Skeletal myoblast implants induce minor propagation delays, but do not promote arrhythmias in the normal swine heart.

AIMS: Whether skeletal myoblast (SM) implants are proarrhythmic is still controversial due to conflicting pre-clinical and clinical data. We hypothesized that if SM implants are arrhythmogenic, they will facilitate the induction of ventricular tachyarrhythmias by promoting heterogeneous propagation of activation wavefronts. METHODS: Skeletal myoblast cells were harvested from 10 pigs. A month later, 125 ± 37 × 10(6) cells were subepicardially injected in an area of ∼2 cm(2) at the anterolateral aspect of the left ventricle. Four weeks later, a ventricular stimulation protocol was conducted. Once explanted, epicardial wavefronts over SM and adjacent control areas were optically mapped. Eight saline-injected animals were used as controls. To compare with clear arrhythmogenic substrates, propagation patterns were also evaluated in infarcted hearts and on a SM-implanted heart following amiodarone infusion. RESULTS: In SM hearts, fibrosis and differentiated SM cells were consistently found and no tachyarrhythmias were induced. Wavefronts propagated homogeneously over SM and adjacent areas, with no late activation zones, as opposed to the infarcted hearts. The time required for the wavefronts to depolarize both areas were similar, becoming only slightly longer at SM areas after an extra-stimulus (P = 0.025). Conduction velocities and APD(90) were also similar. Saline hearts showed similar results. The extent of the conduction delay was not related to the number of injected SM cells. CONCLUSION: In normal swine hearts, myoblast implants promote localized fibrosis and slightly retard epicardial wavefront propagation only after extra-stimuli. However, SM implants are not associated with local re-entry and do not facilitate ventricular tachyarrhythmias in the whole normal heart.

Atherogenesis takes place in cholesterol-fed rabbits when circulating concentrations of endogenous cortisol are increased and inflammation suppressed.

Atherosclerosis is an inflammatory disease, but the response of the endogenous anti-inflammatory system during this process has not been evaluated previously. Cortisol is the end product of this anti-inflammatory system, but is also able to activate cellular processes that induce atherogenesis; however, it is unknown whether atherogenesis occurs when circulating concentrations of endogenous cortisol are increased or when they are decreased. We have evaluated the counter-regulatory responses of cortisol and interleukin-1beta (IL-1beta) during the short- and long-term responses to vascular injury in rabbits fed a 2% cholesterol diet. In the short-term group (n=18), serum cortisol and IL-1beta concentrations were measured after 10, 20 and 30 days. Rabbits developed hypercholesterolemia and hypercortisolemia, with only modest increases in IL-1beta. Although inflammation was low-grade, atherogenesis took place, with subintimal lipid accumulation evident on day 30. In the second group (n=18), we evaluated variables after 40, 60 and 90 days. This group developed hypercholesterolemia, but serum cortisol concentrations were inappropriately normal, while IL-1beta concentrations were elevated 8.6-fold; advanced atherosclerotic plaques were evident on days 60 and 90. These results show that atherogenesis occurs when high endogenous cortisol levels are suppressing inflammation, and are consistent with a promotion of early atherogenesis by high cortisol concentrations.

Nitric oxide inhibits Kv4.3 and human cardiac transient outward potassium current (Ito1).

AIMS: Chronic atrial fibrillation (CAF) is characterized by a shortening of the plateau phase of the action potentials (AP) and a decrease in the bioavailability of nitric oxide (NO). In this study, we analysed the effects of NO on Kv4.3 (I(Kv4.3)) and on human transient outward K(+) (I(to1)) currents as well as the signalling pathways responsible for them. We also analysed the expression of NO synthase 3 (NOS3) in patients with CAF. METHODS AND RESULTS: I(Kv4.3) and I(to1) currents were recorded in Chinese hamster ovary cells and in human atrial and mouse ventricular dissociated myocytes using the whole-cell patch clamp. The expression of NOS3 was analysed by western blotting. AP were recorded using conventional microelectrode techniques in mouse atrial preparations. NO and NO donors inhibited I(Kv4.3) and human I(to1) in a concentration- and voltage-dependent manner (IC(50) for NO: 375.0 +/- 48 nM) as a consequence of the activation of adenylate cyclase and the subsequent activation of the cAMP-dependent protein kinase and the serine-threonine phosphatase 2A. The density of the I(to1) recorded in ventricular myocytes from wild-type (WT) and NOS3-deficient mice (NOS3(-/-)) was not significantly different. Furthermore, the duration of atrial AP repolarization in WT and NOS3(-/-) mice was not different. The increase in NO levels to 200 nM prolonged the plateau phase of the mouse atrial AP and lengthened the AP duration measured at 20 and 50% of repolarization of the human atrial CAF-remodelled AP as determined using a mathematical model. However, the expression of NOS3 was not modified in left atrial appendages from CAF patients. CONCLUSION: Our results suggested that the increase in the atrial NO bioavailability could partially restore the duration of the plateau phase of CAF-remodelled AP by inhibiting the I(to1) as a result of the activation of non-canonical enzymatic pathways.

Modifications by Olmesartan medoxomil treatment of the platelet protein profile of moderate hypertensive patients.

Olmesartan medoxomil is a new angiotensin II receptor blockers (ARB) which exhibits pleiotropic effects that are not fully understood. Our aims were: i) to determine the effect of Olmesartan medoxomil on blood pressure, lipid profile and renal functionality in moderately hypertensive patients with non-controlled blood pressure, ii) to determine if Olmesartan medoxomil may exert anti-inflammatory effects and modify the expression profile of platelet proteins. Thirteen moderate hypertensive patients with non-controlled systolic blood pressure (SBP) and renal function classified as Kidney Disease Outcome Quality Initiative stage 2-3 were included. Patients were treated with Olmesartan medoxomil (20 mg/day) for 6 months. SBP, proteinuria and the plasma levels of cholesterol and low density lipoprotein (LDL)-cholesterol were reduced after the treatment. Olmesartan medoxomil did not modify the circulating plasma levels of a number of proteins associated with inflammation, but reduced the expression level of different platelet proteins including tropomyosin-ß chain isotypes 3 and 4, serotransferrin isotypes 1 to 5, the leukocyte elastase inhibitor and the chloride intracellular channel-protein isotype 1. The expression of the gelsolin precursor isotype 4 was increased in the platelets after the treatment. In summary, Olmesartan medoxomil reduced SBP, total and LDL-cholesterol plasma levels and urinary protein excretion and induced changes in the expression of platelet proteins which may be related to some action of the drug at the megakaryocyte level.

Relationship between vitamin D binding protein and aspirin resistance in coronary ischemic patients: a proteomic study.

Our aim was to analyze the plasma proteome in aspirin (acetylsalicylic acid [ASA])-sensitive and ASA-resistant coronary ischemic patients. Plasma from 19 ASA-sensitive and 19 ASA-resistant patients was analyzed. For the proteomic study, two-dimensional electrophoresis was performed. The expression of one isotype of the fibrinogen gamma chain and three isotypes of haptoglobin was increased in ASA-resistant patients. Three vitamin D binding protein isotypes were increased in ASA-resistant patients. In vitro incubation of vitamin D binding protein (DBP) with blood from healthy volunteers reduced the inhibitory effect of ASA on thromboxane A2 production. DBP may be a new regulator of the inhibitory effect of ASA on platelets.