bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of myocardial infarction with or without subsequent reperfusion on respiratory function of mitochondria in rat heart
Authors: Vega‐Lugo Jesus A. , Parodi‐Rullán Rebecca M. , Soto‐Prado Jadira , Chapa‐Dubocq Xavier , Javadov Sabzali 
Published: November 2023

BackgroundCardiovascular diseases are the leading cause of mortality and morbidity worldwide and coronary heart diseases, particularly myocardial infarction (MI) is the most common heart disease. Cardiac mitochondria play a major role in cell functioning, intracellular Ca2+ regulation, ATP production, and cell death. During MI, the reduction or loss of blood flow induces mitochondrial dysfunction and initiates cell death. Particularly, mitochondria‐mediated cell death during MI is mediated by opening of the mitochondrial permeability transition pores (PTP) in the inner mitochondrial membrane. mPTP opening accompanied by matrix swelling causes ROS production, loss of the membrane potential and ATP depletion leading to cardiac dysfunction. Therefore, PTP inhibition is broadly accepted as a promising therapeutic target for MI. Here we assess the effect of mPTP inhibitor, sanglifehrin A (SfA) on mitochondrial function of the heart during MI with no reperfusion or with subsequent reperfusion.MethodsMI was induced in female rats (BW=200–250g) by coronary artery ligation (CAL) for 30 min without (permanent ligation) or with subsequent reperfusion for 2 and 28 days. Experiments were conducted in the following 6 groups: i) Sham (S, no MI, n=6 and n=11 for 2 and 28 days, respectively); ii) SS (Sham+SfA, n=5 and n=11 for 2 and 28 days, respectively); iii) MI (no reperfusion, n=4 and n=5 for 2 and 28 days, respectively); iv) MI+SfA (n=4 and n=6 for 2 and 28 days, respectively); v) MI+R (MI+reperfusion, n=4 and n=5 for 2 and 28 days, respectively); and vi) MI+RS (MI+reperfusion+SfA, n=6 and n=7 for 2 and 28 days, respectively). SfA (5mg/kg, IV, Novartis) was administered at 25 min after a start of sham surgery or MI. At the end of each experimental protocol, cardiac mitochondria were isolated from left and right ventricles and oxygen consumption was measured using a Clark oxygen electrode. Results were calculated as nmol O2/min per citrate synthase activity.ResultsMitochondria in MI and MI+R groups demonstrated reduced state 3 (49±4 and 56±6, respectively, P<0.01 vs. S) compared to the S group (101±7) at 28 days post‐surgery. Indeed, reperfusion had no additional detrimental effect on mitochondrial dysfunction induced by MI (MI and MI+R). SfA had no effect on respiratory function of mitochondria in MI (MI: 49±4 vs MI+S: 51±5) and MI+R (MI+R: 56±6 vs MI+RS: 51±4) groups. Reperfusion for short (2 days) and long (28 days) affected differently the mitochondrial function in right and left ventricles.ConclusionMI produce considerable damage to mitochondrial function having no difference between reperfused and non‐reperfused hearts.Support or Funding InformationNHLBI NIH (SC1HL118669)
Ischemic Postconditioning Transiently Improves Cardiac Mitochondrial Function during Resuscitation in a Porcine Model of Cardiac Arrest
Authors: Matsuura Timothy R , Yannopoulos Demetris , Shekar Kadambari C , Sebastian Pierre S , Bartos Jason A , Olson Matthew D , Douglas Hunter F , Rees Jennifer N , McKnite Scott H , Aufderheide Tom P , Neumar Robert W , Riess Matthias L 
Published: November 2023

IntroductionIschemic postconditioning (IPC) is a technique of brief interruptions in blood flow at the onset of reperfusion to mitigate reperfusion injury after prolonged ischemia. When applied during cardiopulmonary resuscitation (CPR) following ventricular fibrillation (VF) cardiac arrest (CA) in a porcine model, IPC during CPR (IPC‐CPR) reduced adverse events and improved neurologically favorable survival 48 hours after return of spontaneous circulation (ROSC) compared to standard‐of‐care CPR (S‐CPR). IPC‐CPR also increased cardiac mitochondrial function prior to ROSC after 4 minutes of CPR compared to S‐CPR.ObjectiveWe investigated the effect of IPC‐CPR after prolonged VF CA on cardiac mitochondrial function 6 hours after ROSC.MethodsTwenty‐four female swine were intubated, anesthetized, and surgically prepared for continuous hemodynamic recording. Eight animals received no CA (Naïve, n=8) as a non‐ischemic control. The remaining animals received 15 minutes of untreated VF CA followed by CPR without (S‐CPR, n=8) or with IPC (IPC‐CPR, n=8). IPC was administered via three 20‐second pauses in chest compressions during the first 2 minutes of CPR. After 4 minutes of CPR, defibrillation was attempted. Six hours after ROSC, cardiac mitochondria were isolated via differential centrifugation for assessment of respiration, rate of ATP synthesis, and calcium retention capacity. ANOVA with Newman‐Keuls posthoc test was used for comparisons between treatments. The null‐hypothesis was rejected for p < 0.05.ResultsROSC was obtained in all animals that received a CA. Cardiac mitochondrial function did not differ between Naïve, S‐CPR, and IPC‐CPR treated animals.ConclusionsIn a porcine model of prolonged VF CA, cardiac mitochondrial function normalizes within 6 hours of ROSC. The previously documented reduction in adverse events and improvement in survival with IPC‐CPR treatment may be mediated by acute changes in cardiac mitochondrial function earlier than 6 hours post‐ROSC, or by mechanisms independent of cardiac mitochondrial functionSupport or Funding InformationStipend support was provided by the American Heart Association 16PRE27600038 (TRM). Project support was provided by NIH 1R01 OD016727‐01 (DY).
