Abstract 419: Stim1 is Associated With Calcium Microdomains That are Required for Myofilament Remodeling and Signaling During Cardiac Hypertrophy

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Cory Parks ◽  
Ryan D Sullivan ◽  
Salvatore Mancarella
Keyword(s):  
Cardiac Hypertrophy ◽  
Heart Function ◽  
Cardiac Contractility ◽  
Pressure Overload ◽  
Left Ventricular ◽  
Neonatal Rat ◽  
Excitable Cells ◽  
Rat Cardiomyocytes ◽  
Cell Contractility

Stromal Interaction Protein 1 (STIM1) is the intracellular component of the store operated calcium channels. It is a ubiquitous Ca2+ sensor, prevalently located in the sarcoplasmic reticulum. In non-excitable cells, STIM1 is a key element in the generation of Ca2+signals that lead to gene expression and cell proliferation. A growing body of literature now suggests that STIM1 is important for normal heart function and plays a key role in the development of pathological cardiac hypertrophy. However, the precise mechanisms involving STIM1 and the Ca2+ signaling in excitable cells are not clearly established. We show that in neonatal rat cardiomyocytes, the spatial properties of STIM1-dependent Ca2+ signals determine restricted Ca2+ microdomains that regulate myofilaments remodeling and spatially segregated activation of pro-hypertrophic factors. Indeed, in vivo data obtained from an inducible cardiac restricted STIM1 knockout mouse, exhibited left ventricular dilatation associated with reduced cardiac contractility, which was corroborated by impaired single cell contractility. Furthermore, mice lacking STIM1 showed less adverse structural remodeling in response to pathological pressure overload-induced cardiac hypertrophy (transverse aortic constriction, TAC). We further show that the Ca2+ pool associated with STIM1 is the ON switch for extracellular signal-regulated kinase (ERK1/2)-mediated cytoplasm to nucleus signaling. These results highlight how STIM1-dependent Ca2+ microdomains have a major impact on intracellular Ca2+ homeostasis, cytoskeletal remodeling, signaling and cardiac function, even when excitation-contraction coupling is present.

scholarly journals LCZ696 Ameliorates Oxidative Stress and Pressure Overload-Induced Pathological Cardiac Remodeling by Regulating the Sirt3/MnSOD Pathway

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Shi Peng ◽  
Xiao-feng Lu ◽  
Yi-ding Qi ◽  
Jing Li ◽  
Juan Xu ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Heart Failure ◽  
Cardiac Hypertrophy ◽  
Pressure Overload ◽  
Neonatal Rat ◽  
Cardiomyocyte Hypertrophy ◽  
Rat Cardiomyocytes ◽  
Pathological Cardiac Hypertrophy

Aims. We aimed to investigate whether LCZ696 protects against pathological cardiac hypertrophy by regulating the Sirt3/MnSOD pathway. Methods. In vivo, we established a transverse aortic constriction animal model to establish pressure overload-induced heart failure. Subsequently, the mice were given LCZ696 by oral gavage for 4 weeks. After that, the mice underwent transthoracic echocardiography before they were sacrificed. In vitro, we introduced phenylephrine to prime neonatal rat cardiomyocytes and small-interfering RNA to knock down Sirt3 expression. Results. Pathological hypertrophic stimuli caused cardiac hypertrophy and fibrosis and reduced the expression levels of Sirt3 and MnSOD. LCZ696 alleviated the accumulation of oxidative reactive oxygen species (ROS) and cardiomyocyte apoptosis. Furthermore, Sirt3 deficiency abolished the protective effect of LCZ696 on cardiomyocyte hypertrophy, indicating that LCZ696 induced the upregulation of MnSOD and phosphorylation of AMPK through a Sirt3-dependent pathway. Conclusions. LCZ696 may mitigate myocardium oxidative stress and apoptosis in pressure overload-induced heart failure by regulating the Sirt3/MnSOD pathway.

