Akihiro Iwabu

Thrombospondin-1 is Induced in Rat Myocardial Infarction and its Induction is Accelerated by Ischemia/Reperfusion

Thrombospondin-1 (TSP-1) is a multifunctional, rapid-turnover matricellular protein. Recent studies demonstrated that TSP-1 has a role in regulating inflammatory reactions. Myocardial infarction (Ml) is associated with an inflammatory response, ultimately leading to healing and scar formation. In particular, an enhanced inflammatory reaction and a massive accumulation of monocytes/macrophages is seen with reperfusion after MI. To examine the role of TSP-1 in Ml, we isolated rat TSP-1 complementary DNA (cDNA) and analyzed the level and distribution of the mRNA expression. In infarcted rat hearts, TSP-1 mRNA increased markedly at 6 and 12 hrs after coronary artery ligation (27.97 ± 3.40-fold and 22.77 ± 1.83-fold, respectively, compared with sham-operated hearts). Western blot analysis revealed that TSP-1 protein was transiently induced in the infarcted heart. Using in situ hybridization analysis, TSP-1 mRNA signals were observed in the infiltrating cells at the border area of infarction. We then examined the effect of ischemia/reperfusion (I/R) on TSP-1 mRNA induction in the rats with infarcted hearts. Quantitative reverse transcriptase polymerase chain reaction (RT-PCR) demonstrated that I/R enhanced the TSP-1 mRNA expression approximately 4-fold, as compared with the level in the permanently ligated heart. Finally, we examined the effect of TSP-1 on proinflammatory cytokine release in mononuclear cells. The releases of interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) from human mononuclear cells were enhanced by TSP-1 in a dose-dependent manner. Thus, the immediate and marked increase of TSP-1 expression suggests that TSP-1 has an inflammatory-associated role in MI.

Increased expression of dermatopontin mRNA in the infarct zone of experimentally induced myocardial infarction in rats: comparison with decorin and type I collagen mRNAs

Abstract.Objectives: Dermatopontin, a 22 kDa extracellular matrix (ECM) protein, has been shown to interact with other ECM components, especially decorin, and to regulate ECM formation. We examined dermatopontin mRNA expression in the myocardial infarct zone. Methods: The cDNA encoding the rat dermatopontin was cloned by RT-PCR based on screening results from the Expressed Sequence Tag™ database. The dermatopontin mRNA expression was examined in the infarct zone after experimentally induced myocardial infarction in rats by the methods of Northern blotting and in situ hybridization. The expression of dermatopontin mRNA was compared to that of decorin and type I collagen mRNAs. Results: The isolated clone contained a 609 bp cDNA insert containing a complete open reading frame encoding 202 amino acids. The rat dermatopontin cDNA showed high homology to human and mouse counterparts (>96 %). Northern blotting demonstrated that dermatopontin mRNA expression did not markedly increase on day 2, but was increased on days 7, 14 and 28 by 2.4-, 4.1- and 4.2-fold, respectively, compared to that in preligation hearts. Dermatopontin mRNA expression was regulated almost in parallel with decorin mRNA expression. In situ hybridization demonstrated mRNA signals for dermatopontin in macrophages and spindle-shaped mesenchymal cells (fibroblasts and myofibroblasts) located in the infarct interior zone around infarcted necrotic tissue on day 7. Coexpression of dermatopontin mRNA with decorin and type I collagen mRNAs was observed in spindle-shaped mesenchymal cells. Conclusions: The present results demonstrated the time-dependent increase in the expression of dermatopontin mRNA in parallel with that of decorin mRNA in the infarct zone. Coexpression of dermatopontin mRNA with decorin and type I collagen mRNAs suggests that dermatopontin plays a role in ECM (fibrillar collagen matrix) reformation in the infarct along with decorin and type I collagen.

Concomitant expression of heparin-binding epidermal growth factor-like growth factor mRNA and basic fibroblast growth factor mRNA in myocardial infarction in rats

Abstract Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is mitogenic and chemotactic for many cell types. HB-EGF is induced in pathological states which require cell mitogenesis and proliferation, including angiogenesis, and has been reported to interact functionally with basic fibroblast growth factor (bFGF). To test our hypothesis that HB-EGF mRNA expression is increased in myocardial infarction, we used Northern hybridization in rats to investigate the expression of HB-EGF and EGF receptor mRNAs expression in the infarct zone compared to the expression of bFGF and FGF receptor mRNAs. We also performed in situ hybridization to identify the cells responsible for HB-EGF mRNA production. HB-EGF mRNA rapidly increased after ligation (mean ± SE, 5.6 ± 0.23-fold increase at 6 hours compared to the preligation heart levels) and reached a maximum level (9.1 ± 0.42-fold increase) around 12 hours. HB-EGF mRNA then gradually decreased on day 1 (5.8 ± 1.0-fold increase), day 2 (3.2 ± 0.94-fold increase) and day 3 (1.9 ± 0.33-fold increase) after ligation. Parallel changes in bFGF mRNA expression were observed (6, 12 hours, days 1, 2 and 3; 3.6 ± 0.42-, 5.3 ± 0.12-, 2.3 ± 0.12-, 1.7 ± 0.03- and 0.95 ± 0.03-fold increase, respectively). EGF receptor (ErbB-1) mRNA was gradually increased on day 2 (2.4 ± 0.53-fold increase), day 7(4.0 ± 0.61-fold increase) and day 14 (7.0 ± 0.61-fold increase). Similarly, FGF receptor (FGF receptor-1) mRNA was gradually increased (days 2, 7 and 14; 1.3 ± 0.13-, 1.5 ± 0.17- and 2.3 ± 0.15-fold increase, respectively). Reperfusion after a 2-hour ligation (too late to salvage myocytes) enhanced HB-EGF (12 hours, 16.8 ± 1.8-fold increase) and bFGF (12 hours, 10.4 ± 1.1-fold increase) mRNA expression. The cells responsible for the increased production of HB-EGF mRNA were shown by in situ hybridization to be surviving myocytes located in the infarct peripheral zone around infarct necrotizing tissue. In conclusion, our results demonstrated a rapid increase in HB-EGF mRNA expression concomitant with an increase in bFGF mRNA expression, suggesting that HB-EGF and bFGF might play some role in the course of pathological changes in the infarct in the early inflammatory phase. Reperfusion at times too late to salvage myocytes accelerated sequential changes in the expression of both HB-EGF and bFGF mRNAs.

