Sarcoplasmic Reticulum Calcium ATPase Research Articles

Obesity-induced tissue alterations resist weight loss: A mechanistic review.

Interventions aimed at weight control often have limited effectiveness in combating obesity. This review explores how obesity-induced dysfunction in white (WAT) and brown adipose tissue (BAT), skeletal muscle, and the brain blunt weight loss, leading to retention of stored fat. In obesity, increased adrenergic stimulation and inflammation downregulate β-adrenoreceptors and impair catecholaminergic signalling in adipocytes. This disrupts adrenergic-mediated lipolysis, diminishing lipid oxidation in both white and brown adipocytes, lowering thermogenesis and blunting fat loss. Emerging evidence suggests that WAT fibrosis is associated with worse weight loss outcomes; indeed, limiting collagen and laminin-α4 deposition mitigates WAT accumulation, enhances browning, and protects against high-fat-diet-induced obesity. Obesity compromises mitochondrial oxidative capacity and lipid oxidation in skeletal muscle, impairing its ability to switch between glucose and lipid metabolism in response to varying nutrient levels and exercise. This dysfunctional phenotype in muscle is exacerbated in the presence of obesity-associated sarcopenia. Additionally, obesity suppresses sarcolipin-induced sarcoplasmic reticulum calcium ATPase (SERCA) activation, resulting in reduced oxidative capacity, diminished energy expenditure, and increased adiposity. In the hypothalamus, obesity and overnutrition impair insulin and leptin signalling. This blunts central satiety signals, favouring a shift in energy balance toward energy conservation and body fat retention. Moreover, both obese animals and humans demonstrate impaired dopaminergic signalling and diminished responses to nutrient intake in the striatum, which tend to persist after weight loss. This may result in enduring inclinations toward overeating and a sedentary lifestyle. Collectively, the tissue adaptations described pose significant challenges to effectively achieving and sustaining weight loss in obesity.

Relative sarcolipin (SLN) and sarcoplasmic reticulum Ca2+ ATPase (SERCA1) transcripts levels in closely related endothermic and ectothermic scombrid fishes: Implications for molecular basis of futile calcium cycle non-shivering thermogenesis (NST)

Regional endothermy is the ability of an animal to elevate the temperature of specific regions of the body above that of the surrounding environment and has evolved independently among several fish lineages. Sarcolipin (SLN) is a small transmembrane protein that uncouples the sarcoplasmic reticulum calcium ATPase pump (SERCA1b) resulting in futile Ca2+ cycling and is thought to play a role in non-shivering thermogenesis (NST) in cold-challenged mammals and possibly some fishes. This study investigated the relative expression of sln and serca1 transcripts in three regionally-endothermic fishes (the skipjack, Katsuwonus pelamis, and yellowfin tuna, Thunnus albacares, both of which elevate the temperatures of their slow-twitch red skeletal muscle (RM) and extraocular muscles (EM), as well as the cranial endothermic swordfish, Xiphias gladius), and closely related ectothermic scombrids (the Eastern Pacific bonito, Sarda chiliensis, and Pacific chub mackerel, Scomber japonicus). Using Reverse Transcription quantitative PCR (RT-qPCR) and species-specific primers, relative sln expression trended higher in both the RM and EM for all four scombrid species compared to white muscle. In addition, relative serca1 expression was found to be higher in RM of skipjack and yellowfin tuna in comparison to white muscle. However, neither sln nor serca1 transcripts were higher in swordfish RM, EM or cranial heater tissue in comparison to white muscle. A key phosphorylation site in sarcolipin, threonine 5, is conserved in the swordfish, but is mutated to alanine or valine in tunas and the endothermic smalleye Pacific opah, Lampris incognitus, which should result in increased uncoupling of the SERCA pump. Our results support the role of potential SLN-NST in endothermic tunas and the lack thereof for swordfish.