scholarly journals Cellular Interplay and Cytokine Hierarchy Cause Pathological Cardiac Hypertrophy in RAF1-Mutant Noonan Syndrome

2017 ◽  
Author(s):  
Jiani C. Yin ◽  
Mathew J. Platt ◽  
Xixi Tian ◽  
Xue Wu ◽  
Peter H. Backx ◽  
...  
Keyword(s):  
Cardiac Hypertrophy ◽  
Noonan Syndrome ◽  
Cardiac Contractility ◽  
Pressure Overload ◽  
Neutralizing Antibody ◽  
Cell Types ◽  
Left Ventricular ◽  
Cardiomyocyte Hypertrophy

AbstractNoonan syndrome (NS) is caused by mutations in RAS/ERK pathway genes, and is characterized by craniofacial, growth, cognitive and cardiac defects. NS patients with kinase-activating RAF1 alleles typically develop pathological left ventricular hypertrophy (LVH), which is reproduced in Raf1L613V/+ knock-in mice. Here, using inducible Raf1L613V expression, we show that LVH results from the interplay of cardiac cell types. Cardiomyocyte Raf1L613V enhances Ca2+ sensitivity and cardiac contractility without causing hypertrophy. Raf1L613V expression in cardiomyocytes or activated fibroblasts exacerbates pressure overload-evoked fibrosis. Endothelial/endocardial (EC) Raf1L613V causes cardiac hypertrophy without affecting contractility. Co-culture and neutralizing antibody experiments reveal a cytokine (TNF/IL6) hierarchy in Raf1L613V-expressing ECs that drives cardiomyocyte hypertrophy in vitro. Furthermore, post-natal TNF inhibition normalizes the increased wall thickness and cardiomyocyte hypertrophy in vivo. We conclude that NS cardiomyopathy involves cardiomyocytes, ECs, and fibroblasts, TNF/IL6 signaling components represent potential therapeutic targets, and abnormal EC signaling might contribute to other forms of LVH.

Abstract 276: The Regulatory Effects Of Peroxiredoxin II On Phospholamban Phosphorylation And Cardiac Contractile Function In Vivo

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Wen Zhao ◽  
Xiaojing Shi ◽  
Wenjuan Zhou ◽  
Huimin Wang ◽  
Xuepeng Geng ◽  
...  
Keyword(s):  
Cardiac Contractility ◽  
Left Ventricular ◽  
Active Inhibitor ◽  
Rat Cardiomyocytes ◽  
Cardiac Contractile ◽  
Adenoviral Delivery ◽  
Anti Oxidant ◽  
Contraction And Relaxation ◽  
Phospholamban Phosphorylation

Peroxiredoxin II (prxII), a cytosolic form of the anti-oxidant peroxiredoxin family, was recently found to be decreased in failing human hearts. Interestingly, in hyperdynamic hearts of two genetically modified mouse models with: a) phospholamban ablation; and b) overexpression of the active inhibitor-1 of protein phosphatase 1, the levels of this cellular peroxidase (prxII) were markedly increased. Acute overexpression of prxII by adenoviral-delivery in adult rat cardiomyocytes (Ad-prxII) was associated with decreases in the basal rates of contraction and relaxation, as well as calcium kinetics. Accordingly, Ad-prxII-AS infected cardiomyocytes exhibited enhanced contractile parameters and Ca-kinetics. The depressed or increased contractility by Ad-prxII or Ad-prxII-AS was associated with parallel decreases or increases in phosphorylation of phospholamban (Ser16 and Thr17). To determine the in vivo effects of prxII on cardiac contractility, three transgenic lines (TG) with 2-3 fold cardiac-specific overexpression of prxII were generated and their cardiac morphologic and functional phenotypes were characterized. The TG mice exhibited no alterations in cardiac pathology or morphology up to 4 months of age. However, langendorf perfusions revealed that cardiac contractility, including the rates of contraction and relaxation (±dp/dtmax) as well as the left ventricular end systolic pressure (LVESP), were significantly depressed in TG mice (to 75, 76 and 63%, respectively), compared to WTs (100%). The depressed function was not associated with any alterations in the expression levels of key SR calcium handling proteins: SERCA2, total phospholamban, calsequestrin and ryanodine receptor. However, the levels of the phosphorylated PLN at Ser16 were found to be reduced to 50% in the TG mice, compared to WTs. These findings indicate that prxII, an anti-oxidant protein, may regulate basal cardiac contractile performance in vivo through phospholamban phosphorylation.

