Biomedical subjects

S Izumo

Publications and source records attributed to S Izumo.

At least 181 records · Page 10Linked to original sources

PubMed1993

Response of the hypertrophied left ventricle to tachycardia: importance of maturation.

Pressure overload left ventricular (LV) hypertrophy (LVH) induces ventricular dysfunction during stress, which is commonly attributed to diminished myocardial capillary density and ischemia. Immature hearts with LVH have a normal coronary flow reserve and capillary density. The purpose of this study was to determine 1) whether young lambs with LVH had an abnormal response to chronotropic stress, 2) whether nonischemic mechanisms contributed to the abnormal response, and 3) whether the age at which LVH was induced affected the response. We assessed LV endomyocardial function, perfusion, and Ca(2+)-adenosinetriphosphatase (ATPase) mRNA levels in chronically instrumented lambs with and without LVH and adult sheep with and without LVH. Rapid pacing induced diastolic dysfunction, increased time constant of isovolumic relaxation using an iterative fit (tM), and elevated LV diastolic pressures in young lambs and adult sheep with LVH. During pacing, tM was greater in the adult sheep with LVH than in the young lambs with LVH. Ca(2+)-ATPase mRNA levels were 79% less in adult sheep with LVH than in those without. Ca(2+)-ATPase mRNA levels in lambs with and without LVH and adult sheep without LVH were similar. Diastolic dysfunction occurred in the absence of subendomyocardial hypoperfusion, suggesting a nonischemic mechanism. In adult sheep with LVH diastolic dysfunction was associated with a marked reduction in Ca(2+)-ATPase mRNA levels.

Aging↗

PubMed1993

Cytokeratins 8 and 18 in smooth muscle cells. Detection in human coronary artery, peripheral vascular, and vein graft disease and in transplantation-associated arteriosclerosis.

During development of atherosclerotic lesions, vascular smooth muscle cells (SMCs) undergo changes both phenotypically and in their cytoskeleton composition. An expression of cytokeratins 8 and 18 in SMCs in plaques of the human superficial femoral artery and of cytokeratin 8 in lesions of the aorta was recently described. Since cytokeratins are epithelial markers generally not found in normal adult vascular SMCs, we performed a detailed immunofluorescence microscopy study using a large panel of antibodies against the various cytokeratin polypeptides and other elements of the cytoskeleton. We included lesions of carotid, common and superficial femoral, iliac, and popliteal arteries; the abdominal aorta; and saphenous vein bypass grafts, as well as primary, restenotic, and transplantation-associated lesions of coronary arteries (n = 33). Cytokeratins 8 and 18 were present in myointimal cells of all pathological specimens. Colocalization with smooth muscle alpha-actin identified most cytokeratin-positive cells as SMCs. Only very few cells cosynthesized cytokeratin and desmin, whereas the majority of cytokeratin-positive cells were vimentin-positive. This pattern of cytoskeletal protein synthesis is similar to that found in some fetal and/or neonatal SMCs. These findings suggest that the synthesis of cytokeratins in a subset of SMCs of atherosclerotic lesions is a common phenomenon in coronary artery and peripheral vascular disease as well as graft disease and transplantation-associated arteriosclerosis and that the state of these SMCs is of a "dedifferentiated" fetal type.

Aorta↗

PubMed1993

Molecular characterization of angiotensin II--induced hypertrophy of cardiac myocytes and hyperplasia of cardiac fibroblasts. Critical role of the AT1 receptor subtype.

