摘要:

How a cell responds to stress is a central problem in cardiovascular biology. Diverse physiological stresses (eg, heat, hemodynamics, mutant proteins, and oxidative injury) produce multiple changes in a cell that ultimately affect protein structures and function. Cells from different phyla initiate a cascade of events that engage essential proteins, the molecular chaperones, in decisions to repair or degrade damaged proteins as a defense strategy to ensure survival. Accumulative evidence indicates that molecular chaperones such as the heat shock family of stress proteins (HSPs) actively participate in an array of cellular processes, including cytoprotection. The versatility of the ubiquitous HSP family is further enhanced by stress-inducible regulatory networks, both at the transcriptional and posttranscriptional levels. In the present review, we discuss the regulation and function of HSP chaperones and their clinical significance in conditions such as cardiac hypertrophy, vascular wall injury, cardiac surgery, ischemic preconditioning, aging, and, conceivably, mutations in genes encoding contractile proteins and ion channels. (Circ Res. 1998;83:117-132.)

ISSN:0009-7330    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Experimental autoimmune myocarditis (EAM) resembles the giant cell myocarditis seen in humans, and recurrent forms lead to dilated cardiomyopathy. EAM has been shown to be a T cell-mediated autoimmune myocarditis. We have previously shown that cDNA encoding V beta complementarity-determining region (CDR) 3 from heart- and pericardial space-infiltrating T cells in EAM induced by rod cardiac myosin contains more restricted sequences than that from normal spleen T cells. Recently, it has become apparent that several epitopes of EAM exist in rod cardiac myosin; therefore, T cells infiltrating into lesions may recognize certain epitopes in EAM induced by rod cardiac myosin. In this study, we examined heart- and pericardial space-infiltrating T-cell clonotypes in EAM induced by synthetic peptides of cardiac myosin. EAM was produced by immunization with synthetic peptides corresponding to N-terminally acetylated amino acids 1539 to 1555 of rat cardiac myosin alpha heavy chain. Five of 12 rats receiving synthetic peptides developed macroscopic signs of myocarditis. To examine T-cell receptor (TCR) V beta expression and CDR3 of the TCR beta chain of lesion-infiltrating T cells in EAM, total RNA was isolated from heart, pericardial effusion, spleen, lymph node, and peripheral blood. TCR V beta expression of the T cells infiltrating the lesions revealed a predominance of V beta 4. On the basis of single-strand conformation polymorphism analysis for CDR3 of the TCR V beta 4 chain, heart- and pericardial space-infiltrating T cells were considered to be oligoclonal, whereas spleen, lymph node, and peripheral blood in a rat with EAM and spleen in a native rat were considered to be polyclonal. In the same rat, clonotypes of heart-infiltrating T cells were almost the same as those of pericardial space-infiltrating T cells. Furthermore, on sequence analysis for CDR3 of the TCR V beta 4 chain, the amino acid motifs were similar among T cells infiltrating into lesions of different EAM rats. In the present study, TCR beta chains of heart- and pericardial space-infiltrating T cells in EAM induced by synthesized peptide consisting of 17 amino acids were examined. V beta 4+ T cells with similar V beta CDR3 motifs that infiltrate the heart and pericardial space may recognize the same epitope. (Circ Res. 1998;83:133-140.)

ISSN:0009-7330    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

The congenital long-QT syndrome (LQT), an inherited cardiac arrhythmia characterized in part by prolonged ventricular repolarization, has been linked to 5 loci, 4 of which have been shown to harbor genes that encode ion channels. Previously studied LQT-3 mutations of SCN5A (or hH1), the gene that encodes the human Na+channel alpha-subunit, have been shown to encode voltage-gated Na+channels that reopen during prolonged depolarization and hence directly contribute to the disease phenotype: delayed repolarization. Here, we report the functional consequences of a novel SCN5A mutation discovered in an extended LQT family. The mutation, a single A[right arrow]G base substitution at nucleotide 5519 of the SCN5A cDNA, is expected to cause a nonconservative change from an aspartate to a glycine at position 1790 (D1790G) of the SCN5A gene product. We investigated ion channel activity in human embryonic kidney (HEK 293) cells transiently transfected with wild-type (hH1) or mutant (D1790G) cDNA alone or in combination with cDNA encoding the human Na+channel beta1-subunit(h beta1) using whole-cell patch-clamp procedures. Heteromeric channels formed by coexpression of alpha- and beta1-subunitsare affected: steady-state inactivation is shifted by -16 mV, but there is no D1790G-induced sustained inward current. This effect is independent of the beta1-subunitisoform. We find no significant effect of D1790G on the biophysical properties of monomeric alpha- (hH1) channels. We conclude that the effects of the novel LQT-3 mutation on inactivation of heteromeric channels are due to D1790G-induced changes in alpha- and beta1-interactions. (Circ Res. 1998;83:141-146.)

