Abstract 3426: Myostatin Deletion Preserves Cardiac Function in Senescent Mice

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Michael R Morissette ◽  
Janelle C Stricker ◽  
Anthony Rosenzweig
Keyword(s):  
Cardiac Function ◽  
Rhode Island ◽  
Cardiac Fibrosis ◽  
Physiological Role ◽  
Heart Association ◽  
Negative Regulator ◽  
Heart Weight ◽  
Cardiomyocyte Hypertrophy ◽  
Mrna Levels ◽  
Age Related

Myostatin (MSTN) is a well-known negative regulator of skeletal muscle mass, and MSTN inhibition is being considered as therapy for multiple conditions associated with muscle wasting, including sarcopenia of aging. We have previously shown that MSTN inhibits phenylephrine-induced cardiomyocyte hypertrophy, however whether MSTN has a physiological role in regulating cardiac hypertrophy or function at baseline or with aging remains unclear. To determine if MSTN is dynamically regulated with aging, we performed QRT-PCR on hearts from male wild-type (WT) senescent mice (24 months old (mos)) and rats (32 mos). MSTN mRNA levels were increased in old versus young (4 mos) hearts (2.5- and 4-fold respectively, p<0.05). To study the functional significance of MSTN in aging, we maintained germline MSTN-knockout mice (MSTN −/− ) and their WT littermates for 24 –27 months. We found no difference in heart weight of aged male MSTN −/− compared to WT mice (162.5±17.0 (n=4) vs 153.2±4.2 (n=4) mg, p=0.51), which would argue against an inhibitory role for MSTN in age-related increases in cardiac mass. We also performed echocardiography on unanesthetized senescent MSTN −/− and WT mice. MSTN −/− mice had better fractional shortening (58.1±2.0 (n=7) vs 49.4±1.2 (n=8) %, p=0.002) and smaller LV end-diastolic diameter (3.41±0.19 vs 2.71±0.14 mm, p=0.012) compared to WT. The decreased cardiac function seen in aged WT mice was associated with increased cardiac fibrosis on Masson-Trichrome stained sections. Western blot analysis also demonstrated a 3.3-fold increase in phospholamban phosphorylation in MSTN −/− hearts (p<0.05), compared to WT, while no differences in SERCA2a or calsequestrin protein levels were seen. We conclude that MSTN increases in the heart with aging, and that genetic deletion of MSTN results in improved cardiac function without a difference in heart mass in senescent mice. Decreased cardiac fibrosis and increased inhibition (phosphorylation) of phospholamban likely contribute to the better cardiac function seen in senescent MSTN −/− mice. These results suggest that inhibiting MSTN for sarcopenia in the elderly may also benefit cardiac function and could represent a novel therapeutic approach for ameliorating cardiac dysfunction and/or fibrosis. This research has received full or partial funding support from the American Heart Association, AHA Founders Affiliate (Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, Vermont).

A FVII Deficiency Induces Cardiac Fibrosis in Mice Resulting in Systolic and Diastolic Dysfunction.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1747-1747
Author(s):  
Haifeng Xu ◽  
Mayra Sandoval-Cooper ◽  
Deborah L. Donahue ◽  
Victoria A. Ploplis ◽  
Francis J. Castellino
Keyword(s):  
Cardiac Function ◽  
Cardiac Fibrosis ◽  
Inflammatory Responses ◽  
Coagulation Factor ◽  
Restrictive Cardiomyopathy ◽  
Left Ventricular ◽  
Heart Weight ◽  
Mrna Levels ◽  
Wild Type ◽  
Fvii Deficiency

