Hippocampal Mitochondria Research Articles

Simultaneous use of venlafaxine and calcium channel blockers on tolerance to morphine: The role of mitochondrial damage and oxidative stress in the brain

BackgroundOne of the reasons for tolerance to morphine is increased oxidative stress and dysfunction of cell mitochondria in the hippocampus. Venlafaxine and calcium channel blockers can protect mitochondrial function. The investigation of the role of mitochondrial damage and oxidative stress in the simultaneous use of venlafaxine and calcium channel blockers on the acute analgesic effects of morphine and the induction of tolerance to its effects in mice was assessed. MethodIn this experimental study, to induce tolerance to morphine, NMRI mice were treated with 50 mg/kg morphine for three consecutive days and 5 mg/kg morphine on the fourth day. Venlafaxine (20 mg/kg) alone or in combination with calcium channel blockers, nimodipine (10 mg/kg), and diltiazem (40 mg/kg) was administered 30 min before morphine, and the hot plate test was used. Then, hippocampal mitochondria were isolated by differential centrifugation method, and the levels of mitochondrial dehydrogenase activity, mitochondrial membrane potential, mitochondrial ROS production rate, as well as the content of glutathione and malondialdehyde in hippocampal mitochondria, were measured. ResultsThe administration of venlafaxine-nimodipine and venlafaxine-diltiazem increased morphine's acute analgesic effects (P < 0.05) and reduced the induction and expression of tolerance to the analgesic effects of morphine (P < 0.05). Morphine significantly decreased MTT and GSH and increased MDA, mitochondrial membrane damage, and ROS compared to the control group (P < 0.01). Injection of venlafaxine-nimodipine and also venlafaxine-diltiazem 30 min before morphine can improve these alterations (P < 0.05). Discussion and conclusionOur data showed that the simultaneous use of venlafaxine with calcium channel blockers could increase the acute analgesic effects of morphine and reduce the induction and expression of tolerance to it. Also, the preventive and protective roles of simultaneous administration of venlafaxine and calcium channel blockers on morphine-induced mitochondrial oxidative stress and damage during the tolerance test were achieved.

Ligustilide-loaded liposome ameliorates mitochondrial impairments and improves cognitive function via the PKA/AKAP1 signaling pathway in a mouse model of Alzheimer's disease.

Oxidative stress is an early event in the development of Alzheimer's disease (AD) and maybe a pivotal point of interaction governing AD pathogenesis; oxidative stress contributes to metabolism imbalance, protein misfolding, neuroinflammation and apoptosis. Excess reactive oxygen species (ROS) are a major contributor to oxidative stress. As vital sources of ROS, mitochondria are also the primary targets of ROS attack. Seeking effective avenues to reduce oxidative stress has attracted increasing attention for AD intervention. We developed liposome-packaged Ligustilide (LIG) and investigated its effects on mitochondrial function and AD-like pathology in the APPswe/PS1dE9 (APP/PS1) mouse model of AD, and analyzed possible mechanisms. We observed that LIG-loaded liposome (LIG-LPs) treatment reduced oxidative stress and β-amyloid (Aβ) deposition and mitigated cognitive impairment in APP/PS1 mice. LIG management alleviated the destruction of the inner structure in the hippocampal mitochondria and ameliorated the imbalance between mitochondrial fission and fusion in the APP/PS1 mouse brain. We showed that the decline in cAMP-dependent protein kinase A (PKA) and A-kinase anchor protein 1 for PKA (AKAP1) was associated with oxidative stress and AD-like pathology. We confirmed that LIG-mediated antioxidant properties and neuroprotection were involved in upregulating the PKA/AKAP1 signaling in APPswe cells in vitro. Liposome packaging for LIG is relatively biosafe and can overcome the instability of LIG. LIG alleviates mitochondrial dysfunctions and cognitive impairment via the PKA/AKAP1 signaling pathway. Our results provide experimental evidence that LIG-LPs may be a promising agent for AD therapy.

Hippocampus mitochondrial MnSOD activation by a SIRT3 activator, honokiol, correlates with its deacetylation and upregulation of FoxO3a and PGC1α in a rat model of ammonia neurotoxicity.

