The Impact of Ovariectomy on Calcium Homeostasis and Myofilament Calcium Sensitivity in the Aging Mouse Heart

The role of phosphorylation of myofilaments in regulating cardiac muscle calcium sensitivity and force production is well established. Recently it was shown that trichostatin A (TSA), a class-I and II histone deacetylase (HDAC) inhibitor, improved cardiac contractile function in vivo . Because class-II HDACs are able to translocate to the cytoplasm from the nucleus, it is postulated that some HDACs may interact with contractile proteins and thereby regulate myofilament calcium sensitivity and/or force production. Papillary muscle strips from mouse hearts were skinned for 4 hours and then treated overnight with two structurally dissimilar HDAC inhibitors, TSA and MS275. Both HDAC inhibitors significantly increased myofilament calcium sensitivity as quantified by pCa 50 [Baseline (n=9): 5.75±0.04; TSA (n=6): 5.84±0.02; MS275 (n=7): 5.87±0.03; P <0.05 vs . Baseline], without any significant changes in maximally activated force. Similar increase in calcium sensitivity was also observed when skinned fibers were incubated overnight in a buffer containing acetyl-CoA [acetyl-CoA (n=6): 5.84±0.04; P <0.05 vs . Baseline]. These observations suggest that acetylation of myofilament proteins can regulate myofilament calcium sensitivity. Western blot analyses of skinned fibers revealed that HDAC4 and HDAC5 were specifically associated with myofilament proteins, and acetylation of several myofilament proteins was increased following TSA treatment. One of these acetylated proteins was identified as muscle LIM protein (MLP). Protein-protein interaction analyses and co-localization studies showed that MLP specifically binds to HDAC4. Functional studies with skinned fibers isolated from MLP knock out [MLP −/− ] mice (C57BL6 strain) indicated that TSA-induced increase in calcium sensitivity was completely prevented [MLP −/− -Baseline (n=6): 5.60±0.03; MLP −/− -TSA (n=6): 5.61±0.02; P <NS] compared to wild-type (WT) mice of the same strain [WT-Baseline (n=6): 5.59±0.02; WT-TSA (n=6): 5.70±0.02; P <0.05]. These data demonstrate, for the first time, that class-II HDACs bind to cardiac myofilament proteins, with MLP being one of the binding partners, and play a role in regulating myofilament contractile function.

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Acute exposure to progesterone attenuates cardiac contraction by modifying myofilament calcium sensitivity in the female mouse heart

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00073.2016 ◽

2017 ◽

Vol 312 (1) ◽

pp. H46-H59 ◽

Cited By ~ 8

Author(s):

Hirad A. Feridooni ◽

Jennifer K. MacDonald ◽

Anjali Ghimire ◽

W. Glen Pyle ◽

Susan E. Howlett

Keyword(s):

Ventricular Myocytes ◽

Heart Function ◽

Calcium Sensitivity ◽

Cardiac Contraction ◽

Mouse Heart ◽

Sodium Pentobarbital ◽

Serum Progesterone ◽

Time Courses ◽

Myofilament Calcium Sensitivity ◽

In Pregnancy

Acute application of progesterone attenuates cardiac contraction, although the underlying mechanisms are unclear. We investigated whether progesterone modified contraction in isolated ventricular myocytes and identified the Ca2+ handling mechanisms involved in female C57BL/6 mice (6–9 mo; sodium pentobarbital anesthesia). Cells were field-stimulated (4 Hz; 37°C) and exposed to progesterone (0.001–10.0 μM) or vehicle (35 min). Ca2+ transients (fura-2) and cell shortening were recorded simultaneously. Maximal concentrations of progesterone inhibited peak contraction by 71.4% (IC50 = 160 ± 50 nM; n = 12) and slowed relaxation by 75.4%. By contrast, progesterone had no effect on amplitudes or time courses of underlying Ca2+ transients. Progesterone (1 µM) also abbreviated action potential duration. When the duration of depolarization was controlled by voltage-clamp, progesterone attenuated contraction and slowed relaxation but did not affect Ca2+ currents, Ca2+ transients, sarcoplasmic reticulum (SR) content, or fractional release of SR Ca2+. Actomyosin MgATPase activity was assayed in myofilaments from hearts perfused with progesterone (1 μM) or vehicle (35 min). While maximal responses to Ca2+ were not affected by progesterone, myofilament Ca2+ sensitivity was reduced (EC50 = 0.94 ± 0.01 µM for control, n = 7 vs. 1.13 ± 0.05 μM for progesterone, n = 6; P < 0.05) and progesterone increased phosphorylation of myosin binding protein C. The effects on contraction were inhibited by lonaprisan (progesterone receptor antagonist) and levosimendan (Ca2+ sensitizer). Unlike results in females, progesterone had no effect on contraction or myofilament Ca2+ sensitivity in age-matched male mice. These data indicate that progesterone reduces myofilament Ca2+ sensitivity in female hearts, which may exacerbate manifestations of cardiovascular disease late in pregnancy when progesterone levels are high. NEW & NOTEWORTHY We investigated myocardial effects of acute application of progesterone. In females, but not males, progesterone attenuates and slows cardiomyocyte contraction with no effect on calcium transients. Progesterone also reduces myofilament calcium sensitivity in female hearts. This may adversely affect heart function, especially when serum progesterone levels are high in pregnancy. Listen to this article’s corresponding podcast at https://ajpheart.podbean.com/e/acute-progesterone-modifies-cardiac-contraction/ .