Abstract 285: Cardiac Inflammation and Fibrosis Induced by Heart Failure Are Reversed by Short-Duration Estrogen Therapy

2012 ◽  
Vol 111 (suppl_1) ◽  
Author(s):  
Andrea Iorga ◽  
Rangarajan Nadadur ◽  
Salil Sharma ◽  
Jingyuan Li ◽  
Mansoureh Eghbali
Keyword(s):  
Heart Failure ◽  
Estrogen Therapy ◽  
Pressure Overload ◽  
Decompensated Heart Failure ◽  
Left Ventricular ◽  
Neonatal Rat ◽  
In Vivo Model ◽  
Anti Inflammatory

Heart failure is generally characterized by increased fibrosis and inflammation, which leads to functional and contractile defects. We have previously shown that short-term estrogen (E2) treatment can rescue pressure overload-induced decompensated heart failure (HF) in mice. Here, we investigate the anti-inflammatory and anti-fibrotic effects of E2 on reversing the adverse remodeling of the left ventricle which occurs during the progression to heart failure. Trans-aortic constriction procedure was used to induce HF. Once the ejection fraction reached ∼30%, one group of mice was sacrificed and the other group was treated with E2 (30 αg/kg/day) for 10 days. In vitro, co-cultured neonatal rat ventricular myocytes and fibroblasts were treated with Angiotensin II (AngII) to simulate cardiac stress, both in the presence or absence of E2. In vivo RT-PCR showed that the transcript levels of the pro-fibrotic markers Collagen I, TGFβ, Fibrosin 1 (FBRS) and Lysil Oxidase (LOX) were significantly upregulated in HF (from 1.00±0.16 to 1.83±0.11 for Collagen 1, 1±0.86 to 4.33±0.59 for TGFβ, 1±0.52 to 3.61±0.22 for FBRS and 1.00±0.33 to 2.88±0.32 for LOX) and were reduced with E2 treatment to levels similar to CTRL. E2 also restored in vitro AngII-induced upregulation of LOX, TGFβ and Collagen 1 (LOX:1±0.23 in CTRL, 6.87±0.26 in AngII and 2.80±1.5 in AngII+E2; TGFβ: 1±0.08 in CTRL, 3.30±0.25 in AngII and 1.59±0.21 in AngII+E2; Collagen 1: 1±0.05 in CTRL.2±0.01 in AngII and 0.65±0.02 (p<0.05, values normalized to CTRL)). Furthermore, the pro-inflammatory interleukins IL-1β and IL-6 were upregulated from 1±0.19 to 1.90±0.09 and 1±0.30 to 5.29±0.77 in the in vivo model of HF, respectively, and reversed to CTRL levels with E2 therapy. In vitro, IL-1β was also significantly increased ∼ 4 fold from 1±0.63 in CTRL to 3.86±0.14 with AngII treatment and restored to 1.29±0.77 with Ang+E2 treatment. Lastly, the anti-inflammatory interleukin IL-10 was downregulated from 1.00±0.17 to 0.49±0.03 in HF and reversed to 0.67±0.09 in vivo with E2 therapy (all values normalized to CTRL). This data strongly suggests that one of the mechanisms for the beneficial action of estrogen on left ventricular heart failure is through reversal of inflammation and fibrosis.

