Cardiac involvement in Fabry disease - A non-invasive assessment and the role of specific therapies

Fabry disease is an X-linked inherited metabolic disorder due to the pathogenic mutation of the GLA gene, which codes lysosomal enzyme alpha-galactosidase A. The resultant accumulation of glycosphingolipids causes various systemic symptoms in childhood and adolescence, and major organ damage in adulthood. Cardiac involvement is important as the most frequent cause of death in Fabry disease patients. Progressive left ventricular hypertrophy with varying degrees of contractile dysfunction as well as conduction abnormalities and arrhythmias are typical cardiac features, and these findings can be evaluated in detail via non-invasive modalities, such as an electrocardiogram, echocardiography and cardiac magnetic resonance. In addition, specific therapies of enzyme replacement therapy and pharmacological chaperone therapy are available, and their beneficial effects on cardiac involvement have been reported. This minireview highlights recent evidence concerning non-invasive modalities for assessing cardiac involvement in Fabry disease and the effects of enzyme replacement therapy and pharmacological chaperone therapy on the findings of those modalities.

Constrictive Pericarditis with Cardiac Ascites Caused Spontaneous Bacterial Peritonitis

Patients with constrictive pericarditis (CP) typically present with symptoms related to right-sided heart failure, such as cardiac ascites. Spontaneous bacterial peritonitis (SBP) usually arises in association with ascites secondary to hepatic cirrhosis. We herein report a rare case of CP in which SBP developed due to cardiac ascites, even in the absence of cirrhosis. In this case, pericardiectomy improved both the hemodynamics and the ascites, while therapy with diuretics alone was insufficient. It is important to consider SBP in the differential diagnosis when any abdominal symptoms or an inflammatory response is found in patients with heart failure and cardiac ascites.

The role of native T1 values on the evaluation of cardiac manifestation in Japanese Fabry disease patients

Aims

T1 mapping in cardiac magnetic resonance imaging enables us to distinguish various myocardial diseases showing left ventricular hypertrophy. Fabry disease is a lysosomal storage disorder causing the accumulation of glycosphingolipids into various organs, including the heart, which can be detected by native T1 values in T1 mapping. However, there is no report for the systematic evaluation of native T1 values in Fabry disease in Japan.

Methods and results

We analyzed native T1 values of 30 Fabry disease patients (14 males and 16 females) obtained by 3-T cardiac magnetic resonance imaging. Averaged T1 values were significantly lower in male patients (septal T1: 1149.5 ± 63.3 ms; total T1: 1145.1 ± 59.5 ms) than in female patients (septal T1: 1210.5 ± 45.5 ms; total T1: 1198.8 ± 51.8 ms) (p < 0.01). We compared the native T1 values of Fabry disease patients with those obtained from 15 hypertrophic cardiomyopathy patients (9 males and 6 females). Native T1 values effectively differentiate Fabry disease from hypertrophic cardiomyopathy (septal T1: sensitivity 93.3% and specificity 80.0%; total T1: sensitivity 86.7% and specificity 73.3%). In addition, native T1 values had a significant negative correlation with the left ventricular mass index in male patients at the pre-hypertrophic stage (p < 0.05). In male and female patients without late-gadolinium enhancement, native T1 values also had a significant negative correlation with the left ventricular mass index (p < 0.05).

Conclusion

These results suggest that native T1 values can be used to discriminate Fabry disease from hypertrophic cardiomyopathy and can reflect the accumulation of glycosphingolipids in cardiomyocytes.

Characteristics of the Electrocardiogram in Japanese Fabry Patients Under Long-Term Enzyme Replacement Therapy

Objective: An electrocardiogram (ECG) is an important tool for demonstrating cardiac manifestations in various heart diseases. The present study clarified the characteristics of ECG parameters in Japanese Fabry patients under long-term enzyme replacement therapy (ERT).

Methods: We analyzed the ECGs of 40 Fabry patients (male, n = 17; female, n = 23) before and after treatment with ERT. To evaluate the atrio-ventricular conduction, the PQ interval, corrected PQ and PQ minus P-wave in lead II (Pend-Q) were calculated. The QRS duration, QTc, Sokolow-Lyon index, and strain pattern were also examined.

Results: At the baseline, the shortening of the PQ interval, corrected PQ and Pend-Q was identified in 7.5, 25.0, and 47.5% of cases, respectively. The prolongation of QRS duration and QTc was found in 7.5 and 40.0% of cases, respectively. The strain pattern was mainly identified in female patients, irrespective of left ventricular hypertrophy (LVH). During long-term ERT, the PQ interval, corrected PQ and Pend-Q did not change significantly. The QRS duration was significantly prolonged in both genders, whereas the QTc was significantly prolonged only in male patients. A subgroup analysis revealed that the prolongation of the QRS duration and QTc only occurred in male patients with LVH and only occurred in female patients with the classical type mutation. The prevalence of the strain was significantly increased only in male patients with LVH.

Conclusions: These results suggest that the shortening of the Pend-Q is a specific finding in Japanese Fabry patients, and the strain pattern without LVH in female patients can be considered Fabry disease. During long-term ERT, prolongation of the QRS duration and QTc can indicate the progression of myocardial damage in male patients with LVH and in female patients with the classical type mutation.

