Giant mitochondria in human liver disease

This thematic review aims to provide an overview of the current state of knowledge about the occurrence of giant mitochondria or megamitochondria in liver parenchymal cells. Their presence and accumulation are considered to be a major pathological hallmark of the health and fate of liver parenchymal cells that leads to overall tissue deterioration and eventually results in organ failure. The first description on giant mitochondria dates back to the 1960s, coinciding with the availability of the first generation of electron microscopes in clinical diagnostic laboratories. Detailed accounts on their ultrastructure have mostly been described in patients suffering from alcoholic liver disease, chronic hepatitis, hepatocellular carcinoma and non-alcoholic fatty liver disease. Interestingly, from this extensive literature survey, it became apparent that giant mitochondria or megamitochondria present themselves with or without highly organised crystal-like intramitochondrial inclusions. The origin, formation and potential role of giant mitochondria remain to-date largely unanswered. Likewise, the biochemical composition of the well-organised crystal-like inclusions and their possible impact on mitochondrial function is unclear. Herein, concepts about the possible mechanism of their formation and three-dimensional architecture will be approached. We will furthermore discuss their importance in diagnostics, including future research outlooks and potential therapeutic interventions to cure liver disease where giant mitochondria are implemented.

Giant mitochondria in cardiomyocytes: cellular architecture in health and disease

Giant mitochondria are frequently observed in different disease models within the brain, kidney, and liver. In cardiac muscle, these enlarged organelles are present across diverse physiological and pathophysiological conditions including in ageing and exercise, and clinically in alcohol-induced heart disease and various cardiomyopathies. This mitochondrial aberration is widely considered an early structural hallmark of disease leading to adverse organ function. In this thematic paper, we discuss the current state-of-knowledge on the presence, structure and functional implications of giant mitochondria in heart muscle. Despite its demonstrated reoccurrence in different heart diseases, the literature on this pathophysiological phenomenon remains relatively sparse since its initial observations in the early 60s. We review historical and contemporary investigations from cultured cardiomyocytes to human tissue samples to address the role of giant mitochondria in cardiac health and disease. Finally, we discuss their significance for the future development of novel mitochondria-targeted therapies to improve cardiac metabolism and functionality.

Mitochondrial swelling in cardiomyocytes: Insights from a murine model of Tityus serrulatus scorpion envenomation

Immune system hyperactivation is involved with clinical severity and pathological alterations during scorpion envenomation. In a murine model, mice inoculated with a lethal dose of Tityus serrulatus scorpion venom presented mitochondrial swelling in cardiomyocytes, with other structures such as sarcomeres and intercalated disks preserved. Treatment with dexamethasone or knockout animals to the interleukin-1β receptor do not undergo mitochondrial changes in cardiomyocytes during envenomation.

Loss of hepatic DRP1 exacerbates alcoholic hepatitis by inducing megamitochondria and mitochondrial maladaptation

BACKGROUND AND AIMS

Increased megamitochondria formation and impaired mitophagy in hepatocytes have been linked to the pathogenesis of alcohol-associated liver disease (ALD). This study aims to determine the mechanisms by which alcohol consumption increases megamitochondria formation in the pathogenesis of ALD.

