ATF4-dependent increase in mitochondrial-endoplasmic reticulum tethering following OPA1 deletion in skeletal muscle

Mitochondria and endoplasmic reticulum (ER) contact sites (MERCs) are protein- and lipid-enriched hubs that mediate interorganellar communication by contributing to the dynamic transfer of Ca2+, lipid, and other metabolites between these organelles. Defective MERCs are associated with cellular oxidative stress, neurodegenerative disease, and cardiac and skeletal muscle pathology via mechanisms that are poorly understood. We previously demonstrated that skeletal muscle-specific knockdown (KD) of the mitochondrial fusion mediator optic atrophy 1 (OPA1) induced ER stress and correlated with an induction of Mitofusin-2, a known MERC protein. In the present study, we tested the hypothesis that Opa1 downregulation in skeletal muscle cells alters MERC formation by evaluating multiple myocyte systems, including from mice and Drosophila, and in primary myotubes. Our results revealed that OPA1 deficiency induced tighter and more frequent MERCs in concert with a greater abundance of MERC proteins involved in calcium exchange. Additionally, loss of OPA1 increased the expression of activating transcription factor 4 (ATF4), an integrated stress response (ISR) pathway effector. Reducing Atf4 expression prevented the OPA1-loss-induced tightening of MERC structures. OPA1 reduction was associated with decreased mitochondrial and sarcoplasmic reticulum, a specialized form of ER, calcium, which was reversed following ATF4 repression. These data suggest that mitochondrial stress, induced by OPA1 deficiency, regulates skeletal muscle MERC formation in an ATF4-dependent manner.

Cardiac MAO-A inhibition protects against catecholamine-induced ventricular arrhythmias via enhanced diastolic calcium control

AIMS

A mechanistic link between depression and risk of arrhythmias could be attributed to altered catecholamine metabolism in the heart. Monoamine oxidase-A (MAO-A), a key enzyme involved in catecholamine metabolism and longstanding antidepressant target, is highly expressed in the myocardium. The present study aimed to elucidate the functional significance and underlying mechanisms of cardiac MAO-A in arrhythmogenesis.

METHODS AND RESULTS

Analysis of TriNetX database revealed that depressed patients treated with MAO inhibitors had a lower risk of arrhythmias compared to those treated with selective serotonin reuptake inhibitors. This effect was phenocopied in mice with cardiomyocyte-specific MAO-A deficiency (cMAO-Adef), which showed a significant reduction in both incidence and duration of catecholamine stress-induced ventricular tachyarrhythmias (VT) compared to wildtype mice. Additionally, cMAO-Adef cardiomyocytes exhibited altered Ca2+ handling under catecholamine stimulation, with increased diastolic Ca2+ reuptake, reduced diastolic Ca2+ leak, and diminished systolic Ca2+ release. Mechanistically, cMAO-Adef hearts had reduced catecholamine levels under sympathetic stress, along with reduced levels of reactive oxygen species (ROS) and protein carbonylation, leading to decreased oxidation of Type II PKA and CaMKII. These changes potentiated phospholamban (PLB) phosphorylation thereby enhancing diastolic Ca2+ reuptake while reducing ryanodine receptor 2 (RyR2) phosphorylation to decrease diastolic Ca2+ leak. Consequently, cMAO-Adef hearts exhibited lower diastolic Ca2+ levels and fewer arrhythmogenic Ca2+ waves during sympathetic overstimulation.

CONCLUSIONS

Cardiac MAO-A inhibition exerts an anti-arrhythmic effect by enhancing diastolic Ca2+ handling under catecholamine stress.

TRANSLATIONAL PERSPECTIVE

This study implicates catecholamine metabolism in arrhythmogenesis and reveals that monoamine oxidase is linked to Ca2+ regulation in the heart. It further illustrates therapeutic potential of cardiac MAO-A inhibition as a dual-purpose drug target to simultaneously manage depression and lower arrhythmia risk in affected patients.

Correction: Garza-Lopez et al. Protocols for Generating Surfaces and Measuring 3D Organelle Morphology Using Amira. Cells 2022, 11, 65

In the original publication [...].

Protocols for Generating Surfaces and Measuring 3D Organelle Morphology Using Amira

High-resolution 3D images of organelles are of paramount importance in cellular biology. Although light microscopy and transmission electron microscopy (TEM) have provided the standard for imaging cellular structures, they cannot provide 3D images. However, recent technological advances such as serial block-face scanning electron microscopy (SBF-SEM) and focused ion beam scanning electron microscopy (FIB-SEM) provide the tools to create 3D images for the ultrastructural analysis of organelles. Here, we describe a standardized protocol using the visualization software, Amira, to quantify organelle morphologies in 3D, thereby providing accurate and reproducible measurements of these cellular substructures. We demonstrate applications of SBF-SEM and Amira to quantify mitochondria and endoplasmic reticulum (ER) structures.