Abstract Mice severely deficient in coagulation Factor (F)VII that survive to adulthood have been developed, thus allowing the study of spontaneous bleeding and inflammatory phenotypes under conditions of a deficiency of extrinsic coagulation, especially in organs e.g., the heart, that continually undergo normal mechanical challenge. Mice genetically modified to produce very low levels (∼1% of wild-type) of coagulation FVII (FVIItTA/tTA) spontaneously developed heart abnormalities that were revealed by echocardiography. There were no significant differences between groups at baseline for the hemodynamic and respiratory parameters: temperature and heart rate (HR). The end-systolic functions of FVIItTA/tTA mice heart were comparable to wild-type (WT) controls. However, there were significant changes in the end-diastolic parameters of FVIItTA/tTA hearts. The diameter at end-diastole in FVIItTA/tTA mice was smaller compared to WT mice, which was due to the stiffness of the interventricular wall. When viewed from the parasternal short-axis, these mice had evidence of hypokinesis, indicating alteration of the elastic properties of the left ventricular (LV) wall. Correspondingly, the stroke volume, ejection fraction, fractional shortening, and cardiac output were lower in FVIItTA/tTA mice, compared to WT mice. Mitral valve inflow was compromised in FVIItTA/tTA mice, as demonstrated by the reduced early/late (E/A) filling ratio. We found that the spontaneous impaired cardiac function in FVIItTA/tTA mice was associated with an increased ratio of heart weight to body weight. Decreases in ventricular size, accompanied by reductions in systolic and diastolic functions, suggest a restrictive cardiomyopathy, consistent with an infiltrative myopathic process. Microscopic analysis of mouse hearts showed severe patchy fibrosis in FVIItTA/tTA mice. Hemosiderin deposition in hearts of these mice, along with large increases in inflammatory cells, ultimately resulting in widespread collagen deposition, were found. Significant increases in mRNA levels of TGF-beta, TNF-alpha, and a variety of matrix metalloproteinases, beginning at early ages in FVIItTA/tTA mice, supported the fibrotic pathology. The results of this study demonstrated that hemorrhagic and inflammatory responses to a severe FVII deficiency resulted in the development of cardiac fibrosis, manifest echocardiographically as a restrictive cardiomyopathy, with significantly compromised ventricular diastolic and systolic functions. These data also suggest that a FVII deficiency differentially regulates the expression level of inflammation and extracellular matrix proteins, which result in compromised cardiac function.

Abstract P495:

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Magda C. Diaz ◽  
Raúl Flores-Vergara ◽  
Ivonne Olmedo ◽  
Zully Pedrozo
Keyword(s):  
Heart Failure ◽  
Cardiac Function ◽  
Protein Content ◽  
Cardiac Tissue ◽  
Negative Regulator ◽  
Mrna Levels ◽  
Tubule Formation ◽  
T Tubules ◽  
Factor C ◽  
Old Mice

Background: Transverse tubules (T-tubules) play a key role in cardiac contractility. The expression of Bridging integrator 1 (BIN1), specifically, the cardiac isoforms BIN1+13 and BIN1+ 13+17 promote the formation and ultrastructure of T-tubules and it has been described that the transcriptional factor c-Myc may be a negative regulator of BIN1 expression. Polycystin-1 (PC1) is a mechanosensor in cardiomyocytes, with a crucial role to maintain cardiac function. Our aim was to determine whether PC1 regulates BIN1-induced T-tubule formation by a c-Myc-regulated mechanism. Methods: We used adult C57BL/6 cardiomyocyte-specific knockout mice (PC1 KO). Cardiac function was tested by echocardiography, whereas protein and mRNA content of BIN1, PC1 and c-Myc were measured using western blot and qRT-PCR, respectively. T-tubules were analyzed by transmission electron microscopy (TEM). For statistical analyses, t-test or one-way ANOVA followed by Tukey's test were used. Differences were considered significant at p < 0.05. Results: Survival of PC1 KO mice decreased dramatically after 7 months of age, with clear symptoms of dilated cardiomyopathy and heart failure (decreased fractional shortening and ejection fraction). Ventricular cardiac tissue of PC1 KO mice without (< 7-month-old mice) and with symptoms (7-9-month-old mice) of heart failure (HF) was associated with reduced levels of BIN1 protein content. Total BIN1 mRNA in PC1 KO mice without symptoms did not show differences as compared to controls, but it was significantly decreased in mice with symptoms of HF. Moreover, PC1 KO mice with and without symptoms showed decreased BIN1+13 mRNA levels, whereas BIN1+13+17 mRNA was only increased in mice without symptoms. These changes in BIN1 isoforms were related with T-tubules, which showed increased lumen and decreased intra-luminal density in PC1 KO mice with and without symptoms. Furthermore, c-Myc protein content was increased in cardiac tissue of PC1 KO mice. Conclusion: PC1 may be a regulator of the differential expression of cardiac isoforms of BIN1 in cardiomyocytes by a mechanism that involves negative regulation of c-Myc, related to loss of T-tubule ultrastructure and heart failure development.