APPROACH AND RESULTS

Human alcoholic hepatitis (AH) liver samples were used for electron microscopy, histology, and biochemical analysis. Liver-specific dynamin-related protein 1 (DRP1; gene name DNM1L, an essential gene regulating mitochondria fission ) knockout (L-DRP1 KO) mice and wild-type mice were subjected to chronic plus binge alcohol feeding. Both human AH and alcohol-fed mice had decreased hepatic DRP1 with increased accumulation of hepatic megamitochondria. Mechanistic studies revealed that alcohol feeding decreased DRP1 by impairing transcription factor EB-mediated induction of DNM1L . L-DRP1 KO mice had increased megamitochondria and decreased mitophagy with increased liver injury and inflammation, which were further exacerbated by alcohol feeding. Seahorse flux and unbiased metabolomics analysis showed alcohol intake increased mitochondria oxygen consumption and hepatic nicotinamide adenine dinucleotide (NAD + ), acylcarnitine, and ketone levels, which were attenuated in L-DRP1 KO mice, suggesting that loss of hepatic DRP1 leads to maladaptation to alcohol-induced metabolic stress. RNA-sequencing and real-time quantitative PCR analysis revealed increased gene expression of the cGAS-stimulator of interferon genes (STING)-interferon pathway in L-DRP1 KO mice regardless of alcohol feeding. Alcohol-fed L-DRP1 KO mice had increased cytosolic mtDNA and mitochondrial dysfunction leading to increased activation of cGAS-STING-interferon signaling pathways and liver injury.

CONCLUSION

Alcohol consumption decreases hepatic DRP1 resulting in increased megamitochondria and mitochondrial maladaptation that promotes AH by mitochondria-mediated inflammation and cell injury.

Theoretical approaches used in the modelling of reversible and irreversible mitochondrial swelling in vitro

Existing theoretical approaches were considered that allow modelling of mitochondrial swelling (MS) dynamics. Simple phenomenological kinetic models were reviewed. Simple and extended biophysical and bioenergetic models that ignore mechanical properties of inner mitochondrial membrane (IMM), and similar models that include these mechanical properties were also reviewed. Limitations of these models we considered, as regards correct modelling of MS dynamics. It was found that simple phenomenological kinetic models have significant limitations, due to dependence of the kinetic parameter values estimated by fitting of the experimental data on the experimental conditions. Additionally, such simple models provide no understanding of the detailed mechanisms behind the MS dynamics, nor of the dynamics of various system parameters during MS. Thus, biophysical and bioenergetic models ignoring IMM mechanical properties can't be used to model the transition between reversible and irreversible MS. However, simple and extended biophysical models that include IMM mechanical properties allow modelling the transition to irreversible swelling. These latter models are still limited due to significantly simplified description of biochemistry, compared to those of bioenergetic models. Finally, a strategy of model development is proposed, towards correct interpretation of the mitochondrial life cycle, including the effects of MS dynamics.

Simultaneous Acquisition of Mitochondrial Calcium Retention Capacity and Swelling to Measure Permeability Transition Sensitivity

The loss of mitochondrial cristae integrity and mitochondrial swelling are hallmarks of multiple forms of necrotic cell death. One of the most well-studied and relevant inducers of mitochondrial swelling is matrix calcium (Ca2+). Respiring mitochondria will intake available Ca2+ into their matrix until a threshold is reached which triggers the opening of the mitochondrial permeability transition pore (MPTP). Upon opening of the pore, mitochondrial membrane potential dissipates and the mitochondria begin to swell, rendering them dysfunctional. The total amount of Ca2+ taken up by a mitochondrion prior to the engagement of the MPTP is referred to as mitochondrial Ca2+ retention capacity (CRC). The CRC/swelling assay is a useful tool for observing the dose-dependent event of mitochondrial dysfunction in real-time. In this technique, isolated mitochondria are treated with specific boluses of Ca2+ until they reach CRC and undergo swelling. A fluorometer is utilized to detect an increase in transmitted light passing through the sample as the mitochondria lose cristae density, and simultaneously measures calcium uptake by way of a Ca2+-specific membrane impermeable fluorescent dye. Here we provide a detailed protocol describing the mitochondrial CRC/swelling assay and we discuss how varying amounts of mitochondria and Ca2+ added to the system affect the dose-dependency of the assay. We also report how to validate the assay by using MPTP and calcium uptake inhibitors and troubleshooting common mistakes that occur with this approach.

