Developmental exposure to the Fox River PCB mixture modulates behavior in juvenile mice

Developmental exposures to PCBs are implicated in the etiology of neurodevelopmental disorders (NDDs). This observation is concerning given the continued presence of PCBs in the human environment and the increasing incidence of NDDs. Previous studies reported that developmental exposure to legacy commercial PCB mixtures (Aroclors) or single PCB congeners found in Aroclors caused NDD-relevant behavioral phenotypes in animal models. However, the PCB congener profile in contemporary human samples is dissimilar to that of the legacy Aroclors, raising the question of whether human-relevant PCB mixtures similarly interfere with normal brain development. To address this question, we assessed the developmental neurotoxicity of the Fox River Mixture (FRM), which was designed to mimic the congener profile identified in fish from the PCB-contaminated Fox River that constitute a primary protein source in the diet of surrounding communities. Adult female C57BL/6 J mouse dams (8-10 weeks old) were exposed to vehicle (peanut oil) or FRM at 0.1, 1.0, or 6.0 mg/kg/d in their diet throughout gestation and lactation, and neurodevelopmental outcomes were assessed in their pups. Ultrasonic vocalizations (USVs) and measures of general development were quantified at postnatal day (P) 7, while performance in the spontaneous alternation task and the 3-chambered social approach/social novelty task was assessed on P35. Triiodothyronine (T3) and thyroxine (T4) were quantified in serum collected from the dams when pups were weaned and from pups on P28 and P35. Developmental exposure to FRM did not alter pup weight or body temperature on P7, but USVs were significantly decreased in litters exposed to FRM at 0.1 or 6.0 mg/kg/d in the maternal diet. FRM also impaired male and female pups' performance in the social novelty task. Compared to sex-matched vehicles, significantly decreased social novelty was observed in male and female pups in the 0.1 and 6.0 mg/kg/d dose groups. FRM did not alter performance in the spontaneous alternation or social approach tasks. FRM increased serum T3 levels but decreased serum T4 levels in P28 male pups in the 1.0 and 6.0 mg/kg/d dose groups. In P35 female pups and dams, serum T3 levels decreased in the 6.0 mg/kg/d dose group while T4 levels were not altered. Collectively, these findings suggest that FRM interferes with the development of social communication and social novelty, but not memory, supporting the hypothesis that contemporary PCB exposures pose a risk to the developing brain. FRM had sex, age, and dose-dependent effects on serum thyroid hormone levels that overlapped but did not perfectly align with the FRM effects on behavioral outcomes. These observations suggest that changes in thyroid hormone levels are not likely the major factor underlying the behavioral deficits observed in FRM-exposed animals.

Ketone flux through BDH1 supports metabolic remodeling of skeletal and cardiac muscles in response to intermittent time-restricted feeding

Time-restricted feeding (TRF) has gained attention as a dietary regimen that promotes metabolic health. This study questioned if the health benefits of an intermittent TRF (iTRF) schedule require ketone flux specifically in skeletal and cardiac muscles. Notably, we found that the ketolytic enzyme beta-hydroxybutyrate dehydrogenase 1 (BDH1) is uniquely enriched in isolated mitochondria derived from heart and red/oxidative skeletal muscles, which also have high capacity for fatty acid oxidation (FAO). Using mice with BDH1 deficiency in striated muscles, we discover that this enzyme optimizes FAO efficiency and exercise tolerance during acute fasting. Additionally, iTRF leads to robust molecular remodeling of muscle tissues, and muscle BDH1 flux does indeed play an essential role in conferring the full adaptive benefits of this regimen, including increased lean mass, mitochondrial hormesis, and metabolic rerouting of pyruvate. In sum, ketone flux enhances mitochondrial bioenergetics and supports iTRF-induced remodeling of skeletal muscle and heart.