We have recently reported that honokiol (HKL), by activating mitochondrial SIRT3, normalizes reactive oxygen species level and mitochondrial integrity in hippocampus of the moderate grade hepatic encephalopathy (MoHE) rat model of ammonia neurotoxicity. To delineate the mechanism by which HKL does so, the present study describes activity versus level of the deacetylated mitochondrial Mn-superoxide dismutase (MnSOD) and expression of MnSOD versus levels of its main transcription regulators, FoxO3a and PGC1α, in the hippocampus of the MoHE rats. MoHE in rat was developed by administration of 100 mg/kg bw thioacetamide i.p. for 10 days. The study parameters were compared between the control, the MoHE rats and the MoHE rats treated with HKL (10 mg/Kg b.w.) for 7 days. As compared to control, the hippocampus mitochondria from MoHE rats showed a significantly declined activity of MnSOD vs enhanced lipid peroxidation coinciding with the increased level of its acetylated form. The HKL treatment could, however, normalize all these parameters in those MoHE rats. Also, a significantly reduced expression of MnSOD in the hippocampus of the MoHE rats coincided with a similar decline in transcript level of Foxo3a and Pgc1α. This was consistent with the reduced level of immuno-stained Foxo3a and Pgc1α proteins in hippocampus DG, CA1 and CA3 regions of those MoHE rats. However, all these factors were observed to be restored back to their normal levels due to the treatment with HKL. As HKL is a specific activator of mitochondrial SIRT3, these findings suggest involvement of Sirt3 activation led deacetylation of MnSOD and upregulation of its transcription activators, FoxO3a and PGC1α, in restoring mitochondrial MnSOD level in the hippocampus of the MoHE rat model of ammonia neurotoxicity.

Mitochondrial Bioenergetics, Redox Balance, and Calcium Homeostasis Dysfunction with Defective Ultrastructure and Quality Control in the Hippocampus of Aged Female C57BL/6J Mice.

Aging is a physiological process that generates progressive decline in many cellular functions. There are many theories of aging, and one of great importance in recent years is the mitochondrial theory of aging, in which mitochondrial dysfunction that occurs at advanced age could be responsible for the aged phenotype. In this context, there is diverse information about mitochondrial dysfunction in aging, in different models and different organs. Specifically, in the brain, different studies have shown mitochondrial dysfunction mainly in the cortex; however, until now, no study has shown all the defects in hippocampal mitochondria in aged female C57BL/6J mice. We performed a complete analysis of mitochondrial function in 3-month-old and 20-month-old (mo) female C57BL/6J mice, specifically in the hippocampus of these animals. We observed an impairment in bioenergetic function, indicated by a decrease in mitochondrial membrane potential, O2 consumption, and mitochondrial ATP production. Additionally, there was an increase in ROS production in the aged hippocampus, leading to the activation of antioxidant signaling, specifically the Nrf2 pathway. It was also observed that aged animals had deregulation of calcium homeostasis, with more sensitive mitochondria to calcium overload and deregulation of proteins related to mitochondrial dynamics and quality control processes. Finally, we observed a decrease in mitochondrial biogenesis with a decrease in mitochondrial mass and deregulation of mitophagy. These results show that during the aging process, damaged mitochondria accumulate, which could contribute to or be responsible for the aging phenotype and age-related disabilities.

Gut microbiota-induced microRNA-206-3p increases anxiety-like behaviors by inhibiting expression of Cited2 and STK39