3-Methyladenine prevents energy stress-induced necrotic death of melanoma cells through autophagy-independent mechanisms

We investigated the effect of 3-methyladenine (3MA), a class III phosphatidylinositol 3-kinase (PI3K)-blocking autophagy inhibitor, on cancer cell death induced by simultaneous inhibition of glycolysis by 2-deoxyglucose (2DG) and mitochondrial respiration by rotenone. 2DG/rotenone reduced ATP levels and increased mitochondrial superoxide production, causing mitochondrial swelling and necrotic death in various cancer cell lines. 2DG/rotenone failed to increase proautophagic beclin-1 and autophagic flux in melanoma cells despite the activation of AMP-activated protein kinase (AMPK) and inhibition of mechanistic target of rapamycin complex 1 (mTORC1). 3MA, but not autophagy inhibition with other PI3K and lysosomal inhibitors, attenuated 2DG/rotenone-induced mitochondrial damage, oxidative stress, ATP depletion, and cell death, while antioxidant treatment mimicked its protective action. The protection was not mediated by autophagy upregulation via class I PI3K/Akt inhibition, as it was preserved in cells with genetically inhibited autophagy. 3MA increased AMPK and mTORC1 activation in energy-stressed cells, but neither AMPK nor mTORC1 inhibition reduced its cytoprotective effect. 3MA reduced JNK activation, and JNK pharmacological/genetic suppression mimicked its mitochondria-preserving and cytoprotective activity. Therefore, 3MA prevents energy stress-triggered cancer cell death through autophagy-independent mechanisms possibly involving JNK suppression and decrease of oxidative stress. Our results warrant caution when using 3MA as an autophagy inhibitor.

The very low number of calcium-induced permeability transition pores in the single mitochondrion

Mitochondrial permeability transition (PT) is a phenomenon of stress-induced increase in nonspecific permeability of the mitochondrial inner membrane that leads to disruption of oxidative phosphorylation and cell death. Quantitative measurement of the membrane permeability increase during PT is critically important for understanding the PT's impact on mitochondrial function. The elementary unit of PT is a PT pore (PTP), a single channel presumably formed by either ATP synthase or adenine nucleotide translocator (ANT). It is not known how many channels are open in a single mitochondrion during PT, which makes it difficult to quantitatively estimate the overall degree of membrane permeability. Here, we used wide-field microscopy to record mitochondrial swelling and quantitatively measure rates of single-mitochondrion volume increase during PT-induced high-amplitude swelling. PT was quantified by calculating the rates of water flux responsible for measured volume changes. The total water flux through the mitochondrial membrane of a single mitochondrion during PT was in the range of (2.5 ± 0.4) × 10-17 kg/s for swelling in 2 mM Ca2+ and (1.1 ± 0.2) × 10-17 kg/s for swelling in 200 µM Ca2+. Under these experimental conditions, a single PTP channel with ionic conductance of 1.5 nS could allow passage of water at the rate of 0.65 × 10-17 kg/s. Thus, we estimate the integral ionic conductance of the whole mitochondrion during PT to be 5.9 ± 0.9 nS for 2 mM concentration of Ca2+ and 2.6 ± 0.4 nS for 200 µM of Ca2+. The number of PTPs per mitochondrion ranged from one to nine. Due to the uncertainties in PTP structure and model parameters, PTP count results may be slightly underestimated. However, taking into account that each mitochondrion has ∼15,000 copies of ATP synthases and ANTs, our data imply that PTP activation is a rare event that occurs only in a small subpopulation of these proteins.