scholarly journals Bakuchiol protects against pathological cardiac hypertrophy by blocking NF-κB signaling pathway

2018 ◽  
Vol 38 (5) ◽  
Author(s):  
Zheng Wang ◽  
Lu Gao ◽  
Lili Xiao ◽  
Lingyao Kong ◽  
Huiting Shi ◽  
...  
Keyword(s):  
Cardiac Hypertrophy ◽  
Signaling Pathway ◽  
Pressure Overload ◽  
Neonatal Rat ◽  
Oral Gavage ◽  
Aortic Banding ◽  
Rat Cardiomyocytes ◽  
Pathological Cardiac Hypertrophy ◽  
First Time

Bakuchiol (Bak), a monoterpene phenol isolated from the seeds of Psoralea corylifolia, has been widely used to treat a large variety of diseases in both Indian and Chinese folkloric medicine. However, the effects of Bak on cardiac hypertrophy remain unclear. Therefore, the present study was designed to determine whether Bak could alleviate cardiac hypertrophy. Mice were subjected to aortic banding (AB) to induce cardiac hypertrophy model. Bak of 1 ml/100 g body weight was given by oral gavage once a day from 1 to 8 weeks after surgery. Our data demonstrated for the first time that Bak could attenuate pressure overload-induced cardiac hypertrophy and could attenuate fibrosis and the inflammatory response induced by AB. The results further revealed that the effect of Bak on cardiac hypertrophy was mediated by blocking the activation of the NF-κB signaling pathway. In vitro studies performed in neonatal rat cardiomyocytes further proved that the protective effect of Bak on cardiac hypertrophy is largely dependent on the NF-κB pathway. Based on our results, Bak shows profound potential for its application in the treatment of pathological cardiac hypertrophy, and we believe that Bak may be a promising therapeutic candidate to treat cardiac hypertrophy and heart failure.

A gene therapeutic approach to inhibit calcium and integrin binding protein 1 ameliorates maladaptive remodelling in pressure overload

2018 ◽  
Vol 115 (1) ◽  
pp. 71-82 ◽  
Author(s):  
Andrea Grund ◽  
Malgorzata Szaroszyk ◽  
Janina K Döppner ◽  
Mona Malek Mohammadi ◽  
Badder Kattih ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiac Hypertrophy ◽  
Cardiac Function ◽  
Binding Protein ◽  
Treatment Strategies ◽  
Pressure Overload ◽  
Cellular Growth ◽  
Neonatal Rat ◽  
Rat Cardiomyocytes ◽  
Pathological Cardiac Hypertrophy

Abstract Aims Chronic heart failure is becoming increasingly prevalent and is still associated with a high mortality rate. Myocardial hypertrophy and fibrosis drive cardiac remodelling and heart failure, but they are not sufficiently inhibited by current treatment strategies. Furthermore, despite increasing knowledge on cardiomyocyte intracellular signalling proteins inducing pathological hypertrophy, therapeutic approaches to target these molecules are currently unavailable. In this study, we aimed to establish and test a therapeutic tool to counteract the 22 kDa calcium and integrin binding protein (CIB) 1, which we have previously identified as nodal regulator of pathological cardiac hypertrophy and as activator of the maladaptive calcineurin/NFAT axis. Methods and results Among three different sequences, we selected a shRNA construct (shCIB1) to specifically down-regulate CIB1 by 50% upon adenoviral overexpression in neonatal rat cardiomyocytes (NRCM), and upon overexpression by an adeno-associated-virus (AAV) 9 vector in mouse hearts. Overexpression of shCIB1 in NRCM markedly reduced cellular growth, improved contractility of bioartificial cardiac tissue and reduced calcineurin/NFAT activation in response to hypertrophic stimulation. In mice, administration of AAV-shCIB1 strongly ameliorated eccentric cardiac hypertrophy and cardiac dysfunction during 2 weeks of pressure overload by transverse aortic constriction (TAC). Ultrastructural and molecular analyses revealed markedly reduced myocardial fibrosis, inhibition of hypertrophy associated gene expression and calcineurin/NFAT as well as ERK MAP kinase activation after TAC in AAV-shCIB1 vs. AAV-shControl treated mice. During long-term exposure to pressure overload for 10 weeks, AAV-shCIB1 treatment maintained its anti-hypertrophic and anti-fibrotic effects, but cardiac function was no longer improved vs. AAV-shControl treatment, most likely resulting from a reduction in myocardial angiogenesis upon downregulation of CIB1. Conclusions Inhibition of CIB1 by a shRNA-mediated gene therapy potently inhibits pathological cardiac hypertrophy and fibrosis during pressure overload. While cardiac function is initially improved by shCIB1, this cannot be kept up during persisting overload.

