Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. Myocardial dysfunction, often termed sepsis-induced cardiomyopathy, is a frequent ...complication and is associated with worse outcomes. Numerous mechanisms contribute to sepsis-induced cardiomyopathy and a growing body of evidence suggests that bioenergetic and metabolic derangements play a central role in its development; however, there are significant discrepancies in the literature, perhaps reflecting variability in the experimental models employed or in the host response to sepsis. The condition is characterised by lack of significant cell death, normal tissue oxygen levels and, in survivors, reversibility of organ dysfunction. The functional changes observed in cardiac tissue may represent an adaptive response to prolonged stress that limits cell death, improving the potential for recovery. In this review, we describe our current understanding of the pathophysiology underlying myocardial dysfunction in sepsis, with a focus on disrupted mitochondrial processes.
•Sepsis-induced cardiomyopathy (SIC) is common in septic patients and affects outcome.•Mitochondrial dysfunction is likely to play a central role in SIC pathogenesis.•Mitochondrial dysfunction could be a protective mechanism similar to myocardial hibernation.
There is increasing evidence for the involvement of mitochondrial dysfunction and oxidative stress in the pathogenesis of many of the major neurodegenerative and neuroinflammatory diseases, ...suggesting that mitochondrial and antioxidant pathways may represent potential novel therapeutic targets. Recent years have seen a rapidly growing interest in the use of therapeutic strategies that can limit the defects in, or even to restore, mitochondrial function while reducing free radical generation. The peroxisome proliferation-activated receptor gamma (PPARγ), a ligand-activated transcription factor, has a wide spectrum of biological functions, regulating mitochondrial function, mitochondrial turnover, energy metabolism, antioxidant defence and redox balance, immune responses and fatty acid oxidation. In this review, we explore the evidence for potential beneficial effects of PPARγ agonists in a number of neurological disorders, including Parkinson’s disease, Alzheimer’s disease, Amyotrophic lateral sclerosis and Huntington’s disease, ischaemia, autoimmune encephalomyelitis and neuropathic pain. We discuss the mechanisms underlying those beneficial effects in particular in relation to mitochondrial function, antioxidant defence, cell death and inflammation, and suggest that the PPARγ agonists show significant promise as therapeutic agents in otherwise intractable neurological disease.
•PPARγ promotes oxidative phosphorylation, antioxidant defence and mitochondrial biogenesis.•A number of pharmacological agents activate PPARγ.•Mitochondrial dysfunction and inflammation underpin many neurodegenerative diseases.•PPARγ agonists may prove beneficial for the management of neurodegenerative disease.
Understanding the mechanisms of neuronal dysfunction and death represents a major frontier in contemporary medicine, involving the acute cell death in stroke, and the attrition of the major ...neurodegenerative diseases, including Parkinson's, Alzheimer's, Huntington's and Motoneuron diseases. A growing body of evidence implicates mitochondrial dysfunction as a key step in the pathogenesis of all these diseases, with the promise that mitochondrial processes represent valuable potential therapeutic targets. Each disease is characterised by the loss of a specific vulnerable population of cells—dopaminergic neurons in Parkinson's disease, spinal motoneurons in Motoneuron disease, for example. We discuss the possible roles of cell type-specific calcium signalling mechanisms in defining the pathological phenotype of each of these major diseases and review central mechanisms of calcium-dependent mitochondrial-mediated cell death.