Massive accumulation of globotriaosylceramide in various tissues from a Fabry patient with a high antibody titer against alpha-galactosidase A after 6 years of enzyme replacement therapy

Fabry disease is an X-linked metabolic disorder due to a pathogenic mutation of the GLA gene. The accumulation of globotriaosylceramide (Gb3) damages multiple organs, including the heart, kidney and nervous system, especially in classical type Fabry disease. Enzyme replacement therapy (ERT) using recombinant alpha-galactosidase A has been shown to remove Gb3 from organs and to improve the prognosis of Fabry disease. We herein report the case of a 67-year-old classical type Fabry patient who had been treated with ERT for 6 years and who continuously showed a high antibody titer against recombinant alpha-galactosidase A during therapy. A post-mortem examination was performed after sudden death. A histological examination revealed the massive accumulation of Gb3 in various organs, even after long term ERT. In addition to the typical pathological findings as reported in tissue biopsy samples, the serious accumulation of Gb3 in the cardiac conduction system and the endocrine system was detected. Since the start of ERT for this patient might be too late to improve organ damage and prognosis, ERT should be started before the appearance of major organ involvement for the effective elimination of Gb3 and changes in the therapeutic strategy might be considered if the patient shows a high antibody titer against recombinant alpha-galactosidase A.

Clinical findings of gadolinium-enhanced cardiac magnetic resonance in Fabry patients

BACKGROUND

Fabry disease is one of the causes of left ventricular hypertrophy (LVH) and can be treated with enzyme replacement therapy or pharmacological chaperone therapy. Late gadolinium enhancement (LGE) in cardiac magnetic resonance (CMR) can identify myocardial fibrosis and be used for the stratification in LVH. However, the details of the prevalence and characteristics of LGE in Japanese Fabry patients have not been reported.

METHODS

We evaluated myocardial involvement in 26 Fabry patients (10 males, 16 females) using gadolinium-enhanced CMR. LGE areas were analyzed using the previously reported scoring method. Echocardiography was also performed to evaluate the left ventricular function and left ventricular mass.

RESULTS

LGE on CMR images was positive in 5 out of 26 patients, and all patients with LGE-positive findings suffered from LVH (2 out of 5 male patients and 3 out of 4 female patients with LVH on echocardiography). LGE was specifically localized at the mid-wall in the infero-lateral area of the left ventricle. LGE-positive patients seemed to be older, and tended to have a larger left ventricular mass index and higher B-type natriuretic peptide level than LGE-negative patients.

CONCLUSIONS

These results revealed that specific localization of LGE was present in Fabry patients.

The beneficial effects of long-term enzyme replacement therapy on cardiac involvement in Japanese Fabry patients

Fabry disease is a hereditary disorder that occurs due to the reduction or absence of alpha-galactosidase A activity, which leads to cardiac involvement including left ventricular hypertrophy (LVH). Enzyme replacement therapy (ERT) provides better patient outcomes by preventing serious complications. However, there have been very few studies on the long-term effects of ERT on the cardiac manifestations in Japanese Fabry patients. We retrospectively analyzed the data from the medical records of 42 Fabry patients (male, n = 17; female, n = 25) who were followed at Jikei University Hospital, and in whom the long-term effects of ERT could be evaluated (median follow-up period: male, 11 years; female, 8 years). The slope of the left ventricular mass (LVM) increase was 3.02 ± 3.41 g/m²/year in males and 1.69 ± 2.73 g/m²/year in females. In a subgroup analysis, the slopes of males with and without LVH did not differ to a statistically significant extent; however, the slope in female patients without LVH was significantly smaller than that of female patients with LVH. We then compared our data to the natural historical data that have previously been reported. In comparison to the previously reported data, we found a significant reduction in the LVM changes (g/height^2.7/year) of patients who received long-term ERT (male, 4.07 ± 1.03 to 1.25 ± 1.39; female, 2.31 ± 0.81 to 0.78 ± 1.23). Long-term ERT effectively prevents LVH in Fabry patients. This effect was also observed in the patients with LVH prior to the initiation of ERT.

Tissue thrombin is associated with the pathogenesis of dilated cardiomyopathy

BACKGROUND

Thrombin is a serine protease known to be the final product of the coagulation cascade. However, thrombin plays other physiological roles in processes such as gastric contractions and vessel wound healing, and a state of coagulability is increased in patients with dilated cardiomyopathy (DCM). In this study, we investigate the role of thrombin in the pathogenesis of DCM. The purpose of this study is to clarify the role of thrombin in the pathogenesis of DCM and investigate the possibility of treatment against DCM by thrombin inhibition.

METHODS

We investigated the expression of thrombin in the left ventricles of five patients with DCM who underwent the Batista operation and four patients without heart disease. Furthermore, we investigated the involvement of thrombin in the development of DCM using knock-in mice with a deletion mutation of cardiac troponin T that causes human DCM (∆K210 knock-in mouse) (B6;129-Tnnt2^tm2Mmto) and assessed the effects of a direct thrombin inhibitor, dabigatran on ∆K210 knock-in mice using echocardiographic examinations, the Kaplan-Meier method and Western blotting.

RESULTS

The immunohistochemical analysis showed a strong thrombin expression in the DCM patients compared to the patients without heart disease. In immunohistochemical analysis, a strong thrombin expression was observed in the heart tissues analysis in the ∆K210 knock-in mice. Dabigatran administration significantly improved fractional shortening according to the echocardiographic examination and the survival outcomes in ∆K210 knock-in mice.

CONCLUSION

Tissue thrombin is involved in the pathogenesis of DCM and thrombin inhibition can be beneficial for the treatment of DCM.

Effects of Add-on Therapy Consisting of a Selective Mineralocorticoid Receptor Blocker on Arterial Stiffness in Patients with Uncontrolled Hypertension

OBJECTIVE

Aldosterone plays an important role in the pathogenesis of atherosclerosis; however, the significance of mineralocorticoid receptor blockade for atherosclerosis has not been fully elucidated. In this study, the effect of add-on eplerenone on the degree of arterial stiffness was examined in patients with uncontrolled hypertension.