ISSN:0009-7330    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

The hypothesis that cellular hypertrophy in congestive heart failure (CHF) modulates mechanosensitive (ie, swelling- or stretch-activated) channels was tested. Digital video microscopy and amphotericin-perforated-patch voltage clamp were used to measure cell volume and ion currents in ventricular myocytes isolated from normal dogs and dogs with rapid ventricular pacing-induced CHF. In normal myocytes, osmotic swelling in 0.9x to 0.6x isosmotic solution (296 mOsm/L) was required to elicit an inwardly rectifying swelling-activated cation current (ICir,swell) that reversed near -60 mV and was inhibited by 10 [micro sign]mol/L Gd3+, a mechanosensitive channel blocker. Block of ICir,swell by Gd3+simultaneously reduced the volume of normal cells in hyposmotic solutions by up to [approximate]10%, but Gd3+had no effect on volume in isosmotic solution. In contrast, ICir,swell was persistently activated under isosmotic conditions in CHF myocytes, and Gd3+decreased cell volume by [approximate]8%. Osmotic shrinkage in 1.1x to 1.5x isosmotic solution inhibited both ICir,swell and Gd3+-inducedcell shrinkage in CHF cells, whereas osmotic swelling only slightly increased ICir,swell. The K0.5 and Hill coefficient for Gd3+block of ICir,swell and Gd3+-inducedcell shrinkage were estimated as [approximate]2.0 [micro sign]mol/L and [approximate]1.9, respectively, for both normal and CHF cells. In both groups, the effects of Gd3+on current and volume were blocked by replacing bath Na+and K+and were linearly related with varying Gd3+concentration and the degree of cell swelling. CHF thus altered the set point for and caused persistent activation of ICir,swell. This current may contribute to dysrhythmias, hypertrophy, and altered contractile function in CHF and may be a novel target for therapy. (Circ Res. 1998;83:147-157.)

ISSN:0009-7330    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

The diuretic agent indapamide has been reported to block the slow component of the delayed rectifier K+current (IKs) without altering the rapid component (IKr) or the inward rectifier current and has been used as a pharmacological probe for IKs; however, the effects of indapamide on Na+(INa), L-type Ca2+(ICa), and transient outward K+(Ito) currents have not been determined. We applied tight-seal, whole-cell, patch-clamp techniques to assess the effects of indapamide on INa, Ito, ICa, and IKsin canine atrial myocytes. Indapamide inhibited INa, Ito, and IKsin a concentration-dependent and reversible way, without altering ICa. Block increased with depolarization, with the 50% blocking concentration (EC (50)) decreasing from 129 +/- 26 [micro sign]mol/L (at -60 mV) to 79 +/- 17 [micro sign]mol/L (at -10 mV) for INa, from 174 +/- 19 [micro sign]mol/L (at +10 mV) to 98 +/- 7 [micro sign]mol/L (at +60 mV) for Ito, and from 148 +/- 28 [micro sign]mol/L (at +10 mV) to 86 +/- 18 [micro sign]mol/L (at +60 mV) for IKs. Significant inhibition was seen at concentrations as low as 10 [micro sign]mol/L for all 3 currents. In addition, indapamide effectively inhibited the ultrarapid delayed rectifier current in a voltage-independent way, with an EC50of 138 +/- 7 [micro sign]mol/L at +10 mV. Standard microelectrode experiments showed the effects of indapamide on the action potential to be consistent with the ionic actions seen. We conclude that in addition to its well-recognized IKs-blockingaction, indapamide also inhibits INaand Itoeffectively and with similar potency. Thus, indapamide is not a reliable pharmacological probe with which to study the specific effects of IKsblockade, and INaand Itoblock may contribute to the potential profile of cardiac actions of the compound. (Circ Res. 1998;83:158-166.)