Inhibition of miR-25 ameliorates cardiac and skeletal muscle dysfunction in aged mdx/utrn haploinsufficient (+/−) mice

Dystrophic cardiomyopathy is a significant feature of Duchenne muscular dystrophy (DMD). Increased cardiomyocyte cytosolic calcium (Ca2+) and interstitial fibrosis are major pathophysiological hallmarks that ultimately result in cardiac dysfunction. MicroRNA-25 (miR-25) has been identified as a suppressor of both sarcoplasmic reticulum calcium ATPase 2a (SERCA2a) and mothers against decapentaplegic homolog-7 (Smad7) proteins. In this study, we created a gene transfer using an miR-25 tough decoy (TuD) RNA inhibitor delivered via recombinant adeno-associated virus serotype 9 (AAV9) to evaluate the effect of miR-25 inhibition on cardiac and skeletal muscle function in aged dystrophin/utrophin haploinsufficient mice mdx/utrn (+/-), a validated transgenic murine model of DMD. We found that the intravenous delivery of AAV9 miR-25 TuD resulted in strong and stable inhibition of cardiac miR-25 levels, together with the restoration of SERCA2a and Smad7 expression. This was associated with the amelioration of cardiomyocyte interstitial fibrosis as well as recovered cardiac function. Furthermore, the direct quadricep intramuscular injection of AAV9 miR-25 TuD significantly restored skeletal muscle Smad7 expression, reduced tissue fibrosis, and enhanced skeletal muscle performance in mdx/utrn (+/-) mice. These results imply that miR-25 TuD gene transfer may be a novel therapeutic approach to restore cardiomyocyte Ca2+ homeostasis and abrogate tissue fibrosis in DMD.

IL-37 Modulates Myocardial Calcium Handling via the p-STAT3/SERCA2a Axis in HF-Related Engineered Human Heart Tissue.

Interleukin-37 (IL-37) is a potent anti-inflammatory cytokine belonging to the IL-1 family. This study investigates the regulatory mechanism and reparative effects of IL-37 on HF-related human induced pluripotent stem cells derived cardiomyocytes (hiPSC-CMs) and engineered human heart tissue subjected to hypoxia and H2 O2 treatment. The contractile force and Ca2+ conduction capacity of the tissue are assessed using a stretching platform and high-resolution fluorescence imaging system. This investigation reveals that IL-37 treatment significantly enhances cell viability, calcium transient levels, contractile force, and Ca2+ conduction capacity in HF-related hiPSC-CMs and engineered human heart tissue. Notably, IL-37 facilitates the upregulation of sarcoplasmic reticulum calcium ATPase 2a (SERCA2a) through enhancing nuclear p-STAT3 levels. This effect is mediated by the binding of p-STAT3 to the SERCA2a promoter, providing a novel insight on the reparative potential of IL-37 in HF. IL-37 demonstrates its ability to enhance systolic function by modulating myocardial calcium handling via the p-STAT3/SERCA2a axis in HF-related engineered human heart tissue (as shown in schematic diagram).

Mechanisms involved in the muscle relaxing effects of STW 5 in guinea pig stomach

AbstractIntroductionThe herbal preparation STW 5 ameliorates functional dyspepsia partly by relaxing smooth muscle of the proximal stomach, thus improving gastric accommodation. We explored the unknown pathways responsible for this effect by testing targets known to modulate gastric smooth muscle relaxation.MethodsSTW 5‐induced relaxation of smooth muscle strips from guinea pig gastric corpus before and after pharmacological interventions were recorded with force transducers in an organ bath. ORAI1 mRNA expression was tested in the proximal stomach.Key ResultsBlockade of Ca2+‐activated K+ and Cl− channels, voltage‐gated L‐ or T‐type Ca2+ channels, TRPA1‐, TRPV1‐, adenosine or 5‐HT4 receptors, antagonizing ryanodine receptors, inhibiting cyclooxygenase or sarcoplasmic reticulum calcium ATPase did not affect STW 5‐evoked relaxation. Likewise, protein‐kinase A or G were not involved. However, the relaxation evoked by STW 5 was significantly reduced by phorbol‐12‐myristat‐13‐acetat, an activator of protein‐kinase C, by 2‐ aminoethyldiphenylborinate, an inhibitor of the IP3 receptor‐mediated Ca2+ release from the sarcoplasmic reticulum or by SKF‐96365, a nonselective store‐operated calcium entry (SOCE) blocker. Furthermore, the mixed TRPC3/SOCE inhibitor Pyr3, but not the selective TRPC3 blocker Pyr10, reduced the effect of STW 5. Finally, BTP2, a potent blocker of ORAI‐coupled SOCE, almost abolished STW 5‐evoked relaxation. Expression of ORAI1 could be demonstrated in the corpus/fundus.Conclusions & InferencesSTW 5 inhibited SOCE, most likely ORAI channels, which are modulated by IP3‐ and PKC‐dependent mechanisms. Our findings impact on the design of drugs to induce muscle relaxation and help identify phytochemicals with similar modes of actions to treat gastrointestinal disturbances.