Increasing evidence suggests that angiotensin II (Ang II) may act as a growth factor for the heart. However, direct effects of Ang II on mammalian cardiac cells (myocytes and nonmyocytes), independent of secondary hemodynamic and neurohumoral effects, have not been well characterized. Therefore, we analyzed the molecular phenotype of cultured cardiac cells from neonatal rats in response to Ang II. In addition, we examined the effects of selective Ang II receptor subtype antagonists in mediating the biological effects of Ang II. In myocyte culture, Ang II caused an increase in protein synthesis without changing the rate of DNA synthesis. In contrast, Ang II induced increases in protein synthesis, DNA synthesis, and cell number in nonmyocyte cultures (mostly cardiac fibroblasts). The Ang II-induced hypertrophic response of myocytes and mitogenic response of fibroblasts were mediated primarily by the AT1 receptor. Ang II caused a rapid induction of many immediate-early genes (c-fos, c-jun, jun B, Egr-1, and c-myc) in myocyte and nonmyocyte cultures. Ang II induced "late" markers for cardiac hypertrophy, skeletal alpha-actin and atrial natriuretic factor expression, within 6 hours in myocytes. Ang II also caused upregulation of the angiotensinogen gene and transforming growth factor-beta 1 gene within 6 hours. Induction of immediate-early genes, late genes, and growth factor genes by Ang II was fully blocked by an AT1 receptor antagonist but not by an AT2 receptor antagonist. These results indicate that: (1) Ang II causes hypertrophy of cardiac myocytes and mitogenesis of cardiac fibroblasts, (2) the phenotypic changes of cardiac cells in response to Ang II in vitro closely mimic those of growth factor response in vitro and of load-induced hypertrophy in vivo, (3) all biological effects of Ang II examined here are mediated primarily by the AT1 receptor subtype, and (4) Ang II may initiate a positive-feedback regulation of cardiac hypertrophic response by inducing the angiotensinogen gene and transforming growth factor-beta 1 gene.

Angiotensin II↗

PubMed1993

Signal transduction pathways of angiotensin II--induced c-fos gene expression in cardiac myocytes in vitro. Roles of phospholipid-derived second messengers.

Angiotensin II (Ang II) causes a rapid induction of immediate-early genes and hypertrophy in the cardiac myocyte. However, the signaling mechanism of Ang II-induced immediate-early gene expression in cardiac myocytes has not been characterized. Therefore, we examined signal transduction of Ang II in neonatal rat cardiac myocytes, using c-fos gene expression as a model system. Transient transfection of c-fos reporter gene constructs indicated that the serum response element is not only required but also sufficient for Ang II-induced activation of the c-fos promoter. Ang II is known to cause an increase in [Ca2+]i. We found that Ang II also causes a small increase in cAMP in cardiac myocytes. However, the Ca2+/cAMP response element of the c-fos gene was not sufficient to confer Ang II responsiveness to the c-fos promoter, and inhibitors of protein kinase A had no effects on Ang II-induced c-fos expression. On the other hand, chelating intracellular Ca2+ with BAPTA-AM inhibited Ang II-induced c-fos expression in a dose-dependent manner, suggesting that Ca2+ is required for Ang II-induced signaling. Measurements of phospholipid-derived second messengers revealed that Ang II increased production of inositol trisphosphate, diacylglycerol, phosphatidic acid, and arachidonic acids, resulting in a sustained increase in protein kinase C activity. This and other evidence suggest that Ang II activates phospholipase C, phospholipase D, and possibly phospholipase A2. All of these second-messenger systems are activated through the AT1 receptor. Pharmacological inhibition of phospholipase C or downregulation of protein kinase C significantly suppressed Ang II-induced c-fos expression. In conclusion, Ang II activates multiple phospholipid-derived second-messenger systems via the AT1 receptor in cardiac myocytes. Among these second-messenger systems, phospholipase C and protein kinase C seem essential for Ang II-induced c-fos gene expression, whereas Ca2+ may play a permissive role. Finally, the "Ang II response element" of the c-fos gene maps to the protein kinase C-dependent portion of the serum response element.

Adenylyl Cyclases↗

PubMed1993

Fluid shear stress differentially modulates expression of genes encoding basic fibroblast growth factor and platelet-derived growth factor B chain in vascular endothelium.