Abstract 883: Nadph Oxidase Nox1-dependent Endocytosis and Activation is Regulated by a Conserved Trafficking Motif in Vascular Smooth Muscle Cells

We previously reported that TNF-α-mediated Nox1-dependent redox signaling of vascular smooth muscle cells (SMC) requires endocytosis. However, the molecular mechanisms regulating Nox1 endocytosis are not known. The goal of this study was to identify motifs in the Nox1 protein sequence necessary for Nox1 endocytosis and reactive oxygen species (ROS) generation. Immunoprecipitation of Nox1, after treatment of SMC with TNF-α, showed it to be associated with Early Endosome Antigen 1 (EEA1) and Ras-related protein Rab-5A (Rab5), markers of early endosomes. Analysis of the Nox1 protein sequence identified two conserved putative trafficking motifs, Leucine-Leucine (LL), and Valine-Leucine-Valine (VLV). Biotinylation of SMC plasma membrane proteins under non-stimulated conditions suggested increased levels of Nox1 VLV mutant in the plasma membrane, whereas levels of Nox1 LL mutant where comparable to wildtype (WT) Nox1. Furthermore, cells expressing the VLV mutant showed impaired endocytosis of Nox1 following TNF-α as compared to cells expressing WT Nox1 or the LL mutant. SMC were treated with TNF-α in the presence of Oxyburst, a non-cell permeable redox-sensitive fluorophore whose internalization requires endocytosis. Cells expressing WT or Nox1 LL, but not Nox1 VLV, exhibited punctate intracellular fluorescence, indicating endosomal ROS production. Next, we examined whether the VLV motif is required for Nox1-dependent SMC migration. Transwell migration of SMC was similar in cells expressing WT or the LL Nox1 mutant; however, migration was decreased in cells expressing the Nox1 VLV mutant. Finally, we identified proteins whose association with Nox1 during endocytosis were dependent on the VLV motif. Nox1 WT and VLV mutant were cloned in frame with the biotin ligase BioID2. Following stimulation with TNF-α, Western blotting for anti-biotin, and subsequent mass spectrometry, identified several proteins directly associated with WT Nox1 but not Nox1 VLV. These findings suggest that endosomal compartmentalization of Nox1 and its redox signaling is regulated by a specific motif on Nox1 that is necessary for protein interactions. Targeted inhibition of Nox1 activation is a novel therapeutic strategy in the prevention of vascular disease.

NeuroThera® Efficacy and Safety Trial-3 (NEST-3): a double-blind, randomized, sham-controlled, parallel group, multicenter, pivotal study to assess the safety and efficacy of transcranial laser therapy with the NeuroThera® Laser System for the treatment of acute ischemic stroke within 24 h of stroke onset

RATIONALE

Transcranial laser therapy is undergoing clinical trials in patients with acute ischemic stroke. The NeuroThera® Efficacy and Safety Trial-1 was strongly positive for 90-day functional benefit with transcranial laser therapy, and post hoc analyses of the subsequent NeuroThera® Efficacy and Safety Trial-2 trial suggested a meaningful beneficial effect in patients with moderate to moderately severe ischemic stroke within 24 h of onset. These served as the basis for the NeuroThera® Efficacy and Safety Trial-3 randomized controlled trial.

AIM

The purpose of this pivotal study was to demonstrate safety and efficacy of transcranial laser therapy with the NeuroThera® Laser System in the treatment of subjects diagnosed with acute ischemic stroke.

DESIGN

NeuroThera® Efficacy and Safety Trial-3 is a double-blind, randomized, sham-controlled, parallel group, multicenter, pivotal study that will enroll 1000 subjects at up to 50 sites. All subjects will receive standard medical management based on the American Stroke Association and European Stroke Organization Guidelines. In addition to standard medical management, both groups will undergo the transcranial laser therapy procedure between 4·5 and 24 h of stroke onset. The study population will be randomized into two arms: the sham control group will receive a sham transcranial laser therapy procedure and the transcranial laser therapy group will receive an active transcranial laser therapy procedure. The randomization ratio will be 1:1 and will be stratified to ensure a balanced subject distribution between study arms.