New therapeutic strategy targeting regulation of the SERCA2 complex protects from myocardial ischemia-reperfusion injury

Abstract 7 million people suffer every year from myocardial infarction. There is significant unmet medical need for cardioprotection during MI treatment. The beta-adrenergic receptor/cyclic AMP/protein kinase A (PKA) signalling pathway regulates heart rate and contractility. Activation of cAMP-dependent PKA causes phospholamban (PLB) phosphorylation and its ability to inhibit sarcoplasmic reticulum calcium ATPase (SERCA) is lost. Discrete control of PLB phosphorylation is facilitated by the A-kinase anchoring protein (AKAP) 18g/d, which holds PKA and PLB in close proximity. We are developing a novel drug candidate, named 13M, with a highly selective mechanism of action in cardioprotection currently in pre-clinical phase. Our drug candidate disrupts the AKAP18g/d-PLB protein-protein interaction (PPI) as this may protect from ischemia reperfusion injury (IRI). We used AlphaScreen assay to screen a library of 79,000 small molecular compounds for compounds that disrupted the AKAP18δ-PLB PPI. Following secondary and tertiary screens of sub-libraries, the resulting hits were further characterized and similarity searches carried out to delineate a compound structure for further derivatization. Newly synthesized compounds were further tested in a cell-line based assay to determine compound toxicity. A combination of biochemistry, electrophysiology and heart function experiments demonstrated that the compounds exclusively block the adrenergic effect on SERCA2 without affecting its basal activity. A 40% reduction in infarction size and improved long term cardiac function was observed in an animal disease model for ischemia-reperfusion injury.

Incretin Mimetics Restore the ER-Mitochondrial Axis and Switch Cell Fate Towards Survival in LUHMES Dopaminergic-Like Neurons: Implications for Novel Therapeutic Strategies in Parkinson's Disease.

Parkinson's disease (PD) is a progressive neurodegenerative movement disorder that afflicts more than 10 million people worldwide. Available therapeutic interventions do not stop disease progression. The etiopathogenesis of PD includes unbalanced calcium dynamics and chronic dysfunction of the axis of the endoplasmic reticulum (ER) and mitochondria that all can gradually favor protein aggregation and dopaminergic degeneration. In Lund Human Mesencephalic (LUHMES) dopaminergic-like neurons, we tested novel incretin mimetics under conditions of persistent, calcium-dependent ER stress. We assessed the pharmacological effects of Liraglutide-a glucagon-like peptide-1 (GLP-1) analog-and the dual incretin GLP-1/GIP agonist DA3-CH in the unfolded protein response (UPR), cell bioenergetics, mitochondrial biogenesis, macroautophagy, and intracellular signaling for cell fate in terminally differentiated LUHMES cells. Cells were co-stressed with the sarcoplasmic reticulum calcium ATPase (SERCA) inhibitor, thapsigargin. We report that Liraglutide and DA3-CH analogs rescue the arrested oxidative phosphorylation and glycolysis. They mitigate the suppressed mitochondrial biogenesis and hyper-polarization of the mitochondrial membrane, all to re-establish normalcy of mitochondrial function under conditions of chronic ER stress. These effects correlate with a resolution of the UPR and the deficiency of components for autophagosome formation to ultimately halt the excessive synaptic and neuronal death. Notably, the dual incretin displayed a superior anti-apoptotic effect, when compared to Liraglutide. The results confirm the protective effects of incretin signaling in ER and mitochondrial stress for neuronal degeneration management and further explain the incretin-derived effects observed in PD patients.