Repeat subconcussion in the adult rat gives rise to behavioral deficits similar to a single concussion but different depending upon sex

Although concussions are a popular focus of neurotrauma research, subconcussions occur with higher frequency but are less well-studied. A subconcussion is an impact to the head that does not result in immediately diagnosable concussion but can result in later neurological consequences. Repeat subconcussions can produce behavioral impairments and neuropathology that is similar to or worse than those seen following a single concussion. The current study modified a previously established closed head injury model of concussion to create a subconcussion model and examines sex differences in behavioral responses to repeated subconcussion in the adult rat. Rats received a single concussion, single or repeat subconcussions, or no impact and behavior was monitored from 2 h through 31 days post-injury. A single concussion or repeat subconcussion resulted in deficits in locomotion, righting reflexes, and recognition memory. The degree of deficit induced by repeat subconcussions were either similar (righting reflexes) or greater/more persistent (locomotor deficits and recognition memory) than that of a concussion. Single subconcussion resulted in acute deficits that were mild and limited to righting reflexes and locomotion. Sex differences were observed in responses to repeat subconcussion: females showed greater deficits in righting reflexes, locomotion, and vestibular function, while males showed greater alterations in anxiety and depressive-like behavior. This study established a model of subconcussive impact where a single subconcussive impact resulted in minimal behavioral deficits but repeat subconcussions resulted in deficits similar to or worse than a single concussion. Our data also suggest sex differences in behavioral responses to both concussive and subconcussive impacts.

Proteomics and phosphoproteomics datasets of a muscle-specific STIM1 loss-of-function mouse model

STIM1 is an ER/SR transmembrane protein that interacts with ORAI1 to activate store operated Ca2+ entry (SOCE) upon ER/SR depletion of calcium. Normally highly expressed in skeletal muscle, STIM1 deficiency causes significant changes to mitochondrial ultrastructure that do not occur with loss of ORAI1 or other components of SOCE. The datasets in this article are from large-scale proteomics and phosphoproteomics experiments in an inducible mouse model of skeletal muscle-specific STIM1 knock out (KO). These data reveal statistically significant changes in the relative abundance of specific proteins and sites of protein phosphorylation in STIM1 KO gastrocnemius. Protein samples from five biological replicates of each condition (+/- STIM1) were enzymatically digested, the resulting peptides labeled with tandem mass tag (TMT) reagents, mixed, and fractionated. Phosphopeptides were enriched and a small amount of each input retained for protein abundance analysis. All phosphopeptide and input fractions were analyzed by nano LC-MS/MS on a Q Exactive Plus Orbitrap mass spectrometer, searched with Proteome Discoverer software, and processed with in-house R-scripts for data normalization and statistical analysis. Article published in Molecular Metabolism [1].

Disruption of STIM1-mediated Ca2+ sensing and energy metabolism in adult skeletal muscle compromises exercise tolerance, proteostasis, and lean mass

OBJECTIVE

Stromal interaction molecule 1 (STIM1) is a single-pass transmembrane endoplasmic/sarcoplasmic reticulum (E/SR) protein recognized for its role in a store operated Ca2+ entry (SOCE), an ancient and ubiquitous signaling pathway. Whereas STIM1 is known to be indispensable during development, its biological and metabolic functions in mature muscles remain unclear.

METHODS

Conditional and tamoxifen inducible muscle STIM1 knock-out mouse models were coupled with multi-omics tools and comprehensive physiology to understand the role of STIM1 in regulating SOCE, mitochondrial quality and bioenergetics, and whole-body energy homeostasis.

RESULTS

This study shows that STIM1 is abundant in adult skeletal muscle, upregulated by exercise, and is present at SR-mitochondria interfaces. Inducible tissue-specific deletion of STIM1 (iSTIM1 KO) in adult muscle led to diminished lean mass, reduced exercise capacity, and perturbed fuel selection in the settings of energetic stress, without affecting whole-body glucose tolerance. Proteomics and phospho-proteomics analyses of iSTIM1 KO muscles revealed molecular signatures of low-grade E/SR stress and broad activation of processes and signaling networks involved in proteostasis.

CONCLUSION

These results show that STIM1 regulates cellular and mitochondrial Ca2+ dynamics, energy metabolism and proteostasis in adult skeletal muscles. Furthermore, these findings provide insight into the pathophysiology of muscle diseases linked to disturbances in STIM1-dependent Ca2+ handling.

