Contractile Function Research Articles

Mitochondrial antioxidant SkQ1 attenuates C26 cancer-induced muscle wasting in males and improves muscle contractility in female tumor-bearing mice.

Mitochondrial dysfunction is a hallmark of cancer cachexia (CC). Mitochondrial reactive oxygen species (ROS) are elevated in muscle shortly after tumor onset. Targeting mitochondrial ROS may be a viable option to prevent CC. The aim of this study was to evaluate the efficacy of a mitochondria-targeted antioxidant, SkQ1, to mitigate CC in both biological sexes. Male and female Balb/c mice were injected bilaterally with colon 26 adenocarcinoma (C26) cells (total 1x106 cells) or PBS (equal volume control). SkQ1 was dissolved in drinking water (~250 nmol/kg body weight/day) and administered to mice beginning seven days following tumor induction, while control groups consumed normal drinking water. In vivo muscle contractility of dorsiflexors, deuterium oxide-based protein synthesis, mitochondrial respiration and mRNA content of mitochondrial, protein turnover and calcium channel-related markers were assessed at endpoint (25 days following tumor induction). Two-way ANOVAs, followed by Tukey's post-hoc test when interactions were significant (p≤0.05), were performed. SkQ1 attenuated cancer-induced atrophy, promoted protein synthesis and abated Redd1 and Atrogin induction in gastrocnemius of C26 male mice. In female mice, SkQ1 decreased muscle mass and increased catabolic signaling in the plantaris of tumor-bearing mice, as well as reduced mitochondrial oxygen consumption, regardless of tumor. However, in females SkQ1 enhanced muscle contractility of the dorsiflexors with concurrent induction of Ryr1, Serca1 and Serca2a in TA. In conclusion, the mitochondria-targeted antioxidant SkQ1 may attenuate CC-induced muscle loss in males, while improving muscle contractile function in tumor-bearing female mice, suggesting sexual dimorphism in the effects of this mitochondrial therapy in CC.

Stress triggers irritable bowel syndrome with diarrhea through a spermidine-mediated decline in type I interferon.

Irritable bowel syndrome with diarrhea (IBS-D) is a common and chronic gastrointestinal disorder that is characterized by abdominal discomfort and occasional diarrhea. The pathogenesis of IBS-D is thought to be related to a combination of factors, including psychological stress, abnormal muscle contractions, and inflammation and disorder of the gut microbiome. However, there is still a lack of comprehensive analysis of the logical regulatory correlation among these factors. In this study, we found that stress induced hyperproduction of xanthine and altered the abundance and metabolic characteristics of Lactobacillus murinus in the gut. Lactobacillus murinus-derived spermidine suppressed the basal expression of type I interferon (IFN)-α in plasmacytoid dendritic cells by inhibiting the K63-linked polyubiquitination of TRAF3. The reduction in IFN-α unrestricted the contractile function of colonic smooth muscle cells, resulting in an increase in bowel movement. Our findings provided a theoretical basis for the pathological mechanism of, and new drug targets for, stress-exposed IBS-D.

Sodium octanoate mediates GPR84-dependent and independent protection against sepsis-induced myocardial dysfunction

IntroductionThis study aims to evaluate the therapeutic effects of sodium octanoate (SO), a medium-chain fatty acid salt, on SIMD in a murine model and to explore its underlying mechanisms. MethodsMale mice were subjected to sepsis models through two methods: intraperitoneal injection of lipopolysaccharide (LPS) and cecal ligation and punction (CLP). Mice received interval doses of SO every 2 hours or 4 hours for a total of six times or three times after LPS treatment. The relationship between SO and G protein-coupled receptor 84 (GPR84) was evaluated through GEO data analysis and molecular docking studies. DBA/2 mice were used to study the role of the GPR84 protein in the SO-mediated protection. Energy metabolomics was utilized to comprehensively assess the impact of SO on the levels of cardiac energy metabolic products in septic mice. histone modification identification techniques were used to further identify the specific sites of histone modification in the hearts of SO-treated septic mice. ResultsSO treatment significantly improved myocardial contractile function, restored the oxidative stress imbalance and enhanced the myocardium's resistance to oxidative injury. SO significantly promotes the expression of GPR84. The loss of GPR84 function markedly attenuates the protective effects of SO. SO enhanced myocardial energy metabolism by promoting the synthesis of acetyl-CoA and upregulating genes involved in fatty acid β-oxidation which were abolished by medium-chain acyl-CoA dehydrogenase (MCAD) knockdown. SO induced histone acetylation, particularly at H3K123 and H3K80. ConclusionOur study demonstrates that SO exerts protective effects against SIMD through both GPR84-mediated anti-inflammatory and antioxidant actions and GPR84-independent enhancement of myocardial energy metabolism, possibly mediated by MCAD.