Sarcolipin (sln) and Sarcoplasmic Reticulum calcium ATPase pump (serca1) expression increase in Japanese medaka (Oryzias latipes) skeletal muscle tissue following cold challenge

Endothermy is the process by which organisms maintain a constant body temperature despite dynamic environmental temperatures. There are two mechanisms organisms use to elevate body temperature: shivering thermogenesis (ST) and non-shivering thermogenesis (NST). Skeletal muscle NST is achieved through a futile Ca2+ cycling of sarcoplasmic reticulum Ca2+ ATPase (Serca1) in the presence of sarcolipin (Sln). Here we subjected Japanese medaka to a cold challenge to examine the expression of sln and serca1 transcripts from slow-twitch red and fast-twitch white muscle as environmental temperature decreased. We show a significant increase in relative sln and serca1 transcript expression in skeletal muscle tissues of cold-challenged Japanese medaka. The elevated transcripts support the role of Sln as a component of NST and support previous literature with the increase in serca1. To date, this is the first cold challenge on an ectothermic fish investigating sln transcripts. The ability of medaka to respond to a cold challenge with an increase in key calcium cycling components, specifically the calcium pump and sarcolipin suggest that teleost fish share a conserved transcriptional program in response to cold stimuli with fish species that possess the requisite anatomical adaptations to conserve metabolic heat.

SENP2-mediated SERCA2a deSUMOylation increases calcium overload in cardiomyocytes to aggravate myocardial ischemia/reperfusion injury.

Sarcoplasmic reticulum calcium ATPase 2a (SERCA2a) is a key protein that maintains myocardial Ca 2+ homeostasis. The present study aimed to investigate the mechanism underlying the SERCA2a-SUMOylation (small ubiquitin-like modifier) process after ischemia/reperfusion injury (I/RI) in vitro and in vivo . Calcium transient and systolic/diastolic function of cardiomyocytes isolated from Serca2a knockout (KO) and wild-type mice with I/RI were compared. SUMO-relevant protein expression and localization were detected by quantitative real-time PCR (RT-qPCR), Western blotting, and immunofluorescence in vitro and in vivo . Serca2a-SUMOylation, infarct size, and cardiac function of Senp1 or Senp2 overexpressed/suppressed adenovirus infected cardiomyocytes, were detected by immunoprecipitation, triphenyltetrazolium chloride (TTC)-Evans blue staining, and echocardiography respectively. The results showed that the changes of Fura-2 fluorescence intensity and contraction amplitude of cardiomyocytes decreased in the I/RI groups and were further reduced in the Serca2a KO + I/RI groups. Senp1 and Senp2 messenger ribose nucleic acid (mRNA) and protein expression levels in vivo and in cardiomyocytes were highest at 6 h and declined at 12 h after I/RI. However, the highest levels in HL-1 cells were recorded at 12 h. Senp2 expression increased in the cytoplasm, unlike that of Senp1. Inhibition of Senp2 protein reversed the I/RI-induced Serca2a-SUMOylation decline, reduced the infarction area, and improved cardiac function, while inhibition of Senp1 protein could not restore the above indicators. I/RI activated Senp1 and Senp2 protein expression, which promoted Serca2a-deSUMOylation, while inhibition of Senp2 expression reversed Serca2a-SUMOylation and improved cardiac function.

Lysosomal calcium loading promotes spontaneous calcium release by potentiating ryanodine receptors