BackgroundAnxiety disorder is highly prevalent worldwide and represents a chronic and functionally disabling condition, with high levels of psychological stress characterized by cognitive and physiological symptoms. The purpose of this study is to evaluate the clinical significance of gut microbiota regulating microRNA (miR)-206-3p as a biomarker in the anxiety-like behaviors. MethodsInitially, bioinformatics analysis was performed to predict the related factors for gut microbiota affecting anxiety-like behaviors. Next, the anxiety-like behaviors in mice were measured by multiple experiments. Western blot analysis, immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA) were utilized to measure the levels of 5-hydroxytryptamine (5-HT), brain derived neurotrophic factor (BDNF), and neutrophil expressed (NE) in brain tissues and serum and cAMP responsive element binding protein 1 (CREB) phosphorylation in brain tissues of germ-free (GF) mice. Dual-luciferase reporter gene assay was employed to verify the relationship between miR-206-3p and Cbp/p300 interacting transactivator with Glu/Asp rich carboxy-terminal domain 2 (Cited2)/serine/threonine kinase 39 (STK39). Ectopic expression and depletion experiments of miR-206-3p were conducted to determine the expression of miR-206-3p and mRNA and protein levels of Cited2, and STK39 in HT22 cells and brain tissues. Finally, transmission electron microscope (TEM) was used to observe the effects of miR-206-3p on hippocampal mitochondria and synapses. ResultsGut microbiota could elevate miR-206-3p expression in brain tissues to increase the anxiety-like behaviors. GF mice displayed the increased levels of 5-HT, BDNF, and NE in brain tissues and serum and CREB phosphorylation in brain tissues. Cited2/STK39 was identified as the target genes of miR-206-3p. Upregulated miR-206-3p increased anxiety-like behaviors by promoting degeneration of mitochondria and synapses in hippocampus via downregulation of Cited2 and STK39. ConclusionsIn conclusion, the key findings of the current study demonstrate that gut microbiota aggravated anxiety-like behaviors via the miR-206-3p/Cited2/STK39 axis.

The role of PKC/PKR in aging, Alzheimer's disease, and perioperative neurocognitive disorders.

BackgroundThe incidence of perioperative neurocognitive disorders (PNDs) is reportedly higher in older patients. Mitochondrial and synaptic dysfunctions have consistently been demonstrated in models of aging and neurodegenerative diseases; nonetheless, their role in PND is not well understood.MethodsThe Morris water maze and elevated plus maze tests were used to assess the learning and memory abilities of both C57BL/6 and 3×Tg-AD mice of different ages (8 and 18 months). PND was induced by laparotomy in C57BL/6 mice and 3×Tg-AD mice (8 months old). Markers associated with neuroinflammation, mitochondrial function, synaptic function, and autophagy were assessed postoperatively. The roles of protein kinase C (PKC) and double-stranded RNA-dependent protein kinase (PKR) were further demonstrated by using PKC-sensitive inhibitor bisindolylmaleimide X (BIMX) or PKR−/− mice.ResultsSignificant cognitive impairment was accompanied by mitochondrial dysfunction and autophagy inactivation in both aged C57BL/6 and 3×Tg-AD mice. Laparotomy induced a significant neuroinflammatory response and synaptic protein loss in the hippocampus. Cognitive and neuropathological changes induced by aging or laparotomy were further exacerbated in 3×Tg-AD mice. Deficits in postoperative cognition, hippocampal mitochondria, autophagy, and synapse were significantly attenuated after pharmacological inhibition of PKC or genetic deletion of PKR.ConclusionsOur findings suggest similar pathogenic features in aging, Alzheimer's disease, and PND, including altered mitochondrial homeostasis and autophagy dysregulation. In addition, laparotomy may exacerbate cognitive deficits associated with distinct neuronal inflammation, mitochondrial dysfunction, and neuronal loss independent of genetic background. The dysregulation of PKC/PKR activity may participate in the pathogenesis of these neurodegenerative diseases.

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

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. To clarify if administration of miR-195 inhibitor could enhance the memory deficits through improving hippocampal neuron mitochondrial dysfunction in SAMP8 mice. The expression of miR-195 was detected by RT-qPCR in primary hippocampal neurons and HT-22 cells treated with Aβ1-42. 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. The expression of miR-195 were upregulated in the primary hippocampal neurons and HT-22 cells induced by Aβ1-42. Inhibition of miR-195 ameliorated the mitochondrial dysfunction in HT-22 cells induced by Aβ1-42, 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. 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.