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The Impact of Vitamin D3Supplementation on Mechanisms of Cell Calcium Signaling in Chronic Kidney Disease

BioMed Research International ◽

10.1155/2015/807673 ◽

2015 ◽

Vol 2015 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Ingrid Lajdova ◽

Viera Spustova ◽

Adrian Oksa ◽

Zuzana Kaderjakova ◽

Dusan Chorvat ◽

...

Keyword(s):

Chronic Kidney Disease ◽

Kidney Disease ◽

Calcium Signaling ◽

Calcium Homeostasis ◽

Calcium Release ◽

Calcium Entry ◽

Regulatory Mechanisms ◽

Cell Calcium ◽

Crac Channels ◽

The Impact

Intracellular calcium concentration in peripheral blood mononuclear cells (PBMCs) of patients with chronic kidney disease (CKD) is significantly increased, and the regulatory mechanisms maintaining cellular calcium homeostasis are impaired. The purpose of this study was to examine the effect of vitaminD3on predominant regulatory mechanisms of cell calcium homeostasis. The study involved 16 CKD stages 2-3 patients with vitamin D deficiency treated with cholecalciferol 7000–14000 IU/week for 6 months. The regulatory mechanisms of calcium signaling were studied in PBMCs and red blood cells. After vitaminD3supplementation, serum concentration of 25(OH)D3increased (P<0.001) and[Ca2+]idecreased (P<0.001). The differences in[Ca2+]iwere inversely related to differences in 25(OH)D3concentration (P<0.01). VitaminD3supplementation decreased the calcium entry through calcium release activated calcium (CRAC) channels and purinergic P2X7channels. The function of P2X7receptors was changed in comparison with their baseline status, and the expression of these receptors was reduced. There was no effect of vitaminD3on P2X7pores and activity of plasma membrane Ca2+-ATPases. VitaminD3supplementation had a beneficial effect on[Ca2+]idecreasing calcium entry via CRAC and P2X7channels and reducing P2X7receptors expression.

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PKC catalytic subunit and phenylephrine induce a comparable decrease in myofilament calcium sensitivity

Journal of Molecular and Cellular Cardiology ◽

10.1016/j.yjmcc.2007.03.129 ◽

2007 ◽

Vol 42 (6) ◽

pp. S46

Author(s):

Judit Barta ◽

Jolanda van der Velden ◽

Nicky M. Boontje ◽

Ruud Zaremba ◽

Ger J.M. Stienen

Keyword(s):

Calcium Sensitivity ◽

Catalytic Subunit ◽

Myofilament Calcium Sensitivity

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Effects of Long-Term Running Stress on the Ultrastructure of the Aging Mouse Heart

Gerontology ◽

10.1159/000212850 ◽

1987 ◽

Vol 33 (1) ◽

pp. 19-33 ◽

Cited By ~ 6

Author(s):

Raymond Coleman ◽

Michael Silbermann ◽

David Gershon ◽

Abraham Z. Reznick

Keyword(s):

Mouse Heart ◽

Aging Mouse

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Abstract 219: Histidine Substituted Cardiac Troponin I (a164h) Improves Survival And Protects Cardiac Contractility During Acute Hypoxia In The Aged Murine Heart.