Rapid Intramitochondrial Zn2+ Accumulation in CA1 Hippocampal Pyramidal Neurons After Transient Global Ischemia: A Possible Contributor to Mitochondrial Disruption and Cell Death

Mitochondrial Zn2+ accumulation, particularly in CA1 neurons, occurs after ischemia and likely contributes to mitochondrial dysfunction and subsequent neurodegeneration. However, the relationship between mitochondrial Zn2+ accumulation and their disruption has not been examined at the ultrastructural level in vivo. We employed a cardiac arrest model of transient global ischemia (TGI), combined with Timm's sulfide silver labeling, which inserts electron dense metallic silver granules at sites of labile Zn2+ accumulation, and used transmission electron microscopy (TEM) to examine subcellular loci of the Zn2+ accumulation. In line with prior studies, TGI-induced damage to CA1 was far greater than to CA3 pyramidal neurons, and was substantially progressive in the hours after reperfusion (being significantly greater after 4- than 1-hour recovery). Intriguingly, TEM examination of Timm's-stained sections revealed substantial Zn2+ accumulation in many postischemic CA1 mitochondria, which was strongly correlated with their swelling and disruption. Furthermore, paralleling the evolution of neuronal injury, both the number of mitochondria containing Zn2+ and the degree of their disruption were far greater at 4- than 1-hour recovery. These data provide the first direct characterization of Zn2+ accumulation in CA1 mitochondria after in vivo TGI, and support the idea that targeting these events could yield therapeutic benefits.

Toxicity of multi-wall carbon nanotubes inhalation on the brain of rats

This study was designed to investigate the brain toxicity following the respiratory contact with multi-wall carbon nanotubes (MWCNTs) in male Wistar rats. Rats were exposed to 5 mg/m³ MWCNT aerosol in different sizes and purities for 5 h/day, 5 days/week for 2 weeks in a whole-body exposure chamber. After 2-week exposure, mitochondrial isolation was performed from different parts of rat brain (hippocampus, frontal cortex, and cerebellum) and parameters of mitochondrial toxicity including mitochondrial succinate dehydrogenase (SDH) activity, generation of reactive oxygen species (ROS), mitochondrial membrane potential (MMP) collapse, mitochondrial swelling, and cytochrome c release, ATP level, mitochondrial GSH, and lipid peroxidation were evaluated. Our results demonstrated that MWCNTs with different characteristics, in size and purity, significantly (P < 0.05) decreased SDH activity, GSH, and ATP level, and increased mitochondrial ROS production, lipid peroxidation, mitochondrial swelling, MMP collapse, and cytochrome c release in the brain mitochondria. In conclusion, we suggested that MWCNTs with different characteristics, in size and purity, induce damage in varying degrees on the mitochondrial respiratory chain and increase mitochondrial ROS formation in different parts of rat brain (hippocampus, frontal cortex, and cerebellum).

Fatty Acid Oxidation and Mitochondrial Morphology Changes as Key Modulators of the Affinity for ADP in Rat Heart Mitochondria

Fatty acids are the main respiratory substrates important for cardiac function, and their oxidation is altered during various chronic disorders. We investigated the mechanism of fatty acid-oxidation-induced changes and their relations with mitochondrial morphology and ADP/ATP carrier conformation on the kinetics of the regulation of mitochondrial respiration in rat skinned cardiac fibers. Saturated and unsaturated, activated and not activated, long and medium chain, fatty acids similarly decreased the apparent KmADP. Addition of 5% dextran T-70 to mimic the oncotic pressure of the cellular cytoplasm markedly increased the low apparent KmADP value of mitochondria in cardiac fibers respiring on palmitoyl-l-carnitine or octanoyl-l-carnitine, but did not affect the high apparent KmADP of mitochondria respiring on pyruvate and malate. Electron microscopy revealed that palmitoyl-l-carnitine oxidation-induced changes in the mitochondrial ultrastructure (preventable by dextran) are similar to those induced by carboxyatractyloside. Our data suggest that a fatty acid oxidation-induced conformational change of the adenosine diphosphate (ADP)/adenosine triphosphate (ATP) carrier (M-state to C-state, condensed to orthodox mitochondria) may affect the oxidative phosphorylation affinity for ADP.