METHODS

Forty-seven uncontrolled hypertensive patients who had previously been treated with anti-hypertensive drugs were examined retrospectively. Thirty-two patients received add-on therapy consisting of eplerenone (Group E) and 15 patients received add-on therapy with a Calcium channel blocker (CCB) or an increased dose of CCB (Group C) in addition to their baseline medications. Both the systolic blood pressure (SBP) and diastolic blood pressure (DBP) values were significantly decreased at two and 12 months in Group C. In contrast, neither the SBP nor DBP values were significantly changed at two months and eventually decreased at 12 months in Group E. The degree of arterial stiffness, as evaluated according to the cardio-ankle vascular index (CAVI), did not improve at either two or 12 months in Group C, whereas the CAVI values improved as early as at two months and the improvement was sustained at 12 months in Group E. The extent of change in the CAVI was not associated with the level of changes in the SBP or DBP values in Group E.

CONCLUSION

Treatment with eplerenone added to the patient's baseline medications improves the degree of arterial stiffness as early as at two months after the beginning of treatment, independent of the blood pressure-lowering actions of these drugs in patients with uncontrolled hypertension.

The plasma B-type natriuretic peptide levels are low in males with stable ischemic heart disease (IHD) compared to those observed in patients with non-IHD: a retrospective study

Objective

Although the plasma B-type natriuretic peptide (BNP) level is a marker of heart failure, it is unclear whether BNP per se plays a pivotal role for pathogenic mechanisms underlying the development of ischemic heart disease (IHD). In this study, we retrospectively examined the plasma BNP levels in stable patients with IHD and compared to stable patients with cardiovascular diseases other than IHD.

Methods

The study population was 2088 patients (1698 males and 390 females) who were admitted to our hospital due to IHD (n = 1,661) and non-IHD (n = 427) and underwent cardiac catheterization. Measurements of the hemodynamic parameters and blood sampling were performed.

Results

The plasma BNP levels were significantly lower in the IHD group than in the non-IHD group (p<0.001). The multiple regression analysis examining the logBNP values showed that age, a male gender, low left ventricular ejection fraction, low body mass index, serum creatinine, atrial fibrillation and IHD per se were significant explanatory variables. When the total study population was divided according to gender, the plasma BNP levels were found to be significantly lower in the IHD group than in the non-IHD group among males (p<0.001), but not females (p = NS). Furthermore, a multiple logistic regression analysis of IHD showed the logBNP value to be a significant explanatory variable in males (regression coefficient: −0.669, p<0.001), but not females (p = NS).

Conclusions

The plasma BNP levels were relatively low in stable patients with IHD compared with those observed in stable patients with non-IHD; this tendency was evident in males. Perhaps, the low reactivity of BNP is causally associated with IHD in males. We hope that this study will serve as a test of future prospective studies.

Preconditioning actions of aldosterone through p38 signaling modulation in isolated rat hearts

Although persistent excessive actions of aldosterone have unfavorable effects on the cardiovascular system, primarily via mineralocorticoid receptor (MR)-dependent pathways, the pathophysiological significance of aldosterone cascade activation in heart diseases has not yet been fully clarified. We herein examined the effects of short-term aldosterone stimulation at a physiological dose on cardiac function during ischemia-reperfusion injury (IRI). In order to study the effects of aldosterone preconditioning, male Wistar rat Langendorff hearts were perfused with 10(-9) mol/l of aldosterone for 10 min before ischemia, and the response to IRI was assessed. Although aldosterone did not affect the baseline hemodynamic parameters, preconditioning actions of aldosterone significantly improved the recovery in left ventricular contractility and left ventricular end-diastolic pressure associated with a reduced activity of creatine phosphokinase released into the perfusate after ischemia-reperfusion. Notably, the MR inhibitor eplerenone did not abrogate these beneficial effects. Biochemical analyses revealed that p38MAPK phosphorylation was significantly increased during aldosterone preconditioning before ischemia, whereas its phosphorylation was substantially attenuated during sustained ischemia-reperfusion, compared with the results for in the non-preconditioned control hearts. This dual regulation of p38MAPK was not affected by eplerenone. The phosphorylation levels of other MAPKs were not altered by aldosterone preconditioning. In conclusion, the temporal induction of the aldosterone cascade, at a physiological dose, has favorable effects on cardiac functional recovery and injury following ischemia-reperfusion in a MR-independent manner. Phasic dynamism of p38MAPK activation may play a key role in the physiological compensatory pathway of aldosterone under severe cardiac pathological conditions.

Corticosteroids increase intracellular free sodium ion concentration via glucocorticoid receptor pathway in cultured neonatal rat cardiomyocytes

Background

Glucocorticoids as well as mineralocorticoid have been shown to play essential roles in the regulation of electrical and mechanical activities in cardiomyocytes. Excess of these hormones is an independent risk factor for cardiovascular disease. Intracellular sodium ([Na⁺]_i) kinetics are involved in cardiac diseases, including ischemia, heart failure and hypertrophy. However, intrinsic mediators that regulate [Na⁺]_i in cardiomyocytes have not been widely discussed. Moreover, the quantitative estimation of altered [Na⁺]_i in cultured cardiomyocytes and the association between the level of [Na⁺]_i and the severity of pathological conditions, such as hypertrophy, have not been precisely reported.