Ex vivo modelling of cardiac injury identifies ferroptosis-related pathways as a potential therapeutic avenue for translational medicine

BackgroundHeart failure (HF) is a burgeoning health problem worldwide. Often arising as a result of cardiac injury, HF has become a major cause of mortality with limited availability of effective treatments. Ferroptotic pathways, triggering an iron-dependent form of cell death, are known to be potential key players in heart disease. This form of cell death does not exhibit typical characteristics of programmed cell death, and is mediated by impaired iron metabolism and lipid peroxidation signalling. ObjectivesThe aim of this study is to establish an ex-vivo model of myocardial injury in living myocardial slices (LMS) and to identify novel underlying mechanisms and potential therapeutic druggable target(s). Methods and resultsIn this study, we employed LMS as an ex vivo model of cardiac injury to investigate underlying mechanisms and potential therapeutic targets. Cryoinjury was induced in adult rat LMS, resulting in 30 % tissue damage. Cryoinjured LMS demonstrated impaired contractile function, cardiomyocyte hypertrophy, inflammation, and cardiac fibrosis, closely resembling in vivo cardiac injury characteristics. Proteomic analysis revealed an enrichment of factors associated with ferroptosis in the injured LMS, suggesting a potential causative role. To test this hypothesis, we pharmacologically inhibited ferroptotic pathways using ferrostatin (Fer-1) in the cryoinjured rat LMS, resulting in attenuation of structural changes and repression of pro-fibrotic processes. Furthermore, LMS generated from failing human hearts were used as a model of chronic heart failure. In this model, Fer-1 treatment was observed to reduce the expression of ferroptotic genes, enhances contractile function and improves tissue viability. Blocking ferroptosis-associated pathways in human cardiac fibroblasts (HCFs) resulted in a downregulation of fibroblast activation genes, a decrease in fibroblast migration capacity, and a reduction in reactive oxygen species production. RNA sequencing analysis of Fer-1-treated human LMS implicated metallothioneins as a potential underlying mechanism for the inhibition of these pathways. This effect is possibly mediated through the replenishment of glutathione reserves. ConclusionsOur findings highlight the potential of targeting ferroptosis-related pathways and metallothioneins as a promising strategy for the treatment of heart disease.

Mechanistic insights into Suanzaoren Decoction's improvement of cardiac contractile function in anxiety-induced cardiac insufficiency

Ethnopharmacological relevanceAccording to traditional Chinese medicine, Anxiety-induced cardiac blood insufficiency leads to palpitations and restlessness. Suanzaoren Decoction (SD) is effective in replenishing blood and promoting blood circulation. Clinical practice has shown that it has a better therapeutic effect on cardiac insufficiency. However, its mechanism of action is still unclear. Aim of the studyThe study aims to determine the mechanism by which SD treats chronic restraint stress (CRS)-induced anxiety-induced cardiac insufficiency (ACI). Materials and methodsSD was orally administered to mice with CRS-induced ACI. Firstly, we constructed an anxiety model in mice by CRS. Subsequently, SD was investigated to assess cardiac function and pathological changes through echocardiography, H&E staining, and Masson staining. Thirdly, the function of sympathetic and parasympathetic nerves was evaluated using enzyme-linked immunosorbent assay (ELISA) and enzyme activity assays. Network pharmacology and molecular docking were employed to predict potential targets for SD treatment of cardiac insufficiency. CaMKII expression was scrutinized utilizing publicly accessible databases. CaMKII was identified as a target through immunohistochemistry and Western Blot analysis in mouse hearts. Finally, the therapeutic mechanism of SD was confirmed in injured cardiomyocytes via Western Blot and quantitative PCR. ResultsSD exerted anxiolytic effects by increasing the frequency of entries into and the duration spent in open arms while reducing the time spent in the light chamber and increasing the number of transitions between light and dark chambers. Additionally, it mitigated cardiac insufficiency, as evidenced by the enhancement of left ventricular ejection fraction (LVEF) and attenuation of cardiomyocyte damage and inflammatory infiltration.However, SD did not alleviate the elevated norepinephrine (NE) and decreased Acetylcholine (Ach) in anxiety states. To investigate the mechanism of action of SD, we constructed a Drug-Component-Target-Disease network, identifying 13 potential active compounds. Additionally, leveraging bioinformatics analysis and molecular docking targeting heart diseases characterized by clinical left ventricular ejection fraction (LVEF), we focused on the CaMKII target. The ability of SD to modulate CaMKII expression and phosphorylation in the mouse heart was investigated using immunohistochemistry and Western blotting. SD was found to alleviate NE-injured cardiomyocytes by modulating the Ca2+/CaMKII/MEF2 and GATA4 pathways. ConclusionSD is a potential formula for the treatment of chronic restraint stress (CRS)-induced ACI that ameliorates cardiomyocyte injury and improves cardiac function. Its efficacy is associated with the inhibition of the Ca2+/CaMKII/MEF2 and GATA4 signaling pathways.

