Celina Morales

Ischemic postconditioning reduces infarct size by activation of A1 receptors and K+ATP channels in both normal and hypercholesterolemic rabbits

The effect of ischemic postconditioning (Postcon) in hypercholesterolemic animals is unknown. The objectives were to determine if ischemic preconditioning (IPC) and Postcon reduce infarct size in hypercholesterolemic animals and to assess if A1 receptors and K+ATP channels are involved in Postcon mechanisms. Isolated rabbit hearts were perfused according to the Langendorff technique and subjected to 30 minutes of ischemia and 30 minutes of reperfusion (G1). In Group 2, IPC was performed (1 cycle of 5 minutes ischemia/reperfusion) before 30 minutes of ischemia. In Group 3 (G3), Postcon was performed (2 cycles of 30-second reperfusion/ischemia) after 30 minutes of ischemia. The G3 protocol was repeated in G4 and G5, but during Postcon, an A1 receptor blocker (DPCPX, 200 nM) and glybenclamide (K+ATP, blocker, 0.3 μM) were administered, respectively. The G1 to G5 protocols were repeated in animals fed with an enriched cholesterol diet (1%) for 4 weeks (G6 to G10). The infarct size was measured by triphenyltetrazolium. The infarct size was 16.6 ± 4.6% in G1 and 25.8 ± 7.3% in G6, and IPC and Postcon reduced the infarct area in both normal and hypercholesterolemic animals (G2: 5.1 ± 1.7% [P < 0.05] and G3: 5.4 ± 0.9% [P < 0.05] in normal animals; G7: 4.1 ± 1.6% [P < 0.05] and G8 4.8 ± 0.9% [P < 0.05], in hypercholesterolemic animals). Both DPCPX and glybenclamide abolished the effect reached by Postcon. Thus, Postcon reduces infarct size in normal and hypercholesterolemic animals through the activation of A1 and K+ATP channels.

Histopathologic time course of myocardial infarct in rabbit hearts

INTRODUCTION The histopathologic evolution of myocardial infarct and of remote zones in rabbit hearts was studied. METHODS The left coronary artery of 55 rabbits was ligated and rabbits were sacrificed at 2, 4, 6, 8, 12, 14, 16, 18, 26, 35 and 56 days post-ligature (n=5 per group). Two rabbits were used as control and four were sham-operated. The hearts were excised, cut in slices and stained with hematoxylin-eosin, Massons trichrome and picrosirius red. The histological evaluation was semiquantitative (scale: 0 to ++). RESULTS At day 2, the presence of neutrophils was ++, decreasing suddenly at day 4 and disappearing completely at day 6. The proliferation of cells with features of fibroblasts increased from days 4 to 14 post-occlusion. Coagulation necrosis in mid-myocardium during the first week was ++. Subendocardial myocytolysis was evident from day 2 up to day 56 post-infarction. During the second week, proliferation of lymphocytes and macrophages (++), granulation tissue formation (++) and incipient traces of fibrosis that peaked at day 35 were observed. Scarring was complete at day 56 (++). In remote zones (right ventricle and septum), the proliferation of cells+ on Vimentin was observed at day 2, and perivascular, interstitial and endocardial fibrosis started to increase at day 6 and peaked at day 16. CONCLUSION Although myocardial infarction in rabbits maintains the essence of the infarct chronology, some differences as the early presence of cells+ on Vimentin and subendocardial fibrosis in infarcted areas, and also the rapid increase and early disappearance of neutrophils appear when other species are considered. An interesting finding was the early proliferation of cells with features of fibroblasts in remote zones.

Phosphodiesterase 5A Inhibition Induces Na/H Exchanger Blockade and Protection Against Myocardial Infarction