The redox states of the NAD and NADP pyridine nucleotide pools play critical roles in defining the activity of energy producing pathways, in driving oxidative stress and in maintaining antioxidant ...defences. Broadly speaking, NAD is primarily engaged in regulating energy-producing catabolic processes, whilst NADP may be involved in both antioxidant defence and free radical generation. Defects in the balance of these pathways are associated with numerous diseases, from diabetes and neurodegenerative disease to heart disease and cancer. As such, a method to assess the abundance and redox state of these separate pools in living tissues would provide invaluable insight into the underlying pathophysiology. Experimentally, the intrinsic fluorescence of the reduced forms of both redox cofactors, NADH and NADPH, has been used for this purpose since the mid-twentieth century. In this review, we outline the modern implementation of these techniques for studying mitochondrial redox state in complex tissue preparations. As the fluorescence spectra of NADH and NADPH are indistinguishable, interpreting the signals resulting from their combined fluorescence, often labelled NAD(P)H, can be complex. We therefore discuss recent studies using fluorescence lifetime imaging microscopy (FLIM) which offer the potential to discriminate between the two separate pools. This technique provides increased metabolic information from cellular autofluorescence in biomedical investigations, offering biochemical insights into the changes in time-resolved NAD(P)H fluorescence signals observed in diseased tissues.
•NAD plays a central role in energy-producing pathways.•NADP is crucial for maintaining the antioxidant defence.•The reduced forms, NADH and NADPH, are naturally fluorescent inside living tissues.•Cellular autofluorescence can be used to investigate NAD(P)H redox state.•NAD(P)H FLIM allows the contributions from NADH and NADPH to be separated.
Dimethyl sulfoxide (DMSO) is an important aprotic solvent that can solubilize a wide variety of otherwise poorly soluble polar and nonpolar molecules. This, coupled with its apparent low toxicity at ...concentrations <10%, has led to its ubiquitous use and widespread application. Here, we demonstrate that DMSO induces retinal apoptosis in vivo at low concentrations (5 μl intravitreally dosed DMSO in rat from a stock concentration of 1, 2, 4, and 8% v/v). Toxicity was confirmed in vitro in a retinal neuronal cell line, at DMSO concentrations >1% (v/v), using annexin V, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT), and AlamarBlue cell viability assays. DMSO concentrations > 10% (v/v) have recently been reported to cause cellular toxicity through plasma membrane pore formation. Here, we show the mechanism by which low concentrations (2–4% DMSO) induce caspase‐3 independent neuronal death that involves apoptosis‐inducing factor (AIF) translocation from mitochondria to the nucleus and poly‐(ADP‐ribose)‐polymerase (PARP) activation. These results highlight safety concerns of using low concentrations of DMSO as a solvent for in vivo administration and in biological assays. We recommend that methods other than DMSO are employed for solubilizing drugs but, where no alternative exists, researchers compute absolute DMSO final concentrations and include an untreated control group in addition to DMSO vehicle control to check for solvent toxicity.—Galvao, J., Davis, B., Tilley, M., Normando, E., Duchen, M. R., Cordeiro, M. F. Unexpected low‐dose toxicity of the universal solvent DMSO. FASEB J. 28, 1317–1330 (2014). www.fasebj.org
Mitochondrial permeability transition, as the consequence of opening of a mitochondrial permeability transition pore (mPTP), is a cellular catastrophe. Initiating bioenergetic collapse and cell ...death, it has been implicated in the pathophysiology of major human diseases, including neuromuscular diseases of childhood, ischaemia-reperfusion injury, and age-related neurodegenerative disease. Opening of the mPTP represents a major therapeutic target, as it can be mitigated by a number of compounds. However, clinical studies have so far been disappointing. We therefore address the prospects and challenges faced in translating in vitro findings to clinical benefit. We review the role of mPTP opening in disease, discuss recent findings defining the putative structure of the mPTP, and explore strategies to identify novel, clinically useful mPTP inhibitors, highlighting key considerations in the drug discovery process.
mPTP opening continues to be implicated in multiple disease states, making therapeutic targeting desirable.
mPTP complex bio-architecture remains unresolved, creating difficulties in target-based screening for drug discovery.
CypD-independent inhibitors have provided novel tools and reference compounds for mPTP modulation and may aid in understanding of mPTP complex structure.
Significant challenges in developing mPTP modulators need to be overcome to achieve efficacy and specificity.
Understanding of target validation and a well-defined screening flow and critical path for mPTP inhibitor hit identification is vital for successful drug discovery.
Recent advances and next generation modalities to achieve greater target specificity and to ‘drug the undruggable’ may be necessary to achieve potent and selective target modulation.