ISSN:0009-7330    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Myocardial infarction results in focal areas of ischemia, hypoxia, necrosis, and decreased contractile function. To compensate for loss of contractile function, remaining viable myocytes undergo hypertrophic growth. Prostaglandin F (2) alpha (PGF2alpha), which is released from cells of the myocardium during periods of stress such as hypoxia or ischemia/reperfusion, has recently been shown to stimulate hypertrophic growth in neonatal rat ventricular myocytes. In the present study, we determine which growth-related intracellular pathways are required for PGF2alpha to induce morphological and genetic features characteristic of the hypertrophic phenotype. In cardiomyocytes, PGF2alpha increases the hydrolysis of inositol phosphates and induces the translocation of protein kinase C epsilon to the myocyte membrane, consistent with PGF2alpha receptor coupling to Gq. PGF2alpha also activates the extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase pathways. Surprisingly, studies using pharmacological inhibitors and transfection of dominant-interfering proteins demonstrate that PGF (2) alpha-induced myocyte hypertrophy occurs independent of either PKC, p38, or ERK pathways. Additional studies demonstrate that PGF2alpha stimulates protein tyrosine phosphorylation and activates c-Jun NH2-terminalkinase and suggest that these pathways mediate hypertrophic growth in response to PGF2alpha.(Circ Res. 1998;83:167-178.)

ISSN:0009-7330    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

We examined the influences of Ca2+and crossbridge kinetics on the maximum rate of force development during Ca2+activation of cardiac myofibrils and on the maximum rate of relaxation. Flash photolysis of diazo-2 or nitrophenyl-EGTA was used to produce a sudden decrease or increase, respectively, in [Ca2+] within Triton-skinned trabeculae from rat and guinea pig hearts (22[degree sign]C). Trabeculae from both species had similar Ca2+sensitivities, suggesting that the rate of dissociation of Ca2+from troponin C (koff) is similar in the 2 species. However, the rate of relaxation after diazo-2 photolysis was 5 times faster in the rat (16.1 +/- 0.9 s-1, mean +/- SEM, n=11) than in the guinea pig (2.99 +/- 0.26 s-1, n=7). This indicates that the maximum relaxation rate is limited by crossbridge kinetics rather than by koff. The maximum rates of rapid activation by Ca2+after nitrophenyl-EGTA photolysis (kact) and of force redevelopment after forcible crossbridge dissociation (ktr) were similar and were [approximate]5-fold faster in rat (kact=14.4 +/- 0.9 s-1, ktr=13.0 +/- 0.6 s-1) than in guinea pig (kact=2.57 +/- 0.14 s-1, ktr=2.69 +/- 0.30 s-1) trabeculae. This too may be mainly due to species differences in crossbridge kinetics. Both kactand ktrincreased as [Ca2+] increased. This Ca2+dependence of the rates of force development is consistent with current models for the Ca2+activation of the crossbridge cycle, but these models do not explain the similarity in the maximal rates of activation and relaxation within a given species. (Circ Res. 1998;83:179-186.)