Fluid shear stress has been shown to be an important regulator of vascular structure and function through its effect on the endothelial cell. We have explored the effect of shear stress on the expression of the heparin-binding growth factors platelet-derived growth factor B chain (PDGF-B) and basic fibroblast growth factor (bFGF) in bovine aortic endothelial cells using a purpose-built cone-plate viscometer. Using morphometric analysis, we have mimicked the endothelial cell shape changes encountered in vivo in response to shear stress and correlated these with changes in gene expression. Steady laminar shear stress of 15 and 36 dyn/cm2 both resulted in endothelial cell shape change, but the higher shear stress induced greater and more uniform alignment in the direction of flow and nuclear protrusion after 24 h. Steady laminar shear stress of both 15 and 36 dyn/cm2 induced a significant 3.9- and 4.2-fold decrease, respectively, in PDGF-B mRNA at 9 h. In contrast, steady laminar shear of 15 dyn/cm2 induced a mild and transient 1.5-fold increase in bFGF mRNA while shear of 36 dyn/cm2 induced a significant 4.8-fold increase at 6 h of shear which remained at 2.9-fold at 9 h. Pulsatile and turbulent shear stress showed the same effect as steady laminar shear stress (all at 15 dyn/cm2 time-average magnitude) on PDGF-B and bFGF mRNA content. Cyclic stretch (20% strain, 20/min) of cells grown on silicone substrate did not significantly affect either PDGF-B or bFGF mRNA levels. These results suggest that expression of each peptide growth factor gene is differentially regulated by fluid shear stress in the vascular endothelial cell. These results may have implications on vascular structure and function in response to hemodynamic forces and present a model for the study of transduction of mechanical stimuli into altered gene expression.

Animals↗

PubMed1993

Werner's syndrome associated with spastic paraparesis and peripheral neuropathy.

A Werner's syndrome patient with spastic paraparesis and polyneuropathy had slowing of central and peripheral nerve conduction. Sural nerve biopsy revealed a significantly higher frequency of demyelination and remyelination and a loss of myelinated fibers. These data suggest that the central and peripheral nervous systems are affected in Werner's syndrome.

Adult↗

PubMed1993

Mechanotransduction in stretch-induced hypertrophy of cardiac myocytes.

Mechanical loading of cardiac muscles causes rapid activation of a number of immediate-early (IE) genes and hypertrophy. However, little is known as to how muscle cells sense mechanical load and regulate gene expression. We examined roles of several putative mechanotransducers in stretch-induced hypertrophy of cardiac myocytes grown on a deformable silicone sheet. Using the patch-clamp technique, we found a single class of stretch-activated cation channels which was completely and reversibly blocked by gadolinium. The inhibition of this channel by gadolinium did not affect either stretch-induced expression of the IE genes or hypertrophy. Neither disruption of microtubules with colchicine nor that of actin microfilaments by cytochalasin D prevented the stretch-induced IE gene expression. Arresting contractile activity by tetrodotoxin did not affect the stretch-induced IE gene expression or hypertrophy. These results suggest that stretch-activated cation channels, microtubules, microfilaments, and contractile activity are not the mechanotransducers. Preliminary results suggest that cell stretch may cause a release of a growth factor(s), which in turn initiates a cascade of hypertrophic response of cardiac myocytes.

Amino Acid Sequence↗

PubMed1993

[A case of Werner syndrome associated with spastic paraparesis and peripheral neuropathy].

A 33-year-old woman, whose parents were consanguineously married, was admitted to our hospital because of progressive difficulty in walking and hoarseness in speech. She had been in good health as a child, at age 16 ulcerations appeared on the skin of feet, and have been recurrent. AT age 22, bilateral cataracts were removed. From the age of 26 years, the deformities in the toes and fingers worsened and she had difficulty in walking. At age 32, hoarseness was noticed. The patient was a diminutive woman and the skin was dry, thin and hyperpigmented. The neurological examination revealed mental retardation, spastic paraparesis and polyneuropathy. Electrophysiological studies revealed a slowing of central and peripheral nerve conduction. Sural nerve biopsy revealed a significantly higher incidence of de- and remyelination and a loss of myelinated fibers. These data suggest that the central and peripheral nervous systems are affected in Werner syndrome.