Acute phosphodiesterase 5A inhibition by sildenafil or EMD360527/5 promoted profound inhibition of the cardiac Na+/H+ exchanger (NHE-1), detected by the almost null intracellular pH recovery from an acute acid load (ammonium prepulse) in isolated papillary muscles from Wistar rats. Inhibition of phosphoglycerate kinase-1 (KT5823) restored normal NHE-1 activity, suggesting a causal link between phosphoglycerate kinase-1 increase and NHE-1 inhibition. We then tested whether the beneficial effects of NHE-1 inhibitors against the deleterious postmyocardial infarction (MI) remodeling can be detected after sildenafil-mediated NHE-1 inhibition. MI was induced by left anterior descending coronary artery ligation in Wistar rats, which were randomized to placebo or sildenafil (100 mg kg−1 day−1) for 6 weeks. Sildenafil significantly increased left ventricular phosphoglycerate kinase-1 activity in the post-MI group without affecting its expression. MI increased heart weight/body weight ratio, left ventricular myocyte cross-sectional area, interstitial fibrosis, and brain natriuretic peptide and NHE-1 expression. Sildenafil blunted these effects. Neither a significant change in infarct size nor a change in arterial or left ventricular systolic pressure was detected after sildenafil. MI decreased fractional shortening and the ratio of the maximum rate of rise of LVP divided by the pressure at the moment such maximum occurs, effects that were prevented by sildenafil. Intracellular pH recovery after an acid load was faster in papillary muscles from post-MI hearts (versus sham), whereas sildenafil significantly inhibited NHE-1 activity in both post-MI and sildenafil-treated sham groups. We conclude that increased phosphoglycerate kinase-1 activity after acute phosphodiesterase 5A inhibition blunts NHE-1 activity and protects the heart against post-MI remodeling and dysfunction.

Xanthine oxidase contributes to preconditioning's preservation of left ventricular developed pressure in isolated rat heart: developed pressure may not be an appropriate end-point for studies of preconditioning.

Abstract Studies of preconditioning frequently use the isolated rat heart model in which recovery of post-ischemic function is the end-point. However, function following an episode of ischemia/reperfusion represents a composite of both stunning, which is related to free radical production and is not attenuated by preconditioning, and tissue salvage, the primary effect of preconditioning. Brief ischemia/reperfusion is also known to diminish adenosine release during subsequent ischemia by a mechanism independent of preconditionings anti-infarct effect. Reduced purine release would diminish generation of free radicals by xanthine oxidase in rat heart and thus produce less stunning. In this paradigm preserved post-ischemic function in rat heart might look similar to salvage by preconditioning, but its mechanism would be quite different and not be relevant to the xanthine oxidase-deficient human heart. This hypothesis was tested in isolated rat hearts. Control or ischemically preconditioned hearts were subjected to 30 min of global ischemia and 60 min of reperfusion, either in the presence or absence of 25 μmol/l allopurinol, an inhibitor of xanthine oxidase. In non-preconditioned hearts allopurinol increased left ventricular developed pressure after 60 min of reperfusion from 26 ± 5 mmHg in control hearts to 47 ± 7 mmHg, whereas developed pressure in preconditioned hearts following reperfusion was 59 ± 5 mmHg and was unaffected by allopurinol. Developed pressure in non-preconditioned hearts treated with allopurinol was midway between that for untreated control and preconditioned hearts suggesting that at least 50 % of the recovery of developed pressure in preconditioned hearts may be related to free radical-induced stunning. In xanthine oxidase-deficient rabbit hearts, return of function was not different between non-preconditioned and preconditioned hearts. Therefore, post-ischemic developed pressure in the rat is significantly affected by purine-dependent stunning, and, hence, may be an unreliable marker of tissue salvage and also a poor index of what might be cardioprotective in man.

Galectin-1 Controls Cardiac Inflammation and Ventricular Remodeling during Acute Myocardial Infarction

Galectin-1 (Gal-1), an evolutionarily conserved β-galactoside-binding lectin, plays essential roles in the control of inflammation and neovascularization. Although identified as a major component of the contractile apparatus of cardiomyocytes, the potential role of Gal-1 in modulating heart pathophysiology is uncertain. Here, we aimed to characterize Gal-1 expression and function in the infarcted heart. Expression of Gal-1 was substantially increased in the mouse heart 7 days after acute myocardial infarction (AMI) and in hearts from patients with end-stage chronic heart failure. This lectin was localized mainly in cardiomyocytes and inflammatory infiltrates in peri-infarct areas, but not in remote areas. Both simulated hypoxia and proinflammatory cytokines selectively up-regulated Gal-1 expression in mouse cardiomyocytes, whereas anti-inflammatory cytokines inhibited expression of this lectin or had no considerable effect. Compared with their wild-type counterpart, