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Calcineurin inhibition does not prevent hypertrophy in a rat pressure-overload model
CALCINEURIN INHIBITION DOES NOT PREVENT HYPERTROPHY IN A RAT PRESSURE-OVERLOAD MODEL. AC McMahon. SHL Kesteven, VL Benson and MP Feneley. Dept of Cardiology, St Vincent’s Hospital, Sydney, Australia. Although the calcineurin I NF-AT3 pathway has been shown to be important in the development of skeletal muscle hypertrophy, its role in the development of cardiac hypertrophy remains controversial. The aim of this study was to investigate the effect of calcineurin inhibition on the induction of left ventricular hypertrophy (LVH) in response to a pressure load. Male Wistar rats were randomly assigned to one of two groups: Group 1 received 1 mg/kg FK506 daily by IP injection (FK) and Group 2 received an equivalent volume of saline daily, IP (S) throughout the study. After 3d, half of each group was then subjected to banding of the aortic arch (B). The remaining animals were sham-operated controls (C). All animals were studied 21d after surgery. There was no difference in aortic peak pressure gradient (mean&D) induced between SB and FKB (35*15, n=lO vs 33i16 mmHg, n=9 respectively). Banding induced an increase in LV/body weight ratio of 13t8%, but there was no difference between SB and FKB in the degree of LVH induced (0.228iO.023 vs 0.229+0.034). There was no difference between the 2 groups in the correlation between LVH and peak pressure gradient. These data indicate that inhibition of the calcineurin / NFAT3 pathway has no effect on the development of LVH in this model.
THE ROLE OF TNF-a IN HSI7OMEDIATED CARDIAC ADAPTATION TO ISCHEMIA Xianzhong Meng, Lihua Ao, Yong Song and Alden H. Harken Department of Surgery, University of Colorado Health Sciences Center, Denver, Colorado, USA We have shown that lipopolysaccharide (LPS) induces cardiac adaptation to a subsequent ischemic insult. This cardiac adautive state is associated with the exmession of the inducible heat shock protein 70 (Hsp70) i; the mvocardium. However. the role of Hsn70 in LPS-induced cardiac adaptation rem&s unclear. LPS also induces myocardial TNF-a. While TNP-a up-regulates Hsp70 expression in cultured cardiac myocytes, it is unknown whether in vivo induction of myocardial Hsp70 by LPS requires overproduction of TNF-a. We evaluated the hypothesis that Hsp70 mediates LPS-induced cardiac adaptation and that overproduction of TN&a serves a signal for myocardial Hsp70 expression. Results: LPS (0.5 mg/kg ip) induced the expression of myocardial Hsp70 in rats that was preceded by overproduction of myocardial TNP-a. Hsp70 was localized in cardiac interstitial cells including resident macrophages. Rats treated with LPS acquired cardiac functional resistance to subsequent ischemia and reperfusion. Cardiac functional protection induced bv heat shock is also associated with the exuression of Hsp70 in the interstitial cells. Moreover, liposomal deliverv of recombinant Hsn70 to the interstitial cells of isolated heart similarly enhanced functional resistance to ischemia and reperfusion. Pretreatment of animals with dexamethasone abrogated LPS-induced myocardial TNP-a
production without an influence on either Hsp70
expression or adaptation to ischemia. We conclude that Hsp70 contributes to the mechanism of cardiac adaptation to ischemia and that induction of myocardial Hsp70 and cardiac adaptation by LPS does not require overproduction of TNF-a.