Inverse Correlation Between Seasonal Changes in Home Blood Pressure and Atmospheric Temperature in Treated-Hypertensive Patients

We examined the relationships between home blood pressure (BP) and atmospheric temperature in 20 treated-hypertensive patients. A significant correlation between morning and evening BP and atmospheric temperature was found. For morning systolic blood pressure (SBP), the maximal seasonal difference was 13.2 mmHg with 25.5°C temperature difference. Morning SBP increased by approximately 0.41 mmHg with a 1°C decrease in atmospheric temperature. A similar but weaker correlation with temperature was observed for morning diastolic, evening systolic and diastolic blood pressure (DBP). The present study provides important information in respect to BP changes with atmospheric temperature that should be taken into account in the analysis and treatment of hypertension.

INCREASED EXPRESSION OF BIGLYCAN mRNA IN PRESSURE-OVERLOADED RAT HEART

Biglycan mRNA expression in rat myocardium after abdominal aortic banding with renal ischemia was examined. The Northern blot analysis demonstrated that expression of biglycan mRNA in the pressure-overloaded hearts on days 2, 7, 14 and 28 was 2.88 ± 0.89, 2.32 ± 0.49, 2.17 ± 0.57 and 1.81 ± 0.46-fold higher, respectively, than that in the sham-operated hearts. In situ hybridization showed an increased density of biglycan mRNA signal-positive cells in the pressure-overloaded hearts. The cells with positive signals were spindle-shaped mesenchymal cells in the myocardial interstitium. A marked increase in biglycan mRNA signal expression was also observed in endothelial cells and smooth muscle cells of the thickened myocardial capillary wall. These results demonstrated an increase in biglycan mRNA in the pressure-overloaded heart in mesenchymal cells in the myocardial interstitium, and in endothelial and smooth muscle cells of the capillaries, indicating that biglycan contributes to the ventricular and vascular remodeling in response to pressure overload.

Increased Augmentation Index of the Radial Pressure Waveform in Patients with Paroxysmal Atrial Fibrillation

Objective: The augmentation index, a marker of wave reflection, has been reported to reflect vascular properties and to determine left ventricular (LV) characteristics. We investigated the relationship between the augmentation index and paroxysmal atrial fibrillation (AF). Methods: A total of 244 outpatients (122 patients with paroxysmal AF and 122 age-, and gender-matched controls without paroxysmal AF) were examined during sinus rhythm. The augmentation index was calculated from the radial arterial waveform using applanation tonometry methods. Results: After adjusting for age, gender, heart rate, and medications, the augmentation index was significantly higher in patients with paroxysmal AF than in subjects without paroxysmal AF (means ± SE: 88.9 ± 1.0 and 81.8 ± 1.0%, respectively; p < 0.001). In all subjects, an increase in the augmentation index was significantly correlated with LV hypertrophy and left atrial enlargement. Multiple logistic analysis revealed that an increase in the augmentation index was significantly related with paroxysmal AF, and the adjusted odds ratio of paroxysmal AF was approximately 1.8 for each 10% augmentation index increase (p < 0.01). Conclusion: An increase in the augmentation index was independently associated with paroxysmal AF. This result suggests that enhanced wave reflection may be related to the development of AF.

Effects of Cilostazol on Heart Rate and Its Variability in Patients with Sick Sinus Syndrome

ObjectiveHeart rate (HR) variability is an important factor for the prognosis of heart disease. We examined the effects of cilostazol, a quinolone derivative, on HR and HR variability in patients with sick sinus syndrome.DesignNon-blind sequential single-group study.Patients12 patients, aged 53 to 84 years, with type I or II sick sinus syndrome classified according to the Rubenstein system.MethodsPatients received cilostazol (100 or 200 mg/day) orally for at least 2 months, and 24-hour ambulatory electrocardiogram monitoring was performed before and after the start of cilostazol administration. Plasma atrial natriuretic polypeptide (ANP) levels and cardiothoracic ratio were also measured as markers of heart failure. Twelve age- and gender-matched volunteers were used for control measurements of HR variability.ResultsThe mean HR and minimum HR were significantly increased, by an average of 15 and 10 beats/min, respectively, at 8.6 ± 2.5 weeks (mean ± SD) after the start of cilostazol treatment. The number of pauses (defined as an RR interval >2.5 sec) was significantly decreased. The circadian variation of HR, determined by cosine fitting, was increased by cilostazol treatment and was not different from that of the controls. The time-domain and frequency-domain variability of HR were changed to within or closer to within the control ranges. Plasma ANP level and cardiothoracic ratio were significantly decreased after the initiation of cilostazol treatment.ConclusionCilostazol improved the slow HR in patients with sick sinus syndrome and ameliorated the HR variability, indicating that cilostazol has therapeutic utility for the treatment of the slow HR associated with sick sinus syndrome.