Abstract 28: In Vivo Knockdown of Mirna-15b Results in Increased Cardiac Hypertrophy and Fibrosis in Response to Pressure Overload of the Mouse Heart

2012 ◽  
Vol 111 (suppl_1) ◽  
Author(s):  
Anke J Tijsen ◽  
Ingeborg van der Made ◽  
Elza D van Deel ◽  
Monika Hiller ◽  
Yolan J Reckman ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Cardiac Function ◽  
Cardiac Fibrosis ◽  
Negative Control ◽  
Heart Weight ◽  
Mouse Heart ◽  
Hypertrophic Response ◽  
Wide Range ◽  
Tgfβ Pathway

MiRNAs play an important role in the control of diverse aspects of cardiac function. MiR-15b is highly expressed in the heart and is found consistently upregulated in hypertrophic and failing hearts. To investigate the function of miR-15b in the heart we set out two experiments. In the first experiment we generated two independent transgenic mouse lines that drive miR-15b expression under the αMHC-promotor and show a three and four fold overexpression of miR-15b. Strikingly, both lines show a decrease in heart weight/tibia length of 20% in adult and aged mice when compared to littermate controls. We investigated the response of these transgenic mice to thoracic aorta constriction (TAC) and found no differences in the hypertrophic response or in cardiac function measured by echocardiography between wild-type and transgenic mice. In a second experiment, we inhibited miR-15b using LNA-based antimiRs. In these mice, TAC resulted in an increased hypertrophic response and increased cardiac fibrosis when compared to a negative control antimiR. A wide range of predicted targets of miR-15 belong to the pathways of the TGFβ-superfamily and using a smad-dependent reporter we show that miR-15b inhibits TGFβ-induced Smad activity in HepG2 cells. One of the predicted targets in the TGFβ pathway is TGFβ receptor 1 (TGFβR1), of which the 3’UTR contains six predicted miR-15 binding sites. This suggests that the phenotype in the transgenic mice and after knockdown of miR-15b may be (partly) mediated by repression of TGFβR1. Indeed, in the adult miR-15b transgenic hearts we found a downregulation of TGFβR1 mRNA and protein and we confirmed binding of miR-15 to the TGFβR1 3’UTR by luciferase assays. In conclusion, miR-15b causes a cardiac hypotrophic phenotype at baseline in transgenic mice and inhibition of miR-15b leads to a stronger hypertrophic and fibrotic response after TAC. Furthermore miR-15b inhibits the TGFβ pathway by targeting the TGFβR1 and possibly other targets in this pathway. This research is funded by the Dutch Heart Foundation (NHF grant #2007B077).

scholarly journals Osteopontin RNA aptamer can prevent and reverse pressure overload-induced heart failure

2017 ◽  
Vol 113 (6) ◽  
pp. 633-643 ◽  
Author(s):  
Jihe Li ◽  
Keyvan Yousefi ◽  
Wen Ding ◽  
Jayanti Singh ◽  
Lina A. Shehadeh
Keyword(s):  
Heart Failure ◽  
Cardiac Function ◽  
Cardiac Dysfunction ◽  
Cardiac Fibrosis ◽  
Cardiac Myocyte ◽  
Pressure Overload ◽  
Cardiomyocyte Hypertrophy ◽  
Therapeutic Effects ◽  
Rna Aptamer ◽  
Myocyte Hypertrophy

Aims Cardiac myocyte hypertrophy, the main compensatory response to chronic stress in the heart often progresses to a state of decompensation that can lead to heart failure. Osteopontin (OPN) is an effector for extracellular signalling that induces myocyte growth and fibrosis. Although increased OPN activity has been observed in stressed myocytes and fibroblasts, the detailed and long term effects of blocking OPN signalling on the heart remain poorly defined. Targeting cardiac OPN protein by an RNA aptamer may be beneficial for tuning down OPN pathologic signalling. We aimed to demonstrate the therapeutic effects of an OPN RNA aptamer on cardiac dysfunction. Methods and results In vivo, we show that in a mouse model of pressure overload, treating at the time of surgeries with an OPN aptamer prevented cardiomyocyte hypertrophy and cardiac fibrosis, blocked OPN downstream signalling (PI3K and Akt phosphorylation), reduced expression of extracellular matrix (Lum, Col3a1, Fn1) and hypertrophy (Nppa, Nppb) genes, and prevented cardiac dysfunction. Treating at two months post-surgeries with the OPN aptamer reversed cardiac dysfunction and fibrosis and myocyte hypertrophy. While genetic homozygous deletion of OPN reduced myocardial wall thickness, surprisingly cardiac function and myocardial fibrosis, specifically collagen deposition and myofibroblast infiltration, were worse compared with wild type mice at three months of pressure overload. Conclusion Taken together, these data demonstrate that tuning down cardiac OPN signalling by an OPN RNA aptamer is a novel and effective approach for preventing cardiac hypertrophy and fibrosis, improving cardiac function, and reversing pressure overload-induced heart failure.

