Min In Hearts Research Articles

BJ-PRO-7A and BJ-PRO-10C induce vasodilatation and inotropic effects in normotensive and hypertensive rats: Role of nitric oxide and muscarinic receptors

Bj-PRO-7a and Bj-PRO-10c belong to a family of proline-rich oligopeptides (PROs) identified in Bothrops jararaca (Bj) crude venom. Previous studies have shown an antihypertensive effect evoked by theses peptides. However, the mechanisms underlying the direct effects on vessels and heart remain to be unraveled. Thus, we investigated the effect of the Bj-PRO-7a and Bj-PRO-10c in the aorta and coronary arteries and in cardiac contractility in normotensive (Wistar) and hypertensive (SHR) rats. Pre-constricted aortic rings were exposed to increasing concentrations of Bj-PROs in presence or absence of muscarinic type 1 receptor antagonist (Pirenzepine), nonselective muscarinic receptor antagonist (Atropine), nitric oxide synthase inhibitor (L-NAME), guanylyl cyclase inhibitor (ODQ), adenylyl cyclase inhibitor (MDL), or argininosuccinate synthetase inhibitor (MDLA). The effects of Bj-PROs in the cardiac contractility and coronary vasomotricity were evaluated using Langendorff perfused heart preparation. The rat hearts were perfused with Bj-PRO-7a or Bj-PRO-10c in absence or presence of L-NAME, ODQ or MDL. Both Bj-PROs induced endothelium-dependent vasorelaxation in aortic rings from Wistars and SHRs. These effects were inhibited by L-NAME, ODQ or MDL. Atropine and Pirenzepine blocked the vasorelaxant effect of Bj-PRO-7a in aorta from both strains. MDLA inhibited the Bj-PRO-10c-induced vasorelaxation in aortic rings from SHR, but not Wistar. The Bj-PRO-7a induced coronary vasodilation only in SHR. L-NAME, ODQ and MDL inhibited this effect. Bj-PRO-10c induced coronary vasodilatation in both strains, which was blocked by L-NAME, ODQ and MDL. Bj-PRO-7a decreased the dP/dt max in Wistar hearts and the dP/dt min in Wistar and SHR hearts. These effects were abolished by L-NAME. Bj-PRO-10c decreased dP/dt max and dP/dt min in hearts from normotensive and hypertensive animals, which were abolished in the presence of L-NAME, MDL and ODQ. In summary, the Bj-PROs induced endothelium-dependent vasorelaxation in rat thoracic aorta, coronary vasodilation and negative inotropic effects through mechanisms mediated by activation of nitric oxide pathway.

Effects of neutral sulfate berberine on LPS-induced cardiomyocyte TNF-alpha secretion, abnormal calcium cycling, and cardiac dysfunction in rats1

To evaluate the effect of neutral sulfate berberine on cardiac function, tumor necrosis factor alpha (TNF-alpha) release, and intracellular calcium concentration ([Ca(2+)]i) in cardiomyocytes exposed to lipopolysaccharide (LPS). Primary cultured rat cardiomyocytes were prepared from ventricles of 3-4-day old Sprague-Dawley rats. TNF-alpha concentrations in cell-conditioned media were measured by using a Quantikine enzyme-linked immunosorbent assay kit, and cardiomyocyte [Ca(2+)]i was measured by using Fura-2/AM. The isolated rat hearts were perfused in the Langendorff mode. LPS at doses of 1, 5, 10, and 20 microg/mL markedly stimulated TNF-alpha secretion from cardiomyocytes, and neutral sulfate berberine inhibited LPS-induced TNF-alpha production. Intracellular calcium concentration was significantly decreased after LPS stimulation for 1 h, and increased 2 h after LPS treatment. Pretreatment with neutral sulfate berberine reversed the LPS-induced [Ca(2+)]i alterations, although neutral sulfate berberine did not inhibit a rapid increase in cardiomyocyte [Ca(2+)]i induced by LPS. Perfusion of isolated hearts with LPS (100 microg/mL) for 20 min resulted in significantly impaired cardiac performance at 120 min after LPS challenge: the maximal rate of left ventricular pressure rise and fall (+/-dp/dt(max)) decreased compared with the control. In contrast, +/-dp/dt(max) at 120 min in hearts perfused with neutral sulfate berberine (1 micromol/L) for 10 min followed by 20 min LPS (100 microg/mL) was greater than the corresponding value in the LPS group. Neutral sulfate berberine inhibits LPS-stimulated myocardial TNF-alpha production, impairs calcium cycling, and improves LPS-induced contractile dysfunction in intact heart.