Circulation ◽

10.1161/circ.116.suppl_16.ii_23-a ◽

2007 ◽

Vol 116 (suppl_16) ◽

Author(s):

Nathan Palpant ◽

Sharlene Day ◽

Kimber Converso ◽

Joseph Metzger

Keyword(s):

Cardiac Troponin ◽

Troponin I ◽

Acute Hypoxia ◽

Cardiac Contractility ◽

Systolic Pressure ◽

Calcium Sensitivity ◽

The Elderly ◽

Cardiac Troponin I ◽

Pump Failure ◽

Myofilament Calcium Sensitivity

Contractile dysfunction associated with ischemia is a significant cause of morbidity and mortality particularly in the elderly. Strategies designed to protect the aged heart from ischemia-mediated pump failure are needed. We have generated transgenic (Tg) mice expressing a modified form of adult cardiac troponin I, the Ca ++ -activated molecular switch of the myofilament. Consonant with the fetal isoform, this transgene encodes a histidine substitution (A164H) in the critical switch domain of TnI thus increasing myofilament calcium sensitivity in a pH-dependent manner. We hypothesized that aged mice (24 months), intrinsically susceptible to myocardial dysfunction, would retain improved cardiac contractility at baseline and during an acute hypoxic challenge by means of myofilament-mediated calcium sensitization. Methods/Results: At baseline, by echocardiography, Tg hearts had increased systolic function, with a 26% higher mean ejection fraction compared to nontransgenic (Ntg) mice: 75 ± 3% [Tg: n = 13] vs. 63 ± 4% [Ntg: n = 12], P < 0.05, with no differences in diastolic function between the groups. To study the effects of acute hypoxia on cardiac hemodynamics mice underwent microconductance Millar catheterization while ventilated with 12% oxygen. Aged Tg mice had improved survival compared to Ntg mice: time to pump failure (65% of baseline peak systolic pressure) 11.59 ± 1.25 min. [Tg: n = 3] vs. 4.11 ± 1.90 min. [Ntg: n = 3], P < 0.05. After four minutes of hypoxia, Tg mice had markedly improved cardiac contractility compared to Ntg mice with increased stroke volume (30.05 ± 4.49 uL [Tg] vs. 13.23 ± 3.21 uL [Ntg], P < 0.05), end systolic pressure (106.09 ± 11.81 mmHg [Tg] vs. 64.49 ± 4.05 mmHg [Ntg], P < 0.05) and rate of positive left ventricular pressure development (12958.66 ± 2544.68 mmHg/sec [Tg] vs. 5717.00 ± 745.67 mmHg/sec [Ntg], P = 0.05). Conclusion: An alteration in myofilament calcium sensitivity via a pH-responsive histidine button in cardiac troponin I augments baseline heart function in Tg mice over their lifetime. During acute hypoxia, cTnI A164H improves survival in aged mice by maintaining cardiac contractility, and thus holds promise for the design of gene therapeutics to treat pump failure associated with acute ischemic events in the elderly.

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Abstract 279: A Defective Mechanosensing Promotes Impaired Fibroblast-to-myofibroblast Maturation in the Aging Mouse Heart

Circulation Research ◽

10.1161/res.127.suppl_1.279 ◽

2020 ◽

Vol 127 (Suppl_1) ◽

Author(s):

Aude Angelini ◽

JoAnn Trial ◽

Katarzyna A Cieslik

Keyword(s):

Mass Spectrometry ◽

Cardiac Fibroblasts ◽

Fold Increase ◽

Negative Regulator ◽

Mouse Heart ◽

Aging Heart ◽

Aging Mouse ◽

Student’S T ◽

Scar Contraction ◽

Student’S T Test

In the aging heart, fibroblasts have a reduced ability to mature into myofibroblasts (expressing contractile actin a-SMA), which is necessary for scar contraction in wound healing. The mechanosensing pathway bridges the extracellular matrix (ECM) with the actin cytoskeleton and is altered during aging. We emphasize that changes in this pathway may affect myofibroblast activation. Using various methods (mass spectrometry, qPCR, flow, IF staining, and western), we found several abnormalities in the fibroblasts derived from old mouse hearts: 1) ECM deposited was altered with an increased quantity of collagens and the presence of fibronectin variant Anastellin that opposes myofibroblast maturation; 2) there was a 50% reduction of Kindlin-2, a protein that promotes integrin activation; 3) Polymerized (F-) to monomeric (G-) actin ratio was decreased by 65%, possibly due to a 5-fold increase in pERKs1/2 level, a negative regulator of F-actin; and pERKs inhibition (by 2.5μM, PD-0325901) increased by 2-fold F/G actin ratio; 4) we found an increased cytoplasmic retention of MRTF-A (by 44%), an actin-sensitive co-transcription factor (necessary for a-SMA) that shuttles into the nucleus in response to F-actin formation; 5) pERKs inhibition increased a-SMA transcription by 78%. Thus, the disrupted mechanosensing pathway contributes to the impaired myofibroblast maturation in the aging heart. All experiments were performed in young (3-4 month-old) and old (24-30 month-old) hearts or primary cardiac fibroblasts isolated from male C57BL/6J mice. Unpaired Student’s t-test was used for statistical analysis, n=2 for mass spectrometry and n=4-10 for all other biological repeats.