Ulk1, Not Ulk2, Is Required for Exercise Training-Induced Improvement of Insulin Response in Skeletal Muscle

Unc51 like autophagy activating kinase 1 (Ulk1), the primary autophagy regulator, has been linked to metabolic adaptation in skeletal muscle to exercise training. Here we compared the roles of Ulk1 and homologous Ulk2 in skeletal muscle insulin action following exercise training to gain more mechanistic insights. Inducible, skeletal muscle-specific Ulk1 knock-out (Ulk1-iMKO) mice and global Ulk2 knock-out (Ulk2^–/–) mice were subjected to voluntary wheel running for 6 weeks followed by assessment of exercise capacity, glucose tolerance, and insulin signaling in skeletal muscle after a bolus injection of insulin. Both Ulk1-iMKO and Ulk2^–/– mice had improved endurance exercise capacity post-exercise. Ulk1-iMKO did not improve glucose clearance during glucose tolerance test, while Ulk2^–/– had only marginal improvement. However, exercise training-induced improvement of insulin action in skeletal muscle, indicated by Akt-S473 phosphorylation, was only impaired in Ulk1-iMKO. These data suggest that Ulk1, but not Ulk2, is required for exercise training-induced improvement of insulin action in skeletal muscle, implicating crosstalk between catabolic and anabolic signaling as integral to metabolic adaptation to energetic stress.

Healthcare access for asylum seekers and refugees in England: a mixed methods study exploring service users' and health care professionals' awareness

BACKGROUND

With the aim of decreasing immigration, the British government extended charging for healthcare in England for certain migrants in 2017. There is concern these policies amplify the barriers to healthcare already faced by asylum seekers and refugees (ASRs). Awareness has been shown to be fundamental to access. This article jointly explores (i) health care professionals' (HCPs) awareness of migrants' eligibility for healthcare, and (ii) ASRs' awareness of health services.

METHODS

Mixed methods were used. Quantitative survey data explored HCPs' awareness of migrants' eligibility to healthcare after the extension of charging regulations. Qualitative data from semi-structured interviews with ASRs were analyzed thematically using Saurman's domains of awareness as a framework.

RESULTS

In total 514 HCPs responded to the survey. Significant gaps in HCPs' awareness of definitions, entitlements and charging regulations were identified. 80% of HCP respondents were not confident defining the immigration categories upon which eligibility for care rests. Only a small minority (6%) reported both awareness and understanding of the charging regulations. In parallel, the 18 ASRs interviewed had poor awareness of their eligibility for free National Health Service care and suitability for particular services. This was compounded by language difficulties, social isolation, frequent asylum dispersal accommodation moves, and poverty.

CONCLUSION

This study identifies significant confusion amongst both HCP and ASR concerning eligibility and healthcare access. The consequent negative impact on health is concerning given the contemporary political climate, where eligibility for healthcare depends on immigration status.

Seedling recruitment under isolated trees in a tea plantation provides a template for forest restoration in eastern Africa

Natural regeneration is less expensive than tree planting, but determining what species will arrive and establish to serve as templates for tropical forest restoration remains poorly investigated in eastern Africa. This study summarises seedling recruitment under 29 isolated legacy trees (14 trees comprised of three exotic species and 15 trees comprised of seven native species) in tea plantations in the East Usambara Mountains, Tanzania. Among the findings were that pioneer recruits were very abundant whereas non-pioneers were disproportionately fewer. Importantly, 98% of all recruits were animal-dispersed. The size of legacy trees, driven mostly by the exotic Grevillea robusta, and to some extent, the native Milicia excelsa, explained abundance of recruits. The distribution of bird-dispersed recruits suggested that some bird species use all types of legacy trees equally in this fragmented landscape. In contrast, the distribution of bat-dispersed recruits provided strong evidence that seedling composition differed under native versus exotic legacy trees likely due to fruit bats showing more preference for native legacy trees. Native, as compared to exotic legacy trees, had almost two times more non-pioneer recruits, with Ficus and Milicia excelsa driving this trend. Implications of our findings regarding restoration in the tropics are numerous for the movement of native animal-dispersed tree species in fragmented and disturbed tropical forests surrounded by farmland. Isolated native trees that bear fleshy fruits can attract more frugivores, resulting not only in high recruitment under them, but depending on the dispersal mode of the legacy trees, also different suites of recruited species. When selecting tree species for plantings, to maximize visitation by different dispersal agents and to enhance seedling recruit diversity, bat-dispersed Milicia excelsa and Ficus species are recommended.

Descriptive analysis of the context of child sexual abuse reportedly perpetrated by female suspects: Insights from Saint Mary's Sexual Assault Referral Centre

BACKGROUND

Determining the prevalence and characteristics of female-perpetrated child sexual abuse (CSA) is fraught with difficultly. There is a historical lack of empirical research and a discrepancy between the number of cases that reach the attention of the authorities and its suspected prevalence in society. It is also noted that for a myriad of reasons many CSA reports do not progress through the criminal justice process so many remain as allegations rather than proven or disproven crimes.