Spaceflight-induced contractile and mitochondrial dysfunction in an automated heart-on-a-chip platform

With current plans for manned missions to Mars and beyond, the need to better understand, prevent, and counteract the harmful effects of long-duration spaceflight on the body is becoming increasingly important. In this study, an automated heart-on-a-chip platform was flown to the International Space Station on a 1-mo mission during which contractile cardiac function was monitored in real-time. Upon return to Earth, engineered human heart tissues (EHTs) were further analyzed with ultrastructural imaging and RNA sequencing to investigate the impact of prolonged microgravity on cardiomyocyte function and health. Spaceflight EHTs exhibited significantly reduced twitch forces, increased incidences of arrhythmias, and increased signs of sarcomere disruption and mitochondrial damage. Transcriptomic analyses showed an up-regulation of genes and pathways associated with metabolic disorders, heart failure, oxidative stress, and inflammation, while genes related to contractility and calcium signaling showed significant down-regulation. Finally, in silico modeling revealed a potential link between oxidative stress and mitochondrial dysfunction that corresponded with RNA sequencing results. This represents an in vitro model to faithfully reproduce the adverse effects of spaceflight on three-dimensional (3D)-engineered heart tissue.

Magnetic resonance reveals early lipid deposition in murine prediabetes as predictive marker for cardiovascular injury

People with diabetes have an increased cardiovascular risk and a poorer outcome after myocardial infarction (MI). However, the exact underlying mechanisms are still unclear, as is the question of which non-invasive measures could be used to predict the altered risk for the patient at early stages of the disease and adapt personalized treatment. Here, we used a holistic magnetic resonance approach to monitor longitudinally not only the main target heart, but also liver, peripheral/skeletal muscle, bone marrow, and hematopoiesis during disease development and subsequent MI. In prediabetic mice, we found a strong accumulation of lipids in all organs which preceded even a significant whole-body weight gain. Intramyocellular lipids (IMCLs) were most sensitive to reveal in vivo very early alterations in tissue properties during the prediabetic state. Subsequent induction of MI led to a persistent impairment of contractile function in septal/posterior segments of prediabetic hearts which correlated with their lipid load prior MI. At the same time, prediabetic cardiomyocytes exhibited sarcomere function at its limit resulting in overload and lower compensatory contractility of the healthy myocardium after MI. In summary, we identified IMCLs as very early marker in murine prediabetes and together with the cardiac lipid load as predictive for the functional outcome after MI.

Prospective evaluation of the extensibility of the ascending aorta wall and its vascular prosthesis in a patient with an aneurysm with technically flawless surgical correction and postoperative decrease in functional parameters: A case report

In this clinical case, a patient who had an instrumentally detected aneurysm with the lumen expanding up to 60 mm underwent a surgically flawless prosthetic replacement of the ascending aorta. This treatment led to decreased exercise tolerance, decreased contractile function of the left ventricular myocardium at rest, and enlarged pulmonary artery. The leading factor was a decrease in the volume of systolic expansion of the aorta down to 5 mL (at the initial 13 mL), despite a noticeable increase in the extensibility and a decrease in mechanical stiffness compared with initial indexes of the affected aortic wall. In the literature review, considering mechanical extensibility and elasticity, problems in creating aortic prostheses equivalent to those for healthy biological tissues were discussed.