Chronic Binge Alcohol Upregulates Expression of Genes Related to Apoptosis in Skeletal Muscle of Simian Immunodeficiency Virus‐Infected Rhesus Macaques at End‐Stage Disease
Authors: Duplanty Anthony A , Simon Liz , Molina Patricia E 
Published: November 2023

Alcohol use disorders are more prevalent in HIV patients than the general population. Both chronic alcohol consumption and HIV‐infection have been linked to mitochondrial dysregulation; and this is considered an important mechanism in the pathogenesis of muscle myopathy. Previous studies from our laboratory have demonstrated that chronic binge alcohol (CBA) administration accentuated loss of skeletal muscle (SKM) mass and promoted a dysfunctional skeletal muscle phenotype which was associated with accelerated progression to end‐stage disease, compared with isocaloric sucrose simian immunodeficiency virus (SIV)‐infected (SUC/SIV) macaques. The mechanisms preceding and leading to accentuated SAIDS wasting in CBA/SIV macaques include localized SKM inflammation, increased proteasomal activity, depletion of SKM antioxidant capacity and increased expression of pro‐fibrotic genes. Moreover, CBA/SIV resulted in decreased expression of peroxisome proliferator‐activated receptor‐γ coactivator (PGC)‐1β, a master regulator of mitochondrial homeostasis.PurposeThe aim of this study was to investigate the CBA‐associated alterations in expression of selected mitochondrial genes related to mitophagy and apoptosis in the skeletal muscle of SIV‐infected rhesus macaques at end‐stage disease.MethodsMale rhesus macaques were administered daily CBA (blood alcohol levels ~50 mM) or sucrose (SUC) intragastrically 3 months prior to intravenous SIVmac251 inoculation and continued until animals reached end‐stage criteria. SKM (gastrocnemius) samples were excised at necropsy and total RNA was extracted and mitochondrial gene expression was analyzed by qPCR. SKM tissues excised from a group of uninfected non‐CBA treated animals was used as reference controls.ResultsSIV‐infection resulted in a significant upregulation (P<0.05) of mitophagy‐related gene expression (DRP1, TFEB, PINK1), which was prevented by CBA. CBA suppressed expression of anti‐apoptotic genes (Beclin‐1 and BCL2) and increased expression of pro‐apoptotic genes (BAX and BAK) (P<0.05).ConclusionsThese findings suggest that SIV‐infection disrupts mitochondrial homeostasis and when combined with CBA, results in differential expression of genes involved in apoptotic signaling. We speculate that impaired mitochondrial homeostasis may contribute to the underlying pathophysiology of alcoholic and HIV/AIDS associated myopathy.Support or Funding InformationThis study was supported by grants from the National Institute on Alcohol Abuse and Alcoholism (NIAAA): T32 Postdoctoral Fellowship (AA07577) and the Comprehensive Alcohol Research Center P60 (AA09803) in the department of Physiology, LSU Heath Science Center, New Orleans, LA.
Dietary tributyrin alters satellite cell activity in neonatal swine
Authors: Murray Robert L. , Zhang Wei , Stahl Chad H. 