OBJECTIVES

The study set out to answer the research questions: 'What are the characteristics and context of CSA reportedly perpetrated by females, and what are the similarities and differences in the context of alleged CSA committed by male and female suspects?'

PARTICIPANTS AND SETTING

This study presents data from all service users aged 0-17 years (n = 986) that attended Saint Mary's Sexual Assault Referral Centre (SARC) for a forensic medical examination over a three-year period.

METHODS

Data collection was performed retrospectively from the paper case files recorded at the time of attendance. Due to the small number of female suspects, analysis was restricted to frequency calculations.

RESULTS

Results show females were reportedly involved in the alleged abuse of less than 4% of the children attending SARC. Females appeared more likely to be associated with the alleged abuse of younger children and abuse occurring within the child's home.

CONCLUSIONS

This study's most arresting feature is that despite the large number of CSA cases examined, it was rare to have a female suspect. This study demonstrates how much is still unknown about female-perpetrated CSA.

Identification and activity of monoamine oxidase in the orb-weaving spider Larinioides cornutus

Monoamine oxidase (MAO) is a mitochondrial membrane-bound enzyme that catalyzes the oxidative deamination of monoamines in a wide array of organisms. While the enzyme monoamine oxidase has been studied extensively in its role in moderating behavior in mammals, there is a paucity of research investigating this role in invertebrates, where the latter utilizes this enzyme in a major pathway to degrade monoamines. There is especially a dismal lack of information on how MAO influences activity in invertebrates, particularly in account of the circadian cycle. Previous studies revealed MAO degrades serotonin and norepinephrine in arachnids, but did not investigate other critically important compounds like octopamine. Larinioides cornutus is a species of orb-weaving spider that exhibits diel fluctuations in behavior, specifically levels of aggression. The monoamines octopamine and serotonin have been shown to influence aggressive behaviors in L. cornutus, thus this species was used to investigate if MAO is a potential site of regulation throughout the day. Not only did gene expression of MAO orthologs and MAO activity fluctuate at different times of day, but the enzymatic activity was substrate-specific producing a higher level of degradation of octopamine as compared to serotonin in vitro. This study further supports evidence that MAO has an active role in monoamine inactivation in invertebrates and provides a first look at how MAO ultimately may be regulating behavior in an invertebrate.

Search for Electron Antineutrino Appearance in a Long-Baseline Muon Antineutrino Beam

Electron antineutrino appearance is measured by the T2K experiment in an accelerator-produced antineutrino beam, using additional neutrino beam operation to constrain parameters of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix. T2K observes 15 candidate electron antineutrino events with a background expectation of 9.3 events. Including information from the kinematic distribution of observed events, the hypothesis of no electron antineutrino appearance is disfavored with a significance of 2.40σ and no discrepancy between data and PMNS predictions is found. A complementary analysis that introduces an additional free parameter which allows non-PMNS values of electron neutrino and antineutrino appearance also finds no discrepancy between data and PMNS predictions.

A novel voluntary weightlifting model in mice promotes muscle adaptation and insulin sensitivity with simultaneous enhancement of autophagy and mTOR pathway

Our understanding of the molecular mechanisms underlying adaptations to resistance exercise remains elusive despite the significant biological and clinical relevance. We developed a novel voluntary mouse weightlifting model, which elicits squat-like activities against adjustable load during feeding, to investigate the resistance exercise-induced contractile and metabolic adaptations. RNAseq analysis revealed that a single bout of weightlifting induced significant transcriptome responses of genes that function in posttranslational modification, metabolism, and muscle differentiation in recruited skeletal muscles, which were confirmed by increased expression of fibroblast growth factor-inducible 14 (Fn14), Down syndrome critical region 1 (Dscr1) and Nuclear receptor subfamily 4, group A, member 3 (Nr4a3) genes. Long-term (8 weeks) voluntary weightlifting training resulted in significantly increases of muscle mass, protein synthesis (puromycin incorporation in SUnSET assay) and mTOR pathway protein expression (raptor, 4e-bp-1, and p70S6K proteins) along with enhanced muscle power (specific torque and contraction speed), but not endurance capacity, mitochondrial biogenesis, and fiber type transformation. Importantly, weightlifting training profound improved whole-body glucose clearance and skeletal muscle insulin sensitivity along with enhanced autophagy (increased LC3 and LC3-II/I ratio, and decreased p62/Sqstm1). These data suggest that resistance training in mice promotes muscle adaptation and insulin sensitivity with simultaneous enhancement of autophagy and mTOR pathway.

