Halothane, isoflurane and sevoflurane inhibit NADH:ubiquinone oxidoreductase (complex I) of cardiac mitochondria

Poincaré plot analysis of electrocardiogram uncovers beneficial effects of omaveloxolone in a mouse model of Friedreich's ataxia

BACKGROUND

Friedreich's ataxia (FA) is a rare inherited neuromuscular disorder whereby most patients die of lethal cardiomyopathy and arrhythmias. Mechanisms leading to arrhythmic events in patients with FA are poorly understood.

OBJECTIVE

This study aimed to examine cardiac electrical signal propagation in a mouse model of FA with severe cardiomyopathy and to evaluate effects of omaveloxolone (OMAV), the first Food and Drug Administration-approved therapy.

METHODS

Cardiac-specific MCK-Cre frataxin knockout (FXN-cKO) mice were used to mimic FA cardiomyopathy. In vivo surface electrocardiogram (ECG) recordings, Western blotting, quantitative real-time polymerase chain reaction analysis, and histochemistry were performed.

RESULTS

Characteristics like long QT syndrome, interatrial block, and ST-segment abnormalities in patients with FA were identified in FXN-cKO mice. FXN-cKO mice exhibited sexual dimorphism in electrical signal propagation and cardiac structural integrity. Untreated FA males showed increased ventricular propagation intervals, whereas females exhibited delayed atrial propagation. OMAV showed no significant therapeutic effect on average ECG time intervals but improved chamber-specific waveforms when aggregated frequency distributions were analyzed. The J wave was absent in FXN-cKO male mice but reappeared with OMAV treatment. Poincaré plots revealed disparate idiopathic arrhythmias with multi-clustering events in individual mice with high incidence in FXN-cKO males. OMAV treatment reduced multi-clustering events to a single cluster; however, autonomic nervous system dysfunction still remained.

CONCLUSION

Our study revealed significant electrical propagation disturbances and sexual dimorphism in FXN-cKO mice with severe cardiomyopathy. Poincaré plots identified irregularities in heart rhythm and autonomic nervous system dysfunction. OMAV improved heart function by stabilizing early repolarization and reducing disparate arrhythmias. This work stresses sex-specific ECG interpretations and alternative mathematical approaches for drug testing in FA models.

Unraveling the role and mechanism of mitochondria in postoperative cognitive dysfunction: a narrative review

Postoperative cognitive dysfunction (POCD) is a frequent neurological complication encountered during the perioperative period with unclear mechanisms and no effective treatments. Recent research into the pathogenesis of POCD has primarily focused on neuroinflammation, oxidative stress, changes in neural synaptic plasticity and neurotransmitter imbalances. Given the high-energy metabolism of neurons and their critical dependency on mitochondria, mitochondrial dysfunction directly affects neuronal function. Additionally, as the primary organelles generating reactive oxygen species, mitochondria are closely linked to the pathological processes of neuroinflammation. Surgery and anesthesia can induce mitochondrial dysfunction, increase mitochondrial oxidative stress, and disrupt mitochondrial quality-control mechanisms via various pathways, hence serving as key initiators of the POCD pathological process. We conducted a review on the role and potential mechanisms of mitochondria in postoperative cognitive dysfunction by consulting relevant literature from the PubMed and EMBASE databases spanning the past 25 years. Our findings indicate that surgery and anesthesia can inhibit mitochondrial respiration, thereby reducing ATP production, decreasing mitochondrial membrane potential, promoting mitochondrial fission, inducing mitochondrial calcium buffering abnormalities and iron accumulation, inhibiting mitophagy, and increasing mitochondrial oxidative stress. Mitochondrial dysfunction and damage can ultimately lead to impaired neuronal function, abnormal synaptic transmission, impaired synthesis and release of neurotransmitters, and even neuronal death, resulting in cognitive dysfunction. Targeted mitochondrial therapies have shown positive outcomes, holding promise as a novel treatment for POCD.

Anesthesia management for percutaneous mitral valve repair in a patient with mitochondrial cardiomyopathy and low cardiac function: a case report

BACKGROUND

Mitochondrial cardiomyopathy occurs when impaired mitochondrial energy production leads to myocardial dysfunction. Anesthetic management in such cases is challenging due to risks of circulatory depression associated with anesthesia and mitochondrial dysfunction induced by anesthetics. Although there are reports of anesthetic management for patients with mitochondrial diseases, there are few reports specifically addressing cardiac anesthesia for patients with mitochondrial cardiomyopathy. We present a case where percutaneous mitral valve repair with MitraClip™ was successfully performed under remimazolam anesthesia in a patient with mitochondrial cardiomyopathy who developed functional mitral valve regurgitation due to low cardiac function and cardiomegaly.

CASE PRESENTATION

A 57-year-old woman was diagnosed with chronic cardiac failure, with a 10-year history of dilated cardiomyopathy. She was diagnosed with mitochondrial cardiomyopathy 8 years ago. Over the past 2 years, her cardiac failure worsened, and mitral valve regurgitation gradually developed. Surgical intervention was considered but deemed too risky due to her low cardiac function, with an ejection fraction of 26%. Therefore, percutaneous MitraClip™ implantation was selected. After securing radial artery and central venous catheterization under sedation with dexmedetomidine, anesthesia was induced with a low dose of remimazolam 4 mg/kg/h. Anesthesia was maintained with remimazolam 0.35-1.0 mg/kg/h and remifentanil 0.1 μg/kg/min. Noradrenaline and dobutamine were administered intraoperatively, and the procedure was completed successfully without circulatory collapse. The patient recovered smoothly from anesthesia and experienced no complications. She was discharged on the eighth day after surgery.

CONCLUSION

Anesthesia management with remimazolam appears to be a safe and effective for MitraClip™ implantation in patients with mitochondrial cardiomyopathy.

Cochlear Implantation for Isoleucyl-tRNA Synthetase Mutation-Associated Mitochondrial Disease: A Case Report

Biallelic missense mutations in the nuclear-encoded, cytosolic isoleucyl-tRNA synthetase (IARS) gene are associated with a rare and complex multisystemic phenotype, including growth retardation, intellectual disability, muscular hypotonia, diabetes mellitus, and deafness. These mutations impact the cytosolic isoform of IARS, which plays a crucial role in protein synthesis. The pathogenesis involves mitochondrial dysfunction, despite IARS being primarily a cytosolic enzyme, potentially linking it to the observed clinical manifestations. The efficacy of cochlear implantation for deafness due to IARS mutations and the safety of general anesthesia in such patients remain unclear. This report describes a rare case of progressive sensorineural hearing loss caused by IARS mutation-associated mitochondrial disease, which was successfully treated with cochlear implantation. Additionally, we discuss the safety of general anesthesia in this patient. A Japanese woman with IARS mutation-associated mitochondrial disease was diagnosed with severe bilateral sensorineural hearing loss at five years of age and immediately received hearing aids. Her hearing progressively deteriorated to profound impairment, necessitating cochlear implantation at 26 years of age, which resulted in satisfactory hearing. Furthermore, no perioperative general anesthesia-related adverse events were reported. Our case demonstrates that cochlear implantation can effectively restore hearing. This suggests that sensorineural hearing loss caused by IARS deficiency is primarily due to cochlear dysfunction. This case demonstrated that hearing loss is a crucial feature of IARS mutation-associated mitochondrial disease, which can be mitigated by cochlear implantation. While general anesthesia can be safely administered, careful consideration of anesthetic choices, such as avoiding depolarizing muscle relaxants and prolonged use of propofol, is essential to prevent complications. In this case, general anesthesia was well tolerated without perioperative events, providing valuable insight into the potential safety of such procedures in similar patients. Nevertheless, further studies are needed to confirm these findings across a broader population.

Anesthetic Management for a Child With a Newly Identified Mitochondrial Disease SLC25A46 Mutation: A Case Report

SLC25A46 mutation is a newly recognized mitochondrial mutation causing neurological and muscular abnormalities. We describe a first-ever report of the anesthetic management of a seven-year-old boy with an SLC25A46 mutation during a major orthopedic procedure. The patient was nonverbal and presented with cerebral visual impairment, torticollis, and lower extremity contractures. Because of his new diagnosis of mitochondrial disease and history of delayed awakening after anesthesia, we performed general anesthesia with sevoflurane, a low-dose ketamine infusion, and small doses of fentanyl while avoiding propofol and maintaining normoglycemia and normothermia. No postoperative complications were noted during the recovery period.

Beneficial Effects of Halogenated Anesthetics in Cardiomyocytes: The Role of Mitochondria

In the last few years, the use of anesthetic drugs has been related to effects other than those initially related to their fundamental effect, hypnosis. Halogenated anesthetics, mainly sevoflurane, have been used as a therapeutic tool in patients undergoing cardiac surgery, thanks to the beneficial effect of the cardiac protection they generate. This effect has been described in several research studies. The mechanism by which they produce this effect has been associated with the effects generated by anesthetic preconditioning and postconditioning. The mechanisms by which these effects are induced are directly related to the modulation of oxidative stress and the cellular damage generated by the ischemia/reperfusion procedure through the overexpression of different enzymes, most of them included in the Reperfusion Injury Salvage Kinase (RISK) and the Survivor Activating Factor Enhancement (SAFE) pathways. Mitochondria is the final target of the different routes of pre- and post-anesthetic conditioning, and it is preserved from the damage generated in moments of lack of oxygen and after the recovery of the normal oxygen concentration. The final consequence of this effect has been related to better cardiac function in this type of patient, with less myocardial damage, less need for inotropic drugs to achieve normal myocardial function, and a shorter hospital stay in intensive care units. The mechanisms through which mitochondrial homeostasis is maintained and its relationship with the clinical effect are the basis of our review. From a translational perspective, we provide information regarding mitochondrial physiology and physiopathology in cardiac failure and the role of halogenated anesthetics in modulating oxidative stress and inducing myocardial conditioning.