Published: November 2023

Satellite cells (SC), skeletal muscle stem cells, are responsible for all postnatal muscle growth and repair. Recently, we have shown that physiologically relevant concentrations of butyrate altered myogenesis in SC by enhancing terminal differentiation and the upregulation of myogenin mRNA expression. Our objective in this study was to determine the effect of dietary inclusion of tributyrin (Tb), a butyrate pro‐drug, has on neonatal muscle growth. Thirty neonatal piglets (24±8hrs old) were fed a standard milk replacer formula or formula supplemented with 0.50% (dry matter) spray dried Tb for 17d. Skeletal muscle tissue and SC were isolated from the longissimus dorsi (LD) for analysis of muscle growth parameters. Body weights were recorded daily and showed no difference in average daily body weight gain or feed efficiency. Animals that had received the Tb treatment diet had a significant increase (P<0.05) in the DNA:protein ratio in muscle. However, total concentrations of mTOR and the ratio of phosphorylated‐mTOR: total mTOR were not different between treatments. There was no difference in the relative abundance of the transcription factors Pax7 or MyoD in muscle tissue; however, there was an increase in myogenin expression in the LD from the Tb treated group (P<0.15). There was a numerical increase of in vivo proliferation rates of SC from the Tb group as assessed by BrdU staining. For in vitro analysis of SC behavior, the isolated SC were cultured for 48h in proliferation media and then switched to differentiation media for 96h. RNA was collected every 24h and RT‐PCR reveled a 100‐fold increase over the control group in myogenin expression 24h after they were induced to differentiate (P<0.05). Myogenin expression remained elevated in the Tb treatment group during differentiation (P<0.20), while there was no difference in Pax7 or MyoD expression at any time point. After 48h of differentiation, satellite cell fusion rate was assessed by immunofluorescent staining for myosin heavy chain (MyHC). Satellite cells from tributyrin treated animals had doubled the rate of fusion (P=0.10) over the control animals. Butyrate is a known inhibitor of histone deacetylases (HDACs) and when applied to satellite cells in culture it has arrested cell proliferation and enhanced terminal differentiation. In the present study, we have shown using an in vivo rapid muscle growth model that dietary inclusion of Tb can alter SC dynamics by way of HDAC regulation. Further investigation into the epigenetic targets could elucidate candidate genes for disease pathways and pharmacologic manipulation. Furthermore, we have provided evidence of accelerated myonuclear accretion in the neonatal pig; this may result in enhanced life‐time lean muscle growth which would significantly improve the sustainability of the swine production industry.Support or Funding InformationMaryland Agriculture Experiment Station
Inhibition of Platelet‐Derived Growth Factor Receptor Signaling Reduces Postnatal Tendon Growth in Response to Mechanical Loading
Authors: Disser Nathaniel P , Sugg Kristoffer B , Mendias Christopher L 
Published: November 2023

Platelet‐derived growth factors (PDGFs) and their receptors (PDGFRs) play an important role in the embryonic formation of many different tissue types. Previous studies have demonstrated the importance of PDGF signaling in the regulation of key cellular processes, including fibroblast differentiation, proliferation and extracellular matrix (ECM) synthesis. However, little is known about the role of PDGF signaling in postnatal tendon growth. We hypothesized that due to its importance in mesenchymal cell function, inhibition of PDGF signaling will suppress the growth of adult tendon tissue in response to a mechanical growth stimulus. Six‐month‐old male C57BL/6 mice were subjected to bilateral Achilles tenectomy to induce rapid growth of the synergist plantaris tendon. Intraperitoneal injections of CP‐673,451, a specific inhibitor of PDGFRα and PDGFRβ, or vehicle were administered at 15 mg/kg BID beginning one day prior to synergist ablation and continued every day until the mice were euthanized. Plantaris tendons were harvested at 3 and 10 days postoperatively. Synergist ablation resulted in the growth of new tendon tissue around the outside of the plantaris tendon in both the control and treatment groups, but the cross‐sectional area (CSA) of this new tendon tissue was significantly lower in the PDFGR inhibitor group compared to vehicle controls. Additionally, immunostaining for Ki67 revealed less proliferating cells in the new tendon tissue of the plantaris tendons from the PDGFR inhibitor group. Compared to the control group, there was significant downregulation of type V collagen and matrix metalloproteinase 14 (MMP14) at 3 days, as well as downregulation of genes involved in fibroblast proliferation at 3 and 10 days in the plantaris tendons treated with the PDGFR inhibitor. The results of this study demonstrate that PDGF signaling plays an important role in postnatal tendon growth in response to mechanical loading. The growth of new tendon tissue after synergist ablation was significantly restricted in the presence of PDGFR inhibition. This work lays the foundation for future studies to determine the specific roles of the PDGF isoforms and their receptors in the growth response of adult tendon tissue.Support or Funding InformationNIH grants R01‐AR063649 and F32‐AR067086, and an APS Summer Undergraduate Research Fellowship.