Long-term voluntary running prevents the onset of symptomatic Friedreich's ataxia in mice

The common clinical symptoms of Friedreich's ataxia (FRDA) include ataxia, muscle weakness, type 2 diabetes and heart failure, which are caused by impaired mitochondrial function due to the loss of frataxin (FXN) expression. Endurance exercise is the most powerful intervention for promoting mitochondrial function; however, its impact on FRDA has not been studied. Here we found that mice with genetic knockout and knock-in of the Fxn gene (KIKO mice) developed exercise intolerance, glucose intolerance and moderate cardiac dysfunction at 6 months of age. These abnormalities were associated with impaired mitochondrial respiratory function concurrent with reduced iron regulatory protein 1 (Irp1) expression as well as increased oxidative stress, which were not due to loss of mitochondrial content and antioxidant enzyme expression. Importantly, long-term (4 months) voluntary running in KIKO mice starting at a young age (2 months) completely prevented the functional abnormalities along with restored Irp1 expression, improved mitochondrial function and reduced oxidative stress in skeletal muscle without restoring Fxn expression. We conclude that endurance exercise training prevents symptomatic onset of FRDA in mice associated with improved mitochondrial function and reduced oxidative stress. These preclinical findings may pave the way for clinical studies of the impact of endurance exercise in FRDA patients.

The influence of ecological and life history factors on ectothermic temperature-size responses: Analysis of three Lycaenidae butterflies (Lepidoptera)

Body size has been shown to decrease with increasing temperature in many species, prompting the suggestion that it is a universal ecological response. However, species with complex life cycles, such as holometabolous insects, may have correspondingly complicated temperature-size responses. Recent research suggests that life history and ecological traits may be important for determining the direction and strength of temperature-size responses. Yet, these factors are rarely included in analyses. Here, we aim to determine whether the size of the bivoltine butterfly, Polyommatus bellargus, and the univoltine butterflies, Plebejus argus and Polyommatus coridon, change in response to temperature and whether these responses differ between the sexes, and for P. bellargus, between generations. Forewing length was measured using digital specimens from the Natural History Museum, London (NHM), from one locality in the UK per species. The data were initially compared to annual and seasonal temperature values, without consideration of life history factors. Sex and generation of the individuals and mean monthly temperatures, which cover the growing period for each species, were then included in analyses. When compared to annual or seasonal temperatures only, size was not related to temperature for P. bellargus and P. argus, but there was a negative relationship between size and temperature for P. coridon. When sex, generation, and monthly temperatures were included, male adult size decreased as temperature increased in the early larval stages, and increased as temperature increased during the late larval stages. Results were similar but less consistent for females, while second generation P. bellargus showed no temperature-size response. In P. coridon, size decreased as temperature increased during the pupal stage. These results highlight the importance of including life history factors, sex, and monthly temperature data when studying temperature-size responses for species with complex life cycles.

Comparing Electron Energetics and UV Brightness in Jupiter's Northern Polar Region During Juno Perijove 5

We compare electron and UV observations mapping to the same location in Jupiter's northern polar region, poleward of the main aurora, during Juno perijove 5. Simultaneous peaks in UV brightness and electron energy flux are identified when observations map to the same location at the same time. The downward energy flux during these simultaneous observations was not sufficient to generate the observed UV brightness; the upward energy flux was. We propose that the primary acceleration region is below Juno's altitude, from which the more intense upward electrons originate. For the complete interval, the UV brightness peaked at ~240 kilorayleigh (kR); the downward and upward energy fluxes peaked at 60 and 700 mW/m², respectively. Increased downward energy fluxes are associated with increased contributions from tens of keV electrons. These observations provide evidence that bidirectional electron beams with broad energy distributions can produce tens to hundreds of kilorayleigh polar UV emissions.