ISSN:0009-7330    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Sympathetic nerves have long been suspected of trophic activity, but the nature of their angiogenic factor has not been determined. Neuropeptide Y (NPY), a sympathetic cotransmitter, is the most abundant peptide in the heart and the brain. It is released during nerve activation and ischemia and causes vasoconstriction and smooth muscle cell proliferation. Here we report the first evidence that NPY is angiogenic. At low physiological concentrations, in vitro, it promotes vessel sprouting and adhesion, migration, proliferation, and capillary tube formation by human endothelial cells. In vivo, in a murine angiogenic assay, NPY is angiogenic and is as potent as a basic fibroblast growth factor. The NPY action is specific and is mediated by Y1 and Y2 receptors. The expression of both receptors is upregulated during cell growth; however, Y2 appears to be the main NPY angiogenic receptor. Its upregulation parallels the NPY-induced capillary tube formation on reconstituted basement membrane (Matrigel); the Y2 agonist mimics the tube-forming activity of NPY, whereas the Y2 antagonist blocks it. Endothelium contains not only NPY receptors but also peptide itself, its mRNA, and the "NPY-converting enzyme" dipeptidyl peptidase IV (both protein and mRNA), which terminates the Y1 activity of NPY and cleaves the Tyr1-Pro2from NPY to form an angiogenic Y2 agonist, NPY3-36. Endothelium is thus not only the site of action of NPY but also the origin of the autocrine NPY system, which, together with the sympathetic nerves, may be important in angiogenesis during tissue development and repair. (Circ Res. 1998;83:187-195.)

ISSN:0009-7330    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

In cutaneous veins where purinergic neurotransmission is more prominent compared with in deep vessels, physiological and pathological roles of nerve-released ATP have been described. Neuronally released ATP has been reported to act through activation of unidentified ionotropic P2X receptor(s). This study analyzed P2X receptor subtypes expressed in human saphenous vein smooth muscle and their physiological functions. Transcripts for both hP2X1receptors, already identified in other smooth muscles, and, surprisingly, hP2X7receptors known to be responsible for the cytotoxic effect of ATP in macrophages were detected by Northern blot analysis in total RNA from saphenous vein smooth muscle. ATP and other P2X receptor agonists [alpha beta-methylene-ATP, 2-methylthio-ATP, and 2[prime],3[prime]-(4-benzoyl)benzoyl-ATP] dose-dependently contracted venous rings, but the contraction induced by 2-methylthio-ATP was more transient than that evoked by the other P2X agonists. The effect of hP2X (1) agonists involved the activation of a rapidly desensitizing cation current recorded in freshly isolated myocytes. The action of hP2X7receptor agonists was related to a maintained nondesensitizing cation current. In addition, hP2X7receptor activation formed membrane pores that were permeable to large molecules. hP2X1and hP2X7receptors coexpressed in COS cells did not associate to form heteromultimers. Our data indicate that both hP2X1and hP2X7receptors are expressed as 2 separated populations of channels in human saphenous vein myocytes and are involved in ATP-induced tension. We suggest that cell lysis consequent to hP2X7receptor-induced pore formation contributes to the disorganization and decrease in the amount of contractile myocytes in the media of varicose veins. (Circ Res. 1998;83:196-203.)

ISSN:0009-7330    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

We investigated expression of the 5[prime]-spliced isoform of smooth muscle myosin heavy chain (SM-MHC-B) in smooth muscle cells of cardiac vessels of the left ventricle of normotensive (Wistar-Kyoto) and spontaneously hypertensive rats of the stroke-prone strain by immunofluorescence microscopy. In parallel, liver and bladder were studied for characterization of the nature of vessels expressing SM-MHC-B and for semiquantitative evaluation of its abundance. Smooth muscle cells were detected by staining with a monoclonal antibody specific for alpha-smooth muscle actin. Abundance of the SM-MHC-B isoform in these cells was evaluated by using an antibody raised against the seven-amino acid insert at the 25K/50K junction of the myosin head (a25K/50K) that specifically recognized SM-MHC-B. In the ventricle, a25K/50K immunoreactivity was observed in smooth muscle cells of precapillary arterioles but not in larger vessels or aorta. The a25K/50K immunoresponse of those vessels with the highest expression level of SM-MHC-B closely resembled the signal observed in the smooth muscle layer of urinary bladder known to preferentially express SM-MHC-B. Interestingly, in left ventricles of stroke-prone spontaneously hypertensive rats, there was a significantly reduced fraction of a25K/50K-positive precapillary arterioles compared with normotensive control rats. (Circ Res. 1998;83:204-209.)

ISSN:0009-7330    

出版商:OVID    

年代:1998

数据来源: OVID