Tea polyphenols improve the memory in aging ovariectomized rats by regulating brain glucose metabolism in vivo and in vitro

Tea polyphenols (TP) are the main active components of tea. In our study, the effect of TP on the menopause and aging related memory decline and the mechanisms focused on the brain glucose metabolism were clarified. In vivo, ovariectomy (OVX) combined with D-galactose (D-gal) injection were used to establish the memory decline model. TP administration improved the spatial memory by increasing the expressions of GLUT1, 3 and Tau protein O-GlcNAc glycosylation, decreasing Tau hyper-phosphorylation and the Aβ1-42 level, and improving the morphology of mitochondria in hippocampus. Furthermore, in vitro, PC12 cells were treated with Aβ1-42 and EGCG treatment regulated the mitochondrial respiratory function and glycolytic functions, improved the activities of the key enzymes in glycolysis and tricarboxylic acid cycle, increased the SOD activity and decreased the MDA levels in cells. Our study suggests that TP improve the memory in aging ovariectomized rats by regulating brain glucose metabolism.

Sexually Dimorphic Effects of a Western Diet on Brain Mitochondrial Bioenergetics and Neurocognitive Function.

A Western diet (WD), high in sugars and saturated fats, impairs learning and memory function and contributes to weight gain. Mitochondria in the brain provide energy for neurocognitive function and may play a role in body weight regulation. We sought to determine whether a WD alters behavior and metabolic outcomes in male and female rodents through impacting hippocampal and hypothalamic mitochondrial bioenergetics. Results revealed a sexually dimorphic macronutrient preference, where males on the WD consumed a greater percentage of calories from fat/protein and females consumed a greater percentage of calories from a sugar-sweetened beverage. Both males and females on a WD gained body fat and showed impaired glucose tolerance when compared to same-sex controls. Males on a WD demonstrated impaired hippocampal functioning and an elevated tendency toward a high membrane potential in hippocampal mitochondria. Comprehensive bioenergetics analysis of WD effects in the hypothalamus revealed a tissue-specific adaption, where males on the WD oxidized more fat, and females oxidized more fat and carbohydrates at peak energy demand compared to same-sex controls. These results suggest that adult male rats show a susceptibility toward hippocampal dysfunction on a WD, and that hypothalamic mitochondrial bioenergetics are altered by WD in a sex-specific manner.

Mitochondria Damage as Early Indicator in an APP NL‐G‐F Mouse Model of Alzheimer's Disease

Introduction Traditional transgenic mouse models of Alzheimer's disease (AD) overexpress mutant amyloid precursor protein (APP) in order to increase pathological amyloid b peptide. However, this results in artificial phenotypes due to the non-clinically relevant overexpression of APP peptide species. To overcome these limitations, mice with a single humanized APP knock-in (KI) carrying Swedish (K670N/M671L), Arctic (E693G) and Beyreuther/Iberian (I716F) mutations (APPNL-G-F) have been developed to better reflect the human disease condition. Several groups have characterized the amyloidogenic, neuroinflammatory, and behavioral phenotypes of this mouse. However, to date no group has investigated and characterized the metabolic and mitochondrial phenotype of this mouse at different stages of development. Methods Mitochondria play a key role in both disease onset and progression, therefore detailed mechanistic characterization of mitochondrial and associated-metabolic dysfunction in this novel AD model is essential. Here, we evaluated mitochondria function, dynamics (fission/fusion) and morphology in APPNL-G-F mice using flowcytometry, Immunoblotting and high-resolution mitochondrial respirometry. Results Mitochondria dysfunction was detected as early as 3-4 months (m) of age in the hippocampus of AppNL-G-F mice, with further pathological progression detected at 6-8 m. Hippocampal mitochondria from 6-8 m AppNL-G-F miceexhibited higher membrane potential, decreased ATP production and increased reactive oxygen species (ROS) production. Morphologically, these mitochondria were larger in volume accompanied by lower dynamics (i.e., altered fission/fusion) at 6-8 m. Interestingly, plasma isolated from these 6-8 m AppNL-G-F mice resulted in a mitochondrial dysfunction in Hela cells and human differentiated neurons derived from induced pluripotent stem cells in vitro. Conclusion Our data revealed early mitochondrial dysfunction and associated metabolic changes in the hippocampus and circulatory plasma of AppNL-G-F mice.Further research may help to develop early AD detection based on mitochondrial/metabolic dysfunction.