Abstract P139: Genetic Signature Of Accelerated Cardiac Fibrosis Due To Trpa1 Ablation

Hypertension ◽  
2021 ◽  
Vol 78 (Suppl_1) ◽  
Author(s):  
Shuangtao Ma ◽  
Donna Wang
Keyword(s):  
Matrix Metalloproteinases ◽  
Matrix Protein ◽  
Cardiac Fibrosis ◽  
Collagen Fibers ◽  
Extracellular Matrix Protein ◽  
Myocardial Tissue ◽  
Mrna Levels ◽  
Wild Type ◽  
Genetic Signature ◽  
Age Related

While our previous study demonstrated that loss of transient receptor potential ankyrin 1 ( Trpa1 ) accelerates age-related cardiac fibrosis in mice, the underlying mechanism of potential anti-fibrotic property of TRPA1 remains largely unknown. TRPA1 is a sensor of oxidative stress and may play a protective role in age-related diseases. In this study, we performed quantitative polymerase chain reaction array analyses of the mRNA expression of 84 fibrosis-related genes in the myocardial tissue of 12-month-old Trpa1 -/- mice with significant cardiac fibrosis and age-matched wild-type mice without cardiac fibrosis. The mRNA levels of Col1a2 and Col3a1 in the myocardial tissue were similar between Trpa1 -/- and wild-type mice, suggesting comparable cardiac collagen synthesis in the two strains. Matrix metalloproteinases are major enzymes responsible for degradation of collagen fibers. The results show that the mRNA levels of matrix metalloproteinases, including Mmp1a , Mmp2 , Mmp3 , Mmp8 , Mmp9 , Mmp13 , and Mmp14 , in the heart were similar between Trpa1 -/- and wild-type mice. Nevertheless, we identified 7 significantly changed genes in the heart between the two strains. The expression levels of Acta2 , Inhbe , Ifng , and Ccl11 were significantly increased with fold changes of 3.1, 1.9, 1.9, and 1.5 (all P < 0.05), respectively, while Timp3 , Stat6 , and Ilk were significantly decreased with fold changes of 0.3, 0.5, and 0.7 (all P < 0.05), respectively, in the heart of Trpa1 -/- mice compared with wild-type mice. Acta2 , the most upregulated gene in Trpa1 -/- hearts, is a marker of myofibroblasts. Its upregulation indicates increased differentiation from fibroblasts into myofibroblasts in Trpa1 -/- hearts compared with wild-type hearts. Timp3 , the most downregulated gene in Trpa1 -/- hearts, codes an extracellular matrix protein TIMP3, which not only inhibits matrix metalloproteinases but also regulate post-translational modification of collagen fibers. Taken together, these findings suggest that upregulation of Acta2 and downregulation of Timp3 may serve as genetic signature or play a role in accelerated age-related cardiac fibrosis due to TRPA1 ablation.

Abstract 215: Angiotensin-II-induced Cardiac Remodeling is Reduced in TNFR1-deficient Mice Despite Increased Blood Pressure

Hypertension ◽  
2014 ◽  
Vol 64 (suppl_1) ◽  
Author(s):  
Clemens Duerrschmid ◽  
Fernando Aguirre-Amezquite ◽  
George E Taffet ◽  
Mark L Entman ◽  
Sandra B Haudek
Keyword(s):  
Blood Pressure ◽  
Angiotensin Ii ◽  
Cardiac Function ◽  
Cardiac Fibrosis ◽  
Weight Ratio ◽  
Heart Weight ◽  
Ang Ii ◽  
Long Term Effects ◽  
2D Echocardiography ◽  
Collagen Iii