Methods and results

We herein demonstrate the quantitative estimation of [Na⁺]_i in cultured neonatal rat cardiomyocytes following 24 h of treatment with corticosterone, aldosterone and dexamethasone. The physiological concentration of glucocorticoids increased [Na⁺]_i up to approximately 2.5 mM (an almost 1.5-fold increase compared to the control) in a dose-dependent manner; this effect was blocked by a glucocorticoid receptor (GR) antagonist but not a mineralocorticoid receptor antagonist. Furthermore, glucocorticoids induced cardiac hypertrophy, and the hypertrophic gene expression was positively and significantly correlated with the level of [Na⁺]_i. Dexamethasone induced the upregulation of Na⁺/Ca^{2 +} exchanger 1 at the mRNA and protein levels.

Conclusions

The physiological concentration of glucocorticoids increases [Na⁺]_i via GR. The dexamethasone-induced upregulation of NCX1 is partly involved in the glucocorticoid-induced alteration of [Na⁺]_i in cardiomyocytes. These results provide new insight into the mechanisms by which glucocorticoid excess within a physiological concentration contributes to the development of cardiac pathology.

A technique for quantifying intracellular free sodium ion using a microplate reader in combination with sodium-binding benzofuran isophthalate and probenecid in cultured neonatal rat cardiomyocytes

Background

Intracellular sodium ([Na⁺]_i) kinetics are involved in cardiac diseases including ischemia, heart failure, and hypertrophy. Because [Na⁺]_i plays a crucial role in modulating the electrical and contractile activity in the heart, quantifying [Na⁺]_i is of great interest. Using fluorescent microscopy with sodium-binding benzofuran isophthalate (SBFI) is the most commonly used method for measuring [Na⁺]_i. However, one limitation associated with this technique is that the test cannot simultaneously evaluate the effects of several types or various concentrations of compounds on [Na⁺]_i. Moreover, there are few reports on the long-term effects of compounds on [Na⁺]_i in cultured cells, although rapid changes in [Na⁺]_i during a period of seconds or several minutes have been widely discussed.

Findings

We established a novel technique for quantifying [Na⁺]_i in cultured neonatal rat cardiomyocytes attached to a 96-well plate using a microplate reader in combination with SBFI and probenecid. We showed that probenecid is indispensable for the accurate measurement because it prevents dye leakage from the cells. We further confirmed the reliability of this system by quantifying the effects of ouabain, which is known to transiently alter [Na⁺]_i. To illustrate the utility of the new method, we also examined the chronic effects of aldosterone on [Na⁺]_i in cultured cardiomyocytes.

Conclusions

Our technique can rapidly measure [Na⁺]_i with accuracy and sensitivity comparable to the traditional microscopy based method. The results demonstrated that this 96-well plate based measurement has merits, especially for screening test of compounds regulating [Na⁺]_i, and is useful to elucidate the mechanisms and consequences of altered [Na⁺]_i handling in cardiomyocytes.

Genetic modulation of the SERCA activity does not affect the Ca(2+) leak from the cardiac sarcoplasmic reticulum

The Ca(2+) content in the sarcoplasmic reticulum (SR) determines the amount of Ca(2+) released, thereby regulating the magnitude of Ca(2+) transient and contraction in cardiac muscle. The Ca(2+) content in the SR is known to be regulated by two factors: the activity of the Ca(2+) pump (SERCA) and Ca(2+) leak through the ryanodine receptor (RyR). However, the direct relationship between the SERCA activity and Ca(2+) leak has not been fully investigated in the heart. In the present study, we evaluated the role of the SERCA activity in Ca(2+) leak from the SR using a novel saponin-skinned method combined with transgenic mouse models in which the SERCA activity was genetically modulated. In the SERCA overexpression mice, the Ca(2+) uptake in the SR was significantly increased and the Ca(2+) transient was markedly increased. However, Ca(2+) leak from the SR did not change significantly. In mice with overexpression of a negative regulator of SERCA, sarcolipin, the Ca(2+) uptake by the SR was significantly decreased and the Ca(2+) transient was markedly decreased. Again, Ca(2+) leak from the SR did not change significantly. In conclusion, the selective modulation of the SERCA activity modulates Ca(2+) uptake, although it does not change Ca(2+) leak from the SR.

Depressed Frank-Starling mechanism in the left ventricular muscle of the knock-in mouse model of dilated cardiomyopathy with troponin T deletion mutation ΔK210

It has been reported that the Frank-Starling mechanism is coordinately regulated in cardiac muscle via thin filament "on-off" equilibrium and titin-based lattice spacing changes. In the present study, we tested the hypothesis that the deletion mutation ΔK210 in the cardiac troponin T gene shifts the equilibrium toward the "off" state and accordingly attenuate the sarcomere length (SL) dependence of active force production, via reduced cross-bridge formation. Confocal imaging in isolated hearts revealed that the cardiomyocytes were enlarged, especially in the longitudinal direction, in ΔK210 hearts, with striation patterns similar to those in wild type (WT) hearts, suggesting that the number of sarcomeres is increased in cardiomyocytes but the sarcomere length remains unaltered. For analysis of the SL dependence of active force, skinned muscle preparations were obtained from the left ventricle of WT and knock-in (ΔK210) mice. An increase in SL from 1.90 to 2.20μm shifted the mid-point (pCa50) of the force-pCa curve leftward by ~0.21pCa units in WT preparations. In ΔK210 muscles, Ca(2+) sensitivity was lower by ~0.37pCa units, and the SL-dependent shift of pCa50, i.e., ΔpCa50, was less pronounced (~0.11pCa units), with and without protein kinase A treatment. The rate of active force redevelopment was lower in ΔK210 preparations than in WT preparations, showing blunted thin filament cooperative activation. An increase in thin filament cooperative activation upon an increase in the fraction of strongly bound cross-bridges by MgADP increased ΔpCa50 to ~0.21pCa units. The depressed Frank-Starling mechanism in ΔK210 hearts is the result of a reduction in thin filament cooperative activation.