Cytokine secretory responses of MYD88 skeletal muscle specific knockout to pathogen exposure in vitro
Authors: Mattingly Alex , Laitano Orlando , Garcia Christian , Robinson Gerard , Van Steenbergen David , Clanton Thomas 
Published: November 2023

The role of skeletal muscles in the immune response to pathogens is poorly understood. Though intact skeletal muscles contain toll like receptors (TLRs) and secrete cytokines in response to pathogen exposure, it is unknown whether the cytokines come from muscle fibers or other resident cells. The purpose of this study was to interrupt TLR transduction, only in muscle fibers, in order to isolate their contribution from other cell types. To accomplish this, we created a skeletal muscle specific Myd88 knockout mouse (Myd88skmKO). Myd88 is an adaptor protein, critical to TLR signal transduction in all known TLRs in muscle. To stimulate TLRs, we used lipopolysaccharide (LPS), a potent TLR2 and TLR4 ligand.Matched solei muscles from MYD88skmKO mice (n=18) and background strain‐matched wild type controls (n=8) were excised in oxygenated (95%O2/5%CO2) Krebs solution and placed under 1 g of tension in baths at 35°C. Following a 30‐min acclimation period (T0), the buffer was replaced and muscles were exposed to 1 μg/ml LPS. Bath samples at T0, 1 hr (T1) and 2 hr (T2) were collected, mixed with a protease inhibitor cocktail and stored at −80°C prior to Luminex multiplex analysis.Both Myd88skmKO and control mice secreted significant quantities of cytokines in response to LPS. The response was greater in control mice than MYD88skmKOs in IL‐6 (3.9 fold, p=0.0005), IL‐15 (0.7 fold, p< 0.02) GM‐CSF (3.0 fold, p< 0.02) IL‐12p40 (2.7 fold, p< 0.02), IL12‐p70 (0.6 fold, p< 0.02), and MCP‐1 (1.8 fold, p< 0.05). At T2, control mice secreted greater IL‐6 (10.4 fold, p= 0.0002), GCS‐F (8.6 fold, p= 0.002), MCP‐1 (1.7 fold, p< 0.01) IP‐10 (1.4 fold, p= 0.0145) and KC (4.3 fold, p< 0.03). Interestingly, MYD88skmKOs mice secreted greater MIP‐1α at T1 (0.5 fold, p=0.02). Despite the much greater secretion in controls, LPS treated MYD88skmKOs solei still demonstrated significant secretion of some cytokines over T1 to T2 in IL‐6 (p= 0.0001), KC (p= 0.0001), MCP‐1 (P= 0.0001), MIP‐2 (p<0.04) and GM‐CSF (p< 0.04).In conclusion, solei from MYD88skmKO mice secreted significantly lower amounts of cytokines in response to LPS than controls, with the lone exception of MIP‐1α. This confirms that much of the cytokine secretory response to LPS in whole muscle comes from muscle fibers. However, muscles from Myd88skmKO mice still demonstrated the capacity to secrete some cytokines. This remaining cytokine release may be indicative of remaining MYD88‐independent TLR4 signaling, responses of non‐muscle resident cells or incomplete KO of the MYD88 protein in muscle fibers.Support or Funding InformationSupported by NIH RO1GM118895‐01 and the BK and Betty Stevens Endowment.