The effects of general anesthetics on mitochondrial structure and function in the developing brain

The use of general anesthetics in modern clinical practice is commonly regarded as safe for healthy individuals, but exposures at the extreme ends of the age spectrum have been linked to chronic cognitive impairments and persistent functional and structural alterations to the nervous system. The accumulation of evidence at both the epidemiological and experimental level prompted the addition of a warning label to inhaled anesthetics by the Food and Drug Administration cautioning their use in children under 3  years of age. Though the mechanism by which anesthetics may induce these detrimental changes remains to be fully elucidated, increasing evidence implicates mitochondria as a potential primary target of anesthetic damage, meditating many of the associated neurotoxic effects. Along with their commonly cited role in energy production via oxidative phosphorylation, mitochondria also play a central role in other critical cellular processes including calcium buffering, cell death pathways, and metabolite synthesis. In addition to meeting their immense energy demands, neurons are particularly dependent on the proper function and spatial organization of mitochondria to mediate specialized functions including neurotransmitter trafficking and release. Mitochondrial dependence is further highlighted in the developing brain, requiring spatiotemporally complex and metabolically expensive processes such as neurogenesis, synaptogenesis, and synaptic pruning, making the consequence of functional alterations potentially impactful. To this end, we explore and summarize the current mechanistic understanding of the effects of anesthetic exposure on mitochondria in the developing nervous system. We will specifically focus on the impact of anesthetic agents on mitochondrial dynamics, apoptosis, bioenergetics, stress pathways, and redox homeostasis. In addition, we will highlight critical knowledge gaps, pertinent challenges, and potential therapeutic targets warranting future exploration to guide mechanistic and outcomes research.

A primordial target: Mitochondria mediate both primary and collateral anesthetic effects of volatile anesthetics

One of the unsolved mysteries of medicine is how do volatile anesthetics (VAs) cause a patient to reversibly lose consciousness. In addition, identifying mechanisms for the collateral effects of VAs, including anesthetic-induced neurotoxicity (AiN) and anesthetic preconditioning (AP), has proven challenging. Multiple classes of molecules (lipids, proteins, and water) have been considered as potential VA targets, but recently proteins have received the most attention. Studies targeting neuronal receptors or ion channels had limited success in identifying the critical targets of VAs mediating either the phenotype of "anesthesia" or their collateral effects. Recent studies in both nematodes and fruit flies may provide a paradigm shift by suggesting that mitochondria may harbor the upstream molecular switch activating both primary and collateral effects. The disruption of a specific step of electron transfer within the mitochondrion causes hypersensitivity to VAs, from nematodes to Drosophila and to humans, while also modulating the sensitivity to collateral effects. The downstream effects from mitochondrial inhibition are potentially legion, but inhibition of presynaptic neurotransmitter cycling appears to be specifically sensitive to the mitochondrial effects. These findings are perhaps of even broader interest since two recent reports indicate that mitochondrial damage may well underlie neurotoxic and neuroprotective effects of VAs in the central nervous system (CNS). It is, therefore, important to understand how anesthetics interact with mitochondria to affect CNS function, not just for the desired facets of general anesthesia but also for significant collateral effects, both harmful and beneficial. A tantalizing possibility exists that both the primary (anesthesia) and secondary (AiN, AP) mechanisms may at least partially overlap in the mitochondrial electron transport chain (ETC).

Effects of sevoflurane and its metabolite hexafluoroisopropanol on hypoxia/reoxygenation-induced injury and mitochondrial bioenergetics in murine cardiomyocytes

Background

The volatile anaesthetic sevoflurane protects cardiac tissue from reoxygenation/reperfusion. Mitochondria play an essential role in conditioning. We aimed to investigate how sevoflurane and its primary metabolite hexafluoroisopropanol (HFIP) affect necrosis, apoptosis, and reactive oxygen species formation in cardiomyocytes upon hypoxia/reoxygenation injury. Moreover, we aimed to describe the similarities in the mode of action in a mitochondrial bioenergetics analysis.

Methods

Murine cardiomyocytes were exposed to hypoxia (0.2% O2 for 6 h), followed by reoxygenation (air with 5% CO2 for 2 h) in the presence or absence sevoflurane 2.2% or HFIP 4 mM. Lactate dehydrogenase (LDH) release (necrosis), caspase activation (apoptosis), reactive oxygen species, mitochondrial membrane potential, and mitochondrial function (Seahorse XF analyser) were measured.

Results

Hypoxia/reoxygenation increased cell death by 44% (+31 to +55%, P<0.001). Reoxygenation in the presence of sevoflurane 2.2% or HFIP 4 mM increased LDH release only by +18% (+6 to +30%) and 20% (+7 to +32%), respectively. Apoptosis and reactive oxygen species formation were attenuated by sevoflurane and HFIP. Mitochondrial bioenergetics analysis of the two substances was profoundly different. Sevoflurane did not influence oxygen consumption rate (OCR) or extracellular acidification rate (ECAR), whereas HFIP reduced OCR and increased ECAR, an effect similar to oligomycin, an adenosine triphosphate (ATP) synthase inhibitor. When blocking the metabolism of sevoflurane into HFIP, protective effects of sevoflurane - but not of HFIP - on LDH release and caspase were mitigated.

Conclusion

Together, our data suggest that sevoflurane metabolism into HFIP plays an essential role in cardiomyocyte postconditioning after hypoxia/reoxygenation injury.

Inhibition of mitochondrial respiration by general anesthetic drugs

General anesthetic drugs have been associated with various unwanted effects including an interference with mitochondrial function. We had previously observed increases of lactate formation in the mouse brain during anesthesia with volatile anesthetic agents. In the present work, we used mitochondria that were freshly isolated from mouse brain to test mitochondrial respiration and ATP synthesis in the presence of six common anesthetic drugs. The volatile anesthetics isoflurane, halothane, and (to a lesser extent) sevoflurane caused an inhibition of complex I of the electron transport chain in a dose-dependent manner. Significant effects were seen at concentrations that are reached under clinical conditions (< 0.5 mM). Pentobarbital and propofol also inhibited complex I but at concentrations that were two-fold higher than clinical EC50 values. Only propofol caused an inhibition of complex II. Complex IV respiration was not affected by either agent. Ketamine did not affect mitochondrial respiration. Similarly, all anesthetic agents except ketamine suppressed ATP production at high concentrations. Only halothane increased cytochrome c release indicating damage of the mitochondrial membrane. In summary, volatile general anesthetic agents as well as pentobarbital and propofol dose-dependently inhibit mitochondrial respiration. This action may contribute to depressive actions of the drugs in the brain.

Tandem mass tag-based quantitative proteomic analysis of effects of multiple sevoflurane exposures on the cerebral cortex of neonatal and adult mice

Introduction

Sevoflurane is the most commonly used general anesthetic in pediatric surgery, but it has the potential to be neurotoxic. Previous research found that long-term or multiple sevoflurane exposures could cause cognitive deficits in newborn mice but not adult mice, whereas short-term or single inhalations had little effect on cognitive function at both ages. The mechanisms behind these effects, however, are unclear.

Methods

In the current study, 6- and 60-day-old C57bl mice in the sevoflurane groups were given 3% sevoflurane plus 60% oxygen for three consecutive days, each lasting 2 hours, while those in the control group only got 60% oxygen. The cortex tissues were harvested on the 8th or 62nd day. The tandem mass tags (TMT)pro-based quantitative proteomics combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis, Golgi staining, and western blotting analysis were applied to analyze the influences of multiple sevoflurane anesthesia on the cerebral cortex in mice with various ages. The Morris water maze (MWM) test was performed from postnatal day (P)30 to P36 or P84 to P90 after control or multiple sevoflurane treatment. Sevoflurane anesthesia affected spatial learning and memory and diminished dendritic spines primarily in newborn mice, whereas mature animals exhibited no significant alterations.

Results

A total of 6247 proteins were measured using the combined quantitative proteomics methods of TMTpro-labeled and LC-MS/MS, 443 of which were associated to the age-dependent neurotoxic mechanism of repeated sevoflurane anesthesia. Furthermore, western blotting research revealed that sevoflurane-induced brain damage in newborn mice may be mediated by increasing the levels of protein expression of CHGB, PTEN, MAP2c, or decreasing the level of SOD2 protein expression.

Conclusion

Our findings would help to further the mechanistic study of age-dependent anesthetic neurotoxicity and contribute to seek for effective protection in the developing brain under general anesthesia.

Sevoflurane preconditioning alleviates myocardial ischemia reperfusion injury through mitochondrial NAD+-SIRT3 pathway in rats

OBJECTIVES

Myocardial ischemia reperfusion injury (IRI) occurs occasionally in the process of ischemic heart disease. Sevoflurane preconditioning has an effect on attenuating IRI. Preserving the structural and functional integrity of mitochondria is the key to reduce myocardial IRI. Silent information regulator 3 (SIRT3), a class of nicotinamide adenine dinucleotide (NAD+) dependent deacetylases, is an important signal-regulating molecule in mitochondria. This study aims to explore the role of mitochondrial NAD+-SIRT3 pathway in attenuating myocardial IRI in rats by sevoflurane preconditioning.

METHODS

A total of 60 male Sprague Dawley (SD) rats were randomly divided into 5 groups (n=12): A sham group (Sham group), an ischemia reperfusion group (IR group), a sevoflurane preconditioning group (Sev group, inhaled 2.5% sevoflurane for 30 min), a sevoflurane preconditioning+SIRT3 inhibitor 3-TYP group (Sev+3-TYP group, inhaled 2.5% sevoflurane for 30 min and received 5 mg/kg 3-TYP), and a 3-TYP group (5 mg/kg 3-TYP). Except for the Sham group, the IR model in the other 4 groups was established by ligating the left anterior descending coronary artery. The size of myocardial infarction was determined by double staining. Serum cardiac troponin I (cTnI) level was measured. The contents of NAD+ and ATP, the activities of mitochondrial complexes I, II, and IV, the content of MDA, the activity of SOD, and the changes of mitochondrial permeability were measured. The protein expression levels of SIRT3, SOD2, catalase (CAT), and voltage dependent anion channel 1 (VDAC1) were detected by Western blotting. The ultrastructure of myocardium was observed under transmission electron microscope. MAP and HR were recorded immediately before ischemia (T0), 30 min after ischemia (T1), 30 min after reperfusion (T2), 60 min after reperfusion (T3), and 120 min after reperfusion (T4).