STUDY OUTCOMES

The primary efficacy end point is disability at 90 days (or the last rating), as assessed on the modified Rankin Scale, dichotomized as a success (a score of 0-2) or a failure (a score of 3 to 6).

Phosphorylation of Nox1 regulates association with NoxA1 activation domain

RATIONALE

Activation of Nox1 initiates redox-dependent signaling events crucial in the pathogenesis of vascular disease. Selective targeting of Nox1 is an attractive potential therapy, but requires a better understanding of the molecular modifications controlling its activation.

OBJECTIVE

To determine whether posttranslational modifications of Nox1 regulate its activity in vascular cells.

METHODS AND RESULTS

We first found evidence that Nox1 is phosphorylated in multiple models of vascular disease. Next, studies using mass spectroscopy and a pharmacological inhibitor demonstrated that protein kinase C-beta1 mediates phosphorylation of Nox1 in response to tumor necrosis factor-α. siRNA-mediated silencing of protein kinase C-beta1 abolished tumor necrosis factor-α-mediated reactive oxygen species production and vascular smooth muscle cell migration. Site-directed mutagenesis and isothermal titration calorimetry indicated that protein kinase C-beta1 phosphorylates Nox1 at threonine 429. Moreover, Nox1 threonine 429 phosphorylation facilitated the association of Nox1 with the NoxA1 activation domain and was necessary for NADPH oxidase complex assembly, reactive oxygen species production, and vascular smooth muscle cell migration.

CONCLUSIONS

We conclude that protein kinase C-beta1 phosphorylation of threonine 429 regulates activation of Nox1 NADPH oxidase.

Nox1 NADPH oxidase is necessary for late but not early myocardial ischaemic preconditioning

AIMS

Ischaemic preconditioning (IPC) is an adaptive mechanism that renders the myocardium resistant to injury from subsequent hypoxia. Although reactive oxygen species (ROS) contribute to both the early and late phases of IPC, their enzymatic source and associated signalling events have not yet been understood completely. Our objective was to investigate the role of the Nox1 NADPH oxidase in cardioprotection provided by IPC.

METHODS AND RESULTS

Wild-type (WT) and Nox1-deficient mice were treated with three cycles of brief coronary occlusion and reperfusion, followed by prolonged occlusion either immediately (early IPC) or after 24 h (late IPC). Nox1 deficiency had no impact on the cardioprotection afforded by early IPC. In contrast, deficiency of Nox1 during late IPC resulted in a larger infarct size, cardiac remodelling, and increased myocardial apoptosis compared with WT hearts. Furthermore, expression of Nox1 in WT hearts increased in response to late IPC. Deficiency of Nox1 abrogated late IPC-mediated activation of cardiac nuclear factor-κB (NF-κB) and induction of tumour necrosis factor-α (TNF-α) in the heart and circulation. Finally, knockdown of Nox1 in cultured cardiomyocytes prevented TNF-α induction of NF-κB and the protective effect of IPC on hypoxia-induced apoptosis.

CONCLUSIONS

Our data identify a critical role for Nox1 in late IPC and define a previously unrecognized link between TNF-α and NF-κB in mediating tolerance to myocardial injury. These findings have clinical significance considering the emergence of Nox1 inhibitors for the treatment of cardiovascular disease.

Inhibition of NADPH oxidase by apocynin attenuates progression of atherosclerosis

Of the multiple sources of reactive oxygen species (ROS) in the blood vessel, NADPH oxidases are the primary source. Whereas several studies have implicated NADPH oxidases in the initiation of atherosclerosis, their roles in disease progression are incompletely understood. Our objective was to determine the potential clinical relevance of inhibiting NADPH oxidase in established atherosclerosis. Using a hypercholesteremic murine model of atherosclerosis (ApoE^−/−/LDLR^−/− (AS) mice on normal chow diet), we first established a time-dependent relationship between superoxide levels and lesion size in AS mice. Next, we identified NADPH oxidase as the primary source of ROS in atherosclerotic lesions. Treatment of aortic segments from AS mice with apocynin, which interferes with NADPH oxidase activation in part by preventing translocation of the subunit p47^phox, significantly reduced superoxide levels. Moreover, addition of apocynin to the drinking water of AS mice produced a decrease in lesion size as compared to untreated AS mice, with the effect most pronounced in the thoracoabdominal aorta but absent from the aortic arch. Granulocyte function in AS+apocynin mice was suppressed, confirming efficacy of apocynin treatment. We conclude that apocynin attenuates the progression of atherosclerosis in hypercholesterolemic mice, potentially by its ability to inhibit generation of superoxide by NADPH oxidase.