Adult↗

PubMed1992

Roles of mechano-sensitive ion channels, cytoskeleton, and contractile activity in stretch-induced immediate-early gene expression and hypertrophy of cardiac myocytes.

Mechanical loading of cardiac and skeletal muscles in vivo and in vitro causes rapid activation of a number of immediate-early (IE) genes and hypertrophy of muscle cells. However, little is known as to how muscle cells sense mechanical load and transduce it into intracellular signals of gene regulation. We examined roles of putative cellular mechanotransducers, mechanosensitive ion channels, the cytoskeleton, and contractile activity in stretch-induced hypertrophy of cardiac myocytes grown on a deformable silicone sheet. Using the patch-clamp technique, we found a single class of stretch-activated cation channel that was completely blocked by gadolinium (Gd3+). Inhibition of this channel by Gd3+ did not affect either the stretch-induced expression of IE genes or the increase in protein synthesis. Neither disruption of microtubules with colchicine nor that of actin microfilaments by cytochalasin D prevented the stretch-induced IE gene expression and increase in protein synthesis. Arresting contractile activity of myocytes by high K+, tetrodotoxin, or Ba2+ did not affect the stretch-induced IE gene expression. Tetrodotoxin-arrested myocytes could increase protein synthesis in response to stretch. These results suggest that Gd(3+)-sensitive ion channels, microtubules, microfilaments, and contractile activity may not be necessary for transduction of mechanical stretch into the IE gene expression and hypertrophy. The stimulus of membrane stretch may be transmitted to the cell nucleus through some mechanisms other than electrical or direct mechanical transduction in cardiac myocytes.

Amino Acid Sequence↗

PubMed1992

Molecular characterization of the stretch-induced adaptation of cultured cardiac cells. An in vitro model of load-induced cardiac hypertrophy.

Although it is a well-known fact that hemodynamic load is a major determinant of cardiac muscle mass and its phenotype, little is known as to how mechanical load is converted into intracellular signals of gene regulation. To address this question, we characterized the stretch-induced adaptation of cultured neonatal cardiocytes grown on a stretchable substrate in a serum-free medium. Static stretch (20%) of the cells was applied without cell injury. Stretch caused hypertrophy in myocytes and hyperplasia in non-myocytes. Stretch caused an induction of immediate-early genes such as c-fos, c-jun, c-myc, JE, and Egr-1, but not Hsp70. Immunostaining showed that the stretch-induced Fos protein localized in the nucleus of both myocytes and non-myocytes. Nuclear extracts from stretched myocytes contained DNA binding activity to the AP-1 and Egr-1 consensus sequences. In myocytes, the induction of immediate-early genes was followed by expression of "fetal" genes such as skeletal alpha-actin, atrial natriuretic factor, and beta-myosin heavy chain. DNA transfection experiments showed that the "stretch-response element" of the c-fos gene promoter is present within 356 base pairs of the 5'-flanking region, whereas that of the atrial natriuretic factor and the beta-myosin heavy chain genes is probably located outside of 3412 and 628 base pairs of the 5'-flanking region, respectively. These results demonstrate that the phenotype of stretched cardiocytes in this in vitro model closely mimics that of hemodynamic load-induced hypertrophy in vivo. This model seems to be a suitable system with which to dissect the molecular mechanisms of load-induced hypertrophy of cardiac muscle.

Adaptation, Physiological↗

PubMed1992

Molecular cloning and characterization of the human cardiac Na+/Ca2+ exchanger cDNA.