An immunohistochemical analysis of tissue thrombin expression in the human atria

Objective

Thrombin, the final coagulation product of the coagulation cascade, has been demonstrated to have many physiological effects, including pro-fibrotic actions via protease-activated receptor (PAR)-1. Recent investigations have demonstrated that activation of the cardiac local coagulation system was associated with atrial fibrillation. However, the distribution of thrombin in the heart, especially difference between the atria and the ventricle, remains to be clarified. We herein investigated the expression of thrombin and other related proteins, as well as tissue fibrosis, in the human left atria and left ventricle.

Methods

We examined the expression of thrombin and other related molecules in the autopsied hearts of patients with and without atrial fibrillation. An immunohistochemical analysis was performed in the left atria and the left ventricle.

Results

The thrombin was immunohistologically detected in both the left atria and the left ventricles. Other than in the myocardium, the expression of thrombin was observed in the endocardium and the subendocardium of the left atrium. Thrombin was more highly expressed in the left atrium compared to the left ventricle, which was concomitant with more tissue fibrosis and inflammation, as detected by CD68 expression, in the left atrium. We also confirmed the expression of prothrombin in the left atrium. The expression of PAR-1 was observed in the endocardium, subendocardium and myocardium in the left atrium. In patients with atrial fibrillation, strong thrombin expression was observed in the left atrium.

Conclusions

The strong expression levels of thrombin, prothrombin and PAR-1 were demonstrated in the atrial tissues of human autopsied hearts.

Alpha1-adrenenoceptor stimulation inhibits cardiac excitation-contraction coupling through tyrosine phosphorylation of beta1-adrenoceptor

Adrenoceptor stimulation is a key determinant of cardiac excitation-contraction coupling mainly through the activation of serine/threonine kinases. However, little is known about the role of protein tyrosine kinases (PTKs) activated by adrenergic signaling on cardiac excitation-contraction coupling. A cytoplasmic tyrosine residue in β1-adrenoceptor is estimated to regulate Gs-protein binding affinity from crystal structure studies, but the signaling pathway leading to the phosphorylation of these residues is unknown. Here we show α1-adrenergic signaling inhibits β-adrenergically activated Ca(2+) current, Ca(2+) transients and contractile force through phosphorylation of tyrosine residues in β1-adrenoceptor by PTK. Our results indicate that inhibition of β-adrenoceptor-mediated Ca(2+) elevation by α1-adrenoceptor-PTK signaling serves as an important regulatory feedback mechanism when the catecholamine level increases to protect cardiomyocytes from cytosolic Ca(2+) overload.

Br-DIF-1 accelerates dimethyl sulphoxide-induced differentiation of P19CL6 embryonic carcinoma cells into cardiomyocytes

BACKGROUND AND PURPOSE

Stem cell transplantation therapy is a promising option for treatment of severe ischaemic heart disease. Dimethyl sulphoxide (DMSO) differentiates P19CL6 embryonic carcinoma cells into cardiomyocyte-like cells, but with low differentiation capacity. To improve the degree of this differentiation, we have assessed several derivatives of the differentiation-inducing factor-1 (DIF-1), originally found in the cellular slime mould Dictyostelium discoideum, on P19CL6 cells.

EXPERIMENTAL APPROACH

P19CL6 cells were cultured with each derivative and 1% DMSO for up to 16 days. Differentiation was assessed by measuring the number of beating and non-beating aggregates, and the expression of genes relevant to cardiac tissue. The mechanism of action was investigated using a T-type Ca(2+) channel blocker.

KEY RESULTS

Of all the DIF-1 derivatives tested only Br-DIF-1 showed any effects on cardiomyocyte differentiation. In the presence of 1% DMSO, Br-DIF-1 (0.3-3 µM) significantly and dose-dependently increased the number of spontaneously beating aggregates compared with 1% DMSO alone, by day 16. Expression of mRNA for T-type calcium channels was significantly increased by Br-DIF-1 + 1% DMSO compared with 1% DMSO alone. Mibefradil (a T-type Ca(2+) channel blocker; 100 nM) and a small interfering RNA for the T-type Ca(2+) channel both significantly decreased the beating rate of aggregates induced by Br-DIF-1 + 1% DMSO.

CONCLUSIONS AND IMPLICATIONS

Br-DIF-1 accelerated the differentiation, induced by 1% DMSO, of P19CL6 cells into spontaneously beating cardiomyocyte-like cells, partly by enhancing the expression of the T-type Ca(2+) channel gene.

Role of Ca(2+)/calmodulin-dependent protein kinase II in the regulation of the cardiac L-type Ca(2+) current during endothelin-1 stimulation

Endothelin-1 (ET-1) shows a positive inotropic effect on cardiac muscle. Although the L-type Ca(2+) current (I(Ca)) is one of the important determinants of cardiac excitation-contraction coupling, the effect of ET-1 on the I(Ca) is not always clear. The controversial results appear to be due to different patch-clamp methods. The present study measured the effect of ET-1 on the I(Ca) of rat ventricular myocytes using the perforated patch-clamp technique. The holding potential was set to -40 mV, and depolarization was applied every 10 s. ET-1 (10 nM) increased the I(Ca) in a monophasic manner. The current reached a steady state 15 min after the application of ET-1, when the measurement was done. Endothelin receptor subtype expression was also investigated using Western immunoblotting. ET(A)-receptor protein was expressed, but ET(B)-receptor protein was not expressed, in the cell membranes of rat ventricular myocytes. The effect of ET-1 on the I(Ca) was inhibited by a selective ET(A)-receptor antagonist, BQ-123, but not by a selective ET(B)-receptor antagonist, BQ-788. The effect was inhibited by protein kinase C (PKC) inhibitor chelerythrine and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) inhibitor KN-93, but not by its inactive analog KN-92. The effect of ET-1 was also blocked by another CaMKII inhibitor, autocamtide-2-related inhibitory peptide. These results suggest that ET-1 increases the I(Ca) via the ET(A)-receptor-PKC-CaMKII pathway.