Background: Infusion of angiotensin-II (Ang-II) to wild-type (WT) mice results in hypertension, development of interstitial cardiac fibrosis and hypertrophy, and deterioration of myocardial function. We previously showed that after 1 week of Ang-II infusion, these effects were absent in mice deficient in tumor necrosis factor receptor 1 (TNFR1). We now investigated long-term effects of Ang-II infusion. Methods: WT and TNFR1-KO mice were infused with Ang-II for 6 weeks. Systolic blood pressure (SBP) was measured by tail-cuff plethysmography; cardiac function by 2D-echocardiography and Doppler ultrasound. Hearts were analyzed for collagen deposition (histology) and expression of fibrosis- and hypertrophy- related genes (quantitative PCR). Results: In WT mice, SBP increased within 7 days and remained elevated at 6 weeks (152±4 mmHg); cardiac fibrosis developed after 1 week and persisted at 6 weeks (6.2±1.1% collagen area). By contrast, in TNFR1-KO mice, SBP at 7 days was low, but increased by 6 weeks (144±4 mmHg), whereas cardiac fibrosis was absent at 1 week and did not significantly increase by 6 weeks (2.5±0.5%). In support of these data, collagen I and collagen III mRNA expression at 6 weeks were upregulated in WT (2.9±0.6 and 4.1±0.8 -fold over sham), but not in TNFR1-KO hearts (1.3±0.1 and 1.8±0.2). In both mouse groups, cardiac hypertrophy and cardiac dysfunction developed over time, however, these changes were less prominent in TNFR1-KO mice: at 6 weeks, the heart-weight to body-weight ratio in WT was 6.7±0.4, in TNFR1-KO mice 5.5±0.2; the changes in anterior and posterior wall thicknesses in WT were 44±12% and 32±15%, in TNFR1-KO mice 19±8% and 17±10%; the change in ejection fraction in WT was -67±12%, in TNFR1-KO mice -39±5%; and the change in Tei-index (myocardial performance) in WT was 18±9%, in TNFR1-KO -1±7%. Also, hypertrophy-related atrial natriuretic peptide (ANP) and beta-myosin heavy chain (b-MHC) mRNA were upregulated in WT (4.3±0.9 and 4.3±0.6 -fold over sham), but less in TNFR1-KO hearts (2.6±0.5 and 2.4±0.5). Conclusion: Despite a significant increase in blood pressure over 6 weeks of Ang-II infusion, TNFR1-KO mice developed less cardiac fibrosis and hypertrophy and had better cardiac function compared to WT mice.

scholarly journals Stromal interaction molecule 1 is essential for normal cardiac homeostasis through modulation of ER and mitochondrial function

2014 ◽  
Vol 306 (8) ◽  
pp. H1231-H1239 ◽  
Author(s):  
Helen E. Collins ◽  
Lan He ◽  
Luyun Zou ◽  
Jing Qu ◽  
Lufang Zhou ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Er Stress ◽  
Mitochondrial Function ◽  
Cardiac Fibrosis ◽  
Mitochondrial Fission ◽  
Physiological Role ◽  
Left Ventricular ◽  
Adult Heart ◽  
Stromal Interaction Molecule 1 ◽  
Factor C

The endoplasmic reticulum (ER) Ca2+ sensor stromal interaction molecule 1 (STIM1) has been implicated as a key mediator of store-dependent and store-independent Ca2+ entry pathways and maintenance of ER structure. STIM1 is present in embryonic, neonatal, and adult cardiomyocytes and has been strongly implicated in hypertrophic signaling; however, the physiological role of STIM1 in the adult heart remains unknown. We, therefore, developed a novel cardiomyocyte-restricted STIM1 knockout (crSTIM1-KO) mouse. In cardiomyocytes isolated from crSTIM1-KO mice, STIM1 expression was reduced by ∼92% with no change in the expression of related store-operated Ca2+ entry proteins, STIM2, and Orai1. Immunoblot analyses revealed that crSTIM1-KO hearts exhibited increased ER stress from 12 wk, as indicated by increased levels of the transcription factor C/EBP homologous protein (CHOP), one of the terminal markers of ER stress. Transmission electron microscopy revealed ER dilatation, mitochondrial disorganization, and increased numbers of smaller mitochondria in crSTIM1-KO hearts, which was associated with increased mitochondrial fission. Using serial echocardiography and histological analyses, we observed a progressive decline in cardiac function in crSTIM1-KO mice, starting at 20 wk of age, which was associated with marked left ventricular dilatation by 36 wk. In addition, we observed the presence of an inflammatory infiltrate and evidence of cardiac fibrosis from 20 wk in crSTIM1-KO mice, which progressively worsened by 36 wk. These data demonstrate for the first time that STIM1 plays an essential role in normal cardiac function in the adult heart, which may be important for the regulation of ER and mitochondrial function.