Arsenite induces ferroptosis in the neuronal cells via activation of ferritinophagy

Ferroptosis is a novel form of cell death that involves in the pathophysiological process of diverse brain diseases. However, how arsenite induces ferroptosis in the neuronal cells remains unsolved. In this study, by using in vitro and in vivo models, we demonstrated that arsenite was able to trigger ferroptosis in the neuronal cells. Exposure of arsenite for 6 months at 0.5, 5 and 50 mg/L arsenite via drinking water significantly reduced the number of neurons and caused the pathological changes in the mitochondria of hippocampus. Treatment of arsenite elevated the contents of lipid peroxidation products, disrupted the iron homeostasis, altered the expressions of ferroptosis-related proteins in the hippocampus and PC-12 cells. The results also showed that arsenite significantly decreased the expressions of ferritin and NCOA4, but sharply enhanced the level of autophagy marker LC3B, suggesting the activation of ferritinophagy by arsenite. Co-treatment of arsenite with ferroptosis inhibitor ferrostatin-1, or autophagy inhibitors 3-MA and BafA1, all remarkably attenuated the cytotoxic effects of arsenite. These findings not only present a novel mechanism that arsenite triggers ferroptosis in the neuronal cells via activation of ferritinophagy, but also indicate that regulating ferritinophagy to control iron level may provide a clue for prevention against arsenite neurotoxicity.

Pathologically phosphorylated tau at S396/404 (PHF-1) is accumulated inside of hippocampal synaptic mitochondria of aged Wild-type mice

Brain aging is a natural process characterized by cognitive decline and memory loss. This impairment is related to mitochondrial dysfunction and has recently been linked to the accumulation of abnormal proteins in the hippocampus. Age-related mitochondrial dysfunction could be induced by modified forms of tau. Here, we demonstrated that phosphorylated tau at Ser 396/404 sites, epitope known as PHF-1, is increased in the hippocampus of aged mice at the same time that oxidative damage and mitochondrial dysfunction are observed. Most importantly, we showed that tau PHF-1 is located in hippocampal mitochondria and accumulates in the mitochondria of old mice. Finally, since two mitochondrial populations were found in neurons, we evaluated tau PHF-1 levels in both non-synaptic and synaptic mitochondria. Interestingly, our results revealed that tau PHF-1 accumulates primarily in synaptic mitochondria during aging, and immunogold electron microscopy and Proteinase K protection assays demonstrated that tau PHF-1 is located inside mitochondria. These results demonstrated the presence of phosphorylated tau at PHF-1 commonly related to tauopathy, inside the mitochondria from the hippocampus of healthy aged mice for the first time. Thus, this study strongly suggests that synaptic mitochondria could be damaged by tau PHF-1 accumulation inside this organelle, which in turn could result in synaptic mitochondrial dysfunction, contributing to synaptic failure and memory loss at an advanced age.

Atorvastatin Prevents the Neuron Loss in the Hippocampal Dentate Gyrus Region through its Anti-Oxidant and Anti-Apoptotic Activities.

Atorvastatin is a member of statins, which has shown positive vascular effects, anti-oxidant, anti-platelet, and anti-apoptotic properties. In this study, we hypothesized that atorvastatin could prevent the neurons lost in the hippocampal dentate gyrus region after transient global Ischemia/Reperfusion (I/R) through its anti- oxidant and anti-apoptotic activities. Twenty-four male Wistar rats, 12-13 weeks old and weighing 250-300 g, were divided randomly into four groups: control, I/R, vehicle (I/R treated with NaCl) and experiment (I/R treated with atorvastatin, 10 mg/kg); rats were sacrificed 96 hours after I/R. Quantitative expression of genes (caspase 8, p53, bax, bcl2, cytochrome c) was studied. The MDA level, SOD, CAT, and GPx activities were measured with biochemical tests. To detect apoptotic cells, TUNEL and Nissl staining were performed. Mitochondria were prepared from the hippocampus rats and used for the quantification of mitochondrial ROS, ATP level, GSH content, membrane potential, cytochrome c release, and determination of mitochondrial swelling. Atorvastatin attenuated the overexpression of bax, cytochrome C, p53, and caspase8 mRNAs and induced expression of bcl-2 mRNA (P<0.001). Atorvastatin treatment increased anti-oxidant enzyme levels (P<0.01). Treatment with atorvastatin reduced the number of TUNEL-positive cells. It could decrease the cytochrome c release (P<0.01), inhibit the decrease of MMP (P<0.001) and increase the ATP level (P<0.001) in hippocampal mitochondria compared with the I/R group. Atorvastatin treatment in I/R rats decreases oxidative stress, production of ROS, apoptosis rate in neuronal cells, and improves the mitochondrial function. Hence, atorvastatin has a proper neuronal protective effect against the I/R injury in the brain.