The Na+/Ca2+ exchanger plays important roles in Ca2+ handling in many excitable cells. In particular, the Na+/Ca2+ exchanger is expressed at high levels in the cardiac sarcolemma and is the dominant mechanism of Ca2+ extrusion from the cells. In addition, the exchanger has been suggested to play key roles in digitalis action and in postischemic reperfusion injury of cardiac myocytes. We report here the isolation and characterization of the cDNA encoding the human cardiac Na+/Ca2+ exchanger. Twelve overlapping clones corresponding to 5.6 kilobases of the exchanger cDNA sequence were isolated from 5 x 10(5) phage plaques screened. The sequence predicted a 973-amino acid polypeptide with a putative leader peptide, 11 potential membrane-spanning regions, and one large putative cytoplasmic loop between the fifth and sixth transmembrane helices. When RNA was synthesized in vitro from the cloned cDNA and injected into Xenopus oocytes, it induced expression of Na+/Ca2+ exchange activity at high levels, confirming that this clone encodes the functional Na+/Ca2+ exchanger. Southern blot analysis indicated that the cardiac exchanger gene exists as a single copy in the human genome, although existence of other related genes cannot be ruled out. Northern blot and S1 mapping analyses revealed that the cardiac type exchanger mRNA is expressed most abundantly in the heart and next in the brain. The cardiac-type exchanger mRNA was also expressed in the retina and in skeletal and smooth muscles at very low levels. The levels of mRNA encoding the exchanger were significantly lower in fetal hearts than in adult hearts but were unchanged in the myocardium from patients with end-stage heart failure.

Amino Acid Sequence↗

PubMed1992

Search for human T-cell leukemia virus type I (HTLV-I) proviral sequences by polymerase chain reaction in the central nervous system tissue of HTLV-I-associated myelopathy.

Using the polymerase chain reaction (PCR), proviral DNA sequences of the pol and env regions of human T-cell leukemia virus type I (HTLV-I) were directly amplified in paraffin-embedded and frozen tissue sections of active inflammatory central nervous system (CNS) lesions in three autopsy cases of HTLV-I-associated myelopathy (HAM) with serological confirmation. In parallel, the enumeration of UCHL-1 (monoclonal antibody reactive to T-cells) positive cells in the tissue sections subjected to PCR were carried out. Although the control DNA sequence of parathyroid hormone-like peptide gene was definitely amplified, no signals for HTLV-I proviral sequences were detected in these specimens. The number of UCHL-1 positive cell nuclei was almost on the border line of our PCR sensitivity in formalin-fixed tissue, which was estimated to be 20-200 copies. Therefore, it is unlikely that the central nervous system tissue damage in HAM/TSP is a consequence of productive infection of HTLV-I in the CNS tissue.

Aged↗

PubMed1992

Pathological changes in skeletal muscle in HTLV-I-associated myelopathy.

The main lesion site of HTLV-I-associated myelopathy or tropical spastic paraparesis (HAM/TSP) is the pyramidal tract. In some HAM patients, clinical symptoms and findings indicate neuromuscular involvement, such as muscular atrophy, fasciculation, elevated serum creatine kinase (CK) or significant electrophysiological data. Cases of HAM/TSP complicated with polymyositis or motor neuron disease have been reported. But no investigation has been directed to muscular pathology in many patients of HAM/TSP. We conducted muscle biopsies on 13 HAM patients. Four patients showed neurogenic changes. Six patients showed histological findings indicative of inflammatory myopathy. We investigated surface marker of invading cells in these 6 patients. In all patients, T lymphocytes were more predominant than B lymphocytes and in three of them T helper/inducer cells were more predominant than T suppressor cells. In 2 patients, only slight myopathic change could be seen, such as variation in fiber diameter and increase in the number of internal nuclei. In 1 patient, type 2 fiber atrophy was seen, and was possibly the result of disuse. Disturbance of secondary motor neurons or inflammatory myopathy is thus shown to be possibly associated with HAM/TSP.

