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 ◽  
...  

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.

2021 ◽  
Vol 11 ◽  
Author(s):  
Paula Bollmann ◽  
Franziska Werner ◽  
Marko Jaron ◽  
Tom A. Bruns ◽  
Hartmut Wache ◽  
...  

As part of our ongoing studies on the potential pathophysiological role of serine/threonine phosphatases (PP) in the mammalian heart, we have generated mice with cardiac-specific overexpression of PP2Cβ (PP2C-TG) and compared them with littermate wild type mice (WT) serving as a control. Cardiac fibrosis was noted histologically in PP2C-TG. Collagen 1a, interleukin-6 and the natriuretic peptides ANP and BNP were augmented in PP2C-TG vs. WT (p < 0.05). Left atrial preparations from PP2C-TG were less resistant to hypoxia than atria from WT. PP2C-TG maintained cardiac function after the injection of lipopolysaccharide (LPS, a model of sepsis) and chronic isoproterenol treatment (a model of heart failure) better than WT. Crossbreeding of PP2C-TG mice with PP2A-TG mice (a genetic model of heart failure) resulted in double transgenic (DT) mice that exhibited a pronounced increase of heart weight in contrast to the mild hypertrophy noted in the mono-transgenic mice. The ejection fraction was reduced in PP2C-TG and in PP2A-TG mice compared with WT, but the reduction was the highest in DT compared with WT. PP2A enzyme activity was enhanced in PP2A-TG and DT mice compared with WT and PP2C-TG mice. In summary, cardiac overexpression of PP2Cβ and co-overexpression of both the catalytic subunit of PP2A and PP2Cβ were detrimental to cardiac function. PP2Cβ overexpression made cardiac preparations less resistant to hypoxia than WT, leading to fibrosis, but PP2Cβ overexpression led to better adaptation to some stressors, such as LPS or chronic β-adrenergic stimulation. Hence, the effect of PP2Cβ is context sensitive.


2016 ◽  
Vol 310 (2) ◽  
pp. H269-H278 ◽  
Author(s):  
Matthew J. Brody ◽  
Li Feng ◽  
Adrian C. Grimes ◽  
Timothy A. Hacker ◽  
Timothy M. Olson ◽  
...  

We previously reported that the cardiomyocyte-specific leucine-rich repeat containing protein (LRRC)10 has critical functions in the mammalian heart. In the present study, we tested the role of LRRC10 in the response of the heart to biomechanical stress by performing transverse aortic constriction on Lrrc10-null ( Lrrc10−/−) mice. Mild pressure overload induced severe cardiac dysfunction and ventricular dilation in Lrrc10−/−mice compared with control mice. In addition to dilation and cardiomyopathy, Lrrc10−/−mice showed a pronounced increase in heart weight with pressure overload stimulation and a more dramatic loss of cardiac ventricular performance, collectively suggesting that the absence of LRRC10 renders the heart more disease prone with greater hypertrophy and structural remodeling, although rates of cardiac fibrosis and myocyte dropout were not different from control mice. Lrrc10−/−cardiomyocytes also exhibited reduced contractility in response to β-adrenergic stimulation, consistent with loss of cardiac ventricular performance after pressure overload. We have previously shown that LRRC10 interacts with actin in the heart. Here, we show that His150of LRRC10 was required for an interaction with actin, and this interaction was reduced after pressure overload, suggesting an integral role for LRRC10 in the response of the heart to mechanical stress. Importantly, these experiments demonstrated that LRRC10 is required to maintain cardiac performance in response to pressure overload and suggest that dysregulated expression or mutation of LRRC10 may greatly sensitize human patients to more severe cardiac disease in conditions such as chronic hypertension or aortic stenosis.


2002 ◽  
pp. 795-802 ◽  
Author(s):  
F Fallo ◽  
V Pezzi ◽  
L Barzon ◽  
P Mulatero ◽  
F Veglio ◽  
...  

BACKGROUND: The presence and pathophysiological role of CYP11B1 (11beta-hydroxylase) gene in the zona glomerulosa of human adrenal cortex is still controversial. METHODS: In order to specifically quantify CYP11B1, CYP11B2 (aldosterone synthase) and CYP17(17alpha-hydroxylase) mRNA levels, we developed a real-time RT-PCR assay and examined the expression in a series of adrenal tIssues, including six normal adrenals from patients adrenalectomized for renal cancer and twelve aldosterone-producing adenomas (APA) from patients with primary aldosteronism. RESULTS: CYP11B1 mRNA levels were clearly detected in normal adrenals, which comprised both zona glomerulosa and fasciculata/reticularis cells, but were also measured at a lower range (P<0.05) in APA. The levels of CYP11B2 mRNA were lower (P<0.005) in normal adrenals than in APA. CYP17 mRNAlevels were similar in normal adrenals and in APA. In patients with APA, CYP11B2 and CYP11B1 mRNA levels were not correlated either with basal aldosterone or with the change from basal aldosterone in response to posture or to dexamethasone. No correlation between CYP11B1 mRNA or CYP11B2 mRNA and the percentage of zona fasciculata-like cells was observed in APA. CONCLUSIONS: Real-time RT-PCR can be reliably used to quantify CYP11B1 and CYP11B2 mRNA levels in adrenal tIssues. Expression of CYP11B1 in hyperfunctioning zona glomerulosa suggests an additional formation of corticosterone via 11beta-hydroxylase, providing further substrate for aldosterone biosynthesis. CYP11B1 and CYP11B2 mRNA levels in APA are not related to the in vivo secretory activity of glomerulosa cells, where post-transcriptional factors might ultimately regulate aldosterone production.