Spontaneous calcium release by ryanodine receptors (RyRs) due to intracellular calcium overload results in delayed afterdepolarizations, closely associated with life-threatening arrhythmias. In this regard, inhibiting lysosomal calcium release by two-pore channel 2 (TPC2) knockout has been shown to reduce the incidence of ventricular arrhythmias under β-adrenergic stimulation. However, mechanistic investigations into the role of lysosomal function on RyR spontaneous release remain missing. We investigate the calcium handling mechanisms by which lysosome function modulates RyR spontaneous release, and determine how lysosomes are able to mediate arrhythmias by its influence on calcium loading. Mechanistic studies were conducted using a population of biophysically detailed mouse ventricular models including for the first time modeling of lysosomal function, and calibrated by experimental calcium transients modulated by TPC2. We demonstrate that lysosomal calcium uptake and release can synergistically provide a pathway for fast calcium transport, by which lysosomal calcium release primarily modulates sarcoplasmic reticulum calcium reuptake and RyR release. Enhancement of this lysosomal transport pathway promoted RyR spontaneous release by elevating RyR open probability. In contrast, blocking either lysosomal calcium uptake or release revealed an antiarrhythmic impact. Under conditions of calcium overload, our results indicate that these responses are strongly modulated by intercellular variability in L-type calcium current, RyR release, and sarcoplasmic reticulum calcium-ATPase reuptake. Altogether, our investigations identify that lysosomal calcium handling directly influences RyR spontaneous release by regulating RyR open probability, suggesting antiarrhythmic strategies and identifying key modulators of lysosomal proarrhythmic action.

High oxygen-modified packaging (HiOx-MAP) mediates HIF-1α regulation of tenderness changes during postmortem aging of yak meat

In the present study, we studied the effect of high oxygen-modified packaging (HiOx-MAP) on yak meat tenderness and the underlying mechanism. HiOx-MAP significantly increased the myofibril fragmentation index (MFI) of yak meat. In addition, western blotting showed that the expression of hypoxia-inducible factor (HIF-1α) and ryanodine receptors (RyR) in the HiOx-MAP group was reduced. HiOx-MAP increased the activity of sarcoplasmic reticulum calcium-ATPase (SERCA). The energy disperse spectroscopy (EDS) mapping showed gradually reduced calcium distribution in the treated endoplasmic reticulum. Furthermore, HiOx-MAP treatment increased the caspase-3 activity and the apoptosis rate. The activity of calmodulin protein (CaMKKβ) and AMP-activated protein kinase (AMPK) was down-regulated leading to apoptosis. These results indicated that HiOx-MAP promoted apoptosis during postmortem aging to improve the tenderization of meat.

In Vivo Treatment with a Standardized Green Tea Extract Restores Cardiomyocyte Contractility in Diabetic Rats by Improving Mitochondrial Function through SIRT1 Activation.

Background. Green tea catechins are known to promote mitochondrial function, and to modulate gene expression and signalling pathways that are altered in the diabetic heart. We thus evaluated the effectiveness of the in vivo administration of a standardized green tea extract (GTE) in restoring cardiac performance, in a rat model of early streptozotocin-induced diabetes, with a focus on the underlying mechanisms. Methods. Twenty-five male adult Wistar rats were studied: the control (n = 9), untreated diabetic animals (n = 7) and diabetic rats subjected to daily GTE administration for 28 days (n = 9). Isolated ventricular cardiomyocytes were used for ex vivo measurements of cell mechanics and calcium transients, and molecular assays, including the analysis of functional protein and specific miRNA expression. Results. GTE treatment induced an almost complete recovery of cardiomyocyte contractility that was markedly impaired in the diabetic cells, by preserving mitochondrial function and energy availability, and modulating the expression of the sarcoplasmic reticulum calcium ATPase and phospholamban. Increased Sirtuin 1 (SIRT1) expression and activity substantially contributed to the observed cardioprotective effects. Conclusions. The data supported the hypothesis that green tea dietary polyphenols, by targeting SIRT1, can constitute an adjuvant strategy for counteracting the initial damage of the diabetic heart, before the occurrence of diabetic cardiomyopathy.

Aberrant PLN-R14del Protein Interactions Intensify SERCA2a Inhibition, Driving Impaired Ca2+ Handling and Arrhythmogenesis.