COMPLEMENT INHIBITION WITH AN ANTI-C5 MONOCLONAL ANTIBODY PREVENTS ACUTE CARDIAC TISSUE INJURY IN AN EX VIVO MODEL OF PIG-TO-HUMAN XENOTRANSPLANTATION

Prevention of hyperacute xenograft rejection in the pig-to-primate combination has been accomplished by removal of natural antibodies, complement depletion with cobra venom factor, or prevention of C3 activation with the soluble complement inhibitor sCR1. Although these strategies effectively prevent hyperacute rejection, they do not address the relative contribution of early (C3a, C3b) versus late (C5a, C5b-9) activated complement components to xenogeneic organ damage. To better understand the role of the terminal complement components (C5a, C5b-9) in hyperacute rejection, an anti-human C5 mAb was developed and tested in an ex vivo model of cardiac xenograft rejection. In vitro studies demonstrated that the anti-C5 mAb effectively blocked C5 cleavage in a dose-dependent manner that resulted in complete inhibition of both C5a and C5b-9 generation. Addition of anti-C5 mAb to human blood used to perfuse a porcine heart prolonged normal sinus cardiac rhythm from a mean time of 25.2 min in hearts perfused with unmodified blood to 79,296, or > 360 min when anti-C5 mAb was added to the blood at 50 micrograms/ml, 100 micrograms/ml, or 200 micrograms/ml, respectively. In these experiments, activation of the classical complement pathway was completely inhibited. Hearts perfused with blood containing the highest concentration of anti-C5 mAb had no histologic evidence of hyperacute rejection and no deposition of C5b-9. These experiments suggest that the activated terminal complement components C5a and C5b-9, but not C3a or C3b, play a major role in tissue damage in this porcine-to-human model of hyperacute rejection. They also suggest that targeted inhibition of terminal complement activation by anti-C5 mAbs may be useful in clinical xenotransplantation.

Deleterious effects of digitalis on reperfusion-induced arrhythmias and myocardial injury in ischemic rat hearts: possible involvements of myocardial Na+ and Ca2+ imbalance

Isolated rat hearts were made ischemic for 25 min after an initial recirculating perfusion, followed by 30 min of reperfusion. In some hearts, interventions including administration of ouabain and/or high [K+] in the buffer were performed during the first 10 min of reperfusion. During ischemia, intracellular Na+ (Nai) increased from 15 to 64 mumol/g dry weight (dwt). During reperfusion, Nai declined rapidly (at 10 min of reperfusion: 48 mumol/g dwt, at 30 min: 25 mumol/g dwt) and regular rhythm was recovered within 10 min in hearts without any intervention during reperfusion. 45Ca2+ uptake increased from 0.8 to 7.5 mumol/g dwt after 30 min of reperfusion. Ventricular function recovered by 45%. A 10-min perfusion with 10 or 50 microM of ouabain increased Nai (17 to 21 or 27 mumol/g dwt) with increased left-ventricular (LV) contractile function, but these effects were reversed by combination of high perfusate [K+] (20 mM) in non-ischemic hearts. A 10-min reperfusion with ouabain retarded or stopped the decline in Nai (at 10 min of reperfusion: 54 or 63 mumol/g dwt, at 30 min: 32 or 40 mumol/g dwt). These amounts of ouabain also increased the incidence of ventricular tachyarrhythmias during reperfusion to 30% or 50%, and increased the duration of ventricular fibrillation from 6.5 to 11.5 or 18.0 min. 45Ca2+ uptake reached to 8.8 or 10.0 mumol/g dwt, and function recovered only 35% or 28%. When high perfusate [K+] was combined with ouabain during reperfusion, the retarded decline in Nai, augmented 45Ca2+ uptake, and reduced recovery of function caused by ouabain alone were attenuated. These results suggest that digitalis has toxic effects on reperfused ischemic hearts by inhibition of rapid active outward transport of previously elevated Nai and potentiation of Ca2+ overload.