PDIA1/P4HB is required for efficient proinsulin maturation and ß cell health in response to diet induced obesity

Regulated proinsulin biosynthesis, disulfide bond formation and ER redox homeostasis are essential to prevent Type two diabetes. In ß cells, protein disulfide isomerase A1 (PDIA1/P4HB), the most abundant ER oxidoreductase of over 17 members, can interact with proinsulin to influence disulfide maturation. Here we find Pdia1 is required for optimal insulin production under metabolic stress in vivo. ß cell-specific Pdia1 deletion in young high-fat diet fed mice or aged mice exacerbated glucose intolerance with inadequate insulinemia and increased the proinsulin/insulin ratio in both serum and islets compared to wildtype mice. Ultrastructural abnormalities in Pdia1-null ß cells include diminished insulin granule content, ER vesiculation and distention, mitochondrial swelling and nuclear condensation. Furthermore, Pdia1 deletion increased accumulation of disulfide-linked high molecular weight proinsulin complexes and islet vulnerability to oxidative stress. These findings demonstrate that PDIA1 contributes to oxidative maturation of proinsulin in the ER to support insulin production and ß cell health.

Lessons from the Discovery of Mitochondrial Fragmentation (Fission): A Review and Update

Thirty-five years ago, we described fragmentation of the mitochondrial population in a living cell into small vesicles (mitochondrial fission). Subsequently, this phenomenon has become an object of general interest due to its involvement in the process of oxidative stress-related cell death and having high relevance to the incidence of a pathological phenotype. Tentatively, the key component of mitochondrial fission process is segregation and further asymmetric separation of a mitochondrial body yielding healthy (normally functioning) and impaired (incapable to function in a normal way) organelles with subsequent decomposition and removal of impaired elements through autophagy (mitophagy). We speculate that mitochondria contain cytoskeletal elements, which maintain the mitochondrial shape, and also are involved in the process of intramitochondrial segregation of waste products. We suggest that perturbation of the mitochondrial fission/fusion machinery and slowdown of the removal process of nonfunctional mitochondrial structures led to the increase of the proportion of impaired mitochondrial elements. When the concentration of malfunctioning mitochondria reaches a certain threshold, this can lead to various pathologies, including aging. Overall, we suggest a process of mitochondrial fission to be an essential component of a complex system controlling a healthy cell phenotype. The role of reactive oxygen species in mitochondrial fission is discussed.

Targeting the mitochondrial VDAC in hepatocellular carcinoma using a polyclonal antibody-conjugated to a nitrosyl ruthenium complex

The rational design of anti-cancer agents includes a new approach based on ruthenium complexes that can act as nitric oxide (NO) donor agents against specific cellular targets. One of the most studied classes of those compounds is based on bis(bipyridine) ruthenium fragment and its derivative species. In this work, we present the chemical and cytotoxicity properties against the liver hepatocellular carcinoma cell line HepG2 of cis-[RuII(NO+)Cl(dcbpy)2]2- conjugated to a polyclonal antibody IgG (anti-VDAC) recognizing a cell surface marker. UV-visible bands of the ruthenium complex were assigned with the aid of density functional theory, which also allowed estimation of the structures that explain the biological effects of the ruthenium complex-IgG conjugate. The interaction of cis-[RuII(NO+)Cl(dcbpy)2]3- with mitochondria was evaluated due to the potential of these organelles as anti-cancer targets, and considering they interact with the anti-VDAC antibody. The cytotoxicity of cis-[RuII(NO+)Cl(dcbpy)2]3--anti-VDAC antibody was up to 80% greater in comparison to the free cis-[RuII(NO+)Cl(dcbpy)2]3- complex. We suggest that this effect is due to site-specific interaction of the complex followed by NO release.

Upregulation of Cabin1 During Injury to Renal Tubular Epithelial Cells in Rats

INTRODUCTION

Calcineurin-binding protein 1 (Cabin1) interacts with calcineurin and p53, but its function in renal tubular epithelial cell (RTEC) is unclear. We established 5/6 nephrectomized rats and angiotensin II-induced injury to the RTECs in vitro, to observe the expression of Cabin1 during RTEC injury.