Phospholamban (PLN), a key modulator of Ca2+-homeostasis, inhibits sarcoplasmic reticulum (SR) calcium-ATPase (SERCA2a) and regulates cardiac contractility. The human PLN mutation R14del has been identified in arrhythmogenic cardiomyopathy patients worldwide and is currently extensively investigated. In search of the molecular mechanisms mediating the pathological phenotype, we examined PLN-R14del associations to known PLN-interacting partners. We determined that PLN-R14del interactions to key Ca2+-handling proteins SERCA2a and HS-1-associated protein X-1 (HAX-1) were enhanced, indicating the super-inhibition of SERCA2a’s Ca2+-affinity. Additionally, histidine-rich calcium binding protein (HRC) binding to SERCA2a was increased, suggesting the inhibition of SERCA2a maximal velocity. As phosphorylation relieves the inhibitory effect of PLN on SERCA2a activity, we examined the impact of phosphorylation on the PLN-R14del/SERCA2a interaction. Contrary to PLN-WT, phosphorylation did not affect PLN-R14del binding to SERCA2a, due to a lack of Ser-16 phosphorylation in PLN-R14del. No changes were observed in the subcellular distribution of PLN-R14del or its co-localization to SERCA2a. However, in silico predictions suggest structural perturbations in PLN-R14del that could impact its binding and function. Our findings reveal for the first time that by increased binding to SERCA2a and HAX-1, PLN-R14del acts as an enhanced inhibitor of SERCA2a, causing a cascade of molecular events contributing to impaired Ca2+-homeostasis and arrhythmogenesis. Relieving SERCA2a super-inhibition could offer a promising therapeutic approach for PLN-R14del patients.

Highly Selective SERCA2a Activators: Preclinical Development of a Congeneric Group of First-in-Class Drug Leads against Heart Failure.

The stimulation of sarcoplasmic reticulum calcium ATPase SERCA2a emerged as a novel therapeutic strategy to efficiently improve overall cardiac function in heart failure (HF) with reduced arrhythmogenic risk. Istaroxime is a clinical-phase IIb compound with a double mechanism of action, Na+/K+ ATPase inhibition and SERCA2a stimulation. Starting from the observation that istaroxime metabolite PST3093 does not inhibit Na+/K+ ATPase while stimulates SERCA2a, we synthesized a series of bioisosteric PST3093 analogues devoid of Na+/K+ ATPase inhibitory activity. Most of them retained SERCA2a stimulatory action with nanomolar potency in cardiac preparations from healthy guinea pigs and streptozotocin (STZ)-treated rats. One compound was further characterized in isolated cardiomyocytes, confirming SERCA2a stimulation and in vivo showing a safety profile and improvement of cardiac performance following acute infusion in STZ rats. We identified a new class of selective SERCA2a activators as first-in-class drug candidates for HF treatment.

Basal Vascular Smooth Muscle Cell Tone in eNOS Knockout Mice Can Be Reversed by Cyclic Stretch and Is Independent of Age.

Introduction and Aims: Endothelial nitric oxide synthase (eNOS) knockout mice develop pronounced cardiovascular disease. In the present study, we describe the alterations in aortic physiology and biomechanics of eNOS knockout and C57Bl/6 control mice at 2–12 months of age, including a thorough physiological investigation of age and cyclic stretch-dependent VSMC contractility and aortic stiffness. Methods and Results: Peripheral blood pressure and aortic pulse wave velocity were measured in vivo, and aortic biomechanical studies and isometric contractions were investigated ex vivo. Age-dependent progression of aortic stiffness, peripheral hypertension, and aortic contractility in eNOS knockout mice was absent, attenuated, or similar to C57Bl/6 control mice. Voltage-gated calcium channel (VGCC)-dependent calcium influx inversely affected isometric contraction and aortic stiffening by α1-adrenergic stimulation in eNOS knockout mice. Baseline aortic stiffness was selectively reduced in eNOS knockout mice after ex vivo cyclic stretch exposure in an amplitude-dependent manner, which prompted us to investigate cyclic stretch dependent regulation of aortic contractility and stiffness. Aortic stiffness, both in baseline conditions and after activation of vascular smooth muscle cell (VSMC) contraction, was reduced with increasing cyclic stretch amplitude. This cyclic stretch dependency was attenuated with age, although aged eNOS knockout mice displayed better preservation of cyclic stretch-dependency compared to C57Bl/6 control mice. Store operated calcium entry-medicated aortic stiffening as induced by inhibiting sarcoplasmic reticulum calcium ATPase pumps with 10 µM CPA was most pronounced in the aorta of aged mice and at low cyclic stretch amplitude, but independent of eNOS. Basal aortic tonus and VSMC depolarization were highly dependent on eNOS, and were most pronounced at low cyclic stretch, with attenuation at increasing cyclic stretch amplitude. Conclusion: eNOS knockout mice display attenuated progression of arterial disease as compared to C57Bl/6 control mice. Basal VSMC tone in eNOS knockout mice could be reduced by ex vivo exposure to cyclic stretch through stretch-dependent regulation of cytosolic calcium. Both baseline and active aortic stiffness were highly dependent on cyclic stretch regulation, which was more pronounced in young versus aged mice. Other mediators of VSMC contraction and calcium handling were dependent on cyclic stretch mechanotransduction, but independent of eNOS.