RESULTS

After ischemia reperfusion, the content of NAD+ in cardiac tissues and the expression level of SIRT3 protein were decreased (both P<0.01), and an obvious myocardial injury occurred, including the increase of myocardial infarction size and serum cTnI level (both P<0.01). Correspondingly, the mitochondria also showed obvious damage on energy metabolism, antioxidant function, and structural integrity, which was manifested as: the activities of mitochondrial complexes I, II, and IV, ATP content, protein expression levels of SOD2 and CAT were decreased, while MDA content, VDAC1 protein expression level and mitochondrial permeability were increased (all P<0.01). Compared with the IR group, the content of NAD+ in cardiac tissues and the expression level of SIRT3 protein were increased in the Sev group (both P<0.01); the size of myocardial infarction and the level of serum cTnI were decreased in the Sev group (both P<0.01); the activities of mitochondrial complexes I, II, and IV, ATP content, protein expression levels of SOD2 and CAT were increased, while MDA content, VDAC1 protein expression level, and mitochondrial permeability were decreased in the Sev group (all P<0.01). Compared with the Sev group, the content of NAD+ in cardiac tissues and the expression level of SIRT3 protein were decreased in the Sev+3-TYP group (both P<0.01); the size of myocardial infarction and the level of serum cTnI were increased in the Sev+3-TYP group (both P<0.01); the activities of mitochondrial complexes I, II, and IV, ATP content, protein expression levels of SOD2 and CAT were decreased, while MDA content, VDAC1 protein expression level, and mitochondrial permeability were increased in the Sev+3-TYP group (all P<0.01).

CONCLUSIONS

Sevoflurane preconditioning attenuates myocardial IRI through activating the mitochondrial NAD+-SIRT3 pathway to preserve the mitochondrial function.

Assessing Drug-Induced Mitochondrial Toxicity in Cardiomyocytes: Implications for Preclinical Cardiac Safety Evaluation

Drug-induced cardiotoxicity not only leads to the attrition of drugs during development, but also contributes to the high morbidity and mortality rates of cardiovascular diseases. Comprehensive testing for proarrhythmic risks of drugs has been applied in preclinical cardiac safety assessment for over 15 years. However, other mechanisms of cardiac toxicity have not received such attention. Of them, mitochondrial impairment is a common form of cardiotoxicity and is known to account for over half of cardiovascular adverse-event-related black box warnings imposed by the U.S. Food and Drug Administration. Although it has been studied in great depth, mitochondrial toxicity assessment has not yet been incorporated into routine safety tests for cardiotoxicity at the preclinical stage. This review discusses the main characteristics of mitochondria in cardiomyocytes, drug-induced mitochondrial toxicities, and high-throughput screening strategies for cardiomyocytes, as well as their proposed integration into preclinical safety pharmacology. We emphasize the advantages of using adult human primary cardiomyocytes for the evaluation of mitochondrial morphology and function, and the need for a novel cardiac safety testing platform integrating mitochondrial toxicity and proarrhythmic risk assessments in cardiac safety evaluation.

Isoflurane inhibition of endocytosis is an anesthetic mechanism of action

The mechanisms of volatile anesthetic action remain among the most perplexing mysteries of medicine. Across phylogeny, volatile anesthetics selectively inhibit mitochondrial complex I, and they also depress presynaptic excitatory signaling. To explore how these effects are linked, we studied isoflurane effects on presynaptic vesicle cycling and ATP levels in hippocampal cultured neurons from wild-type and complex I mutant (Ndufs4(KO)) mice. To bypass complex I, we measured isoflurane effects on anesthetic sensitivity in mice expressing NADH dehydrogenase (NDi1). Endocytosis in physiologic concentrations of glucose was delayed by effective behavioral concentrations of isoflurane in both wild-type (τ [unexposed] 44.8 ± 24.2 s; τ [exposed] 116.1 ± 28.1 s; p < 0.01) and Ndufs4(KO) cultures (τ [unexposed] 67.6 ± 16.0 s; τ [exposed] 128.4 ± 42.9 s; p = 0.028). Increasing glucose, to enhance glycolysis and increase ATP production, led to maintenance of both ATP levels and endocytosis (τ [unexposed] 28.0 ± 14.4; τ [exposed] 38.2 ± 5.7; reducing glucose worsened ATP levels and depressed endocytosis (τ [unexposed] 85.4 ± 69.3; τ [exposed] > 1,000; p < 0.001). The block in recycling occurred at the level of reuptake of synaptic vesicles into the presynaptic cell. Expression of NDi1 in wild-type mice caused behavioral resistance to isoflurane for tail clamp response (EC₅₀ Ndi1(-) 1.27% ± 0.14%; Ndi1(+) 1.55% ± 0.13%) and halothane (EC₅₀ Ndi1(-) 1.20% ± 0.11%; Ndi1(+) 1.46% ± 0.10%); expression of NDi1 in neurons improved hippocampal function, alleviated inhibition of presynaptic recycling, and increased ATP levels during isoflurane exposure. The clear alignment of cell culture data to in vivo phenotypes of both isoflurane-sensitive and -resistant mice indicates that inhibition of mitochondrial complex I is a primary mechanism of action of volatile anesthetics.

Ndufs4 knockout mouse models of Leigh syndrome: pathophysiology and intervention

Mitochondria are small cellular constituents that generate cellular energy (ATP) by oxidative phosphorylation (OXPHOS). Dysfunction of these organelles is linked to a heterogeneous group of multisystemic disorders, including diabetes, cancer, ageing-related pathologies and rare mitochondrial diseases. With respect to the latter, mutations in subunit-encoding genes and assembly factors of the first OXPHOS complex (complex I) induce isolated complex I deficiency and Leigh syndrome. This syndrome is an early-onset, often fatal, encephalopathy with a variable clinical presentation and poor prognosis due to the lack of effective intervention strategies. Mutations in the nuclear DNA-encoded NDUFS4 gene, encoding the NADH:ubiquinone oxidoreductase subunit S4 (NDUFS4) of complex I, induce 'mitochondrial complex I deficiency, nuclear type 1' (MC1DN1) and Leigh syndrome in paediatric patients. A variety of (tissue-specific) Ndufs4 knockout mouse models were developed to study the Leigh syndrome pathomechanism and intervention testing. Here, we review and discuss the role of complex I and NDUFS4 mutations in human mitochondrial disease, and review how the analysis of Ndufs4 knockout mouse models has generated new insights into the MC1ND1/Leigh syndrome pathomechanism and its therapeutic targeting.

Anesthetic management of patients with carnitine deficiency or a defect of the fatty acid β-oxidation pathway: A narrative review

Carnitine is essential for the transport of long-chain fatty acids from the cytoplasm to the mitochondrial matrix. The carnitine shuttle transports long-chain fatty acylcarnitine to the mitochondrial matrix. Subsequently, long-chain fatty acyl CoA, which is split from long-chain fatty acylcarnitine by carnitine palmitoyltransferase II, undergoes fatty acid β-oxidation. Acetyl CoA is produced from long-chain fatty acyl CoA via fatty acid β-oxidation and aids in the synthesis of adenosine triphosphate via the tricarboxylic acid cycle and electron transport chain. In addition, in the fasting state, it leads to ketone body production in the liver and glucose production via gluconeogenesis. However, patients with compromised fatty acid β-oxidation, owing to carnitine deficiency as well as defects in carnitine transport and the fatty acid β-oxidation pathway, develop hypoglycemia, cardiomyopathy, arrhythmia, and hypotonia. These conditions are attributed to the accumulation of released fatty acids and acylcarnitine. This review aimed to shed light on the anesthetic management of patients with compromised fatty acid β-oxidation undergoing various surgeries by assessing relevant case reports associated with fatty acid β-oxidation disorder in PubMed. Pre-anesthetic and intraoperative evaluation should include monitoring of glucose and carnitine levels and specific cardiac tests, such as echocardiography. Considering that propofol is dissolved in 10% long-chain fatty acids, propofol infusion should be avoided because of increased long-chain fatty acid loading in patients with compromised fatty acid β-oxidation. Thus, anesthesia using opioids (remifentanil and fentanyl), midazolam, dexmedetomidine, etomidate, and non-depolarizing neuromuscular blocking agents would be appropriate in such patients.

Ndufs4 knockout mouse models of Leigh syndrome: pathophysiology and intervention

Mitochondria are small cellular constituents that generate cellular energy (ATP) by oxidative phosphorylation (OXPHOS). Dysfunction of these organelles is linked to a heterogeneous group of multisystemic disorders, including diabetes, cancer, ageing-related pathologies and rare mitochondrial diseases. With respect to the latter, mutations in subunit-encoding genes and assembly factors of the first OXPHOS complex (complex I) induce isolated complex I deficiency and Leigh syndrome. This syndrome is an early-onset, often fatal, encephalopathy with a variable clinical presentation and poor prognosis due to the lack of effective intervention strategies. Mutations in the nuclear DNA-encoded NDUFS4 gene, encoding the NADH:ubiquinone oxidoreductase subunit S4 (NDUFS4) of complex I, induce ‘mitochondrial complex I deficiency, nuclear type 1’ (MC1DN1) and Leigh syndrome in paediatric patients. A variety of (tissue-specific) Ndufs4 knockout mouse models were developed to study the Leigh syndrome pathomechanism and intervention testing.

Here, we review and discuss the role of complex I and NDUFS4 mutations in human mitochondrial disease, and review how the analysis of Ndufs4 knockout mouse models has generated new insights into the MC1ND1/Leigh syndrome pathomechanism and its therapeutic targeting.

Mechanisms underlying neonate-specific metabolic effects of volatile anesthetics

Volatile anesthetics (VAs) are widely used in medicine, but the mechanisms underlying their effects remain ill-defined. Though routine anesthesia is safe in healthy individuals, instances of sensitivity are well documented, and there has been significant concern regarding the impact of VAs on neonatal brain development. Evidence indicates that VAs have multiple targets, with anesthetic and non-anesthetic effects mediated by neuroreceptors, ion channels, and the mitochondrial electron transport chain. Here, we characterize an unexpected metabolic effect of VAs in neonatal mice. Neonatal blood β-hydroxybutarate (β-HB) is rapidly depleted by VAs at concentrations well below those necessary for anesthesia. β-HB in adults, including animals in dietary ketosis, is unaffected. Depletion of β-HB is mediated by citrate accumulation, malonyl-CoA production by acetyl-CoA carboxylase, and inhibition of fatty acid oxidation. Adults show similar significant changes to citrate and malonyl-CoA, but are insensitive to malonyl-CoA, displaying reduced metabolic flexibility compared to younger animals.