Abstract 1582: Adenosine A3 Receptor Deficiency Exerts Unanticipated Protective Effects on Pressure Overloaded-Induced Left Ventricular Hypertrophy and Dysfunction in Mice

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Zhongbing Lu ◽  
John Fassett ◽  
Xin Xu ◽  
Xinli Hu ◽  
Guangshuo Zhu ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Ventricular Hypertrophy ◽  
Pressure Overload ◽  
Heart Association ◽  
Left Ventricular ◽  
Neonatal Rat ◽  
Protective Effects ◽  
Rat Cardiomyocytes ◽  
Extracellular Adenosine ◽  
Myocardial Oxidative Stress

Endogenous adenosine can protect the overloaded heart against the development of hypertrophy and heart failure, but the contribution of A 1 receptors (A 1 R) and A 3 receptors(A 3 R) is not known. To test the hypothesis A 1 R and A 3 R can protect the heart against systolic overload, we exposed A 3 R gene deficient (A 3 R KO) mice and A 1 R KO mice to transverse aortic constriction (TAC). Contrary to our hypothesis, A 3 R KO attenuated 5 weeks TAC-induced left ventricular (LV) hypertrophy (ratio of ventricular mass/body weight increased to 7.6 ±0.3 mg/g in wild type (Wt) mice as compared with 6.3±0.4 mg/g in KO), fibrosis and dysfunction (LV ejection fraction decreased to 43±2.5% and 55±4.2% in Wt and KO mice, respectively). A 3 R KO also attenuated the TAC-induced increases of myocardial ANP and the oxidative stress markers 3-nitrotyrosine(3-NT ) and 4-hydroxynonenal. In addition, A 3 R KO significantly attenuated TAC-induced activation of multiple MAP kinase pathways, and the activation of Akt-GSK signaling pathway. In contrast, A 1 R-KO increased TAC-induced mortality, but did not alter ventricular hypertrophy or dysfunction compared to Wt mice. In mice in which extracellular adenosine production was impaired by CD73 KO, TAC caused greater hypertrophy and dysfunction, and increased myocardial 3-NT, indicates that extracellular adenosine protects heart against TAC-induced ventricular oxidative stress and hypertrophy. In neonatal rat cardiomyocytes induced to hypertrophy with phenylephrine, the adenosine analogue 2-chloroadenosine (CADO) reduced cell area, protein synthesis, ANP and 3-NT. Antagonism of A3R significantly potentiated the anti-hypertrophic effects of CADO. Our data demonstrated that extracellular adenosine exerts protective effects on the overloaded heart, but A 3 R act counter to the protective effect of adenosine. The data suggest that selective attenuation of A 3 R activity might be a novel approach to attenuate pressure overload-induced myocardial oxidative stress, LV hypertrophy and dysfunction. This research has received full or partial funding support from the American Heart Association, AHA Midwest Affiliate (Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, South Dakota & Wisconsin).