DYAD CLEFT Ca KINETICS SUGGEST LOW BUT NOT HIGH AFFINITY Ca BINDING SITES Sivan Vadakkadath Meethal, Katherine T. Potter, David Redon, Robert A. Haworth, Department of Surgery, University of Wisconsin, Madison, USA The Ca-binding
properties of dyad clefts could in theory
impact excitation-contraction coupling, but there is little experimental evidence for this. We investigated this issue. First we modelled the rate of rise of cytosolic [CaFura-21
resulting from Ca current measured under action potential voltage clamp, modelling for dyad clefts with or without high (N = 1.6X10-’ ‘mol/cm*, & = 13pM) or low (N = 2X10~‘“molkm2, & = l.lmM) aftinity Ca binding sites (Peskoff et.al., J. Membr. Biol. 129: 59-69 (1992)). Predictions were then compared with the measured rate of
rise of [CaFura-21,in field stimulated fura- loaded rat heart cells treated with thapsigargin (5pM) & ryanodine (1pM). Models predicted a delay in the rise of [CaPura-
21which increasedwith Ca binding. With no Ca binding the predicted rise in [CaFura-21was near linear 4-12 msec after stimulation with a delay of 1.59 msec, and with low affinity Ca binding the delay was 3.71 msec. Models with high affinity Ca binding sitespredicted near-linearity only >lOmsec after stimulation, with delays around 8-10msec. The measuredrate of rise of [CaFura-21was linear within 4-12 msec after stimulation, with a delay of 2.90 +/- 0.40 msec.These results suggestthat low but not high affinity Ca binding sitesare present in the dyad cleft.
Alexandra Meynier, Jeannine Uuminier, And& Grandgirard and Luc Demaison. INRA, Unite de Nutrition Lipidique, France. Dietary oxysterols (OS) might trigger the development of 8thaosclerosia Smee atherosclerosisreduces the oxygen supply, this could alter the metabclism of cardiac.mitocbondria lbe aim of the study was to evaluate the inthrence of dietary oxysterols on coronary atherosclerosis and mitoehcndrial tirnction. Golden Syrian hamsterswere fed four diGsrent diets for three months :i/ a low fat diet containing 2.5% of a mixture of corn and tish oils (4:l w/w, group LF); iii a similar diet supplema~ted with OS (2.6 pg/day/animal, group LF+OS); iii/ a high fat diet containing 2.5% of the oil mixture + 3 % cholesterol (Chol) + 15% lard (group HF); iv/ a same diet than group HF supplemented with OS (2.6 pg/day/8nimal, group HF+OS). The main ecmnary artey was oteerved by eleetrun n&x-y. The respiratay characteristicsof cardiac mitoctmndria were evaluated using dif&nt substrates.The amount of Cbol and OS were measured out in the plasma and mitochcndrii. Jn plasma, Chol and several OS were higher in groups I-F than in groups LF. Cholestanetriol was increased by the presence of OS in the diet. In group HP, atherosclerosisdid not develop. Atherosclerosis developed in the two groups whose diets were supplemented with OS. Thus the development of atbaosclercsis necessitatedonly tbe presence of OS in the diet. The prwence of OS in the diet (groups LF+OS and HF+OS) reduced the S-oxidation rate of cardiac mitochondria, without affecting the respiration of glutamate and pyruvate. These changes were nbt associated with modifications of the Cboi and OS eompesition of mitechondrial membranes. In conclusi0n, OS, but not Chol, triggered corcmary athaosclerosis in the hamster. The development of atbaoscterosis can be assessedby measuring the Soxidation rate of isolated eardiic mitocbondria
THE ROLE OF TNF-a IN HSI7OMEDIATED CARDIAC ADAPTATION TO ISCHEMIA Xianzhong Meng, Lihua Ao, Yong Song and Alden H. Harken Department of Surgery, University of Colorado Health Sciences Center, Denver, Colorado, USA We have shown that lipopolysaccharide (LPS) induces cardiac adaptation to a subsequent ischemic insult. This cardiac adautive state is associated with the exmession of the inducible heat shock protein 70 (Hsp70) i; the mvocardium. However. the role of Hsn70 in LPS-induced cardiac adaptation rem&s unclear. LPS also induces myocardial TNF-a. While TNP-a up-regulates Hsp70 expression in cultured cardiac myocytes, it is unknown whether in vivo induction of myocardial Hsp70 by LPS requires overproduction of TNF-a. We evaluated the hypothesis that Hsp70 mediates LPS-induced cardiac adaptation and that overproduction of TN&a serves a signal for myocardial Hsp70 expression. Results: LPS (0.5 mg/kg ip) induced the expression of myocardial Hsp70 in rats that was preceded by overproduction of myocardial TNP-a. Hsp70 was localized in cardiac interstitial cells including resident macrophages. Rats treated with LPS acquired cardiac functional resistance to subsequent ischemia and reperfusion. Cardiac functional protection induced bv heat shock is also associated with the exuression of Hsp70 in the interstitial cells. Moreover, liposomal deliverv of recombinant Hsn70 to the interstitial cells of isolated heart similarly enhanced functional resistance to ischemia and reperfusion. Pretreatment of animals with dexamethasone abrogated LPS-induced myocardial TNP-a
production without an influence on either Hsp70
expression or adaptation to ischemia. We conclude that Hsp70 contributes to the mechanism of cardiac adaptation to ischemia and that induction of myocardial Hsp70 and cardiac adaptation by LPS does not require overproduction of TNF-a.