Contributions of synaptic and astrocyte physiology to the anaesthetised encephalogram revealed using a computational model

BACKGROUND

General anaesthesia is known to enhance inhibitory synaptic transmission to produce characteristic effects on the EEG and reduction in brain metabolism secondary to reduced neuronal activity. Evidence suggests that anaesthesia might have a direct effect on synaptic metabolic processes, and this relates to anaesthesia sensitivity. We explored elements of synaptic transmission looking for possible contributions to the anaesthetised EEG and how it may modulate anaesthesia sensitivity.

METHODS

We developed a Hodgkin-Huxley-type neural network computer simulation capable of mimicking anaesthetic prolongation of gamma-aminobutyric acid (GABA)ergic inhibitory postsynaptic potentials (IPSPs), and capable of altering postsynaptic ion homeostasis and neurotransmitter recycling. We examined their interactions on simulated electrocorticography (sECoG), and compared these with published anaesthesia EEG spectra.

RESULTS

The sECoG spectra from the model were comparable with published normal awake EEG spectra. Prolongation of IPSP duration in the model caused inhibition of high frequencies and saturation of low frequencies with a peak in keeping with current evidence. IPSP prolongation alone was unable to reproduce alpha rhythms or the generalised increase in EEG power found with anaesthesia. Adding inhibition of postsynaptic ion homeostasis to IPSP prolongation helped retain alpha rhythms, increased sECoG power, and antagonised the slow-wave saturation peak in a dose-dependent fashion that appeared dependent on the postsynaptic membrane potential, providing a plausible mechanism for how metabolic changes can modulate anaesthesia sensitivity.

CONCLUSIONS

Our model suggests how metabolic processes can modulate anaesthesia and produce non-receptor dependent drug sensitivity.

Mitochondria and Pharmacologic Cardiac Conditioning-At the Heart of Ischemic Injury

Pharmacologic cardiac conditioning increases the intrinsic resistance against ischemia and reperfusion (I/R) injury. The cardiac conditioning response is mediated via complex signaling networks. These networks have been an intriguing research field for decades, largely advancing our knowledge on cardiac signaling beyond the conditioning response. The centerpieces of this system are the mitochondria, a dynamic organelle, almost acting as a cell within the cell. Mitochondria comprise a plethora of functions at the crossroads of cell death or survival. These include the maintenance of aerobic ATP production and redox signaling, closely entwined with mitochondrial calcium handling and mitochondrial permeability transition. Moreover, mitochondria host pathways of programmed cell death impact the inflammatory response and contain their own mechanisms of fusion and fission (division). These act as quality control mechanisms in cellular ageing, release of pro-apoptotic factors and mitophagy. Furthermore, recently identified mechanisms of mitochondrial regeneration can increase the capacity for oxidative phosphorylation, decrease oxidative stress and might help to beneficially impact myocardial remodeling, as well as invigorate the heart against subsequent ischemic insults. The current review highlights different pathways and unresolved questions surrounding mitochondria in myocardial I/R injury and pharmacological cardiac conditioning.

Anesthetic Hypersensitivity in a Case-Controlled Series of Patients With Mitochondrial Disease

BACKGROUND

Children with mitochondrial disease undergo anesthesia for a wide array of surgical procedures. However, multiple medications used for their perioperative care can affect mitochondrial function. Defects in function of the mitochondrial electron transport chain (ETC) can lead to a profound hypersensitivity to sevoflurane in children. We studied the sensitivities to sevoflurane, during mask induction and maintenance of general anesthesia, in children presenting for muscle biopsies for diagnosis of mitochondrial disease.

METHODS

In this multicenter study, 91 children, aged 6 months to 16 years, presented to the operating room for diagnostic muscle biopsy for presumptive mitochondrial disease. General anesthesia was induced by a slow increase of inhaled sevoflurane concentration. The primary end point, end-tidal (ET) sevoflurane necessary to achieve a bispectral index (BIS) of 60, was recorded. Secondary end points were maximal sevoflurane used to maintain a BIS between 40 and 60 during the case, and maximum and minimum heart rate and blood pressures. After induction, general anesthesia was maintained according to the preferences of the providers directing the cases. Primary data were analyzed comparing data from patients with complex I deficiencies to other groups using nonparametric statistics in SPSS v.27.

RESULTS

The median sevoflurane concentration to reach BIS of 60 during inductions (ET sevoflurane % [BIS = 60]) was significantly lower for patients with complex I defects (0.98%; 95% confidence interval [CI], 0.5-1.4) compared to complex II (1.95%; 95% CI, 1.2-2.7; P < .001), complex III (2.0%; 95% CI, 0.7-3.5; P < .001), complex IV (2.0%; 95% CI, 1.7-3.2; P < .001), and normal groups (2.2%; 95% CI, 1.8-3.0; P < .001). The sevoflurane sensitivities of complex I patients did not reach significance when compared to patients diagnosed with mitochondrial disease but without an identifiable ETC abnormality (P = .172). Correlation of complex I activity with ET sevoflurane % (BIS = 60) gave a Spearman's coefficient of 0.505 (P < .001). The differences in sensitivities between groups were less during the maintenance of the anesthetic than during induction.

CONCLUSIONS

The data indicate that patients with complex I dysfunction are hypersensitive to sevoflurane compared to normal patients. Hypersensitivity was less common in patients presenting with other mitochondrial defects or without a mitochondrial diagnosis.

Anesthesia-Sepsis-Associated Alterations in Liver Gene Expression Profiles and Mitochondrial Oxidative Phosphorylation Complexes

Background: Hepatic dysfunction plays a major role in adverse outcomes in sepsis. Volatile anesthetic agents may protect against organ dysfunction in the setting of critical illness and infection. The goal of this study was to study the impact of Sepsis-inflammation on hepatic subcellular energetics in animals anesthetized with both Propofol (intravenous anesthetic agent and GABA agonist) and Isoflurane (volatile anesthetic i.e., VAA).

Methods: Sprague-Dawley rats were anesthetized with Propofol or isoflurane. Rats in each group were randomized to celiotomy and closure (control) or cecal ligation and puncture “CLP” (Sepsis-inflammation) for 8 h.

Results: Inflammation led to upregulation in hepatic hypoxia-inducible factor-1 in both groups. Rats anesthetized with isoflurane also exhibited increases in bcl-2, inducible nitric oxide synthase, and heme oxygenase-1(HO-1) during inflammation, whereas rats anesthetized with Propofol did not. In rats anesthetized with isoflurane, decreased mRNA, protein (Complex II, IV, V), and activity levels (Complex II/III,IV,V) were identified for all components of the electron transport chain, leading to a decrease in mitochondrial ATP. In contrast, in rats anesthetized with Propofol, these changes were not identified after exposure to inflammation. RNA-Seq and real-time quantitative PCR (qPCR) expression analysis identified a substantial difference between groups (isoflurane vs. Propofol) in mitogen-activated protein kinase (MAPK) related gene expression following exposure to Sepsis-inflammation.

Conclusions: Compared to rats anesthetized with Propofol, those anesthetized with isoflurane exhibit more oxidative stress, decreased oxidative phosphorylation protein expression, and electron transport chain activity and increased expression of organ-protective proteins.

Mitochondrial Complex I Mutations Predispose Drosophila to Isoflurane Neurotoxicity

BACKGROUND

General anesthetics influence mitochondrial homeostasis, placing individuals with mitochondrial disorders and possibly carriers of recessive mitochondrial mutations at increased risk of perioperative complications. In Drosophila, mutations in the ND23 subunit of complex I of the mitochondrial electron transport chain-analogous to mammalian NDUFS8-replicate key characteristics of Leigh syndrome, an inherited mitochondrial disorder. The authors used the ND23 mutant for testing the hypothesis that anesthetics have toxic potential in carriers of mitochondrial mutations.

METHODS

The authors exposed wild-type flies and ND23 mutant flies to behaviorally equivalent doses of isoflurane or sevoflurane in 5%, 21%, or 75% oxygen. The authors used percent mortality (mean ± SD, n ≥ 3) at 24 h after exposure as a readout of toxicity and changes in gene expression to investigate toxicity mechanisms.

RESULTS

Exposure of 10- to 13-day-old male ND23 flies to isoflurane in 5%, 21%, or 75% oxygen resulted in 16.0 ± 14.9% (n = 10), 48.2 ± 16.1% (n = 9), and 99.2 ± 2.0% (n = 10) mortality, respectively. Comparable mortality was observed in females. In contrast, under the same conditions, mortality was less than 5% for all male and female groups exposed to sevoflurane, except 10- to 13-day-old male ND23 flies with 9.6 ± 8.9% (n = 16) mortality. The mortality of 10- to 13-day-old ND23 flies exposed to isoflurane was rescued by neuron- or glia-specific expression of wild-type ND23. Isoflurane and sevoflurane differentially affected expression of antioxidant genes in 10- to 13-day-old ND23 flies. ND23 flies had elevated mortality from paraquat-induced oxidative stress compared with wild-type flies. The mortality of heterozygous ND23 flies exposed to isoflurane in 75% oxygen increased with age, resulting in 54.0 ± 19.6% (n = 4) mortality at 33 to 39 days old, and the percent mortality varied in different genetic backgrounds.

CONCLUSIONS

Mutations in the mitochondrial complex I subunit ND23 increase susceptibility to isoflurane-induced toxicity and to oxidative stress in Drosophila. Asymptomatic flies that carry ND23 mutations are sensitized to hyperoxic isoflurane toxicity by age and genetic background.