Overlap of gallbladder dysfunction and irritable bowel syndrome: clinical and microbiological features and therapeutic possibilities

Objective — to analyse the clinical and microbiological features in patients with an overlap between gallbladder dysfunction (GBD) and irritable bowel syndrome (IBS) and a complex assessment of the effectiveness and safety of using ursodeoxycholic acid (Ursis) in these patients. Materials and methods. Under our observation were 115 patients with the overlap of GBD and IBS aged from 19 to 52. The majority of them were women (62.6%). All patients complained of abdominal pain, mostly without clear localization or in the right hypochondrium and along the course of the large intestine. Constipation was diagnosed in 83 (72.2%) patients, and meteorism in 89 (77.4%) patients. Therefore, 62 patients with the overlap of GBD and IBS, who had abdominal pain, constipation and meteorism, were selected for further study. During the study, all patients kept a diary in which the frequency and nature of bowel movements, the severity of abdominal pain, and the degree of meteorism were recorded. All patients before and after treatment underwent an ultrasound examination of the abdominal cavity, which included the study of the contractile function of the gallbladder, the emptying coefficient of the gallbladder, the thickness and density of its wall, and the density of bile. Changes in the main bacterial enterotypes were analyzed by qRT‑PCR using primers targeting 16S rRNA. We studied Bacteroidetes, Firmicutes, Actinobacteria, as well as the content of butyrate‑producing bacteria (Faecalibacterium prausnitzii and Akkermansia muciniphila) and methanogens (Methanobrevibacter smithii and Methanosphaera stadmanae). Results. Before treatment, all patients had abdominal pain of moderate intensity (6.9±0.7 points), mostly without clear localization, constipation, with a frequency of defecation (1.4±0.5) times a week, and meteorism. Before treatment, patients with an overlap of GBD and IBS had changes in the contractile function of the gallbladder with a decrease in the emptying ratio, a thickening of the gallbladder wall and an increase in its density and bile density, as well as a disturbance of the intestinal microbiome (an increase in the number of Firmicutes, Actinobacteria and methanogenic archaea and a decrease in Bacteroidetes and butyrate‑producing bacteria). Conclusions. The use of Ursis® medication in the complex therapy of patients with a GBD and IBS overlap is effective and safe. The aplication of Ursis® led to a more pronounced positive clinical dynamics (a decrease in the intensity of abdominal pain, normalization of the frequency of bowel movements, a decrease in meteorism and an improvement in general well‑being) than in the patients of the comparison group. After treatment with Ursis® the coefficient of emptying of the gallbladder increased, the thickness and density of its wall decreased. The use of the drug Ursis® in the complex therapy of patients with the overlap of GBD and IBS contributed to the improvement of intestinal flora: an increase in the number of Bacteroidetes and butyrate‑producing bacteria (Faecalibacterium prausnitzii and Akkermansia muciniphila), and a decrease in the content of methanogens (Methanobrevibacter smithii and Methanosphaera stadmanae).

PDE5 inhibitor potentially improves polyuria and bladder storage and voiding dysfunctions in type 2 diabetic rats.

Bladder dysfunction associated with type 2 diabetes mellitus (T2DM) includes urine storage and voiding disorders. We examined pathological conditions of the bladder wall in a rat T2DM model and evaluated the effects of the phosphodiesterase-5 (PDE-5) inhibitor tadalafil. Male Otsuka Long-Evans Tokushima Fatty (OLETF) rats and Long-Evans Tokushima Otsuka (LETO) rats were used as the T2DM and control groups, respectively. Tadalafil was orally administered for 12 weeks. Micturition behavior was monitored using metabolic cages, and bladder function was evaluated by cystometry. Bladder blood flow was evaluated by laser speckle imaging, and an organ bath bladder distention test was used to measure adenosine triphosphate (ATP) release from the bladder urothelium. The expression levels of vesicular nucleotide transporter (VNUT), hypoxia markers, pro-inflammatory cytokines and growth factors in the bladder wall were measured using real-time polymerase chain reaction and enzyme-linked immunosorbent assay. Bladder wall contractions in response to KCl and carbachol were monitored using bladder-strip tests. With aging, OLETF rats had higher micturition frequency and greater urine volume than LETO rats. Although bladder capacity was not significantly different, non-voiding bladder contraction occurred more frequently in OLETF rats than in LETO rats. Bladder blood flow was decreased and ATP release was increased with higher VNUT expression in OLETF rats than in LETO rats. These effects were suppressed by tadalafil administration, with accompanying decreased HIF-1α, 8-OHdG, IL-6, TNF-α, IGF-1, and bFGF expression. The impaired contractile responses of bladder strips to KCl and carbachol in OLETF rats with aging were restored by tadalafil administration. The T2DM rats had polyuria, increased ATP release induced by decreased bladder blood flow and impaired contractile function. PDE5 inhibition improved these changes and may prevent T2DM-associated urinary frequency and bladder storage and voiding dysfunctions.