The Effect of Skeletal Muscle AMPK on the Regulation and Localization of the Dystrophin‐Associated Protein Complex
Authors: Dial Athan G , Lally James S , Bujak Adam L , Steinberg Gregory R , Ljubicic Vladimir 
Published: November 2023

The dystrophin‐associated protein complex (DAPC) is composed of proteins that are highly expressed along the sarcolemma. The DAPC provides a mechanical link between the intracellular cytoskeleton and extracellular matrix. Additionally, increasing evidence shows the importance of the DAPC as a mechanosensor and signal transducer across the sarcolemma. The signalling molecule AMP‐activated protein kinase (AMPK) is a powerful regulator of phenotypic plasticity. Chronic pharmacological AMPK stimulation induces the expression of DAPC components, whereas reduced AMPK activity results in DAPC dysfunction. However, a more comprehensive understanding of the influence of AMPK on the DAPC is lacking. Therefore, the purpose of this study was to investigate the role of AMPK in the expression of the DAPC in skeletal muscle. Extensor digitorum longus (EDL) and soleus (SOL) muscles representing fast glycolytic and slow oxidative tissues, respectively, were obtained from wild‐type (WT) mice, as well as from mice deficient in both isoforms of the AMPK‐β subunit in skeletal muscle (AMPK‐MKO). Immunofluorescence imaging was performed to measure the expression and localization of DAPC components dystrophin, β‐dystroglycan (β‐DG), γ‐sarcoglycan, (γ‐SG), neuronal nitric oxide synthase (nNOS), and laminin. β‐DG content was found to be ~2.2‐fold higher (p < 0.05) in SOL compared to EDL muscles from WT animals. However, this fiber type difference was not seen in the muscles from AMPK‐MKO mice. The expression of nNOS was significantly higher (+86%) in the SOL relative to the EDL muscles in AMPK‐MKO animals. This fiber type specificity was not observed in WT mice. The levels of dystrophin, γ‐SG, and laminin were similar between muscle types in both WT and AMPK‐MKO mice, and all DAPC components were similar between genotypes. We next investigated potential regulators of DAPC transcription, including myogenin and myoD. Western blot analyses revealed that the expression of both myogenin and myoD were downregulated by 40–60% (p < 0.05) in EDL and SOL muscles from AMPK‐MKO versus WT mice, which suggests that alternative factors may be contributing to the similar level of DAPC expression between genotypes. Indeed, computational analysis of the 3′ untranslated regions of DAPC components revealed multiple regulatory elements that have been shown to affect mRNA stability in skeletal muscle, such as binding sites for RNA‐binding proteins AUF1, HuR, and KSRP, as well as for microRNAs. Our results suggest that the absence of AMPK in skeletal muscle initiates a compensatory cascade of events at multiple levels of gene expression that coordinate to maintain basal levels of DAPC expression. Thus, although chronic AMPK activation induces DAPC content in skeletal muscle, it appears that AMPK is not essential for the maintenance of DAPC expression.Support or Funding InformationNatural Science and Engineering Research CouncilCanadian Research Chairs
Delayed Reinnervation During Muscle Regeneration After NO‐Donor Pre‐Treatment
Authors: Daneshvar Nasibeh , Anderson Judy E 
Published: November 2023

Activation of satellite cells (SCs) toward myogenesis leads to structural regeneration of damaged myofibers and reinnervation is essential to muscle function. SC activation is mediated by NO (a signaling and neurotransmitter molecule) and manipulation of the NO signal is shown to enhance muscle repair and promote growth in older mice in combination with exercise. SCs up‐regulate mRNA expression of a neural chemorepellent, semaphorin 3A (Sema3A) that peaks 6–8 days after muscle injury. Since Sema3A expression is implicated in regulating the timing of axon growth toward regenerating fibers, we hypothesized that premature activation of SC before an injury would advance Sema3A synthesis and disrupt the process of reinnervation. The time‐ course of reinnervation in regenerating tibialis anterior muscle (TA) of 6–10‐week‐old C57BL6 mice was examined after injury by crush (a large traumatic injury) or injection of cardiotoxin (CTX, which damages only fibers). We tested whether early activation of SC before injury using a 2‐day daily pre‐treatment with isosorbide dinitrate (ISDN, an NO‐donor drug) affects the process of new‐fiber innervation post‐injury. Muscle was collected 0, 4, 6, 8, 10, and 14 days after unilateral TA injury (n=4–5 per time point in crush, CTX, and respective control groups). The position of the nuclei and the length of the newly‐formed myotubes were used to track muscle regeneration on coded slides. CTX‐injured muscles had noticeably more advanced formation of neuromuscular junctions (NMJs) and faster fiber regeneration compared to crush‐ injured muscles at the same time point post‐injury. Combined staining of NMJs for acetylcholinesterase (AchE, silver staining) and acetylcholine receptors (AchRs, α‐bungarotoxin epifluorescence) on coded slides, revealed immature or mature NMJs (positive for AchE and AchRs) by day 14 in untreated crush‐ or CTX‐injured muscles, respectively. ISDN pre‐treatment in both crush‐ and CTX‐injured muscles delayed NMJ development on myotubes up to day 14 post‐injury. Results are consistent with the action of Sema3A as a neural chemorepellent, since SC activation before injury resulted in delayed myotube reinnervation. Therapeutic manipulation of Sema3A during regeneration, in time and/or concentration, may have potential to improve reinnervation and muscle function in conditions where nerve‐muscle interactions are disrupted by injury or disease.Support or Funding InformationSupported by a NSERC Discovery grant (to JEA) and a University of Manitoba Graduate Fellowship (to ND)