2008 ◽  
Vol 294 (6) ◽  
pp. H2889-H2897 ◽  
Author(s):  
Qianwen Wang ◽  
Rajakumar V. Donthi ◽  
Jianxun Wang ◽  
Alex J. Lange ◽  
Lewis J. Watson ◽  
...  

During ischemia and heart failure, there is an increase in cardiac glycolysis. To understand if this is beneficial or detrimental to the heart, we chronically elevated glycolysis by cardiac-specific overexpression of phosphatase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2) in transgenic mice. PFK-2 controls the level of fructose-2,6-bisphosphate (Fru-2,6-P2), an important regulator of phosphofructokinase and glycolysis. Transgenic mice had over a threefold elevation in levels of Fru-2,6-P2. Cardiac metabolites upstream of phosphofructokinase were significantly reduced, as would be expected by the activation of phosphofructokinase. In perfused hearts, the transgene caused a significant increase in glycolysis that was less sensitive to inhibition by palmitate. Conversely, oxidation of palmitate was reduced by close to 50%. The elevation in glycolysis made isolated cardiomyocytes highly resistant to contractile inhibition by hypoxia, but in vivo the transgene had no effect on ischemia-reperfusion injury. Transgenic hearts exhibited pathology: the heart weight-to-body weight ratio was increased 17%, cardiomyocyte length was greater, and cardiac fibrosis was increased. However, the transgene did not change insulin sensitivity. These results show that the elevation in glycolysis provides acute benefits against hypoxia, but the chronic increase in glycolysis or reduction in fatty acid oxidation interferes with normal cardiac metabolism, which may be detrimental to the heart.


Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Michael R Morissette ◽  
Janelle C Stricker ◽  
Anthony Rosenzweig

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).


1994 ◽  
Vol 266 (4) ◽  
pp. E560-E566 ◽  
Author(s):  
J. E. Friedman

The objective of these studies was to determine the molecular basis for the activation of phosphoenolpyruvate carboxykinase (PEPCK) gene transcription during prolonged submaximal exercise. Mice were fed a high-carbohydrate diet for 1 wk and exercised continuously by swimming for up to 120 min. The level of hepatic PEPCK mRNA increased progressively during exercise, reaching 510% above control, whereas transcription of the PEPCK gene increased 1,000%, before decreasing to control levels within 60 min of recovery. In transgenic mice carrying a chimeric gene consisting of the PEPCK promoter linked to a reporter gene for bovine growth hormone (bGH), PEPCK(-460)-bGH, the level of hepatic bGH mRNA increased by 490% in response to exercise, similar to the increase in the expression of the native PEPCK gene. However, in transgenic mice with a deletion of the glucocorticoid regulatory unit, PEPCK(-355)-bGH, bGH mRNA did not increase above control values. In transgenic mice with a block mutation in adenosine 3',5'-cyclic monophosphate (cAMP) regulatory regions -90/-82 and -250/-234, PEPCK cAMP response element 1 (CRE-1)/P3(1)-bGH, exercise increased bGH mRNA 260% above controls. Adrenalectomy (Adx) had no effect on PEPCK mRNA levels in nonexercised mice, whereas in adrenalectomized (Adx)-exercised mice, PEPCK mRNA increased only 80% above basal, and, in Adx mice injected with dexamethasone, PEPCK mRNA increased with exercise 570% above controls. Exercise was also associated with a large increase in transcription of the gene for the transcription factor CCAAT/enhancer-binding protein beta (C/EBP-beta) and a smaller rise in transcription of c-jun gene, both of which returned to control levels during recovery.(ABSTRACT TRUNCATED AT 250 WORDS)


2012 ◽  
Vol 111 (suppl_1) ◽  
Author(s):  
Anke J Tijsen ◽  
Ingeborg van der Made ◽  
Elza D van Deel ◽  
Monika Hiller ◽  
Yolan J Reckman ◽  
...  

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).