Vgll2 as an integrative regulator of mitochondrial function and contractility specific to skeletal muscle.

During skeletal muscle adaptation to physiological or pathophysiological signals, contractile apparatus and mitochondrial function are coordinated to alter muscle fiber type. Although recent studies have identified various factors involved in modifying contractile proteins and mitochondrial function, the molecular mechanisms coordinating contractile and metabolic functions during muscle fiber transition are not fully understood. Using a gene-deficient mouse approach, our previous studies uncovered that vestigial-like family member 2 (Vgll2), a skeletal muscle-specific transcription cofactor activated by exercise, is essential for fast-to-slow adaptation of skeletal muscle. The current study provides evidence that Vgll2 plays a role in increasing muscle mitochondrial mass and oxidative capacity. Transgenic Vgll2 overexpression in mice altered muscle fiber composition toward the slow type and enhanced exercise endurance, which contradicted the outcomes observed with Vgll2 deficiency. Vgll2 expression was positively correlated with the expression of genes related to mitochondrial function in skeletal muscle, mitochondrial DNA content, and protein abundance of oxidative phosphorylation complexes. Additionally, Vgll2 overexpression significantly increased the maximal respiration of isolated muscle fibers and enhanced the suppressive effects of endurance training on weight gain. Notably, no additional alteration in expression of myosin heavy chain genes was observed after exercise, suggesting that Vgll2 plays a direct role in regulating mitochondrial function, independent of its effect on contractile components. The observed increase in exercise endurance and metabolic efficiency may be attributed to the acute upregulation of genes promoting fatty acid utilization as a direct consequence of Vgll2 activation facilitated by endurance exercise. Thus, the current study establishes that Vgll2 is an integrative regulator of mitochondrial function and contractility in skeletal muscle.

Functional outcome of the anterior vaginal wall in a pelvic surgery injury rat model after treatment with stem cell-derived progenitors of smooth muscle cells

BackgroundStem-cell-derived therapy is a promising option for tissue regeneration. Human iPSC-derived progenitors of smooth muscle cells (pSMCs) exhibit limited proliferation and differentiation, which minimizes the risk of tumor formation while restoring smooth muscle cells (SMCs). Up to 29% of women suffer from recurrence of vaginal prolapse after prolapse surgery. Therefore, there is a need for therapies that can restore vaginal function. SMCs contribute to vaginal tone and contractility. We sought to examine whether human pSMCs can restore vaginal function in a rat model.MethodsFemale immunocompromised RNU rats were divided into 5 groups: intact controls (n = 12), VSHAM (surgery + saline injection, n = 35), and three cell-injection groups (surgery + cell injection using pSMCs from three patients, n = 14/cell line). The surgery to induce vaginal injury was analogous to prolapse surgery. Menopause was induced by surgical ovariectomy. The vagina, urethra, bladder were harvested 10 weeks after surgery (5 weeks after cell injection). Organ bath myography was performed to evaluate the contractile function of the vagina, and smooth muscle thickness was examined by tissue immunohistochemistry. Collagen I, collagen III, and elastin mRNA and protein expressions in tissues were assessed.ResultsVaginal smooth muscle contractions induced by carbachol and KCl in the cell-injection groups were significantly greater than those in the VSHAM group. Collagen I protein expression in the vagina of the cell-injections groups was significantly higher than in the VSHAM group. Vaginal elastin protein expression was similar between the cell-injection and VSHAM groups. In the urethra, gene expression levels of collagen I, III, and elastin were all significantly greater in the cell-injection groups than in the VSHAM group. Collagen I, III, and elastin protein expression of the urethra did not show a consistent trend between cell-injection groups and the VSHAM group.ConclusionsHuman iPSC-derived pSMCs transplantation appears to be associated with improved contractile function of the surgically injured vagina in a rat model. This is accompanied by changes in extracellular protein expression the vagina and urethra. These observations support further efforts in the translation of pSMCs into a treatment for regenerating the surgically injured vagina in women who suffer recurrent prolapse after surgery.