Influence of low-grade inflammation on plasma B-type natriuretic peptide levels

OBJECTIVE

B-type natriuretic peptide (BNP) is a cardiac hormone. The results of previous in vitro studies suggest that neurohumoral factors, and not only hemodynamic factors, may cause BNP secretion. In this study, we examined the impact of serum C-reactive protein (CRP) levels on the relationship between echocardiographic parameters and plasma BNP levels in patients with cardiovascular diseases.

METHODS AND PATIENTS

The study population comprised 417 patients who visited our cardiovascular unit with a problem. Both blood sampling and echocardiography were performed within one month.

RESULTS

Multiple regression analysis showed that plasma BNP levels were negatively correlated with male gender, body mass index, and estimated glomerular filtration rate, and positively correlated with serum CRP levels and left ventricular end-systolic dimension (LVDs). The study population was divided into two groups based on the 75th percentile of the serum CRP levels. Single regression analysis showed that a regression line between LVDs and plasma BNP levels was steeper in the group of patients with CRP levels above the 75th percentile. Multiple regression analysis revealed that the interaction term (LVDs×CRP) was significant, which means LVDs had more impact on plasma BNP levels at higher CRP levels.

CONCLUSION

Plasma BNP levels increased with respect to the severity of cardiac dysfunction and serum CRP levels, and should therefore be considered a collective or total marker for life-threatening conditions including systemic inflammation, and not simply as a marker of cardiac dysfunction in patients with cardiovascular diseases.

[Calcium antagonists: current and future applications based on new evidence. Cardio-protective effect of calcium antagonists]

Calcium antagonists block calcium influx through the L-type calcium channel to produce dilatation of resistant arteries including coronary arteries. Due to arterial vasodilatation, calcium antagonists have beneficial effects for ischemic heart disease, left ventricular hypertrophy and heart failure. Some of calcium antagonists are known to have the inhibitory action for T-type or N-type calcium channel which might be beneficial for the inhibition of reactive tachycardia. Calcium antagonists may also retard the progression of atherosclerosis to prevent cardiovascular events.

Prediction of functional outcome in acute cerebral hemorrhage using diffusion tensor imaging at 3T: a prospective study

BACKGROUND AND PURPOSE

Early evaluation of the pyramidal tract is a prerequisite in patients with intracerebral hemorrhage (ICH) in order to decide the optimal treatment or to assess appropriate rehabilitation. The aim of this study was to evaluate and predict the neuromotor and functional outcome of an ICH by using diffusion tensor imaging (DTI) in the acute phase.

MATERIALS AND METHODS

Eighteen patients with a hemiparetic supratentorial ICH were prospectively studied with DTI within 2 days after onset. A region-of-interest-based analysis was performed for the fractional anisotropy (FA) of the pyramidal tract in the cerebral peduncles. The degree of paresis was assessed at day 0 and day 28 by paresis grading (PG). The functional outcome was evaluated by the modified Rankin Scale (mRS).

RESULTS

The FA in the affected side was significantly lower compared with that of the unaffected side (P = .001) with the mean diffusivity remaining unchanged (P = .50). The ratio of the FA (rFA) in the affected side to the unaffected side was significantly correlated with the PG at day 0 and 28 and the mRS score at day 28 (P = .002, r = -0.674; P < .001, r = -0.767; and P = .002, r = -0.676). The rFA for the good and poor outcomes based on the PG was significantly different (P < .001). The cutoff point of the rFA for the good and poor outcomes was set at 0.85 (sensitivity, 100%, specificity, 100%).

CONCLUSIONS

We conclude that DTI can evaluate the motor deficit quantitatively and may predict the functional outcome in patients with an ICH who were scanned within 2 days after the ICH onset.

Inhibition of the renin-angiotensin system prevents re-hospitalization of heart failure patients with preserved ejection fraction

BACKGROUND

Approximately half of the patients with chronic heart failure (CHF) show preserved systolic function, but less is known about CHF with preserved ejection fraction (EF).

METHODS AND RESULTS

In a retrospective analysis, patients with CHF who had been admitted to hospital were divided into 2 groups: reduced EF (EF < or = 40%) and preserved EF (EF >40%). The rate of preserved EF was 53.5% and those with preserved EF were older, more likely to be female, and had a lower serum hemoglobin concentration than those in the reduced EF group. In the multivariate analysis, only older age was independently related to CHF with preserved EF. CHF patients with preserved EF who were successfully discharged from hospital and then followed at the outpatient clinic were reviewed and re-hospitalization for CHF was examined by Cox hazard univariate analysis, which showed that prior CHF hospitalization, absence of hypertension, and non-use of angiotensin-converting enzyme inhibitor (ACEI) and/or angiotensin-receptor blocker (ARB) were predictors. In the multivariate analysis, non-use of ACEI/ARB was the sole predictor for CHF re-hospitalization.

CONCLUSIONS

CHF patients with preserved EF are older than those with reduced EF and use of ACEI/ARB prevents their re-hospitalization.

Decreased renal function as an independent predictor of re-hospitalization for congestive heart failure

BACKGROUND

Patients with congestive heart failure (CHF) are often re-hospitalized, worsening both their quality of life and prognosis. Although renal dysfunction reportedly increases the risk of CHF, the association between renal dysfunction and re-hospitalization for CHF remains unclear.