Potentiation of the apoptotic signaling pathway in both the striatum and hippocampus and neurobehavioral impairment in rats exposed chronically to a low-dose of cadmium.

Cadmium (Cd) is a highly toxic heavy metal. It accumulates in biological tissues, especially in fish which constitutes a first rank food for humans, particularly in the coastal areas. This study investigates the effect of long-term exposure to low Cd concentration (17 μg/kg/day) in rat striatum and hippocampus. In this study, the neurobehavioral ability changes were assessed by applying cognitive standard testing at the end of the rats' exposure period. In addition, the examination of mitochondrial swelling was performed at the same time of evaluation of its redox status in the brain regions studied through stress parameters (GSH, MDA, GST, and CAT). This study examined also whether this long-term exposure can modify the apoptotic signaling pathway via assessment of apoptotic markers (caspase-8 and 9, Bax, Bcl-2, and Cyt-c) in cell lysates. The results of this study showed changes in neurobehavioral abilities of animals and a stronger mitochondrial swelling associated with a significant decrease in antioxidant systems (GSH, GST, and CAT) and conversely an increase in the lipoperoxidation end product (MDA) in both the striatal and hippocampal mitochondria. In addition, the results revealed a significant increase in pro-apoptotic intracellular components such as caspase-9, Cyt-c, and Bax, and showed also an evident decrease in Bcl-2 levels. In conclusion, our results reported that chronic exposure to Cd produces behavioral and cognitive perturbations, enhances oxidative stress associated with mitochondrial edema and Cyt-c leakage, and, ultimately, potentiates apoptosis signaling pathway in both brain regions in rats.

Ketamine treatment affects hippocampal but not cortical mitochondrial function in prepubertal rats.

Previous reports have shown that ketamine triggered apoptosis in immature developing brain involving mitochondrial-mediated pathways. However, no data for ketamine effects on hippocampal and cortical mitochondrial function are available in prepubertal rats. Twenty-one-day-old Sprague-Dawley rats received ketamine (40mg/kg i.p.) for 3days and were killed 24hr after thelast injection. Hippocampal mitochondria from ketamine-treated rats showed decreased malate-glutamate state 4 and 3 respiratory rates and an inhibition in complex I and IV activities. Hippocampal mitochondrial membrane depolarization and mitochondrial permeability transition induction were observed. This was not reflected in an increment of H2 O2 production probably due to increased Mn-SOD and catalase activities, 24hr after treatment. Interestingly, increased H2 O2 production rates and cardiolipin oxidation were found in hippocampal mitochondria shortly after ketamine treatment (45min). Unlike the hippocampus, ketamine did not affect mitochondrial parameters in the brain cortex, being the area less vulnerable to suffer ketamine-induced oxidative damage. Results provide evidences that exposure of prepubertal rats to ketamine leads to an induction of mitochondrial ROS generation at early stages of treatment that was normalized by the triggering of antioxidant systems. Although hippocampal mitochondria from prepubertal rats were capable of responding to the oxidative stress, they remain partially dysfunctional.

Electroacupuncture and Moxibustion Regulate Hippocampus Glia and Mitochondria Activation in DSS-Induced Colitis Mice.