DYAD CLEFT Ca KINETICS SUGGEST LOW BUT NOT HIGH AFFINITY Ca BINDING SITES Sivan Vadakkadath Meethal, Katherine T. Potter, David Redon, Robert A. Haworth, Department of Surgery, University of Wisconsin, Madison, USA The Ca-binding
properties of dyad clefts could in theory
impact excitation-contraction coupling, but there is little experimental evidence for this. We investigated this issue. First we modelled the rate of rise of cytosolic [CaFura-21
resulting from Ca current measured under action potential voltage clamp, modelling for dyad clefts with or without high (N = 1.6X10-’ ‘mol/cm*, & = 13pM) or low (N = 2X10~‘“molkm2, & = l.lmM) aftinity Ca binding sites (Peskoff et.al., J. Membr. Biol. 129: 59-69 (1992)). Predictions were then compared with the measured rate of
rise of [CaFura-21,in field stimulated fura- loaded rat heart cells treated with thapsigargin (5pM) & ryanodine (1pM). Models predicted a delay in the rise of [CaPura-
21which increasedwith Ca binding. With no Ca binding the predicted rise in [CaFura-21was near linear 4-12 msec after stimulation with a delay of 1.59 msec, and with low affinity Ca binding the delay was 3.71 msec. Models with high affinity Ca binding sitespredicted near-linearity only >lOmsec after stimulation, with delays around 8-10msec. The measuredrate of rise of [CaFura-21was linear within 4-12 msec after stimulation, with a delay of 2.90 +/- 0.40 msec.These results suggestthat low but not high affinity Ca binding sitesare present in the dyad cleft.
Alexandra Meynier, Jeannine Uuminier, And& Grandgirard and Luc Demaison. INRA, Unite de Nutrition Lipidique, France. Dietary oxysterols (OS) might trigger the development of 8thaosclerosia Smee atherosclerosisreduces the oxygen supply, this could alter the metabclism of cardiac.mitocbondria lbe aim of the study was to evaluate the inthrence of dietary oxysterols on coronary atherosclerosis and mitoehcndrial tirnction. Golden Syrian hamsterswere fed four diGsrent diets for three months :i/ a low fat diet containing 2.5% of a mixture of corn and tish oils (4:l w/w, group LF); iii a similar diet supplema~ted with OS (2.6 pg/day/animal, group LF+OS); iii/ a high fat diet containing 2.5% of the oil mixture + 3 % cholesterol (Chol) + 15% lard (group HF); iv/ a same diet than group HF supplemented with OS (2.6 pg/day/8nimal, group HF+OS). The main ecmnary artey was oteerved by eleetrun n&x-y. The respiratay characteristicsof cardiac mitoctmndria were evaluated using dif&nt substrates.The amount of Cbol and OS were measured out in the plasma and mitochcndrii. Jn plasma, Chol and several OS were higher in groups I-F than in groups LF. Cholestanetriol was increased by the presence of OS in the diet. In group HP, atherosclerosisdid not develop. Atherosclerosis developed in the two groups whose diets were supplemented with OS. Thus the development of atbaosclercsis necessitatedonly tbe presence of OS in the diet. The prwence of OS in the diet (groups LF+OS and HF+OS) reduced the S-oxidation rate of cardiac mitochondria, without affecting the respiration of glutamate and pyruvate. These changes were nbt associated with modifications of the Cboi and OS eompesition of mitechondrial membranes. In conclusi0n, OS, but not Chol, triggered corcmary athaosclerosis in the hamster. The development of atbaoscterosis can be assessedby measuring the Soxidation rate of isolated eardiic mitocbondria