scholarly journals IL-6 deficiency attenuates p53 protein accumulation in aged male mouse hippocampus

2019 ◽  
Vol 21 (1) ◽  
pp. 29-43 ◽  
Author(s):  
Izabela Bialuk ◽  
Magdalena Cieślińska ◽  
Oksana Kowalczuk ◽  
Tomasz A. Bonda ◽  
Jacek Nikliński ◽  
...  
Keyword(s):  
P53 Protein ◽  
Mrna Level ◽  
Negative Regulator ◽  
Lower Amount ◽  
Protein Accumulation ◽  
Mrna Levels ◽  
Memory Decline ◽  
Mdm2 Protein ◽  
Age Related ◽  
Excessive Accumulation

Abstract Our earlier studies demonstrated slower age-related memory decline in IL-6-deficient than in control mice. Therefore, in the present study we evaluated the effect of IL-6 deficiency and aging on expression of p53, connected with accumulation of age-related cellular damages, in hippocampus of 4- and 24-month-old IL-6-deficient C57BL/6J (IL-6KO) and wild type control (WT) mice. The accumulation of p53 protein in hippocampus of aged IL-6KO mice was significantly lower than in aged WT ones, while p53 mRNA level was significantly higher in IL-6-deficient mice, what indicates that the effect was independent on p53 transcription. Presence of few apoptotic cells in hippocampal dentate gyrus and lack of changes in levels of pro-apoptotic Bax, antiapoptotic Bcl-2, as well as in p21 protein in aged animals of both genotypes, points to low transcriptional activity of p53, especially in aged WT mice. Because the amount of p53 protein did not correlate with the level of Mdm2 protein, its main negative regulator, other than Mdm2-dependent mechanism was involved in p53 build-up. Significantly higher mRNA levels of autophagy-associated genes: Pten, Tsc2, and Dram1 in IL-6KO mice, in conjunction with significantly lower amount of Bcl-2 protein in 4-month-old IL-6KO mice, suggests that lack of IL-6/STAT3/Bcl-2 signaling could account for better autophagy performance in these mice, preventing excessive accumulation of proteins. Taken together, attenuated p53 protein build-up, absence of enhanced apoptosis, and transcriptional up-regulation of autophagy-associated genes imply that IL-6 deficiency may protect hippocampus from age-related accumulation of cellular damages.

scholarly journals Mechanisms of Systolic Cardiac Dysfunction in PP2A, PP5 and PP2AxPP5 Double Transgenic Mice

2021 ◽  
Vol 22 (17) ◽  
pp. 9448
Author(s):  
Mara-Francine Dörner ◽  
Peter Boknik ◽  
Friedrich Köpp ◽  
Igor B. Buchwalow ◽  
Joachim Neumann ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Natriuretic Peptide ◽  
Cardiac Fibrosis ◽  
Relaxation Times ◽  
Heart Weight ◽  
Mrna Levels ◽  
Adrenergic Stimulation ◽  
Pathophysiological Role ◽  
Double Transgenic Mice