METHODS AND RESULTS

Patients with CHF and decreased renal function were reviewed. The estimated glomerular filtration rate (GFR) was calculated with the Modification of Diet in Renal Disease equation. Patients with decreased renal function (estimated GFR on admission <45 ml .min(-1) . 1.73 m(-2)) were re-hospitalized more frequently than were patients with preserved renal function (estimated GFR on admission >or=45). Patients with decreased renal function were older and had higher rates of anemia, worsening renal function during hospitalization, and previous hospitalization for CHF. Independent predictors of re-hospitalization for CHF identified with multivariate analysis were age, previous hospitalization for CHF, decreased renal function, and non-use of an angiotensin-converting enzyme inhibitor or angiotensin-receptor blocker.

CONCLUSIONS

Renal dysfunction is an independent predictor of re-hospitalization for CHF, so careful follow-up is needed, even after discharge.

Paraplegia following surgery for medulloblastoma in the posterior fossa

Postoperative paraplegia following non-spinal surgical procedures is very rare. We report a rare case of medulloblastoma in which paraplegia occurred after surgery. A 4-year-old boy suffered frequent vomiting and was found to have a tumour in the fourth ventricle associated with obstructive hydrocephalus. The tumour had already disseminated in the upper cervical spinal cord and thoracic cord. After surgical removal of the fourth ventricular tumour in the prone position, the patient developed paraplegia of the lower extremities. The cause of this complication may be the intraoperative patient position, overflexion of the neck, and/or imbalance of the subarachnoid pressure between rostral and caudal thoracic spinal cord by removing cerebrospinal fluid at the operative site. We report a rare complication of paraplegia associated with intracranial surgery.

Mobile epidermoid tumours of the lumbar spinal canal

A case of a 19-year-old female with a mobile epidermoid tumour in the lumbar spinal canal is reported. Magnetic resonance images taken twice before surgery revealed movement of the tumour from L2 to L1-2 in a 2-week interval. At surgery the tumour, which was shiny and fragile, was totally removed and the pain disappeared after surgery. This is the first reported case of a mobile epidermoid tumour in the lumbar region.

Interaction of α 1 -Adrenoceptor Subtypes With Different G Proteins Induces Opposite Effects on Cardiac L-type Ca 2+ Channel

We examined the effect of α 1 -adrenoceptor subtype-specific stimulation on L-type Ca 2+ current ( I Ca ) and elucidated the subtype-specific intracellular mechanisms for the regulation of L-type Ca 2+ channels in isolated rat ventricular myocytes. We confirmed the protein expression of α 1A - and α 1B -adrenoceptor subtypes at the transverse tubules (T-tubules) and found that simultaneous stimulation of these 2 receptor subtypes by nonsubtype selective agonist, phenylephrine, showed 2 opposite effects on I Ca (transient decrease followed by sustained increase). However, selective α 1A -adrenoceptor stimulation (≥0.1 μmol/L A61603) only potentiated I Ca , and selective α 1B -adrenoceptor stimulation (10 μmol/L phenylephrine with 2 μ mol/L WB4101) only decreased I Ca . The positive effect by α 1A -adrenoceptor stimulation was blocked by the inhibition of phospholipase C (PLC), protein kinase C (PKC), or Ca 2+ /calmodulin-dependent protein kinase II (CaMKII). The negative effect by α 1B -adrenoceptor stimulation disappeared after the treatment of pertussis toxin or by the prepulse depolarization, but was not attriburable to the inhibition of cAMP-dependent pathway. The translocation of PKCδ and ε to the T-tubules was observed only after α 1A -adrenoceptor stimulation, but not after α 1B -adrenoceptor stimulation. Immunoprecipitaion analysis revealed that α 1A -adrenoceptor was associated with G q/11 , but α 1B -adrenoceptor interacted with one of the pertussis toxin-sensitive G proteins, G o . These findings demonstrated that the interactions of α 1 -adrenoceptor subtypes with different G proteins elicit the formation of separate signaling cascades, which produce the opposite effects on I Ca . The coupling of α 1A -adrenoceptor with G q/11 -PLC-PKC-CaMKII pathway potentiates I Ca . In contrast, α 1B -adrenoceptor interacts with G o , of which the βγ-complex might directly inhibit the channel activity at T-tubules.

Embolization of Arteriovenous Malformation. Efficacy and Safety of Preoperative Embolization Followed by Surgical Resection of AVM

SUMMARY

Treatment options for cerebral arteriovenous malformation (AVM) are still controversial due to the recent result of stereotactic radiosurgery and the improved result of microsurgical resection. We investigated previously treated AVM cases and discussed the efficacy and safety of preoperative embolization especially for microsurgical resection of high-grade AVM in the Spetzler-Martin grading. Efficacy of preoperative embolization was evaluated based on 126 previously treated AVM cases at Shinshu University Hospital during the last 25 years. The safety of embolization was evaluated based on our previously-embolized 58 AVM cases (91 procedures) in the last 11 years after introduction of preoperative embolization for AVM. In all 126 cases, 82 were treated before introduction of embolization and 44 were treated after introduction of embolization. In 82 cases of the pre-embolization era, 63 lesions were removed totally in 63 AVMs (77%), partially resected in 11 (13%) and untreated in eight (10%). In 74 surgically removed cases, 11 (15%) cases showed severe intra/postoperative bleeding. In 44 cases of the embolization era, lesions were removed totally in 29 AVMs (66%), disappeared only with embolization in one (2%), disappeared with radiosurgery in seven (16%) and were untreated in five (11%). In 32 surgically removed cases, only one (2%) case showed severe intra/postoperative bleeding. In all 58 embolized cases, 44 were surgically removed, six were treated with radiosurgery, one was eliminated with embolization alone and six were partially obliterated and followed up for their location. In 91 procedures for 58 cases, two haemorrhagic and three ischemic complications occurred, three were transient and two remained having neurological deficits. The introduction of preoperative embolization improved the total removal rate and reduced the intra/postoperative bleeding rate in surgical removal of AVM. The total risk of embolization is low and well-designed preoperative embolization makes surgical resection safer even in high-grade AVM in the Spetzler-Martin grading.