Role of myofibrillogenesis regulator-1 in myocardial hypertrophy

2006 ◽  
Vol 290 (1) ◽  
pp. H279-H285 ◽  
Author(s):  
Xiuhua Liu ◽  
Tianbo Li ◽  
Sheng Sun ◽  
Feifei Xu ◽  
Yiguang Wang
Keyword(s):  
Rna Interference ◽  
Cardiac Hypertrophy ◽  
Protein Expression ◽  
Western Blotting ◽  
Left Ventricular ◽  
Neonatal Rat ◽  
Heart Weight ◽  
Homologous Gene ◽  
Ang Ii ◽  
Rat Cardiomyocytes

Myofibrillogenesis regulator-1 (MR-1) is a novel homologous gene, identified from a human skeletal muscle cDNA library, that interacts with contractile proteins and exists in human myocardial myofibrils. The present study investigated MR-1 protein expression in hypertrophied myocardium and MR-1 involvement in cardiac hypertrophy. Cardiac hypertrophy was induced by abdominal aortic stenosis (AAS) in Sprague-Dawley rats. Left ventricular (LV) hypertrophy was assessed by the ratio of LV wet weight to whole heart weight (LV/HW) or LV weight to body weight (LV/BW). Rat MR-1 (rMR-1) expression in the myocardium was detected by immunohistochemical and Western blotting analysis. Hypertrophy was induced by ANG II incubation in cultured neonatal rat cardiomyocytes. The effect of rMR-1 RNA interference on ANG II-induced hypertrophy was studied by transfection of cardiomyocytes with an RNA interference plasmid, pSi-1, which targets rMR-1. Hypertrophy in cardiomyocytes was assessed by [3H]Leu incorporation and myocyte size. rMR-1 protein expression in cardiomyocytes was detected by Western blotting. We found that AAS resulted in a significant increase in LV/HW and LV/BW: 89% and 86%, respectively ( P < 0.01). Immunohistochemistry and Western blot analysis demonstrated upregulated rMR-1 protein expression in hypertrophic myocardium. ANG II induced a 24% increase in [3H]Leu incorporation and a 65.8% increase in cell size compared with control cardiomyocytes ( P < 0.01), which was prevented by treatment with losartan, an angiotensin (AT1) receptor inhibitor, or transfection with pSi-1. rMR-1 expression increased in ANG II-induced hypertrophied cardiomyocytes, and pSi-1 transfection abolished the upregulation. These findings suggest that MR-1 is associated with cardiac hypertrophy in rats in vivo and in vitro.

Diverse regulation of IP3 and ryanodine receptors by pentazocine through σ1-receptor in cardiomyocytes

2013 ◽  
Vol 305 (8) ◽  
pp. H1201-H1212 ◽  
Author(s):  
Hideaki Tagashira ◽  
Md. Shenuarin Bhuiyan ◽  
Kohji Fukunaga
Keyword(s):  
Cardiac Hypertrophy ◽  
Diastolic Pressure ◽  
Ryanodine Receptors ◽  
Pressure Overload ◽  
Left Ventricular ◽  
Female Rats ◽  
In Vivo Studies ◽  
Atp Production ◽  
Cultured Cardiomyocytes