EDITOR’S PERSPECTIVE

Dynamic Variations in Brain Glycogen are Involved in Modulating Isoflurane Anesthesia in Mice

General anesthesia severely affects the metabolites in the brain. Glycogen, principally stored in astrocytes and providing the short-term delivery of substrates to neurons, has been implicated as an affected molecule. However, whether glycogen plays a pivotal role in modulating anesthesia–arousal remains unclear. Here, we demonstrated that isoflurane-anesthetized mice exhibited dynamic changes in the glycogen levels in various brain regions. Glycogen synthase (GS) and glycogen phosphorylase (GP), key enzymes of glycogen metabolism, showed increased activity after isoflurane exposure. Upon blocking glycogenolysis with 1,4-dideoxy-1,4-imino-D-arabinitol (DAB), a GP antagonist, we found a prolonged time of emergence from anesthesia and an enhanced δ frequency in the EEG (electroencephalogram). In addition, augmented expression of glycogenolysis genes in glycogen phosphorylase, brain (Pygb) knock-in (Pygb^H11/H11) mice resulted in delayed induction of anesthesia, a shortened emergence time, and a lower ratio of EEG-δ. Our findings revealed a role of brain glycogen in regulating anesthesia–arousal, providing a potential target for modulating anesthesia.

Safety of drug use in patients with a primary mitochondrial disease: An international Delphi-based consensus

Clinical guidance is often sought when prescribing drugs for patients with primary mitochondrial disease. Theoretical considerations concerning drug safety in patients with mitochondrial disease may lead to unnecessary withholding of a drug in a situation of clinical need. The aim of this study was to develop consensus on safe medication use in patients with a primary mitochondrial disease. A panel of 16 experts in mitochondrial medicine, pharmacology, and basic science from six different countries was established. A modified Delphi technique was used to allow the panellists to consider draft recommendations anonymously in two Delphi rounds with predetermined levels of agreement. This process was supported by a review of the available literature and a consensus conference that included the panellists and representatives of patient advocacy groups. A high level of consensus was reached regarding the safety of all 46 reviewed drugs, with the knowledge that the risk of adverse events is influenced both by individual patient risk factors and choice of drug or drug class. This paper details the consensus guidelines of an expert panel and provides an important update of previously established guidelines in safe medication use in patients with primary mitochondrial disease. Specific drugs, drug groups, and clinical or genetic conditions are described separately as they require special attention. It is important to emphasise that consensus-based information is useful to provide guidance, but that decisions related to drug prescribing should always be tailored to the specific needs and risks of each individual patient. We aim to present what is current knowledge and plan to update this regularly both to include new drugs and to review those currently included.

Sevoflurane as opposed to propofol anesthesia preserves mitochondrial function and alleviates myocardial ischemia/reperfusion injury

BACKGROUND

Pharmacological interventions reducing myocardial ischemia and reperfusion (I/R) injury include the administration of anesthetics. Both sevoflurane as well as propofol have been shown to elicit cardiac protection via distinct molecular mechanisms. We investigated the hypothesis that sevoflurane in contrary to propofol anesthesia elicits cardiac protection against I/R-injury via mitochondrial mechanisms of disease.

METHODS

Male New Zealand white rabbits (n = 42) were subjected 30 min of coronary artery occlusion followed by 3 h of reperfusion. After induction with pentobarbital, the animals either received sevoflurane or propofol to maintain general anesthesia. Infarct size was determined gravimetrically after triphenyltetrazolium chlorid-staining. Cardiac mitochondria were isolated and mitochondrial oxygen consumption was measured using a Clark electrode. Mitochondrial respiratory chain complex activities (I-IV) were analyzed utilizing specific assays. Data are mean ± SD.

RESULTS

Sevoflurane anesthesia significantly decreased the resulting myocardial infarct size compared to propofol anesthesia (p = 0.0275 vs. propofol). Mitochondria from animals receiving propofol anesthesia showed a significantly reduced mitochondrial respiratory control ratio (p = 0.01909 vs. sham) and impaired activities of respiratory complex I (p = 0.0147 vs. sham; p < 0.01 vs. sevoflurane) as well as respiratory complex IV (p = 0.0181 vs. sham). Mitochondrial dysfunction was absent in sevoflurane anesthesized animals. Furthermore, a significantly higher portion of complex I was found to be in its deactive form during I/R-injury in animals receiving sevoflurane anesthesia (p = 0.0123 vs. propofol).

CONCLUSIONS

Sevoflurane as opposed to propofol anesthesia preserved mitochondrial respiration and elicited cardiac protection against I/R-injury.

Evidence of variations of endogenous halogenated volatile organic compounds in alveolar breath after mental exercise-induced oxidative stress

BACKGROUND

The effect of oxygen on markers of oxidative stress has not been totally elucidated because previous studies have yielded conflicting results.

METHODS

A method for the collection and gas chromatography-mass spectrometry of the halogenated volatile organic compounds in human alveolar breath is described. A transportable apparatus sampled specifically alveolar breath; the volatile organic compounds were captured in a thermal desorption tube, Carbotrap 200®. The sample was thermally desorbed from the trap in an automated gas chromatography with mass spectrometry detection and peak fragmentation. Compounds were identified by reference to a computer-based library of mass spectra.

RESULTS

Trichlorotrifluoroethane, tetrafluoroethane, dichlorodifluoromethane were identified in alveolar breath of healthy volunteers after mental exercise-induced oxidative stress. The effects of halogenated alkanes were investigated on electron transport chain activity. These agents impaired the NADH oxidation suggesting an inhibition of the complex I (NADH: ubiquinone oxidoreductase) of the electron transport chain. These inhibitory effects are suspected likely to fight against oxidative stress deleterious reactions.

CONCLUSION

Chemical inhibition of the oxidative burst in human body trough these halogenated inhibitors is a new concept of significant practical, medical, biological and scientific interest.

MitoRACE: evaluating mitochondrial function in vivo and in single cells with subcellular resolution using multiphoton NADH autofluorescence

KEY POINTS

We developed a novel metabolic imaging approach that provides direct measures of the rate of mitochondrial energy conversion with single-cell and subcellular resolution by evaluating NADH autofluorescence kinetics during the mitochondrial redox after cyanide experiment (mitoRACE). Measures of mitochondrial NADH flux by mitoRACE are sensitive to physiological and pharmacological perturbations in vivo. Metabolic imaging with mitoRACE provides a highly adaptable platform for evaluating mitochondrial function in vivo and in single cells with potential for broad applications in the study of energy metabolism.

ABSTRACT

Mitochondria play a critical role in numerous cell types and diseases, and structure and function of mitochondria can vary greatly among cells or within different regions of the same cell. However, there are currently limited methodologies that provide direct assessments of mitochondrial function in vivo, and contemporary measures of mitochondrial energy conversion lack the spatial resolution necessary to address cellular and subcellular heterogeneity. Here, we describe a novel metabolic imaging approach that provides direct measures of mitochondrial energy conversion with single-cell and subcellular resolution by evaluating NADH autofluorescence kinetics during the mitochondrial redox after cyanide experiment (mitoRACE). MitoRACE measures the rate of NADH flux through the steady-state mitochondrial NADH pool by rapidly inhibiting mitochondrial energetic flux, resulting in an immediate, linear increase in NADH fluorescence proportional to the steady-state NADH flux rate, thereby providing a direct measure of mitochondrial NADH flux. The experiments presented here demonstrate the sensitivity of this technique to detect physiological and pharmacological changes in mitochondrial flux within tissues of living animals and reveal the unique capability of this technique to evaluate mitochondrial function with single-cell and subcellular resolution in different cell types in vivo and in cell culture. Furthermore, we highlight the potential applications of mitoRACE by showing that within single neurons, mitochondria in neurites have higher energetic flux rates than mitochondria in the cell body. Metabolic imaging with mitoRACE provides a highly adaptable platform for evaluating mitochondrial function in vivo and in single cells, with potential for broad applications in the study of energy metabolism.

Effects of isoflurane on complex II‑associated mitochondrial respiration and reactive oxygen species production: Roles of nitric oxide and mitochondrial KATP channels

Volatile anesthetics may protect the heart against ischemia‑reperfusion injury via the direct action on mitochondrial complexes and by regulating the production of reactive oxygen species (ROS). Recently, we reported that isoflurane induced the attenuation of mitochondrial respiration caused by complex I substrates. This process was not associated with endogenous production of mitochondrial nitric oxide (NO). In the present study, we investigated the effects of isoflurane on mitochondrial respiration and ROS production using complex II substrates. The detailed mechanism of these effects was explored with regards to NO production and the expression of mitochondrial ATP‑dependent K+ (mKATP) channels. Mitochondria were isolated from the heart of Sprague‑Dawley rats. The respiratory rates of mitochondria (0.5 mg/ml) were measured via polarography at 28˚C with computer‑controlled Clark‑type O2 electrodes. The complex II substrate succinate (5 mM) was used; 0.25 mM of isoflurane was administered prior to ADP‑initiated state 3 respiration. The mitochondrial membrane potential (ΔΨm) was measured under treatment with the substrate succinate, or succinate in the presence of the complex I inhibitor rotenone. The detection was achieved in a cuvette‑based spectrophotometer operating at wavelengths of 503 nm (excitation) 527 nm (emission) in the presence of 50 nM of the fluorescent dye rhodamine 123. The H2O2 release rates in the mitochondria were measured spectrophotometrically with succinate, or succinate and rotenone using the fluorescent dye Amplex red (12.5‑25 µM). The results indicated that isoflurane increased the state 3 and 4 respiration rates caused by succinate, which were higher than those noted in the control group in the presence of succinate alone. The NOS inhibitor L‑NIO or the NO‑sensitive guanylyl cyclase 1H‑[1,2,4]oxadiazolo[4,3‑a]quinoxalin‑1‑one did not inhibit the increase in the respiration rate (state 3) induced by isoflurane. The ROS scavengers SPBN and manganese (III) tetrakis (4‑benzoic acid) porphyrin chloride inhibited the increase in the respiration rate (state 3 and 4) induced by isoflurane. This effect was not noted for the putative KATP channel blockers 5‑hydroxydecanoic acid and glibenclamide. Isoflurane caused a greater decrease in the concentration of H2O2 during ADP‑initiated state 3 respiration, and L‑N5‑(1‑Iminoethyl)‑ornithine did not inhibit this effect. In conclusion, isoflurane was determined to modulate mitochondrial respiration and ROS production caused by the complex II substrate succinate. These effects were independent of endogenous mitochondrial NO generation and mitochondrial KATP channel opening.