Telecontrolled micromanipulator system (NeuRobot) for minimally invasive neurosurgery

BACKGROUND

To perform less invasive neurosurgery, a telecontrolled micromanipulator system has been developed and applied to clinical situations. Basic experiments for telesurgery have also been conducted.

METHOD

A cadaver head was used to carry out surgical simulation of the opening of the sylvian fissure and third ventriculostomy. After obtaining permission from the Ethical Committee of Shinshu University School of Medicine, part of the recurrent meningioma in a 45-year-old man was removed. As basic experiment for telesurgery, surgical simulation was also conducted in a rat brain with the operating console transported to a hospital 40 km distant from the University.

FINDINGS

Opening of the sylvian fissure and third ventriculostomy were accurately performed. Tumour removal in a patient with recurrent meningioma was safely achieved. Surgical simulation in the rat brain was accurately and correctly carried out, operated on from a hospital 40 km distant.

CONCLUSIONS

The NeuRobot, telecontrolled micromanipulator system, can be used as a tool for less invasive neurosurgery.

Renal Insufficiency is Related to Painless Myocardial Infarction

BACKGROUND

Acute myocardial infarction (MI) sometimes occurs without painful symptoms and in such cases, prognosis is worsened by delays in diagnosis and revascularization. Renal insufficiency induces many types of neuropathy, but the relation between renal insufficiency and painless MI remains unclear.

METHODS AND RESULTS

Patients with MI and elevated creatine kinase levels were retrospectively analyzed. Renal insufficiency (serum creatinine concentration > or =1.5 mg/dl) and other characteristics (age, sex, body mass index, hypertension, smoking, diabetes mellitus, dyslipidemia, history of stroke, previous MI, hemodialysis, and atrial fibrillation) were compared between patients who had MI with painful symptoms (painful MI, n=131) and patients who had MI without painful symptoms (painless MI, n=18). Other variables compared were the time from symptom onset to admission, peak creatine kinase concentration, Killip class, site of MI, emergency coronary angiography, postprocedural Thrombolysis In Myocardial Infarction grade III flow, and in-hospital death. Univariate analysis identified older age, renal insufficiency, and previous MI as predictors of painless MI. Patients with painless MI showed higher rates of Killip class > or =II and in-hospital death and a longer time from symptom onset to admission. However, multivariate analysis identified only renal insufficiency as an independent predictor of painless MI.

CONCLUSIONS

MI without painful symptoms frequently develops in patients who have renal insufficiency, so the possibility of painless MI should be evaluated in such patients to ensure early diagnosis and treatment.

Pulmonary embolism and deep vein thrombosis complicating acute aortic dissection during medical treatment

Acute aortic dissection of Stanford type A with intramural hematoma was diagnosed based on computed tomography (CT) findings in a 60-year-old man. During medical treatment, pulmonary embolism and deep vein thrombosis developed. CT revealed thrombosis in the right pulmonary artery, and 99mTc pulmonary perfusion scintigraphy showed defects in the right lung field. CT showed thrombus in the common iliac vein. An inferior vena caval filter was placed because anticoagulation therapy was contraindicated. A CT scan before discharge showed no thrombus in the pulmonary artery or common iliac vein, but a newly captured thrombus was found inside the filter.

Intracellular mechanism of the negative inotropic effect induced by alpha1-adrenoceptor stimulation in mouse myocardium

Alpha(1)-adrenoceptor stimulation (alpha(1)ARS) shows a positive inotropic effect in most mammalian myocardium. In mouse myocardium, however, alpha(1)ARS showed the negative inotropic effect, of which intracellular mechanisms are not fully clarified. The purpose of this study is to investigate the intracellular mechanism of the negative inotropic effect by alpha(1)ARS in C57BL/6 mouse myocardium. We used isolated ventricular papillary muscles of C57BL/6 strain mouse which is widely used for genetic manipulation. We simultaneously measured isometric tension and intracellular Ca(2+) concentration ([Ca(2+)](i)) using the aequorin method. In twitch contraction, phenylephrine concentration-dependently (1-100 microM) decreased tension without significant changes in the Ca(2+) transient, and these effects were completely blocked by prazosin (3 microM) or calphostin C (a PKC inhibitor, 1 microM). Phorbol 12-myristate 13-acetate (PMA) (a PKC activator, 1 microM) decreased tension as observed in phenylephrine. After PMA application, the negative inotropic effect of phenylephrine disappeared. To estimate the Ca(2+) sensitivity, tetanic contraction was produced, and the relation between [Ca(2+)](i) and tension at a steady state was measured. Phenylephrine (10 microM) decreased the Ca(2+) sensitivity, and PMA showed a similar Ca(2+) desensitizing effect. These results suggest that the negative inotropic effect of phenylephrine in mouse myocardium can be explained by the decrease in the Ca(2+) sensitivity through the activation of PKC. The present result indicates that the effect of alpha(1)ARS differs among species and strains of experiment animals. Thus, we should be careful about using the results of mouse myocardium to understand the functions of the human heart.