2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
Julia U Sprenger ◽  
Viacheslav O Nikolaev

PURPOSE: cAMP is a central regulator of cardiac function and disease. This global second messenger acts in a compartmentalized fashion, and changes in cAMP dynamics are linked to cardiac diseases. In this project, we visualized cAMP signals directly in such microdomains to gain insights into the molecular mechanisms involved in cAMP compartmentation and its alterations in hypertrophy. Methods: We generated transgenic mice expressing a new Förster resonance energy transfer (FRET)-based cAMP sensor Epac1-camps-PLN to measure cAMP dynamics in the microdomain around the sarco/endoplasmic reticulum Ca2+-ATPase 2 (SERCA2). This sensor is targeted to SERCA2 via phospholamban (PLN). Results: Colocalization and cell fractionation analysis confirmed proper localization of the sensor in transgenic mouse hearts. qPCR analysis revealed a two-fold overexpression of PLN. However, no adverse cardiac phenotype could be detected by histological analysis and heart weight to body weight ratios. Local cAMP dynamics were measured using freshly isolated adult ventricular myocytes and compared to cAMP signals in the bulk cytosol using cardiomyocytes from Epac1-camps mice. We detected the predominant role of phosphodiesterases (PDEs) 4 and 3 in the SERCA2 compartment under basal conditions. These PDEs were responsible for shaping the microdomain and its segregation from the cytosolic compartment. Interestingly, beta1-adrenergic stimulation led to a stronger increase of local cAMP in the SERCA2 compartment compared to the bulk cytosol. 8 weeks after transverse aortic constriction (TAC), PDE4 activity was downregulated in the SERCA2 microdomain compared to sham cardiomyocytes. Conclusion: We successfully generated transgenic mice expressing the targeted Epac1-camps-PLN biosensor to visualize cAMP dynamics in the SERCA2 compartment. We could show distinct cAMP dynamics around the SERCA2 compartment compared to the bulk cytosol and uncovered its alterations in hypertrophied cardiomyocytes


2005 ◽  
Vol 83 (2) ◽  
pp. 123-130 ◽  
Author(s):  
Sheila A Doggrell ◽  
Janet C Wanstall

On release from cardiac mast cells, α-chymase converts angiotensin I (Ang I) to Ang II. In addition to Ang II formation, α-chymase is capable of activating TGF-β1 and IL-1β, forming endothelins consisting of 31 amino acids, degrading endothelin-1, altering lipid metabolism, and degrading the extracellular matrix. Under physiological conditions the role of chymase in the mast cells of the heart is uncertain. In pathological situations, chymase may be secreted and have important effects on the heart. Thus, in animal models of cardiomyopathy, pressure overload, and myocardial infarction, there are increases in both chymase mRNA levels and chymase activity in the heart. In human diseased heart homogenates, alterations in chymase activity have also been reported. These findings have raised the possibility that inhibition of chymase may have a role in the therapy of cardiac disease. The selective chymase inhibitors developed to date include TY-51076, SUN-C8257, BCEAB, NK320, and TEI-E548. These have yet to be tested in humans, but promising results have been obtained in animal models of myocardial infarction, cardiomyopathy, and tachycardia-induced heart failure. It seems likely that orally active inhibitors of chymase could have a place in the treatment of cardiac diseases where injury-induced mast cell degranulation contributes to the pathology.Key words: cardiac chymase, pathophysiological role, inhibition.


2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Gang Luo ◽  
Hongxia Xu ◽  
Yinuo Huang ◽  
Dapeng Mo ◽  
Ligang Song ◽  
...  

The main causes of Alzheimer’s disease remain elusive. Previous data have implicated the BACE-1 protein as a central player in the pathogenesis of Alzheimer’s disease. However, many inhibitors of BACE-1 have failed during preclinical and clinical trials for AD treatment. Therefore, uncovering the exact role of BACE-1 in AD may have significant impact on the future development of therapeutic agents. Three- and six-month-old female APP/PS1 double transgenic mice were used to study abnormal accumulation of BACE-1 protein in brains of mice here. Immunofluorescence, immunohistochemistry, and western blot were performed to measure the distributing pattern and expression level of BACE-1. We found obvious BACE-1 protein accumulation in 3-month-old APP/PS1 mice, which had increased by the time of 6 months. Coimmunostaining results showed BACE-1 surrounded amyloid plaques in brain sections. The abnormal protein expression might not be attributable to the upregulation of BACE-1 protein, as no significant difference of protein expression was observed between wild-type and APP/PS1 mice. With antibodies against BACE-1 and CD31, we found a high immunoreactive density of BACE-1 protein on the outer layer of brain blood vessels. The aberrant distribution of BACE-1 in APP/PS1 mice suggests BACE-1 may be involved in the microvascular abnormality of AD.


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