Impact of inflammation on brain subcellular energetics in anesthetized rats

Background

Emerging data suggests that volatile anesthetic agents may have organ protection properties in the setting of critical illness. The purpose of this study was to better understand the effect of inflammation on cerebral subcellular energetics in animals exposed to two different anesthetic agents—a GABA agonist (propofol) and a volatile agent (isoflurane).

Results

Forty-eight Sprague–Dawley rats were anesthetized with isoflurane or propofol. In each group, rats were randomized to celiotomy and closure (sham) or cecal ligation and puncture (inflammation [sepsis model]) for 8 h. Brain tissue oxygen saturation and the oxidation state of cytochrome aa₃ were measured. Brain tissue was extracted using the freeze-blow technique. All rats experienced progressive increases in tissue oxygenation and cytochrome aa₃ reduction over time. Inflammation had no impact on cytochrome aa₃, but isoflurane caused significant cytochrome aa₃ reduction. During isoflurane (not propofol) anesthesia, inflammation led to an increase in lactate (+ 0.64 vs. − 0.80 mEq/L, p = 0.0061). There were no differences in ADP:ATP ratios between groups. In the isoflurane (not propofol) group, inflammation increased the expression of hypoxia-inducible factor-1α (62%, p = 0.0012), heme oxygenase-1 (67%, p = 0.0011), and inducible nitric oxide synthase (31%, p = 0.023) in the brain. Animals exposed to inflammation and isoflurane (but not propofol) exhibited increased expression of protein carbonyls (9.2 vs. 7.0 nM/mg protein, p = 0.0050) and S-nitrosylation (49%, p = 0.045) in the brain. RNA sequencing identified an increase in heat shock protein 90 and NF-κβ inhibitor mRNA in the inflammation/isoflurane group.

Conclusions

In the setting of inflammation, rats exposed to isoflurane show increased hypoxia-inducible factor-1α expression despite a lack of hypoxia, increased oxidative stress in the brain, and increased serum lactate, all of which suggest a relative increase in anaerobic metabolism compared to propofol. Differences in oxidative stress as well as heat shock protein 90 and NF-κβ inhibitor may account for the differential expression of cerebral hypoxia-inducible factor-1α during inflammation.

Electronic supplementary material

The online version of this article (10.1186/s12868-019-0514-8) contains supplementary material, which is available to authorized users.

Metabolic Disorders and Anesthesia

Purpose of Review

Metabolic disorders encompass a group of inherited inborn errors of metabolism that are uncommonly encountered but can pose challenges when encountered during the perioperative period. Hence, it is paramount that anesthesiologists are experienced and familiar with management of these conditions.

Recent Findings

Hundreds of inborn errors of metabolism have already been identified, yet new metabolic disorders continue to be discovered with advancements in genomic science.

Summary

In our general review, we define the more common metabolic disorders encountered in perioperative medicine and discuss the perioperative anesthetic considerations and challenges associated with each disorder. The following disorders are covered in our review: disorders of carbohydrate metabolism, disorders of amino acid metabolism, disorders of branched-chain amino acid metabolism, organic acidemias, mitochondrial disorders, lysosomal storage disorders, metal metabolism disorders, and urea cycle disorders.

Permeabilised skeletal muscle reveals mitochondrial deficiency in malignant hyperthermia-susceptible individuals

BACKGROUND

Individuals genetically susceptible to malignant hyperthermia (MH) exhibit hypermetabolic reactions when exposed to volatile anaesthetics. Mitochondrial dysfunction has previously been associated with the MH-susceptible (MHS) phenotype in animal models, but evidence of this in human MH is limited.

METHODS

We used high resolution respirometry to compare oxygen consumption rates (oxygen flux) between permeabilised human MHS and MH-negative (MHN) skeletal muscle fibres with or without prior exposure to halothane. A substrate-uncoupler-inhibitor titration protocol was used to measure the following components of the electron transport chain under conditions of oxidative phosphorylation (OXPHOS) or after uncoupling the electron transport system (ETS): complex I (CI), complex II (CII), CI+CII and, as a measure of mitochondrial mass, complex IV (CIV).

RESULTS

Baseline comparisons without halothane exposure showed significantly increased mitochondrial mass (CIV, P=0.021) but lower flux control ratios in CI+CII_(OXPHOS) and CII_(ETS) of MHS mitochondria compared with MHN (P=0.033 and 0.005, respectively) showing that human MHS mitochondria have a functional deficiency. Exposure to halothane triggered a hypermetabolic response in MHS mitochondria, significantly increasing mass-specific oxygen flux in CI_(OXPHOS), CI+CII_(OXPHOS), CI+CII_(ETS), and CII_(ETS) (P=0.001-0.012), while the rates in MHN samples were unaltered by halothane exposure.

CONCLUSIONS

We present evidence of mitochondrial dysfunction in human MHS skeletal muscle both at baseline and after halothane exposure.

Mitochondrial Function in Astrocytes Is Essential for Normal Emergence from Anesthesia in Mice

WHAT WE ALREADY KNOW ABOUT THIS TOPIC

In mice, restriction of loss of the mitochondrial complex I gene Ndufs4 to glutamatergic neurons confers a profound hypersensitivity to volatile anesthetics.Astrocytes are crucial to glutamatergic synapse functioning during excitatory transmission.

WHAT THIS ARTICLE TELLS US THAT IS NEW

In a tamoxifen-activated astrocyte-specific Ndufs4(KO) mouse, the induction EC50s for tail clamp in both isoflurane and halothane were similar between the control and astrocyte-specific Ndufs4(KO) mice at 3 weeks after 4-hydroxy tamoxifen injection. However, the emergent concentrations in both anesthetics for the astrocyte-specific Ndufs4(KO) mice were half that of the controls.Similarly, the induction EC50s for loss of righting reflex were similar between the control and astrocyte-specific Ndufs4(KO) mice; concentrations for regain of righting reflex in both anesthetics for the astrocyte-specific Ndufs4(KO) mice were much less than the control.Thus, mitochondrial complex I function within astrocytes is essential for normal emergence from anesthesia.

BACKGROUND

In mice, restriction of loss of the mitochondrial complex I gene Ndufs4 to glutamatergic neurons confers a profound hypersensitivity to volatile anesthetics similar to that seen with global genetic knockout of Ndufs4. Astrocytes are crucial to glutamatergic synapse functioning during excitatory transmission. Therefore, the authors examined the role of astrocytes in the anesthetic hypersensitivity of Ndufs4(KO).

METHODS

A tamoxifen-activated astrocyte-specific Ndufs4(KO) mouse was constructed. The specificity of the astrocyte-specific inducible model was confirmed by using the green fluorescent protein reporter line Ai6. Approximately 120 astrocyte-specific knockout and control mice were used for the experiments. Mice were anesthetized with varying concentrations of isoflurane or halothane; loss of righting reflex and response to a tail clamp were determined and quantified as the induction and emergence EC50s. Because norepinephrine has been implicated in emergence from anesthesia and astrocytes respond to norepinephrine to release gliotransmitters, the authors measured norepinephrine levels in the brains of control and knockout Ndufs4 animals.

RESULTS

The induction EC50s for tail clamp in both isoflurane and halothane were similar between the control and astrocyte-specific Ndufs4(KO) mice at 3 weeks after 4-hydroxy tamoxifen injection (induction concentration, EC50(ind)-isoflurane: control = 1.27 ± 0.12, astrocyte-specific knockout = 1.21 ± 0.18, P = 0.495; halothane: control = 1.28 ± 0.05, astrocyte-specific knockout = 1.20 ± 0.05, P = 0.017). However, the emergent concentrations in both anesthetics for the astrocyte-specific Ndufs4(KO) mice were less than the controls for tail clamp; (emergence concentration, EC50(em)-isoflurane: control = 1.18 ± 0.10, astrocyte-specific knockout = 0.67 ± 0.11, P < 0.0001; halothane: control = 1.08 ± 0.09, astrocyte-specific knockout = 0.59 ± 0.12, P < 0.0001). The induction EC50s for loss of righting reflex were also similar between the control and astrocyte-specific Ndufs4(KO) mice (EC50(ind)-isoflurane: control = 1.02 ± 0.10, astrocyte-specific knockout = 0.97 ± 0.06, P = 0.264; halothane: control = 1.03 ± 0.05, astrocyte-specific knockout = 0.99 ± 0.08, P = 0.207). The emergent concentrations for loss of righting reflex in both anesthetics for the astrocyte-specific Ndufs4(KO) mice were less than the control (EC50(em)-isoflurane: control = 1.0 ± 0.07, astrocyte-specific knockout = 0.62 ± 0.12, P < 0.0001; halothane: control = 1.0 ± 0.04, astrocyte-specific KO = 0.64 ± 0.09, P < 0.0001); N ≥ 6 for control and astrocyte-specific Ndufs4(KO) mice. For all tests, similar results were seen at 7 weeks after 4-hydroxy tamoxifen injection. The total norepinephrine content of the brain in global or astrocyte-specific Ndufs4(KO) mice was unchanged compared to control mice.

CONCLUSIONS

The only phenotype of the astrocyte-specific Ndufs4(KO) mouse was a specific impairment in emergence from volatile anesthetic-induced general anesthesia. The authors conclude that normal mitochondrial function within astrocytes is essential for emergence from anesthesia.

Perioperative Inflammation and Its Modulation by Anesthetics

Surgery and other invasive procedures, which are routinely performed during general anesthesia, may induce an inflammatory response in the patient. This inflammatory response is an inherent answer of the body to the intervention and can be both beneficial and potentially harmful. The immune system represents a unique evolutionary achievement equipping higher organisms with an effective defense mechanism against exogenous pathogens. However, not only bacteria might evoke an immune response but also other noninfectious stimuli like the surgical trauma or mechanical ventilation may induce an inflammatory response of varying degree. In these cases, the immune system activation is not always beneficial for the patients and might carry the risk of concomitant, harmful effects on host cells, tissues, or even whole organ systems. Research over the past decades has contributed substantial information in which ways surgical patients may be affected by inflammatory reactions. Modulations of the patient's immune system may be evoked by the use of anesthetic agents, the nature of surgical trauma and the use of any supportive therapy during the perioperative period. The effects on the patient may be manifold, including various proinflammatory effects. This review focuses on the causes and effects of inflammation in the perioperative period. In addition, we also highlight possible approaches by which inflammation in the perioperative may be modulated in the future.

