Daisuke Katoh

Arachidonate 12/15-lipoxygenase-induced inflammation and oxidative stress are involved in the development of Diabetic Cardiomyopathy

Diabetes affects cardiac structure and function, and it has been suggested that diabetes leads to cardiomyopathy. Arachidonate 12/15-lipoxygenase (LOX) has been suggested to play an important role in atherogenesis and heart failure. However, the role of 12/15-LOX in diabetic cardiomyopathy has not been examined. In this study, we investigated the effects of cardiac 12/15-LOX on diabetic cardiomyopathy. We created streptozotocin (STZ)-induced diabetic mice and compared them with Alox15-deficient mice. Expression of 12/15-LOX and inflammatory cytokines such as tumor necrosis factor (TNF)-α and nuclear factor (NF)-κB were upregulated in STZ-induced diabetic hearts. Disruption of 12/15-LOX significantly improved STZ-induced cardiac dysfunction and fibrosis. Moreover, deletion of 12/15-LOX inhibited the increases of TNF-α and NF-κB as well as the production of STZ-induced reactive oxygen species in the heart. Administration of N-acetylcysteine in diabetic mice prevented STZ-induced cardiac fibrosis. Neonatal cultured cardiomyocytes exposed to high glucose conditions induced the expression of 12/15-LOX as well as TNF-α, NF-κB, and collagen markers. These increases were inhibited by treatment of the 12/15-LOX inhibitor. Our results suggest that cardiac 12/15-LOX–induced inflammation and oxidative stress are involved in the development of diabetic cardiomyopathy and that inhibition of 12/15-LOX could be a novel treatment for this condition.

Aerobic interval exercise training in the afternoon reduces attacks of coronary spastic angina in conjunction with improvement in endothelial function, oxidative stress, and inflammation.

BackgroundCoronary spasm plays an important role in the pathogenesis of ischemic heart disease. Endothelial function is impaired in patients with coronary spasm. Exercise training has been shown to improve endothelial function. ObjectiveWe examined the effects of aerobic interval exercise training (AIT) on attacks in conjunction with endothelial function in patients with coronary spastic angina. Participants and methodsThe study participants were 26 patients with rest angina (19 men and 7 women, mean age 61.7±11.7 years) in whom coronary spasm was documented and no severe organic lesions were found. The numbers of attacks and of individuals with attacks were examined in conjunction with endothelial function, oxidative stress, inflammation, and insulin resistance before and after 3 successive days of AIT. ResultsThe number of attacks/patient and the ratio of patients with attacks/5 days decreased [from 2 (1, 7) to 0 (0, 2), P<0.001, and from 23/26 (88.5%) to 10/26 (38.5%), P<0.001] in conjunction with the improvement in endothelial function assessed by improved flow-mediated dilatation (4.8±2.7 vs. 6.9±2.8%, P<0.001), plasma levels of diacron-reactive oxygen metabolites (363±58 vs. 349±61 U.CARR, P=0.001), interleukin-6[1.63 (1.33, 2.22) vs. 1.39 (1.09, 2.02) pg/ml, P=0.012], high-sensitivity C-reactive protein [0.087 (0.041, 0.136) vs. 0.063 (0.028, 0.085) mg/dl, P=0.028], and homeostasis model assessment-insulin resistance [1.79 (1.41, 2.39) vs. 1.54 (1.17, 1.79) mg/dl µU/ml, P=0.005] after AIT. ConclusionAIT in the afternoon suppressed the attacks in conjunction with improvement in endothelial function, oxidative stress, inflammation, and insulin resistance in patients with coronary spastic angina.

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.

High incidence of provoked coronary spasm in the presence of a stent after myocardial infarction: therapeutic and prognostic implications.

ObjectivesCoronary spasm is implicated in the pathogenesis of acute coronary syndromes including acute myocardial infarction (AMI). Stent implantation in the primary percutaneous coronary intervention is the first choice of treatment for patients with AMI. However, the relationship between coronary spasm and stent implantation after AMI and its clinical implications remain unknown. We examined the incidence and clinical implications of provoked coronary spasm after stent implantation in patients with AMI. MethodsFifty-seven patients (43 men and 14 women with a mean age of 65.1±12.5 years) with ST elevation AMI who had undergone a stent implantation were the participants of this study. They underwent a provocation test for coronary spasm by intracoronary injection of acetylcholine 2–5 weeks after the attack. The patients with provoked spasms were given calcium channel blockers, and all the participants of the study were followed up for an average of 35.0±26.9 months. ResultsCoronary spasm was induced in 40 (70.2%) and multivessel spasm in 17 (29.8%) of the 57 patients. Spasms occurred in 31 (55.4%) of the infarct-related arteries (IRAs) and 33 (30.6%) of the non-IRAs. There was no significant difference (&khgr;2=1.01, P=0.314) in the major cardiac events between the spasm group and nonspasm group during the follow-up. ConclusionCoronary spasm was provoked with a high frequency in both the IRAs and non-IRAs after stent implantation in patients with AMI. Calcium channel blockers may be useful to improve the prognosis in patients with AMI after stent implantation by suppressing coronary spasm.

Transient decrease in serum potassium level during ischemic attack of acute coronary syndrome: Paradoxical contribution of plasma glucose level and glycohemoglobin

BackgroundAlthough a decrease in serum potassium level has been suggested to be a fairly common observation in acute coronary syndrome (ACS), there have so far been no definitive reports directly demonstrating the transient potassium decrease (the potassium dip) during ischemic attack of ACS compared to stable phase in individual patients. To understand the pathophysiological significance of the potassium dip, we examined the changes in serum potassium level throughout ischemic attack and evaluated the clinical factors affecting it.MethodsThe degree of the potassium dip during ischemic attack (as indicated by ΔK, ΔK = K at discharge − K on admission) was examined in 311 consecutive patients with ACS who required urgent hospitalization in our institution.ResultsSerum potassium level during ischemic attack was significantly decreased compared to that during stable phase (P < 0.001). Multiple regression analysis revealed that plasma glucose level during attack was the sole factor which was positively correlated with ΔK (P < 0.01), while HbA1c level was negatively correlated (P < 0.05). The medication profiles and renal function had no impact on ΔK. A longer hospitalization period, higher incidence of myocardial infarction and higher peak creatine kinase level were observed in patients with a larger ΔK.ConclusionsWe have clearly demonstrated that there is a transient decrease in serum potassium level during ischemic attack of ACS compared to stable phase. The degree of the potassium dip was tightly correlated with glucose level, which overwhelmed the diabetic condition, and it also indicates the disease severity. The present study therefore promotes awareness of the significance of monitoring potassium level in parallel with glucose level in patients with ACS.

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.

Increased urinary aldosterone excretion is associated with subcutaneous not visceral, adipose tissue area in obese individuals: a possible manifestation of dysfunctional subcutaneous adipose tissue

Aldosterone is reported to be associated with obesity and is a risk factor for metabolic syndrome. Metabolic abnormalities are more strongly associated with visceral adipose tissue (VAT) than with subcutaneous adipose tissue (SAT).

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

BackgroundIntracellular 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.FindingsWe 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.ConclusionsOur 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.

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-Tnnt2tm2Mmto) 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.

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+/Ca2 + 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.