MATERIALS AND METHODS

Sprague-Dawley rats were sacrificed at 4 and 8 weeks after 5/6 nephrectomy. Renal pathology and mitochondrial damage were detected by light and electrical microscope. The distribution of E-cadherin and α-smad were detected by indirect immunofluorescence staining. Cabin1 protein expression was detected by Western blot.

RESULTS

Obvious tubulointerstitial fibrosis was found in the nephrectomized rats at 8 weeks after 5/6 nephrectomy, accompanied by the increasing levels of creatinine, as well as the disruption of E-cadherin and overexpression of α-smad in RTECs. Moreover, the mitochondria became swollen and mitochondrial cristae were disrupted and poorly defined in the RTECs. Compared to the sham-operated rats, Cabin1 protein expression was significantly increased at 8 weeks after 5/6 nephrectomy, while angiotensin II-induced Cabin1 protein expression significantly increased 48 hours after stimulation in normal rat kidney epithelial cells.

CONCLUSIONS

Injury to the RTEC and Cabin1 protein overexpression occurred in a time-dependent manner both in vitro and in vivo. Cabin1 may become a potential molecular target in RTEC injury.

Chronic and low exposure to a pharmaceutical cocktail induces mitochondrial dysfunction in liver and hyperglycemia: Differential responses between lean and obese mice

Pharmaceuticals are found in the environment but the impact of this contamination on human and animal health is poorly known. The liver could be particularly targeted since a significant number of these drugs are hepatotoxic, in particular via oxidative stress and mitochondrial dysfunction. Notably, the latter events can also be observed in liver diseases linked to obesity, so that the obese liver might be more sensitive to drug toxicity. In this study, we determined the effects of a chronic exposure to low doses of pharmaceuticals in wild-type and obese mice, with a particular focus on mitochondrial function. To this end, wild-type and ob/ob mice were exposed for 4 months to a cocktail of 11 pharmaceuticals provided in drinking water containing 0.01, 0.1, or 1 mg/L of each drug. At the end of the treatment, liver mitochondria were isolated and different parameters were measured. Chronic exposure to the pharmaceuticals reduced mitochondrial respiration driven by succinate and palmitoyl-l-carnitine in wild-type mice and increased antimycin-induced ROS production in ob/ob mice. Hyperglycemia and hepatic histological abnormalities were also observed in treated ob/ob mice. Investigations were also carried out in isolated liver mitochondria incubated with the mixture, or with each individual drug. The mitochondrial effects of the mixture were different from those observed in treated mice and could not be predicted from the results obtained with each drug. Because some of the 11 drugs included in our cocktail can be found in water at relatively high concentrations, our data could be relevant in environmental toxicology. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1375-1389, 2017.

Wnt Signaling Prevents the Aβ Oligomer-Induced Mitochondrial Permeability Transition Pore Opening Preserving Mitochondrial Structure in Hippocampal Neurons