Adult↗

PubMed1992

Physiological fluid shear stress causes downregulation of endothelin-1 mRNA in bovine aortic endothelium.

We report here that the level of endothelin-1 (ET-1) mRNA from bovine aortic endothelial cells grown in vitro is rapidly (within 1 h of exposure) and significantly (fivefold) decreased in response to fluid shear stress of physiological magnitude. The downregulation of ET-1 mRNA occurs in a dose-dependent manner that exhibits saturation above 15 dyn/cm2. The decrease is complete prior to detectable changes in endothelial cell shape and is maintained throughout and following alignment in the direction of blood flow. Peptide levels of ET-1 secreted into the media are also reduced in response to fluid shear stress. Cyclical stretch experiments demonstrated no changes in ET-1 mRNA, while increasing media viscosity with dextran showed that the downregulation is a specific response to shear stress and not to fluid velocity. Although both pulsatile and turbulent shear stress of equal time-average magnitude elicited the same decrease in ET-1 mRNA as steady laminar shear (15 dyn/cm2), low-frequency reversing shear stress did not result in any change. These results show that the magnitude as well as the dynamic character of fluid shear stress can modulate expression of ET-1 in vascular endothelium.

Animals↗

PubMed1992

Differences in cardiac calcium release channel (ryanodine receptor) expression in myocardium from patients with end-stage heart failure caused by ischemic versus dilated cardiomyopathy.

The molecular basis for the systolic and diastolic dysfunction characteristic of end-stage heart failure in humans remains poorly understood. It has been proposed that both abnormal calcium handling and defects in the contractile apparatus may contribute to the myocardial dysfunction. Two channels, the calcium release channel (CRC) or ryanodine receptor of the sarcoplasmic reticulum (SR), and the slow calcium channel or dihydropyridine receptor (DHPR) of the transverse tubule, play key roles in regulating intracellular calcium concentration and in excitation-contraction (E-C) coupling in the heart. The DHPR serves as the voltage sensor and plasma membrane calcium channel resulting in activation of the CRC during E-C coupling in heart muscle. In this study, we investigated the levels of CRC expression in several forms of end-stage heart failure in humans. A cardiac CRC cDNA was cloned from rabbit and used as a probe for Northern blot analyses to determine mRNA levels in the left ventricles of normal (n = 4) and cardiomyopathic (n = 34) human hearts from patients undergoing cardiac transplantation. Compared with normal patients, patients with ischemic cardiomyopathy (n = 18) showed a 28% decrease in CRC mRNA levels (p less than 0.025) and patients with idiopathic dilated cardiomyopathy (n = 14) a nonsignificant 12% increase. In these same hearts, alpha-actin levels were unchanged in end-stage heart failure, as has been previously reported. This is the first report indicating that the expression of the CRC mRNA is abnormal in end-stage human heart failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Expression of A-, B-, and C-type natriuretic peptide genes in failing and developing human ventricles. Correlation with expression of the Ca(2+)-ATPase gene.

Brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) are novel natriuretic peptides, originally isolated from porcine brain. Similar to atrial natriuretic peptide (ANP), BNP is also synthesized in and secreted from cardiocytes, but CNP is not expressed at significant levels in normal adult myocardium. Previous studies have indicated that the serum level and ventricular expression of the ANP gene were augmented in patients with heart failure. Recently, the serum level of BNP was also reported to increase in human heart failure. To examine whether or not the expression of these natriuretic peptides is regulated in ventricular myocardium in a concordant manner, we performed Northern blot analysis using total cellular RNA isolated from the diseased left ventricles of 30 cardiac transplant recipients with end-stage heart failure, seven ventricles from organ donors (control group), and two ventricles of artificially aborted 17- and 19-week-old fetuses. The levels of mRNAs encoding both BNP and ANP increased significantly (p less than 0.01) in the left ventricular myocardium from the patients with end-stage heart failure as compared with the control group. The levels of BNP mRNA correlated positively with those of ANP mRNA (r = 0.73, p less than 0.01) and negatively with those of sarcoplasmic reticulum Ca(2+)-ATPase mRNA (r = -0.66, p less than 0.01) in the left ventricular myocardium from the patients with heart failure. There was also a negative correlation between the levels of ANP and the sarcoplasmic reticulum Ca(2+)-ATPase mRNAs (r = -0.65, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Age-related differences in the expression of proto-oncogene and contractile protein genes in response to pressure overload in the rat myocardium.