NeuroThera® Efficacy and Safety Trial-3 (NEST-3): a double-blind, randomized, sham-controlled, parallel group, multicenter, pivotal study to assess the safety and efficacy of transcranial laser therapy with the NeuroThera® Laser System for the treatment of acute ischemic stroke within 24 h of stroke onset

RATIONALE

Transcranial laser therapy is undergoing clinical trials in patients with acute ischemic stroke. The NeuroThera® Efficacy and Safety Trial-1 was strongly positive for 90-day functional benefit with transcranial laser therapy, and post hoc analyses of the subsequent NeuroThera® Efficacy and Safety Trial-2 trial suggested a meaningful beneficial effect in patients with moderate to moderately severe ischemic stroke within 24 h of onset. These served as the basis for the NeuroThera® Efficacy and Safety Trial-3 randomized controlled trial.

AIM

The purpose of this pivotal study was to demonstrate safety and efficacy of transcranial laser therapy with the NeuroThera® Laser System in the treatment of subjects diagnosed with acute ischemic stroke.

DESIGN

NeuroThera® Efficacy and Safety Trial-3 is a double-blind, randomized, sham-controlled, parallel group, multicenter, pivotal study that will enroll 1000 subjects at up to 50 sites. All subjects will receive standard medical management based on the American Stroke Association and European Stroke Organization Guidelines. In addition to standard medical management, both groups will undergo the transcranial laser therapy procedure between 4·5 and 24 h of stroke onset. The study population will be randomized into two arms: the sham control group will receive a sham transcranial laser therapy procedure and the transcranial laser therapy group will receive an active transcranial laser therapy procedure. The randomization ratio will be 1:1 and will be stratified to ensure a balanced subject distribution between study arms.

STUDY OUTCOMES

The primary efficacy end point is disability at 90 days (or the last rating), as assessed on the modified Rankin Scale, dichotomized as a success (a score of 0-2) or a failure (a score of 3 to 6).

Ga-As (808 nm) laser irradiation enhances ATP production in human neuronal cells in culture

OBJECTIVE

The aim of the present study was to investigate whether Ga-As laser irradiation can enhance adenosine triphosphate (ATP) production in normal human neural progenitor (NHNP) cells in culture.

METHODS

NHNP were grown in tissue culture and were treated by Ga-As laser (808 nm, 50 mW/cm(2), 0.05 J/cm(2)), and ATP was determined at 10 min after laser application.

RESULTS

The quantity of ATP in laser-treated cells was 7513 +/- 970 units, which was significantly higher (p < 0.05) than the non-treated cells, which comprised 3808 +/- 539 ATP units.

CONCLUSION

Laser application to NHNP cells significantly increases ATP production in these cells. These findings may explain the beneficial effects of low-level laser therapy (LLLT) in stroked rats. Tissue culture of NHNP cells might offer a good model to study the mechanisms associated with promotion of ATP production in the nervous system by LLLT.

As young as you feel: age identification among the elderly

1. Understanding and integrating an individual's perceptions about age and health status is fundamental to making accurate assessments and implementing interventions that are personally acceptable and clinically appropriate. 2. The concept of chronological age has limited validity for the explanation of behavior because it wrongly assumes homogeneity in individual lifestyles among age cohorts. 3. Older adults tend to perceive themselves as mentally and physically younger than their chronological age. 4. Nurses who interact with individuals in a manner based solely on their chronological age may exhibit disrespect and underestimate the potential for the client's involvement in self-care activities.

A comparison of diazepam and phenoperidine in premedication for upper gastrointestinal endoscopy: a randomized double blind controlled study

A variety of agents are used as premedication for upper gastrointestinal endoscopy (U.G.E.). To our knowledge, no double blind studies have been performed to compare their value. In this study phenoperidine (2 mg i.v.) was compared with diazepam (t mg i.v.) in 200 consecutive patients undergoing elective U.G.E. The study was randomized and double blind in regard to both endoscopists and patients. All patients were given atropine (0.4 mg i.v.) and a throat spray with 2% amethocaine. Patients who needed supplemental medication were given diazepam and excluded from final analysis. A graded questionnaire was recorded by endoscopists and patients after U.G.E., and a further anonymous questionnaire was returned by patients four days later. Statistical analysis revealed that phenoperidine was superior at facilitating intubation and providing more relaxation as judged by the endoscopist. Patient questionnaires, four days after U.G.E., indicated less distress during intubation and examination with phenoperidine. Nausea, vomiting, amnesia and phlebitis were uncommon after either phenoperidine or diazepam.