Objectives To study the influence of electroacupuncture (EA) and moxibustion on the hippocampus astrocyte and microglia activation in the ulcerative colitis model and to evaluate the mitochondria activity. Methods 2.5% dextran sodium sulfate-induced colitis mice were treated by EA or moxibustion. Intestinal pathological structure was observed by hematoxylin and eosin (H&E) staining; the expression of GFAP or S100b (markers for astrocyte), Iba-1 (a marker for microglia), and Mitofilin (a marker for mitochondria) in hippocampus was detected by immunofluorescence staining or western blot. Results The results demonstrated that both EA and moxibustion could improve the morphology of distal colonic mucosal epithelia in DSS-induced colitis mice. Expression of GFAP in the hippocampus was significantly increased after EA or moxibustion treatment. The effects were further supported by WB results. Meanwhile, expression of mitofilin in the hippocampus CA1 and CA3 regions showed the same trend as that of GFAP. Expression of Iba-1 in the hippocampus showed no significant difference after EA or moxibustion treatment, while the state of microglia changed from resting in control mice to activated state in colitis mice. Conclusion EA and moxibustion were able to modulate the activation of astrocyte, microglial, and mitochondria in the hippocampus area in the colitis model.

Sex differences and gonadal hormone regulation of brain cardiolipin, a key mitochondrial phospholipid.

Cardiolipin (CL) is a phospholipid that is almost exclusively located in the inner mitochondrial membrane of eukaryotic cells. As a result of its unique structure and distribution, CL establishes non-covalent bonds with a long list of proteins involved in ATP production, mitochondria biogenesis, mitophagy and apoptosis. Thus, the amount of CL, as well as its fatty acid composition and location, strongly impacts upon mitochondrial-dependent functions and therefore the metabolic homeostasis of different tissues. The brain is particularly sensitive to mitochondrial dysfunction as a result of its high metabolic demand. Several mitochondrial related-neurodegenerative disorders, as well as physiological ageing, show altered CL metabolism. Furthermore, mice lacking enzymes involved in CL synthesis show cognitive impairments. CL content and metabolism are regulated by gonadal hormones in the developing and adult brain. In neuronal cultures, oestradiol increases CL content, whereas adult ovariectomy decreases CL content and alters CL metabolism in the hippocampal mitochondria. Transient sex differences in brain CL metabolism have been detected during development. At birth, brain CL has a higher proportion of unsaturated fatty acids in the brain of male mice than in the brain of females. In addition, the expression of enzymes involved in CL de novo and recycling synthetic pathways is higher in males. Most of these sex differences are abolished by the neonatal androgenisation of females, suggesting a role for testosterone in the generation of sex differences in brain CL. The regulation of brain CL by gonadal hormones may be linked to their homeostatic and protective actions in neural cells, as well as the manifestation of sex differences in neurodegenerative disorders.

Global brain ischemia in rats is associated with mitochondrial release and downregulation of Mfn2 in the cerebral cortex, but not the hippocampus.

Mitochondria are crucial for neuronal cell survival and death through their functions in ATP production and the intrinsic pathway of apoptosis. Mitochondrial dysfunction is considered to play a central role in several serious human diseases, including neurodegenerative diseases, such as Parkinson's and Alzheimer's disease and ischemic neurodegeneration. The aim of the present study was to investigate the impact of transient global brain ischemia on the expression of selected proteins involved in mitochondrial dynamics and mitochondria-associated membranes. The main foci of interest were the proteins mitofusin 2 (Mfn2), dynamin-related protein 1 (DRP1), voltage-dependent anion-selective channel 1 (VDAC1) and glucose-regulated protein 75 (GRP75). Western blot analysis of total cell extracts and mitochondria isolated from either the cerebral cortex or hippocampus of experimental animals was performed. In addition, Mfn2 was localized intracellularly by laser scanning confocal microscopy. It was demonstrated that 15-min ischemia, or 15-min ischemia followed by 1, 3, 24 or 72 h of reperfusion, was associated with a marked decrease of the Mfn2 protein in mitochondria isolated from the cerebral cortex, but not in hippocampal mitochondria. Moreover, a translocation of the Mfn2 protein to the cytoplasm was documented immediately after global brain ischemia in the neurons of the cerebral cortex by laser scanning confocal microscopy. Mfn2 translocation was followed by decreased expression of Mfn2 during reperfusion. Markedly elevated levels of the VDAC1 protein were also documented in total cell extracts isolated from the hippocampus of rats after 15 min of global brain ischemia followed by 3 h of reperfusion, and from the cerebral cortex of rats after 15 min of global brain ischemia followed by 72 h of reperfusion. The mitochondrial Mfn2 release observed during the early stages of reperfusion may thus represent an important mechanism of mitochondrial dysfunction associated with neuronal dysfunction or death induced by global brain ischemia.