Isoflurane disrupts excitatory neurotransmitter dynamics via inhibition of mitochondrial complex I

BACKGROUND

The mechanisms of action of volatile anaesthetics are unclear. Volatile anaesthetics selectively inhibit complex I in the mitochondrial respiratory chain. Mice in which the mitochondrial complex I subunit NDUFS4 is knocked out [Ndufs4(KO)] either globally or in glutamatergic neurons are hypersensitive to volatile anaesthetics. The volatile anaesthetic isoflurane selectively decreases the frequency of spontaneous excitatory events in hippocampal slices from Ndufs4(KO) mice.

METHODS

Complex I inhibition by isoflurane was assessed with a Clark electrode. Synaptic function was measured by stimulating Schaffer collateral fibres and recording field potentials in the hippocampus CA1 region.

RESULTS

Isoflurane specifically inhibits complex I dependent respiration at lower concentrations in mitochondria from Ndufs4(KO) than from wild-type mice. In hippocampal slices, after high frequency stimulation to increase energetic demand, short-term synaptic potentiation is less in KO compared with wild-type mice. After high frequency stimulation, both Ndufs4(KO) and wild-type hippocampal slices exhibit striking synaptic depression in isoflurane at twice the 50% effective concentrations (EC₅₀). The pattern of synaptic depression by isoflurane indicates a failure in synaptic vesicle recycling. Application of a selective A₁ adenosine receptor antagonist partially eliminates isoflurane-induced short-term depression in both wild-type and Ndufs4(KO) slices, implicating an additional mitochondria-dependent effect on exocytosis. When mitochondria are the sole energy source, isoflurane completely eliminates synaptic output in both mutant and wild-type mice at twice the (EC₅₀) for anaesthesia.

CONCLUSIONS

Volatile anaesthetics directly inhibit mitochondrial complex I as a primary target, limiting synaptic ATP production, and excitatory vesicle endocytosis and exocytosis.

Effects of isoflurane, sevoflurane, propofol and alfaxalone on brain metabolism in dogs assessed by proton magnetic resonance spectroscopy (1H MRS)

Background

The purpose of this study was to determine the effects of isoflurane, sevoflurane, propofol and alfaxalone on the canine brain metabolite bioprofile, measured with single voxel short echo time proton magnetic resonance spectroscopy at 3 Tesla. Ten adult healthy Beagle dogs were assigned to receive isoflurane, sevoflurane, propofol and alfaxalone at 3 different dose rates each in a randomized cross-over study design. Doses for isoflurane, sevoflurane, propofol and alfaxalone were F_E’Iso 1.7 vol%, 2.1 vol%, 2.8 vol%, F_E’Sevo 2.8 vol%, 3.5 vol% and 4.7 vol%, 30, 45 and 60 mg kg^− 1 h^− 1 and 10, 15 and 20 mg kg^− 1 h^− 1 respectively. A single voxel Point Resolved Spectroscopy Sequence was performed on a 3 T MRI scanner in three brain regions (basal ganglia, parietal and occipital lobes). Spectral data were analyzed with LCModel. Concentration of total N-acetylaspartate (tNAA), choline, creatine, inositol and glutamine and glutamate complex (Glx) relative to water content was obtained. Plasma concentration of lactate, glucose, triglycerides, propofol and alfaxalone were determined. Statistics were performed using repeated measures ANOVA or Wilcoxon Sign Rank test with alpha = 5%.

Results

Plasma glucose increased with isoflurane, sevoflurane and alfaxalone but decreased with propofol. Plasma lactate increased with all anesthetics (isoflurane > sevoflurane > propofol > alfaxalone). Cerebral lactate could not be detected. Only minor changes in cerebral metabolite concentrations of tNAA, choline, inositol, creatine and Glx occurred with anesthetic dose changes.

Conclusion

The metabolomic profile detected with proton magnetic resonance spectroscopy at 3 Tesla of canine brain showed only minor differences between doses and anesthetics related to tNAA, choline, creatine, inositol and Glx.

Volatile anesthesia for a pediatric patient with very long-chain acyl-coenzyme A dehydrogenase deficiency: A case report

We report the case of a 3-year-old boy with very long-chain acyl-coenzyme A dehydrogenase deficiency presenting for adenotonsillectomy who was successfully and safely managed with a balanced anesthetic including sevoflurane. The anesthetic management is described, and the controversy surrounding volatile anesthetics in these patients is discussed.

Exercise training impacts exercise tolerance and bioenergetics in gastrocnemius muscle of non-obese type-2 diabetic Goto-Kakizaki rat in vivo

The functional and bioenergetics impact of regular physical activity upon type-2 diabetic skeletal muscle independently of confounding factors of overweight remains undocumented. Here, gastrocnemius muscle energy fluxes, mitochondrial capacity and mechanical performance were assessed noninvasively and longitudinally in non-obese diabetic Goto-Kakizaki rats using magnetic resonance (MR) imaging and dynamic 31-phosphorus MR spectroscopy (³¹P-MRS) throughout a 6-min fatiguing bout of exercise performed before, in the middle (4-week) and at the end of an 8-week training protocol consisting in 60-min daily run on a treadmill. The training protocol reduced plasmatic insulin level (-61%) whereas blood glucose and non-esterified fatty acids levels remained unaffected, thereby indicating an improvement of insulin sensitivity. It also increased muscle mitochondrial citrate synthase activity (+45%) but this increase did not enhance oxidative ATP synthesis capacity in working muscle in vivo while glycolytic ATP production was increased (+33%). On the other hand, the training protocol impaired maximal force-generating capacity (-9%), total amount of force produced (-12%) and increased ATP cost of contraction (+32%) during the fatiguing exercise. Importantly, these deleterious effects were transiently worsened in the middle of the 8-week period, in association with reduced oxidative capacity and increased basal [P_i]/[PCr] ratio (an in vivo biomarker of muscle damage). These data demonstrate that the beneficial effect of regular training on insulin sensitivity in non-obese diabetic rat occurs separately from any improvement in muscle mitochondrial function and might be linked to an increased capacity for metabolizing glucose through anaerobic process in exercising muscle.

The Effect of Mitochondrial Complex I-Linked Respiration by Isoflurane Is Independent of Mitochondrial Nitric Oxide Production

BACKGROUND

Anesthetic preconditioning (APC) of the myocardium is mediated in part by reversible alteration of mitochondrial function. Nitric oxide (NO) inhibits mitochondrial respiration and may mediate APC-induced cardioprotection. In this study, the effects of isoflurane on different states of mitochondrial respiration during the oxidation of complex I-linked substrates and the role of NO were investigated.

METHODS

Mitochondria were isolated from Sprague-Dawley rat hearts. Respiration rates were measured polarographically at 28ºC with a computer-controlled Clark-type O2 electrode in the mitochondria (0.5 mg/mL) with complex I substrates glutamate/malate (5 mM). Isoflurane (0.25 mM) was administered before or after adenosine diphosphate (ADP)-initiated state 3 respiration. The NO synthase (NOS) inhibitor L-N5-(1-iminoethyl)-ornithine (L-NIO, 10 μM) and the NO donor S-nitroso-N-acetylpenicillamine (SNAP, 1 μM) were added before or after the addition of ADP.

RESULTS

Isoflurane administered in state 2 increased state 2 respiration and decreased state 3 respiration. This attenuation of state 3 respiration by isoflurane was similar when it was given during state 3. L-NIO did not alter mitochondrial respiration or the effect of isoflurane. SNAP only, added in state 3, decreased state 3 respiration and enhanced the isoflurane-induced attenuation of state 3 respiration.

CONCLUSION

Isoflurane has clearly distinguishable effects on different states of mitochondrial respiration during the oxidation of complex I substrates. The uncoupling effect during state 2 respiration and the attenuation of state 3 respiration may contribute to the mechanism of APC-induced cardioprotection. These effects of isoflurane do not depend on endogenous mitochondrial NO, as the NOS inhibitor L-NIO did not alter the effects of isoflurane on mitochondrial respiration.

Assessing the influence of isoflurane anesthesia on cardiac metabolism using hyperpolarized [1-13 C]pyruvate

Isoflurane is a frequently used anesthetic in small-animal dissolution dynamic nuclear polarization-magnetic resonance imaging (DNP-MRI) studies. Although the literature suggests interactions with mitochondrial metabolism, the influence of the compound on cardiac metabolism has not been assessed systematically to date. In the present study, the impact of low versus high isoflurane concentration was examined in a crossover experiment in healthy rats. The results revealed that cardiac metabolism is modulated by isoflurane concentration, showing increased [1-¹³ C]lactate and reduced [¹³ C]bicarbonate production during high isoflurane relative to low isoflurane dose [average differences: +16% [1-¹³ C]lactate/total myocardial carbon, -22% [¹³ C]bicarbonate/total myocardial carbon; +51% [1-¹³ C]lactate/[¹³ C]bicarbonate]. These findings emphasize that reproducible anesthesia is important when studying cardiac metabolism. As the depth of anesthesia is difficult to control in an experimental animal setting, careful study design is required to exclude confounding factors.

The in vitro zebrafish heart as a model to investigate the chronotropic effects of vapor anesthetics

In addition to their intended clinical actions, all general anesthetic agents in common use have detrimental intrasurgical and postsurgical side effects on organs and systems, including the heart. The major cardiac side effect of anesthesia is bradycardia, which increases the probability of insufficient systemic perfusion during surgery. These side effects also occur in all vertebrate species so far examined, but the underlying mechanisms are not clear. The zebrafish heart is a powerful model for studying cardiac electrophysiology, employing the same pacemaker system and neural control as do mammalian hearts. In this study, isolated zebrafish hearts were significantly bradycardic during exposure to the vapor anesthetics sevoflurane (SEVO), desflurane (DES), and isoflurane (ISO). Bradycardia induced by DES and ISO continued during pharmacological blockade of the intracardiac portion of the autonomic nervous system, but the chronotropic effect of SEVO was eliminated during blockade. Bradycardia evoked by vagosympathetic nerve stimulation was augmented during DES and ISO exposure; nerve stimulation during SEVO exposure had no effect. Together, these results support the hypothesis that the cardiac chronotropic effect of SEVO occurs via a neurally mediated mechanism, while DES and ISO act directly upon cardiac pacemaker cells via an as yet unknown mechanism.