Alzheimer's disease (AD) is a neurodegenerative disorder mainly known for synaptic impairment and neuronal cell loss, affecting memory processes. Beside these damages, mitochondria have been implicated in the pathogenesis of AD through the induction of the mitochondrial permeability transition pore (mPTP). The mPTP is a non-selective pore that is formed under apoptotic conditions, disturbing mitochondrial structure and thus, neuronal viability. In AD, Aβ oligomers (Aβos) favor the opening of the pore, activating mitochondria-dependent neuronal cell death cascades. The Wnt signaling activated through the ligand Wnt3a has been described as a neuroprotective signaling pathway against amyloid-β (Aβ) peptide toxicity in AD. However, the mechanisms by which Wnt signaling prevents Aβos-induced neuronal cell death are unclear. We proposed here to study whether Wnt signaling protects neurons earlier than the late damages in the progression of the disease, through the preservation of the mitochondrial structure by the mPTP inhibition. To study specific events related to mitochondrial permeabilization we performed live-cell imaging from primary rat hippocampal neurons, and electron microscopy to analyze the mitochondrial morphology and structure. We report here that Wnt3a prevents an Aβos-induced cascade of mitochondrial events that leads to neuronal cell death. This cascade involves (a) mPTP opening, (b) mitochondrial swelling, (c) mitochondrial membrane potential loss and (d) cytochrome c release, thus leading to neuronal cell death. Furthermore, our results suggest that the activation of the Wnt signaling prevents mPTP opening by two possible mechanisms, which involve the inhibition of mitochondrial GSK-3β and/or the modulation of mitochondrial hexokinase II levels and activity. This study suggests a possible new approach for the treatment of AD from a mitochondrial perspective, and will also open new lines of study in the field of Wnt signaling in neuroprotection.

Testosterone deprivation accelerates cardiac dysfunction in obese male rats

Low testosterone level is associated with increased risks of cardiovascular diseases. As obese-insulin-resistant condition could impair cardiac function and that the incidence of obesity is increased in aging men, a condition of testosterone deprivation could aggravate the cardiac dysfunction in obese-insulin-resistant subjects. However, the mechanism underlying this adverse effect is unclear. This study investigated the effects of obesity on metabolic parameters, heart rate variability (HRV), left ventricular (LV) function, and cardiac mitochondrial function in testosterone-deprived rats. Orchiectomized or sham-operated male Wistar rats (n=36per group) were randomly divided into groups and were given either a normal diet (ND, 19.77% of energy fat) or a high-fat diet (HFD, 57.60% of energy fat) for 12weeks. Metabolic parameters, HRV, LV function, and cardiac mitochondrial function were determined at 4, 8, and 12weeks after starting each feeding program. We found that insulin resistance was observed after 8weeks of the consumption of a HFD in both sham (HFS) and orchiectomized (HFO) rats. Neither the ND sham (NDS) group nor ND orchiectomized (NDO) rats developed insulin resistance. The development of depressed HRV, LV contractile dysfunction, and increased cardiac mitochondrial reactive oxygen species production was observed earlier in orchiectomized (NDO and HFO) rats at week 4, whereas HFS rats exhibited these impairments later at week 8. These findings suggest that testosterone deprivation accelerates the impairment of cardiac autonomic regulation and LV function via increased oxidative stress and impaired cardiac mitochondrial function in obese-orchiectomized male rats.

Development of a Novel Thyroid Function Fluctuated Animal Model for Thyroid-Associated Ophthalmopathy

Background

The establishment of a suitable and stable animal model is critical for research on thyroid-associated ophthalmopathy (TAO). In clinical practice, we found that patients treated with I-131 often exhibit TAO; therefore, we aimed to establish a novel thyroid function fluctuated animal model of TAO by simulating the clinical treatment process.

Methods

We treated SD rats with I-131 to damage the thyroid and then used sodium levothyroxine (L-T4) to supplement the thyroid hormone (TH) levels every seven days, leading to a fluctuating level of thyroid hormones that simulated the status of clinical TAO patients. Rats administered normal saline were considered as a control. The weight, intraocular pressure, and serum T3, T4, TSH and TRAb levels of the rats were measured, and the pathological changes were analyzed by H&E staining and transmission electron microscopy (TEM).

Results

The experimental rats (TAO group) exhibited significantly reduced weight and elevated intraocular pressure compared with the control rats. Meanwhile, the serum levels of T3 and T4 were up-regulated in the TAO group, but the TSH level decreased during the 10-week study. Moreover, increased numbers of blood vessels and inflammatory cell infiltrations were observed in the orbital tissues of the TAO rats, while no abnormal changes occurred in the control rats. The orbital myofibrils in the TAO rats appeared fractured and dissolved, with twisted structures. Mitochondrial swelling and vacuoles within the endoplasmic reticulum, swelling nerve fibers, shedding nerve myelin, and macrophages were found in the TAO group.