Transient Post-Natal Exposure to Xenoestrogens Induces Long-Term Alterations in Cardiac Calcium Signaling

Today, non-communicable disorders are widespread worldwide. Among them, cardiovascular diseases represent the main cause of death. At the origin of these diseases, exposure to challenges during developmental windows of vulnerability (peri-conception, in utero, and early infancy periods) have been incriminated. Among the challenges that have been described, endocrine disruptors are of high concern because of their omnipresence in the environment. Worrisomely, since birth, children are exposed to a significant number of endocrine disruptors. However, the role of such early exposure on long-term cardiac health is poorly described. In this context, based on a model of rats exposed postnatally and transiently to an estrogenic compound prototype (estradiol benzoate, EB), we aimed to delineate the effects on the adult heart of such transient early exposure to endocrine disruptors and identify the underlying mechanisms involved in the potential pathogenesis. We found that this transient post-natal exposure to EB induced cardiac hypertrophy in adulthood, with increased cardiomyocyte size. The evaluation of cardiac calcium signaling, through immunoblot approaches, highlighted decreased expression of the sarcoplasmic reticulum calcium ATPase 2 (SERCA2) and decreased Nuclear Factor of Activated T Cells (NFAT3) phosphorylation as a potential underlying mechanism of cardiac hypertrophy. Furthermore, the treatment of cardiomyocytes with EB in vitro induced a decrease in SERCA2 protein levels. Overall, our study demonstrates that early transient exposure to EB induces permanent cardiac alterations. Together, our data highlight SERCA2 down-regulation as a potential mechanism involved in the cardiac pathogenesis induced by EB. These results suggest programming of adult heart dysfunctions such as arrhythmia and heart failures by early exposure to endocrine disruptors and could open new perspectives for treatment and prevention.

Deep learning accelerates discovery of novel modulators targeting cardiac calcium transport

Sarcoplasmic reticulum calcium ATPase (SERCA) is a transmembrane pump critical for calcium transport from the cytosol to the lumen of the sarcoplasmic reticulum in cardiac cells. Deregulation and deactivation of the SERCA pump is a hallmark of heart failure; thus, the development of SERCA activating drugs has emerged as a promising approach for the treatment for this condition. We used a virtual screening strategy developed by our group that incorporates machine learning classifiers and deep learning generators for data augmentation to design SERCA modulators that stimulate intracellular Ca2+ transport in cardiac cells.

Mitochondria Isolated from Hearts Subjected to Ischemia/Reperfusion Benefit from Adenine Nucleotide Translocase 1 Overexpression.