As part of our ongoing studies on the potential pathophysiological role of serine/threonine phosphatases (PP) in the mammalian heart, we have generated transgenic mice with cardiac muscle cell-specific overexpression of PP2Acα (PP2A) and PP5 (PP5). For further studies we crossbred PP2A and PP5 mice to obtain PP2AxPP5 double transgenic mice (PP2AxPP5, DT) and compared them with littermate wild-type mice (WT) serving as a control. The mortality of DT mice was greatly enhanced vs. other genotypes. Cardiac fibrosis was noted histologically and mRNA levels of collagen 1α, collagen 3α and fibronectin 1 were augmented in DT. DT and PP2A mice exhibited an increase in relative heart weight. The ejection fraction (EF) was reduced in PP2A and DT but while the EF of PP2A was nearly normalized after β-adrenergic stimulation by isoproterenol, it was almost unchanged in DT. Moreover, left atrial preparations from DT were less sensitive to isoproterenol treatment both under normoxic conditions and after hypoxia. In addition, levels of the hypertrophy markers atrial natriuretic peptide and B-type natriuretic peptide as well as the inflammation markers interleukin 6 and nuclear factor kappa B were increased in DT. PP2A enzyme activity was enhanced in PP2A vs. WT but similar to DT. This was accompanied by a reduced phosphorylation state of phospholamban at serine-16. Fittingly, the relaxation times in left atria from DT were prolonged. In summary, cardiac co-overexpression of PP2A and PP5 were detrimental to animal survival and cardiac function, and the mechanism may involve dephosphorylation of important regulatory proteins but also fibrosis and inflammation.

scholarly journals Neutrophil PAD4 negatively influences cardiac function and remodeling with increasing age

2021 ◽  
Vol 42 (Supplement_1) ◽  
Author(s):  
S Van Bruggen ◽  
J Van Wauwe ◽  
P Carai ◽  
L Frederix ◽  
L Vangilbergen ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiac Function ◽  
Cardiac Fibrosis ◽  
Essential Gene ◽  
Heart Function ◽  
Systolic Function ◽  
Natural Aging ◽  
Collagen Deposition ◽  
National Budget ◽  
Age Related

Abstract Background Aging can be viewed as a status of chronic inflammation, in which neutrophils have a lower threshold for activation. The enzyme peptidylarginine deiminase 4 (PAD4), which catalyzes the conversion of arginine to citrulline, will be activated in a certain population of neutrophils. When this conversion takes place on the histones, neutrophils can form neutrophil extracellular traps (NETs), which are both prothrombotic and proinflammatory. Mice lacking this enzyme systemically were previously reported to be protected from age-related fibrosis. Purpose We aimed to study the long-term effect of neutrophils on cardiac health during the process of natural aging. We hypothesized that neutrophil PAD4, and in consequence NETs, are involved in cardiac fibrosis development, which in turn will result in impaired cardiac function. Methods We generated a mouse model of impaired NET release capability via deletion of PAD4, a NET-essential gene, under the neutrophil-specific promoter (PAD4fl/flMRP8Cre+). In order to study heart failure (HF) development, these specific deletion mice and their littermate controls were aged for a period of two years (coinciding with approximately 70 years of age in the human population; the age at which HF is the number one cause of hospitalization), after which cardiac function and remodeling were evaluated by echocardiography and histology, respectively. A separate set of young mice (12 weeks) were evaluated in parallel. Results We performed a comprehensive echocardiography analysis including both structural and functional parameters. As for systolic function, we could see that in old wild type (WT) mice, ejection fraction (EF) significantly decreased as compared to EF in young and healthy (YH) mice (YH - 67±6%, WT - 53±10%; p&lt;0.0001) (Figure 1B). However, this decrease in systolic function was absent in the old PAD4fl/flMRP8Cre+ mice, with EF being comparable to the YH group (PAD4fl/flMRP8Cre+ - 67±7%; p=0.9169) (figure 1 A,B). As for diastolic function, again we could see a marked decrease in E/A ratio in the WT as compared to the YH population (YH- 1.50±0.23, WT – 1.21±0.17; p&lt;0.0001), while this functional deterioration was absent in aged PAD4fl/flMRP8Cre+ animals (PAD4fl/flMRP8Cre+ - 1.38±0.21; p=0.0837) (Figure 1 C,D). To link this decline in heart function to tissue remodeling, we quantified collagen deposition in the heart. We saw that natural aging resulted in an increase in cardiac collagen deposition in the WT population as compared to YH mice (YH – 0.86±0.63%, WT – 4.02±1.71%). This increased collagen deposition was absent in the neutrophil deletion mice (PAD4fl/flMRP8Cre+ - 1.7±0.76%). Additionally, when comparing WT to PAD4 deletion-mice, we saw that the increase in collagen deposition is significantly higher in the WT mice (p&lt;0.0001). Conclusion Our data confirms neutrophil PAD4 involvement in heart failure progression by promoting cardiac fibrosis, resulting in cardiac dysfunction. FUNDunding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Fonds Wetenschappelijk Onderzoek (FWO) - Vlaanderen

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