Drug rechallenge following drug-induced liver injury

Drug-induced hepatocellular injury is identified internationally by alanine aminotransferase (ALT) levels equal to or exceeding 5× the upper limit of normal (ULN) appearing within 3 months of drug initiation, after alternative causes are excluded. Upon withdrawing the suspect drug, ALT generally decrease by 50% or more. With drug readministration, a positive rechallenge has recently been defined by an ALT level of 3-5× ULN or greater. Nearly 50 drugs are associated with positive rechallenge after drug-induced liver injury (DILI): antimicrobials; and central nervous system, cardiovascular and oncology therapeutics. Drugs associated with high rates of positive rechallenge exhibit multiple risk factors: daily dose >50 mg, an increased incidence of ALT elevations in clinical trials, immunoallergic clinical injury, and mitochondrial impairment in vitro. These drug factors interact with personal genetic, immune, and metabolic factors to influence positive rechallenge rates and outcomes. Drug rechallenge following drug-induced liver injury is associated with up to 13% mortality in prospective series of all prescribed drugs. In recent oncology trials, standardized systems have enabled safer drug rechallenge with weekly liver chemistry monitoring during the high-risk period and exclusion of patients with hypersensitivity. However, high positive rechallenge rates with other innovative therapeutics suggest that caution should be taken with rechallenge of high-risk drugs.

CONCLUSION

For critical medicines, drug rechallenge may be appropriate when 1) no safer alternatives are available, 2) the objective benefit exceeds the risk, and 3) patients are fully informed and consent, can adhere to follow-up, and alert providers to hepatitis symptoms. To better understand rechallenge outcomes and identify key risk factors for positive rechallenge, additional data are needed from controlled clinical trials, prospective registries, and large health care databases. (Hepatology 2017;66:646-654).

The Effects of Fentanyl on Hepatic Mitochondrial Function

BACKGROUND

Remifentanil interferes with hepatic mitochondrial function. The aim of the present study was to evaluate whether hepatic mitochondrial function is affected by fentanyl, a more widely used opioid than remifentanil.

METHODS

Human hepatoma HepG2 cells were exposed to fentanyl or pretreated with naloxone (an opioid receptor antagonist) or 5-hydroxydecanoate (5-HD, an inhibitor of mitochondrial adenosine triphosphate (ATP)-sensitive potassium [mitoKATP] channels), followed by incubation with fentanyl. Mitochondrial function and metabolism were then analyzed.

RESULTS

Fentanyl marginally reduced maximal mitochondrial complex-specific respiration rates using exogenous substrates (decrease in medians: 11%-18%; P = 0.003-0.001) but did not affect basal cellular respiration rates (P = 0.834). The effect on stimulated respiration was prevented by preincubation with naloxone or 5-HD. Fentanyl reduced cellular ATP content in a dose-dependent manner (P < 0.001), an effect that was not significantly prevented by 5-HD and not explained by increased total ATPase concentration. However, in vitro ATPase activity of recombinant human permeability glycoprotein (an ATP-dependent drug efflux transporter) was significantly stimulated by fentanyl (P = 0.004).

CONCLUSIONS

Our data suggest that fentanyl reduces stimulated mitochondrial respiration of cultured human hepatocytes by a mechanism that is blocked by a mitoKATP channel antagonist. Increased energy requirements for fentanyl efflux transport may offer an explanation for the substantial decrease in cellular ATP concentration.

Cyclophilin D Modulates the Cardiac Mitochondrial Target of Isoflurane, Sevoflurane, and Desflurane

BACKGROUND

Volatile anesthetics are known to limit myocardial ischemia-reperfusion injuries. Mitochondria were shown to be major contributors to cardioprotection. Cyclophilin D (CypD) is one of the main regulators of mitochondria-induced cell death. We compared the effect of isoflurane, sevoflurane, and desflurane in the presence or absence of CypD, to clarify its role in the mechanism of cardioprotection induced by these anesthetics.

METHODS

Oxidative phosphorylation, mitochondrial membrane potential, and H2O2 production were measured in isolated mitochondria from wild-type (WT) or CypD knockout mice in basal conditions and after hypoxia-reoxygenation in the presence or absence of volatile anesthetics.

RESULTS

All volatile anesthetics inhibited mitochondrial state 3 of complex I, decreased membrane potential, and increased adenosine diphosphate consumption duration in both WT and CypD knockout mice. However, they differently modified H2O2 production after stimulation by succinate: CypD ablation reduced H2O2 production, isoflurane decreased H2O2 level in WT but not in CypD knockout mice, sevoflurane affected both lines whereas desflurane increased H2O2 production in CypD knockout and had no effect on WT mice.

CONCLUSIONS

This study showed different effects of isoflurane, sevoflurane, and desflurane on mitochondrial functions and highlighted the implication of CypD in the regulation of adenosine diphosphate consumption and complex I-induced radical oxygen species production.

A review of anaesthetic outcomes in patients with genetically confirmed mitochondrial disorders

Mitochondrial disorders are a clinically and biochemically diverse group of disorders which may involve multiple organ systems. General anaesthesia (GA) poses a potential risk of decompensation in children with mitochondrial disorders, and there is little guidance for anaesthetists and other clinicians regarding the optimal anaesthetic agents and perioperative management to provide to patients with mitochondrial disease[15]. The aim of this review was to document adverse events and perioperative complications from GA in patients with genetically confirmed mitochondrial disorders. A retrospective chart review of patients with genetically confirmed mitochondrial disorders who had undergone GA was undertaken. The indication for GA, anaesthetic agents utilised, length of admission and post anaesthetic complications were documented and analysed. Twenty-six patients with genetically proven mitochondrial disease underwent 65 GAs. Thirty-four (52%), received propofol as their induction agent. Thirty-three (51%) patients received sevoflurane for the maintenance of anaesthesia, while 8 (12%) received isoflurane and 24 (37%) received propofol. The duration of most GAs was short with 57 (87%) lasting less than 1 h. Perioperative complications occurred in five patients while under GA including ST segment depression, hypotension and metabolic acidosis in one. All five patients were stabilised successfully and none required ICU admission as a consequence of their perioperative complications. The duration of hospital stay post GA was <24 h in 25 (38%) patients.

CONCLUSION

No relationship between choice of anaesthetic agent and subsequent perioperative complication was observed. It is likely that individual optimisation on a case-by-case basis is more important overall than choice of any one particular technique. What is Known: • General anaesthesia (GA) poses a potential risk of decompensation in children with mitochondrial disorders. • There is a great diversity in the anaesthetic approaches undertaken in this cohort, and little guidance exists for anaesthetists and other clinicians regarding the optimal anaesthetic agents and perioperative management to provide to patients with mitochondrial disease. What is New: • In this study of 26 patients with genetically confirmed mitochondrial disease who underwent 65 GAs, no relationship between choice of anaesthetic agent and subsequent perioperative complication was observed • It is likely that individual optimisation on a case-by-case basis is more important overall than choice of any one particular technique.

Drug induced mitochondrial dysfunction: Mechanisms and adverse clinical consequences

Several commonly used medications impair mitochondrial function resulting in adverse effects or toxicities. Drug induced mitochondrial dysfunction may be a consequence of increased production of reactive oxygen species, altered mitochondrial permeability transition, impaired mitochondrial respiration, mitochondrial DNA damage or inhibition of beta-oxidation of fatty acids. The clinical manifestation depends on the specific drug and its effect on mitochondria. Given the ubiquitous presence of mitochondria and its central role in cellular metabolism, drug-mitochondrial interactions may manifest clinically as hepatotoxicity, enteropathy, myelosuppression, lipodystrophy syndrome or neuropsychiatric adverse effects, to name a few. The current review focuses on specific drug groups which adversely affect mitochondria, the mechanisms involved and the clinical consequences based on the data available from experimental and clinical studies. Knowledge of these adverse drug-mitochondrial interactions may help the clinicians foresee potential issues in individual patients, prevent adverse drug reactions or alter drug regimens to enhance patient safety.

Isoflurane Preconditioning Induces Neuroprotection by Up-Regulation of TREK1 in a Rat Model of Spinal Cord Ischemic Injury

This study aimed to explore the neuroprotection and mechanism of isoflurane on rats with spinal cord ischemic injury. Total 40 adult male Sprague-Dawley rats were divided into the four groups (n=10). Group A was sham-operation group; group B was ischemia group; group C was isoflurane preconditioning group; group D was isoflurane preconditioning followed by ischemia treatment group. Then the expressions of TWIK-related K⁺ channel 1 (TREK1) in the four groups were detected by immunofluorescent assay, real time-polymerase chain reactions (RT-PCR) and western blot. The primary neurons of rats were isolated and cultured under normal and hypoxic conditions. Besides, the neurons under two conditions were transfected with green fluorescent protein (GFP)-TREK1 and lentivirual to overexpress and silence TREK1. Additionally, the neurons were treated with isoflurane or not. Then caspase-3 activity and cell cycle of neurons under normal and hypoxic conditions were detected. Furthermore, nicotinamide adenine dinucleotide hydrate (NADH) was detected using NAD+/NADH quantification colorimetric kit. Results showed that the mRNA and protein expressions of TREK1 increased significantly in group C and D. In neurons, when TREK1 silenced, isoflurane treatment improved the caspase-3 activity. In hypoxic condition, the caspase-3 activity and sub-G1 cell percentage significantly increased, however, when TREK1 overexpressed the caspase-3 activity and sub-G1 cell percentage decreased significantly. Furthermore, both isoflurane treatment and overexpression of TREK1 significantly decreased NADH. In conclusion, isoflurane-induced neuroprotection in spinal cord ischemic injury may be associated with the up-regulation of TREK1.