Conclusion

Rats treated with I-131 and sodium levothyroxine exhibited characteristics similar to those of TAO patients in the clinic, providing an effective and simple method for the establishment of a stable animal model for research on the pathogenesis and treatment of TAO.

From mitochondrial large amplitude swelling to the permeability transition - a short historic overview

An outline of studies on the mitochondrial large conductance permeability pore is presented starting from the early observations in the 1950s on the large amplitude mitochondrial swelling, through the concept of the permeability transition and various theories on the structure of the related permeability transition pore, up to its present identification as a part of mitochondrial (F₁F_O) ATPase/ATP synthase.

Time-Dependent Progression of Demyelination and Axonal Pathology in MP4-Induced Experimental Autoimmune Encephalomyelitis

Background

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) characterized by inflammation, demyelination and axonal pathology. Myelin basic protein/proteolipid protein (MBP-PLP) fusion protein MP4 is capable of inducing chronic experimental autoimmune encephalomyelitis (EAE) in susceptible mouse strains mirroring diverse histopathological and immunological hallmarks of MS. Limited availability of human tissue underscores the importance of animal models to study the pathology of MS.

Methods

Twenty-two female C57BL/6 (B6) mice were immunized with MP4 and the clinical development of experimental autoimmune encephalomyelitis (EAE) was observed. Methylene blue-stained semi-thin and ultra-thin sections of the lumbar spinal cord were assessed at the peak of acute EAE, three months (chronic EAE) and six months after onset of EAE (long-term EAE). The extent of lesional area and inflammation were analyzed in semi-thin sections on a light microscopic level. The magnitude of demyelination and axonal damage were determined using electron microscopy. Emphasis was put on the ventrolateral tract (VLT) of the spinal cord.

Results

B6 mice demonstrated increasing demyelination and severe axonal pathology in the course of MP4-induced EAE. In addition, mitochondrial swelling and a decrease in the nearest neighbor neurofilament distance (NNND) as early signs of axonal damage were evident with the onset of EAE. In semi-thin sections we observed the maximum of lesional area in the chronic state of EAE while inflammation was found to a similar extent in acute and chronic EAE. In contrast to the well-established myelin oligodendrocyte glycoprotein (MOG) model, disease stages of MP4-induced EAE could not be distinguished by assessing the extent of parenchymal edema or the grade of inflammation.

Conclusions

Our results complement our previous ultrastructural studies of B6 EAE models and suggest that B6 mice immunized with different antigens constitute useful instruments to study the diverse histopathological aspects of MS.

Ellagic acid, a polyphenolic compound, selectively induces ROS-mediated apoptosis in cancerous B-lymphocytes of CLL patients by directly targeting mitochondria

To investigate the effects ofellagic acid (EA) on the cytotoxicity, B-lymphocytes isolated from CLL patients and healthy individuals. Flow cytometric assay was used to measure the percentage of apoptosis versus necrosis, intracellular active oxygen radicals (ROS), mitochondrial membrane potential (MMP) and the caspase-3 activity and then mitochondria were isolated from both groups B-lymphocytes and parameters of mitochondrial toxicity was investigated. Based on our results EA decreased the percentage of viable cells and induced apoptosis. EA increased ROS formation, mitochondria swelling, MMP decrease and cytochrome c release in mitochondria isolated from CLL BUT NOT healthy B-lymphocytes while pre-treatment with cyclosporine A and Butylated hydroxyl toluene (BHT) prevented these effects. Our results suggest that EA can act as an anti cancer candidate by directly and selectively targeting mitochondria could induce apoptosis through mitochondria pathway with increasing ROS production which finally ends in cytochrome c release, caspase 3 activation and apoptosis in cancerous B-lymphocytes isolated from CLL patients.