While a pathway for Ca 2+ accumulation into mitochondria has long been established, its functional significance is only now becoming clear in relation
to cell physiology and pathophysiology. The ...observation that mitochondria take up Ca 2+ during physiological Ca 2+ signalling in a variety of cell types leads to four questions: (i) âWhat is the impact of mitochondrial Ca 2+ uptake on mitochondrial function?â (ii) âWhat is the impact of mitochondrial Ca 2+ uptake on Ca 2+ signalling?â (iii) âWhat are the consequences of impaired mitochondrial Ca 2+ uptake for cell function?â and finally (iv) âWhat are the consequences of pathological Ca 2+ c signalling for mitochondrial function?â These will be addressed in turn. Thus: (i) accumulation of Ca 2+ into mitochondria regulates mitochondrial metabolism and causes a transient depolarisation of mitochondrial membrane potential.
(ii) Mitochondria may act as a spatial Ca 2+ buffer in many cells, regulating the local Ca 2+ concentration in cellular microdomains. This process regulates processes dependent on local cytoplasmic Ca 2+ concentration (Ca 2+ c ), particularly the flux of Ca 2+ through IP 3 -gated channels of the endoplasmic reticulum (ER) and the channels mediating capacitative Ca 2+ influx through the plasma membrane. Consequently, mitochondrial Ca 2+ uptake plays a substantial role in shaping Ca 2+ c signals in many cell types. (iii) Impaired mitochondrial Ca 2+ uptake alters the spatiotemporal characteristics of cellular Ca 2+ c signalling and downregulates mitochondrial metabolism. (iv) Under pathological conditions of cellular Ca 2+ c overload, particularly in association with oxidative stress, mitochondrial Ca 2+ uptake may trigger pathological states that lead to cell death. In the model of glutamate excitotoxicity, microdomains of
Ca 2+ c are apparently central, as the pathway to cell death seems to require the local activation of neuronal nitric oxide synthase
(nNOS), itself held by scaffolding proteins in close association with the NMDA receptor. Mitochondrial Ca 2+ uptake in combination with NO production triggers the collapse of mitochondrial membrane potential, culminating in delayed
cell death.
Lysosomal storage disorders (LSDs) are rare inherited debilitating and often fatal disorders. Caused by mutations affecting lysosomal proteins, LSDs are characterized by the accumulation of ...undegraded material in lysosomes and by lysosomal dysfunction. Although LSDs are multisystemic diseases, the majority display neurologic symptoms and neurodegeneration. Only recently has a role emerged for mitochondrial dysfunction in the pathophysiology of LSDs, suggesting an impact of lysosomal dysfunction on mitochondria. Moreover, mitochondrial damage may also cause lysosomal dysfunction, further supporting the activity of common signaling pathways and crosstalk between the two organelles. In this review we explore the mechanisms linking lysosomal and mitochondrial dysfunction to assess whether specific mitochondrial pathways represent a new therapeutic frontier in the management of LSDs.
Diabetes is a global health problem caused primarily by the inability of pancreatic β-cells to secrete adequate levels of insulin. The molecular mechanisms underlying the progressive failure of ...β-cells to respond to glucose in type-2 diabetes remain unresolved. Using a combination of transcriptomics and proteomics, we find significant dysregulation of major metabolic pathways in islets of diabetic βV59M mice, a non-obese, eulipidaemic diabetes model. Multiple genes/proteins involved in glycolysis/gluconeogenesis are upregulated, whereas those involved in oxidative phosphorylation are downregulated. In isolated islets, glucose-induced increases in NADH and ATP are impaired and both oxidative and glycolytic glucose metabolism are reduced. INS-1 β-cells cultured chronically at high glucose show similar changes in protein expression and reduced glucose-stimulated oxygen consumption: targeted metabolomics reveals impaired metabolism. These data indicate hyperglycaemia induces metabolic changes in β-cells that markedly reduce mitochondrial metabolism and ATP synthesis. We propose this underlies the progressive failure of β-cells in diabetes.
PDF