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High-throughput assessment of calcium sensitivity in skinned cardiac myocytes

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.2001.281.2.h969 ◽

2001 ◽

Vol 281 (2) ◽

pp. H969-H974 ◽

Cited By ~ 18

Author(s):

Chee Chew Lim ◽

Michiel H. B. Helmes ◽

Douglas B. Sawyer ◽

Mohit Jain ◽

Ronglih Liao

Keyword(s):

Cardiac Myocytes ◽

High Throughput ◽

High Throughput Screening ◽

Rapid Determination ◽

Isometric Force ◽

Calcium Sensitivity ◽

Pharmacological Agents ◽

Length Changes ◽

Myofilament Calcium Sensitivity ◽

High Degree

Isolated permeabilized cardiac myocytes have been used in the study of myofilament calcium sensitivity through measurement of the isometric force-pCa curve. Determining this force-pCa relationship in skinned myocytes is relatively expensive and carries a high degree of variability. We therefore attempted to establish an alternative high-throughput method to measure calcium sensitivity in cardiac myocytes. With the use of commercially available software that allows for precise measurement of sarcomere spacing, we measured sarcomere length changes in unloaded skinned cardiac myocytes over a range of calcium concentrations. With the use of this technique, we were able to accurately detect acute increases or decreases in myofilament calcium sensitivity after exposure to 10 mM caffeine or 5 mM 2,3-butanedione monoxime, respectively. This technique allows for the simple and rapid determination of myofilament calcium sensitivity in cardiac myocytes in a reproducible and inexpensive manner and could be used for high-throughput screening of pharmacological agents and/or transgenic mouse models for changes in myofilament calcium sensitivity.

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Myogenic contractility is more dependent on myofilament calcium sensitization in term fetal than adult ovine cerebral arteries

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00134.2007 ◽

2007 ◽

Vol 293 (1) ◽

pp. H548-H556 ◽

Cited By ~ 6

Author(s):

Renan J. Sandoval ◽

Elisha R. Injeti ◽

James M. Williams ◽

William T. Georthoffer ◽

William J. Pearce

Keyword(s):

Calcium Influx ◽

Cerebral Arteries ◽

Calcium Sensitivity ◽

Cytosolic Calcium ◽

Stretch Ratio ◽

Myogenic Tone ◽

Postnatal Maturation ◽

Calcium Sensitization ◽

Myofilament Calcium Sensitivity ◽

Krebs Buffer

Regulation of cytosolic calcium and myofilament calcium sensitivity varies considerably with postnatal age in cerebral arteries. Because these mechanisms also govern myogenic tone, the present study used graded stretch to examine the hypothesis that myogenic tone is less dependent on calcium influx and more dependent on myofilament calcium sensitization in term fetal compared with adult cerebral arteries. Term fetal and adult posterior communicating cerebral arteries exhibited similar myogenic responses, with peak tensions averaging 24 and 26% of maximum contractile force produced in any given tissue in response to an isotonic Krebs buffer containing 122 mM K+ (Kmax) at optimum stretch ratios (working diameter/unstressed diameter) of 2.19 and 2.23, respectively. Graded stretch increased cytosolic Ca2+ concentration at stretch ratios >2.0 in adult arteries, but increased Ca2+ concentration only at stretch ratios >2.3 in fetal arteries. In permeabilized arteries, myogenic tone peaked at a stretch ratio of 2.1 in both fetal and adult arteries. The fetal %Kmax values at peak myogenic tone were not significantly different at either pCa 7.0 (23%) or pCa 5.5 (25%) but were significantly less at pCa 8.0 (8.4 ± 2.3%). Conversely, adult %Kmax values at peak myogenic tone were significantly less at both pCa 8.0 (10.4 ± 1.8%) and pCa 7.0 (16%) than at pCa 5.5 (27%). The maximal extents of stretch-induced increases in myosin light chain phosphorylation in intact fetal (20%) and adult (17%) arteries were similar. The data demonstrate that the cerebrovascular myogenic response is highly conserved during postnatal maturation but is mediated differently in fetal and adult cerebral arteries.

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Carnitine palmitoyl transferase-I activity in the aging mouse heart

Mechanisms of Ageing and Development ◽

10.1016/0047-6374(94)01552-w ◽

1995 ◽

Vol 79 (2-3) ◽

pp. 127-136 ◽

Cited By ~ 25

Author(s):

Jeff A. Odiet ◽

Michaël E.T.I. Boerrigter ◽

Jeanne Y. Wei

Keyword(s):

Mouse Heart ◽

Carnitine Palmitoyl Transferase ◽

Aging Mouse ◽

Carnitine Palmitoyl Transferase I

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