Comprehensive evaluation of right ventricular function in patients with acute pulmonary embolism

Objective. To study indices of right ventricular (RV) longitudinal deformation at transthoracic echocardiography (TTE) in patients with acute pulmonary embolism (APE), to determine their threshold values; to study indices of right ventricular-arterial coupling (RVAC) in patients with APE, to determine their threshold values.Methods. We examined 34 patients with acute massive and submassive pulmonary embolism. The diagnosis was made on the basis of computed-tomography pulmonary angiogram. The mean age was 61 ±13 years. Of these, 16 were women (47,1%) and 18 were men (52,9%). As a control group, 30 healthy individuals were examined: 14 males and 16 females. The mean age of the healthy individuals was 39±9,8 years. Echocardiography was performed on Vivid E95 (GE HealthCare, USA) with data postprocessing on EchoPak workstation. The indices of right ventricular (RV) systolic and diastolic function, the magnitude of global longitudinal deformation of the right ventricle (GLS RV) and longitudinal deformation of the right ventricular free wall (RVFWLS) were studied using two-dimensional speckle-tracking echocardiography. We studied indices of right ventricular-arterial coupling (RVAC). We determined the relationship of longitudinal deformation of RV and RVAC with other indices of its systolic function. Results. Mean values of traditional parameters of RV contractile function were within normal limits, whereas mean values of longitudinal strain in APE were significantly lower than normal. There was also a significant decrease ( P < 0,0001) of all measured parameters of right ventricular-arterial coupling in patients with APE in comparison with the control group.Conclusions. When longitudinal deformation parameters are included in the criteria of RV dysfunction in APE, its detectability increases from 26,47% to 61,77%. The revealed decrease of right ventricular-arterial coupling parameters in APE indicates a more frequent disturbance of the connection between RV and the small circle of blood circulation

Impaired Upper Airway Muscle Function with Excessive or Deficient Dietary Intake of Selenium in Rats.

Obstructive sleep apnoea (OSA) involves impaired upper airway muscle function and is linked to several pathologies including systemic hypertension, daytime somnolence and cognitive decline. Selenium is an essential micronutrient that exerts many of its effects through selenoproteins. Evidence indicates that either deficient or excessive dietary selenium intake can result in impaired muscle function, termed nutritional myopathy. To investigate the effects of selenium on an upper airway muscle, the sternohyoid, rats were fed on diets containing deficient, normal (0.5 ppm sodium selenite) or excessive (5 ppm selenite) selenium for a period of two weeks. Sternohyoid contractile function was assessed ex vivo. Serum selenium levels and activity of the glutathione antioxidant system were determined by biochemical assays. The abundance of three key muscle selenoproteins (selenoproteins -N, -S and -W (SELENON, SELENOS and SELENOW)) in sternohyoid muscle were quantified by immunoblotting. Levels of these selenoproteins were also compared between rats exposed to chronic intermittent hypoxia, a model of OSA, and sham treated animals. Although having no detectable effect on selected organ masses and whole-body weight, either selenium-deficient or -excessive diets severely impaired sternohyoid contractile function. These changes did not involve altered fibre size distribution. These dietary interventions resulted in corresponding changes in serum selenium concentrations but did not alter the activity of glutathione-dependent antioxidant systems in sternohyoid muscle. Excess dietary selenium increased the abundance of SELENOW protein in sternohyoid muscles but had no effect on SELENON or SELENOS. In contrast, chronic intermittent hypoxia increased SELENON, decreased SELENOW and had no significant effect on SELENOS in sternohyoid muscle. These findings indicate that two-week exposure to selenium-deficient or -excessive diets drastically impaired upper airway muscle function. In the sternohyoid, SELENON, SELENOS and SELENOW proteins show distinct alterations in level following exposure to different dietary selenium intakes, or to chronic intermittent hypoxia. Understanding how alterations in Se and selenoproteins impact sternohyoid muscle function has the potential to be translated into new therapies for prevention or treatment of OSA.

Unacylated Ghrelin Protects Against Age-Related Loss of Muscle Mass and Contractile Dysfunction in Skeletal Muscle.