Voluntary running protects against neuromuscular dysfunction following hindlimb ischemia-reperfusion in mice

Ischemia-reperfusion (IR) due to temporary restriction of blood flow causes tissue/organ damages under various disease conditions, including stroke, myocardial infarction, trauma, and orthopedic surgery. In the limbs, IR injury to motor nerves and muscle fibers causes reduced mobility and quality of life. Endurance exercise training has been shown to increase tissue resistance to numerous pathological insults. To elucidate the impact of endurance exercise training on IR injury in skeletal muscle, sedentary and exercise-trained mice (5 wk of voluntary running) were subjected to ischemia by unilateral application of a rubber band tourniquet above the femur for 1 h, followed by reperfusion. IR caused significant muscle injury and denervation at neuromuscular junction (NMJ) as early as 3 h after tourniquet release as well as depressed muscle strength and neuromuscular transmission in sedentary mice. Despite similar degrees of muscle atrophy and oxidative stress, exercise-trained mice had significantly reduced muscle injury and denervation at NMJ with improved regeneration and functional recovery following IR. Together, these data suggest that endurance exercise training preserves motor nerve and myofiber structure and function from IR injury and promote functional regeneration. NEW & NOTEWORTHY This work provides the first evidence that preemptive voluntary wheel running reduces neuromuscular dysfunction following ischemia-reperfusion injury in skeletal muscle. These findings may alter clinical practices in which a tourniquet is used to modulate blood flow.

Exercise-induced mitophagy in skeletal muscle occurs in the absence of stabilization of Pink1 on mitochondria

Maintenance of mitochondrial quality is essential for skeletal muscle function and overall health. Exercise training elicits profound adaptations to mitochondria to improve mitochondrial quality in skeletal muscle. We have recently demonstrated that acute exercise promotes removal of damaged/dysfunctional mitochondria via mitophagy in skeletal muscle during recovery through the Ampk-Ulk1 signaling cascade. In this Extra View, we explore whether Pink1 is stabilized on mitochondria following exercise as the signal for mitophagy. We observed no discernable presence of Pink1 in isolated mitochondria from skeletal muscle at any time point following acute exercise, in contrast to clear evidence of stabilization of Pink1 on mitochondria in HeLa cells following treatment with the uncoupler carbonyl cyanide m-chlorophenyl hydrazone (CCCP). Taken together, we conclude that Pink1 is not involved in exercise-induced mitophagy in skeletal muscle.

Search for CP Violation in Neutrino and Antineutrino Oscillations by the T2K Experiment with 2.2×10^{21} Protons on Target

The T2K experiment measures muon neutrino disappearance and electron neutrino appearance in accelerator-produced neutrino and antineutrino beams. With an exposure of 14.7(7.6)×10^{20} protons on target in the neutrino (antineutrino) mode, 89 ν_{e} candidates and seven anti-ν_{e} candidates are observed, while 67.5 and 9.0 are expected for δ_{CP}=0 and normal mass ordering. The obtained 2σ confidence interval for the CP-violating phase, δ_{CP}, does not include the CP-conserving cases (δ_{CP}=0, π). The best-fit values of other parameters are sin^{2}θ_{23}=0.526_{-0.036}^{+0.032} and Δm_{32}^{2}=2.463_{-0.070}^{+0.071}×10^{-3}  eV^{2}/c^{4}.

Mitochondrial protein S-nitrosation protects against ischemia reperfusion-induced denervation at neuromuscular junction in skeletal muscle

Deterioration of neuromuscular junction (NMJ) integrity and function is causal to muscle atrophy and frailty, ultimately hindering quality of life and increasing the risk of death. In particular, NMJ is vulnerable to ischemia reperfusion (IR) injury when blood flow is restricted followed by restoration. However, little is known about the underlying mechanism(s) and hence the lack of effective interventions. New evidence suggests that mitochondrial oxidative stress plays a causal role in IR injury, which can be precluded by enhancing mitochondrial protein S-nitrosation (SNO). To elucidate the role of IR and mitochondrial protein SNO in skeletal muscle, we utilized a clinically relevant model and showed that IR resulted in significant muscle and motor nerve injuries with evidence of elevated muscle creatine kinase in the serum, denervation at NMJ, myofiber degeneration and regeneration, as well as muscle atrophy. Interestingly, we observed that neuromuscular transmission improved prior to muscle recovery, suggesting the importance of the motor nerve in muscle functional recovery. Injection of a mitochondria-targeted S-nitrosation enhancing agent, MitoSNO, into ischemic muscle prior to reperfusion reduced mitochondrial oxidative stress in the motor nerve and NMJ, attenuated denervation at NMJ, and resulted in accelerated functional recovery of the muscle. These findings demonstrate that enhancing mitochondrial protein SNO protects against IR-induced denervation at NMJ in skeletal muscle and accelerates functional regeneration. This could be an efficacious intervention for protecting neuromuscular injury under the condition of IR and other related pathological conditions.

