein (control). Rats were sacrificed after treatment and the striatum was dissected. Results showed that rats subjected to ovariectomy presented a significant increase in Na(+),K(+)-ATPase, succinate dehydrogenase and complex II activities. Treatment with isoflavones-rich soy diet was able to reverse the increase of Na(+),K(+)-ATPase activity, but was not effective in reversing the changes caused by ovariectomy on succinate dehydrogenase and complex II activities. Since ovariectomy mimics postmenopausal changes, our findings suggest that dysfunction of brain energy metabolism may be related to neurological symptoms observed in some postmenopausal women.

Genistein reduced the neural apoptosis in the brain of ovariectomised rats by modulating mitochondrial oxidative stress

The present study was undertaken to investigate the antioxidant effect of chronic ingestion of genistein (Gen) against neural death in the brain of ovariectomised (Ovx) rats. The rats were randomly divided into five groups, i.e. sham-operated (sham), Ovx-only, Ovx with 17β-oestradiol, Ovx with low (15 mg/kg) and high (30 mg/kg) doses of Gen (Gen-L and Gen-H), and were orally administered daily with drugs or vehicle for 6 weeks. The learning and memory abilities were measured by Morris water maze test. Oxidative damages in the brain were evaluated by the level of superoxide dismutase (SOD), malondialdehyde (MDA) and monoamine oxidase (MAO) activities. Neural apoptosis was shown by terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) staining and caspase-3 activity. In the visual learning and memory test, there were no significant differences among the population means of the five groups. While in the probe trial test, the Gen-L group instead of the Gen-H group exhibited reduced escape latency and increased memory frequency than the Ovx group. Although both doses of Gen could reduce acetylcholinesterase activity, only a low dose of Gen could diminish MDA activity significantly in frontal cortex and enhance SOD content in the hippocampus. In contrast, MAO content was decreased in the cortex by either dose of Gen, while in the hippocampus, only a high dose of Gen appeared to be effective. Interestingly, Gen at both the doses could attenuate the increased number of TUNEL-positive neurons and caspase-3 activity in Ovx rats. These results suggest that Gen confers protection against Ovx-induced neurodegeneration by attenuating oxidative stress, lipid peroxidation and the mitochondria-mediated apoptotic pathway in a region- and dose-dependent manner.

Ginkgo biloba extract EGb761 protects against mitochondrial dysfunction in platelets and hippocampi in ovariectomized rats

Using ovariectomized middle-aged rats to mimic the post-menopausal pathophysiological changes in women, we have previously demonstrated that estrogen withdrawal and age-related decrease in the functional reserve of mitochondria might co-operate to induce persistent mitochondrial dysfunction, which may be critical in inducing degenerative processes in the brain later in post-menopausal women. The standardized Ginkgo biloba extract EGb761 has long been considered a natural antioxidant. More recently it has also proposed to have direct protective effects on the mitochondria. In this work, effects of EGb761 on mitochondrial function in platelets and hippocampi of ovariectomized and sham-operated rats were investigated. It was found that EGb761 protected against the decrease of cytochrome c oxidase (COX) activity, mitochondrial ATP (adenosine-5'-triphosphate) content and mitochondrial glutathione (GSH) content in both platelets and hippocampi of ovariectomized rats, suggesting its peripheral and central effects against estrogen withdrawal-induced degeneration. In contrast, in sham-operated rats, EGb761 increased mitochondrial GSH content in platelets but failed to show similar effect on hippocampi, suggesting that EGb761 may help to enhance the functional reserve of mitochondria, but this effect was limited to the outside of the central nervous system. EGb761 displayed similar effects on platelets and hippocampi of ovariectomized rats but showed differential effects on platelets and hippocampi of sham-operated rats, possibly because estrogen withdrawal induced an increase of blood brain barrier (BBB) permeability. Therefore, while EGb761's effect may be limited to the outside of the nervous system under normal physiological conditions, EGb761 may be a potential protective agent against central neurodegeneration in post-menopausal women.

Regulation of mitochondrial respiratory chain biogenesis by estrogens/estrogen receptors and physiological, pathological and pharmacological implications

There has been increasing evidence pointing to the mitochondrial respiratory chain (MRC) as a novel and important target for the actions of 17beta-estradiol (E(2)) and estrogen receptors (ER) in a number of cell types and tissues that have high demands for mitochondrial energy metabolism. This novel E(2)-mediated mitochondrial pathway involves the cooperation of both nuclear and mitochondrial ERalpha and ERbeta and their co-activators on the coordinate regulation of both nuclear DNA- and mitochondrial DNA-encoded genes for MRC proteins. In this paper, we have: 1) comprehensively reviewed studies that reveal a novel role of estrogens and ERs in the regulation of MRC biogenesis; 2) discussed their physiological, pathological and pharmacological implications in the control of cell proliferation and apoptosis in relation to estrogen-mediated carcinogenesis, anti-cancer drug resistance in human breast cancer cells, neuroprotection for Alzheimer's disease and Parkinson's disease in brain, cardiovascular protection in human heart and their beneficial effects in lens physiology related to cataract in the eye; and 3) pointed out new research directions to address the key questions in this important and newly emerging area. We also suggest a novel conceptual approach that will contribute to innovative regimens for the prevention or treatment of a wide variety of medical complications based on E(2)/ER-mediated MRC biogenesis pathway.

New insights into mitochondrial structure during cell death

Mitochondria play a pivotal role in the cascade of events associated with cell death pathways that are involved with several forms of neurodegeneration. Recent findings show that in the Bax/Bak-dependent pathway of apoptosis, the release of cytochrome c from mitochondria is a consequence of two carefully coordinated events: opening of crista junctions triggered by OPA1 oligomer disassembly and formation of outer membrane pores. Both steps are necessary for the complete release of pro-apoptotic proteins. The remodeling of mitochondrial structure accompanies this pathway, including mitochondrial fission, and cristae and crista junction alterations. Yet, there is controversy surrounding the timing of certain remodeling events and whether they are necessary early events required for the release of pro-apoptotic factors or are simply a downstream after-effect. Here, we analyze the current knowledge of mitochondrial remodeling during cell death and discuss what structural alterations occur to this organelle during neurodegeneration, focusing on the higher resolution structural correlates obtained by electron microscopy and electron tomography.