Sarcopenia, the progressive loss of muscle mass and function, universally affects older adults and is closely associated with frailty and reduced quality of life. Despite the inevitable consequences of sarcopenia and its relevance to healthspan, no pharmacological therapies are currently available. Ghrelin is a gut-released hormone that increases appetite and body weight through acylation. Acylated ghrelin activates its receptor, growth hormone secretagogue receptor 1a (GHSR1a), in the brain by binding to it. Studies have demonstrated that acyl and unacylated ghrelin (UnAG) both have protective effects against acute pathological conditions independent of receptor activation. Here, we investigated the long-term effects of UnAG in age-associated muscle atrophy and contractile dysfunction in mice. Four-month-old and 18-month-old mice were subjected to either UnAG or control treatment for 10 months. UnAG did not affect food consumption or body weight. Gastrocnemius and quadriceps muscle weights were reduced by 20%-30% with age, which was partially protected against by UnAG. Specific force, force per cross-sectional area, measured in isolated extensor digitorum longus muscle was diminished by 30% in old mice; however, UnAG prevented the loss of specific force. UnAG also protected from decreases in mitochondrial respiration and increases in hydrogen peroxide generation of skeletal muscle of old mice. Results of bulk mRNA-seq analysis and our contractile function data show that UnAG reversed neuromuscular junction impairment that occurs with age. Collectively, our data revealed the direct role of UnAG in mitigating sarcopenia in mice, independent of food consumption or body weight, implicating UnAG treatment as a potential therapy against sarcopenia.

Intimal Macrovascular Pericytes: Their Role in Vascular Biology and Atherogenesis.

Atherosclerosis remains a major challenge to global healthcare despite decades of research and constant trials of novel therapeutic approaches. One feature that makes atherosclerosis treatment so elusive is an insufficient understanding of its origins and the early stages of the pathological process, which limits our means of effective prevention of the disease. Macrovascular pericytes are cells with distinct shapes that are located in the arterial wall of larger vessels and are in many aspects similar to microvascular pericytes that maintain the functionality of small vessels and capillaries. This cell type combines the residual contractile function of smooth muscle cells with a distinct stellar shape that allows these cells to make numerous contacts between themselves and the adjacent endothelial layer. Moreover, pericytes can take part in the immune defense and are able to take up lipids in the course of atherosclerotic lesion development. In growing atherosclerotic plaques, the morphology and function of pericytes change dramatically due to phagocytic and synthetic phenotypes that are actively involved in lipid accumulation and extracellular matrix synthesis. In this review, we summarize our knowledge of this less-studied cell type and its role in atherosclerosis.

Calix[4]arene С-956 as a selective inhibitor of Ca2+-pump of the plasma membrane and a modulator of the contractile function in the myometrium

Background. At present, creating and testing pharmacological instruments for selective inhibition of Са2+-pump of the plasma membrane, which would become the foundation for medical preparations, for instance, for the treatment of the impaired excitability of the cardiac and smooth muscles, remains critically significant. We have demon­strated in our previous experiments that calix[4]arene С-956 is effective in inhibi­ting Са2+, Mg2+-ATPase activity of the plasma membrane of myometrium cells. The aim of this study was to investigate the regularities and mechanisms of the impact of calix[4]arene С-956 on Са2+-transporting activity of Са2+, Mg2+-ATPase of the plasma membrane (PM) and the contractile function of rat myometrium. Materials and Methods. The experiments were conducted using outbred white non-pregnant rats. Ca2+-transporting activity of myocytes PM preparations loaded with Ca2+-sensitive fluorescent probe fluo-4 AM was investigated. The registration of the contractile activity in the preparations of longitudinal smooth muscles of uterine horns with preserved endothelium was done in the isometric mode. Results. It was determined that calix[4]arene C-956 causes blocking of the transport function of the calcium pump of preparations of plasma membranes of uterine myocytes. The C-956 compound causes an increase in the amplitude of spontaneous contractions and a change in their mechanokinetic parameters during a short-term effect on multicellular preparations of rat myometrium. Calix[4]arene C-956 also significantly affects the contractions caused by high-potassium depolarization of the PM and oxytocin, increa­sing their amplitude and decreasing the rate of relaxation. Blocking the synthesis of nitric oxide significantly enhances the effects of C-956 on spontaneous and high-potassium- and oxytocin-induced contractions of the myometrium. Conclusions. The results of our research indicate that the main target of the action of calix[4]arene C-956 on myocytes is the calcium pump of the PM. With the preliminary inhibition of nitric oxide synthases followed by the use of C-956, we were able to fully demonstrate the contribution of the calcium pump of the PM to the regulation of uterine contractions.

Respiratory performance in Duchenne muscular dystrophy: Clinical manifestations and lessons from animal models.