Reperfusion is the only feasible therapy following myocardial infarction, but reperfusion has been shown to damage mitochondrial function and disrupt energy production in the heart. Adenine nucleotide translocase 1 (ANT1) facilitates the transfer of ADP/ATP across the inner mitochondrial membrane; therefore, we tested whether ANT1 exerts protective effects on mitochondrial function during ischemia/reperfusion (I/R). The hearts of wild-type (WT) and transgenic ANT1-overexpressing (ANT1-TG) rats were exposed to I/R injury using the standard Langendorff technique, after which mitochondrial function, hemodynamic parameters, infarct size, and components of the contractile apparatus were determined. ANT1-TG hearts expressed higher ANT protein levels, with reduced levels of oxidative 4-hydroxynonenal ANT modifications following I/R. ANT1-TG mitochondria isolated from I/R hearts displayed stable calcium retention capacity (CRC) and improved membrane potential stability compared with WT mitochondria. Mitochondria isolated from ANT1-TG hearts experienced less restricted oxygen consumption than WT mitochondria after I/R. Left ventricular diastolic pressure (Pdia) decreased in ANT1-TG hearts compared with WT hearts following I/R. Preserved diastolic function was accompanied by a decrease in the phospho-lamban (PLB)/sarcoplasmic reticulum calcium ATPase (SERCA2a) ratio in ANT1-TG hearts compared with that in WT hearts. In addition, the phosphorylated (P)-PLB/PLB ratio increased in ANT1-TG hearts after I/R but not in WT hearts, which indicated more effective calcium uptake into the sarcoplasmic reticulum in ANT1-TG hearts. In conclusion, ANT1-TG rat hearts coped more efficiently with I/R than WT rat hearts, which was reflected by preserved mitochondrial energy balance, diastolic function, and calcium dynamics after reperfusion.

Alterations in the Nucleocytoplasmic Transport in Heart Transplant Rejection

Nucleocytoplasmic transport is a crucial process for cell function. Previous studies have observed alterations in different molecules involved in it, relating them to ventricular function. However, there are no published data evaluating possible differences in the expression of these molecules in heart transplantation (HT) recipients. Our objective is to evaluate whether its levels are related to the appearance of cellular rejection (CR) during the first year after HT. A prospective clinical cohort that included patients undergoing HT between January 2017 and January 2019 (n=46). Blood samples for the analysis of importin 5 (IMP5), nucleoporin 153 (Nup153); RAN-GTPaseAP1 (RanGAP1), and sarcoplasmic reticulum calcium ATPase (ATP-aseCaTransp) were collected approximately 2 months post-HT. The levels obtained were correlated with the incidence of at least moderate CR during the first year of follow-up. Results showed that 17.39% of the patients had at least moderate CR during the first year of follow-up. Higher levels of IMP5, Nup153, and RanGAP1 were observed in this group. This difference was statistically significant in the case of Nup153 and RanGAP1 (15.94 ± 14.00 vs 28.62 ± 23.61, P=.048; 21.95 ± 15.97 vs 40.90 ± 27.16, P=.026, respectively); there was an opposite trend in the ATP-aseCaTransp case. Patients with at least a moderate degree of CR during follow-up showed higher serum levels of IMP5, Nup153, and RanGAP1. The prognostic usefulness of the determination of these biomarkers and whether their elevation during follow-up would facilitate early, noninvasive identification of patients with CR remains to be clarified.

Motor Unit Force Potentiation and Calcium Handling Protein Concentration in Rat Fast Muscle After Resistance Training.

Post-tetanic potentiation (PTP) of force depends on intramuscular Ca2+ levels and sensitivity and may be affected by fatigue. The aim of this study was to determine the ability of isolated fast fatigue-resistant (FR) and fast-fatigable (FF) motor units (MUs) to potentiate force evoked with single and 40-Hz electrical stimulation after 5 weeks of voluntary weight-lifting training. Tetanic contractions evoked by gradually increasing (10–150 Hz) stimulation frequency served as conditioning stimulation. Additionally, the concentration of myosin light chain kinase and proteins engaged in calcium handling was measured in rat fast medial gastrocnemius muscle. After the training, the potentiation of twitch force and peak rate of force development was increased in FF but not FR MUs. Force potentiation of 40-Hz tetanic contractions was increased in both fast MU types. After the training, the twitch duration of FR MUs was decreased, and FF MUs were less prone to high-frequency fatigue during conditioning stimulation. Muscle concentration of triadin was increased, whereas concentrations of ryanodine receptor 1, junctin, FKBP12, sarcoplasmic reticulum calcium ATPase 1, parvalbumin, myosin light chain kinase, and actomyosin adenosine triphosphatase content were not modified. After short-term resistance training, the twitch contraction time and twitch:tetanus force ratio of FR MUs are decreased, and PTP ability is not changed. However, PTP capacity is increased in response to submaximal activation. In FF MUs increase in PTP ability coexists with lesser fatigability. Further work is required to find out if the increase in triadin concentration has any impact on the observed contractile response.