Distinct differences in rates of oxygen consumption and ATP synthesis of regionally isolated non-synaptic mouse brain mitochondria.

Brain mitochondrial dysfunction has been implicated in several neurodegenerative diseases. The distribution and efficiency of mitochondria display large heterogeneity throughout the regions of the brain. This may imply that the selective regional susceptibility of neurodegenerative diseases could be mediated through inherent differences in regional mitochondrial function. To investigate regional cerebral mitochondrial energetics, the rates of oxygen consumption and adenosine-5'-triphosphate (ATP) synthesis were assessed in isolated non-synaptic mitochondria of the cerebral cortex, hippocampus, and striatum of the male mouse brain. Oxygen consumption rates were assessed using a Seahorse XFe96 analyzer and ATP synthesis rates were determined by an online luciferin-luciferase coupled luminescence assay. Complex I- and complex II-driven respiration and ATP synthesis, were investigated by applying pyruvate in combination with malate, or succinate, as respiratory substrates, respectively. Hippocampal mitochondria exhibited the lowest basal and adenosine-5'-diphosphate (ADP)-stimulated rate of oxygen consumption when provided pyruvate and malate. However, hippocampal mitochondria also exhibited an increased proton leak and an elevated relative rate of oxygen consumption in response to the uncoupler carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP), showing a large capacity for uncoupled respiration in the presence of pyruvate. When the complex II-linked substrate succinate was provided, striatal mitochondria exhibited the highest respiration and ATP synthesis rate, whereas hippocampal mitochondria had the lowest. However, the mitochondrial efficiency, determined as ATP produced/O2 consumed, was similar between the three regions. This study reveals inherent differences in regional mitochondrial energetics and may serve as a tool for further investigations of regional mitochondrial function in relation to neurodegenerative diseases.

Dephosphorylation by calcineurin regulates translocation of dynamin-related protein 1 to mitochondria in hepatic ischemia reperfusion induced hippocampus injury in young mice

Hepatic ischemia reperfusion (HIR) has been found to induce brain injury and cognitive dysfunction. Dynamin-related protein 1 (Drp1) mediated mitochondrial fission involves oxidative stress, apoptosis and several neurological diseases. In this study, we investigated whether Drp1 translocation to mitochondria was implicated in HIR induced hippocampus injury in young mice, and further detected the role of calcineurin in the regulation of mitochondrial dynamics. 2-week C57BL/6 mice were chosen to make HIR model. Western blot was used to detect mitochondrial dynamics regulating proteins in whole hippocampal tissues and extracted mitochondria. Transmission electron microscopy was used to observe mitochondrial morphology. TUNEL staining and ELISA (serum S100β/NSE concentrations) were used to evaluate neurons apoptosis and brain injury respectively. Drp1 inhibitor Mdivi-1 and calcineurin inhibitor FK506 were utilized to further confirm the role of Drp1 and calcineurin. Results showed that HIR affected mitochondrial dynamics in a fission-dominant manner with translocation of Drp1 to mitochondria in hippocampus of young mice. HIR induced increased expression of calcineurin and dephosphorylation of Drp1 at Ser637 in hippocampus. Treatment with Mdivi-1 and FK506 upregulated the phosphorylation of Drp1, inhibited Drp1 translocation to mitochondria, and alleviated mitochondrial fragmentation after HIR. What’s more, Mdivi-1 and FK506 restrained cytochrome c release and cleaved caspase-3 expression, ameliorated hippocampal neurons apoptosis, and decreased serum S100β/NSE concentrations as well. These data suggest that calcineurin mediated Drp1 dephosphorylation and translocation to mitochondria play a crucial role in HIR induced mitochondrial fragmentation and neurons apoptosis in hippocampus.