Dynamin-Related Protein 1 Deficiency Promotes Recovery from AKI

The proximal tubule epithelium relies on mitochondrial function for energy, rendering the kidney highly susceptible to ischemic AKI. Dynamin-related protein 1 (DRP1), a mediator of mitochondrial fission, regulates mitochondrial function; however, the cell-specific and temporal role of DRP1 in AKI in vivo is unknown. Using genetic murine models, we found that proximal tubule-specific deletion of Drp1 prevented the renal ischemia-reperfusion-induced kidney injury, inflammation, and programmed cell death observed in wild-type mice and promoted epithelial recovery, which associated with activation of the renoprotective β-hydroxybutyrate signaling pathway. Loss of DRP1 preserved mitochondrial structure and reduced oxidative stress in injured kidneys. Lastly, proximal tubule deletion of DRP1 after ischemia-reperfusion injury attenuated progressive kidney injury and fibrosis. These results implicate DRP1 and mitochondrial dynamics as an important mediator of AKI and progression to fibrosis and suggest that DRP1 may serve as a therapeutic target for AKI.

Conditional MitoTimer reporter mice for assessment of mitochondrial structure, oxidative stress, and mitophagy

Assessment of structural and functional changes of mitochondria is vital for biomedical research as mitochondria are the power plants essential for biological processes and tissue/organ functions. Others and we have developed a novel reporter gene, pMitoTimer, which codes for a redox sensitive mitochondrial targeted protein that switches from green fluorescence protein (GFP) to red fluorescent protein (DsRed) when oxidized. It has been shown in transfected cells, transgenic C. elegans and Drosophila m., as well as somatically transfected adult skeletal muscle that this reporter gene allows quantifiable assessment of mitochondrial structure, oxidative stress, and lysosomal targeting of mitochondria-containing autophagosomes. Here, we generated CAG-CAT-MitoTimer transgenic mice using a transgene containing MitoTimer downstream of LoxP-flanked bacterial chloramphenicol acetyltransferase (CAT) gene with stop codon under the control of the cytomegalovirus (CMV) enhancer fused to the chicken β-actin promoter (CAG). When CAG-CAT-MitoTimer mice were crossbred with various tissue-specific (muscle, adipose tissue, kidney, and pancreatic tumor) or global Cre transgenic mice, the double transgenic offspring showed MitoTimer expression in tissue-specific or global manner. Lastly, we show that hindlimb ischemia-reperfusion caused early, transient increases of mitochondrial oxidative stress, mitochondrial fragmentation and lysosomal targeting of autophagosomes containing mitochondria as well as a later reduction of mitochondrial content in skeletal muscle along with mitochondrial oxidative stress in sciatic nerve. Thus, we have generated conditional MitoTimer mice and provided proof of principle evidence of their utility to simultaneously assess mitochondrial structure, oxidative stress, and mitophagy in vivo in a tissue-specific, controllable fashion.

Ampk phosphorylation of Ulk1 is required for targeting of mitochondria to lysosomes in exercise-induced mitophagy

Mitochondrial health is critical for skeletal muscle function and is improved by exercise training through both mitochondrial biogenesis and removal of damaged/dysfunctional mitochondria via mitophagy. The mechanisms underlying exercise-induced mitophagy have not been fully elucidated. Here, we show that acute treadmill running in mice causes mitochondrial oxidative stress at 3-12 h and mitophagy at 6 h post-exercise in skeletal muscle. These changes were monitored using a novel fluorescent reporter gene, pMitoTimer, that allows assessment of mitochondrial oxidative stress and mitophagy in vivo, and were preceded by increased phosphorylation of AMP activated protein kinase (Ampk) at tyrosine 172 and of unc-51 like autophagy activating kinase 1 (Ulk1) at serine 555. Using mice expressing dominant negative and constitutively active Ampk in skeletal muscle, we demonstrate that Ulk1 activation is dependent on Ampk. Furthermore, exercise-induced metabolic adaptation requires Ulk1. These findings provide direct evidence of exercise-induced mitophagy and demonstrate the importance of Ampk-Ulk1 signaling in skeletal muscle.Exercise is associated with biogenesis and removal of dysfunctional mitochondria. Here the authors use a mitochondrial reporter gene to demonstrate the occurrence of mitophagy following exercise in mice, and show this is dependent on AMPK and ULK1 signaling.