Cardiac adaptation to hemodynamic stress involves both quantitative (hypertrophy) and qualitative (pattern of gene expression) changes. Our previous studies have shown that advancing age in the rat is associated with diminished capacity to develop left ventricular hypertrophy in response to either ascending aortic constriction (AoC). In this study, we examined whether the expression of protooncogenes and contractile protein genes in response to AoC differs between adult (9-mo-old) and old (18-mo-old) rats. RNA was isolated from the left ventricles of AoC animals of both age groups subjected to a similar hemodynamic stress. Immediately after AoC, the levels of the ventricular expression of c-fos and c-jun protooncogenes were markedly lower in the old rats than in the adult animals. 5 d after the operation, the ratio of beta- to alpha-myosin heavy chain mRNAs increased significantly after AoC in both age groups. In contrast, AoC was associated with a marked reduction in the levels of mRNAs encoding sarcoplasmic reticulum Ca(2+)-ATPase (by 69%) and cardiac calsequestrin (by 49%) in the old rats but not in the adults. The mRNAs encoding atrial natriuretic factor and skeletal alpha-actin increased in response to AoC only in the adult rats. There were no significant differences in expression of the cardiac alpha-actin mRNA among the experimental groups. These data suggest that (a) the expression of protooncogenes in response to acute pressure overload is significantly reduced in the aged rats and (b) the pattern of expression of the contractile protein gene in response to AoC in the old rats differs qualitatively as well as quantitatively from that in younger animals. These age-related differences may play a role in the higher frequency of heart failure in the aged during hemodynamic stress.

Actins↗

PubMed1992

Expression of dihydropyridine receptor (Ca2+ channel) and calsequestrin genes in the myocardium of patients with end-stage heart failure.

Cytoplasmic free calcium ions (Ca2+) play a central role in excitation-contraction coupling of cardiac muscle. Abnormal Ca2+ handling has been implicated in systolic and diastolic dysfunction in patients with end-stage heart failure. The current study tests the hypothesis that expression of genes encoding proteins regulating myocardial Ca2+ homeostasis is altered in human heart failure. We analyzed RNA isolated from the left ventricular (LV) myocardium of 30 cardiac transplant recipients with end-stage heart failure (HF) and five organ donors (normal control), using cDNA probes specific for the cardiac dihydropyridine (DHP) receptor (the alpha 1 subunit of the DHP-sensitive Ca2+ channel) and cardiac calsequestrin of sarcoplasmic reticulum (SR). In addition, abundance of DHP binding sites was assessed by ligand binding techniques (n = 6 each for the patients and normal controls). There was no difference in the level of cardiac calsequestrin mRNA between the HF patients and normal controls. In contrast, the level of mRNA encoding the DHP receptor was decreased by 47% (P less than 0.001) in the LV myocardium from the patients with HF compared to the normal controls. The number of DHP binding sites was decreased by 35-48%. As reported previously, expression of the SR Ca(2+)-ATPase mRNA was also diminished by 50% (P less than 0.001) in the HF group. These data suggest that expression of the genes encoding the cardiac DHP receptor and SR Ca(2+)-ATPase is reduced in the LV myocardium from patients with HF. Altered expression of these genes may be related to abnormal Ca2+ handling in the failing myocardium, contributing to LV systolic and diastolic dysfunction in patients with end-stage heart failure.

Adolescent↗