Duchenne muscular dystrophy (DMD) is a fatal genetic neuromuscular disease. Lack of dystrophin in skeletal muscles leads to intrinsic weakness, injury, subsequent degeneration and fibrosis, decreasing contractile function. Dystropathology eventually presents in all inspiratory and expiratory muscles of breathing, severely curtailing their critical function. In people with DMD, premature death is caused by respiratory or cardiac failure. There is an urgent need to develop therapies that improve quality of life and extend life expectancy in DMD. Surprisingly, there is a dearth of information on respiratory control in animal models of DMD, and respiratory outcome measures are often limited or absent in clinical trials. Characterization of respiratory performance in murine and canine models has revealed extensive remodelling of the diaphragm, the major muscle of inspiration. However, significant compensation by extradiaphragmatic muscles of breathing is evident in early disease, contributing to preservation of peak respiratory system performance. Loss of compensation afforded by accessory muscles in advanced disease is ultimately associated with compromised respiratory performance. A new and potentially more translatable murine model of DMD, the D2.mdx mouse, has recently been developed. Respiratory performance in D2.mdx mice is yet to be characterized fully. However, based on histopathological features, D2.mdx mice might serve as useful preclinical models, facilitating the testing of new therapeutics that rescue respiratory function. This review summarizes the pathophysiological mechanisms associated with DMD both in humans and in animal models, with a focus on breathing. We consider the translational value of each model to human DMD and highlight the urgent need for comprehensive characterization of breathing in representative preclinical models to better inform human trials.

Identification and characterisation of functional Kir6.1-containing ATP-sensitive potassium channels in the cardiac ventricular sarcolemmal membrane.

The canonical Kir6.2/SUR2A ventricular KATP channel is highly ATP-sensitive and remains closed under normal physiological conditions. These channels activate only when prolonged metabolic compromise causes significant ATP depletion and then shortens the action potential to reduce contractile activity. Pharmacological activation of KATP channels is cardioprotective, but physiologically, it is difficult to understand how these channels protect the heart if they only open under extreme metabolic stress. The presence of a second KATP channel population could help explain this. Here, we characterise the biophysical and pharmacological behaviours of a constitutively active Kir6.1-containing KATP channel in ventricular cardiomyocytes. Patch-clamp recordings from rat ventricular myocytes in combination with well-defined pharmacological modulators was used to characterise these newly identified K+ channels. Action potential recording, calcium (Fluo-4) fluorescence measurements and video edge detection of contractile function were used to assess functional consequences of channel modulation. Our data show a ventricular K+ conductance whose biophysical characteristics and response to pharmacological modulation were consistent with Kir6.1-containing channels. These Kir6.1-containing channels lack the ATP-sensitivity of the canonical channels and are constitutively active. We conclude there are two functionally distinct populations of ventricular KATP channels: constitutively active Kir6.1-containing channels that play an important role in fine-tuning the action potential and Kir6.2/SUR2A channels that activate with prolonged ischaemia to impart late-stage protection against catastrophic ATP depletion. Further research is required to determine whether Kir6.1 is an overlooked target in Comprehensive in vitro Proarrhythmia Assay (CiPA) cardiac safety screens.

Spatially clustered type I interferon responses at injury borderzones

Sterile inflammation after myocardial infarction is classically credited to myeloid cells interacting with dead cell debris in the infarct zone1,2. Here we show that cardiomyocytes are the dominant initiators of a previously undescribed type I interferon response in the infarct borderzone. Using spatial transcriptomics analysis in mice and humans, we find that myocardial infarction induces colonies of interferon-induced cells (IFNICs) expressing interferon-stimulated genes decorating the borderzone, where cardiomyocytes experience mechanical stress, nuclear rupture and escape of chromosomal DNA. Cardiomyocyte-selective deletion of Irf3 abrogated IFNIC colonies, whereas mice lacking Irf3 in fibroblasts, macrophages, neutrophils or endothelial cells, Ccr2-deficient mice or plasmacytoid-dendritic-cell-depleted mice did not. Interferons blunted the protective matricellular programs and contractile function of borderzone fibroblasts, and increased vulnerability to pathological remodelling. In mice that died after myocardial infarction, IFNIC colonies were immediately adjacent to sites of ventricular rupture, while mice lacking IFNICs were protected from rupture and exhibited improved survival3. Together, these results reveal a pathological borderzone niche characterized by a cardiomyocyte-initiated innate immune response. We suggest that selective inhibition of IRF3 activation in non-immune cells could limit ischaemic cardiomyopathy while avoiding broad immunosuppression.