Although pentazocine binds to σ1-receptor (σ1R) with high affinity, the physiological relevance of its binding remains unclear. We first confirmed that σ1R stimulation with pentazocine rescues contractile dysfunction following pressure overload (PO)-induced cardiac hypertrophy ovariectomized (OVX) female rats. In in vivo studies, vehicle, pentazocine (0.5–1.0 mg/kg ip), and NE-100 (1.0 mg/kg po), a σ1R antagonist, were administered for 4 wk (once daily) starting from the onset of aortic banding after OVX. We also examined antihypertrophic effects of pentazocine (0.5–1 μM) in cultured cardiomyocytes exposed to angiotensin II. Pentazocine administration significantly inhibited PO-induced cardiac hypertrophy and rescued hypertrophy-induced impairment of cardiac dysfunctions such as left ventricular end-diastolic pressure, left ventricular developed pressure, and left ventricular contraction and relaxation (±dp/dt) rates. Coadministration of NE-100 with pentazocine eliminated pentazocine-induced amelioration of heart dysfunction. Interestingly, pentazocine administration inhibited PO-induced σ1R reduction and inositol-1,4,5-trisphosphate (IP3) receptor type 2 (IP3R2) upregulation in heart. Therefore, the reduced mitochondrial ATP production following PO was restored by pentazocine administration. Furthermore, we found that σ1R binds to the ryanodine receptor (RyR) in addition to IP3 receptor (IP3R) in cardiomyocytes. The σ1R/RyR complexes were decreased following OVX-PO and restored by pentazocine administration. We noticed that pentazocine inhibits the ryanodine-induced Ca2+ release from sarcoplasmic reticulum (SR) in cultured cardiomyocytes. Taken together, the stimulation of σ1R by pentazocine rescues cardiac dysfunction by restoring IP3R-mediated mitochondrial ATP production and by suppressing RyR-mediated Ca2+ leak from SR in cardiomyocytes.

scholarly journals Orai1 Channel Inhibition Preserves Left Ventricular Systolic Function and Normal Ca 2+ Handling After Pressure Overload

Circulation ◽  
2020 ◽  
Vol 141 (3) ◽  
pp. 199-216 ◽  
Author(s):  
Fiona Bartoli ◽  
Marc A. Bailey ◽  
Baptiste Rode ◽  
Philippe Mateo ◽  
Fabrice Antigny ◽  
...  
Keyword(s):  
Cardiac Hypertrophy ◽  
Systolic Function ◽  
Systolic Dysfunction ◽  
Pressure Overload ◽  
Left Ventricular Systolic Function ◽  
Left Ventricular ◽  
Specific Expression ◽  
Channel Inhibition

Background: Orai1 is a critical ion channel subunit, best recognized as a mediator of store-operated Ca 2+ entry (SOCE) in nonexcitable cells. SOCE has recently emerged as a key contributor of cardiac hypertrophy and heart failure but the relevance of Orai1 is still unclear. Methods: To test the role of these Orai1 channels in the cardiac pathophysiology, a transgenic mouse was generated with cardiomyocyte-specific expression of an ion pore-disruptive Orai1 R91W mutant (C-dnO1). Synthetic chemistry and channel screening strategies were used to develop 4-(2,5-dimethoxyphenyl)-N-[(pyridin-4-yl)methyl]aniline (hereafter referred to as JPIII), a small-molecule Orai1 channel inhibitor suitable for in vivo delivery. Results: Adult mice subjected to transverse aortic constriction (TAC) developed cardiac hypertrophy and reduced ventricular function associated with increased Orai1 expression and Orai1-dependent SOCE (assessed by Mn 2+ influx). C-dnO1 mice displayed normal cardiac electromechanical function and cellular excitation-contraction coupling despite reduced Orai1-dependent SOCE. Five weeks after TAC, C-dnO1 mice were protected from systolic dysfunction (assessed by preserved left ventricular fractional shortening and ejection fraction) even if increased cardiac mass and prohypertrophic markers induction were observed. This is correlated with a protection from TAC-induced cellular Ca 2+ signaling alterations (increased SOCE, decreased [Ca 2+ ] i transients amplitude and decay rate, lower SR Ca 2+ load and depressed cellular contractility) and SERCA2a downregulation in ventricular cardiomyocytes from C-dnO1 mice, associated with blunted Pyk2 signaling. There was also less fibrosis in heart sections from C-dnO1 mice after TAC. Moreover, 3 weeks treatment with JPIII following 5 weeks of TAC confirmed the translational relevance of an Orai1 inhibition strategy during hypertrophic insult. Conclusions: The findings suggest a key role of cardiac Orai1 channels and the potential for Orai1 channel inhibitors as inotropic therapies for maintaining contractility reserve after hypertrophic stress.

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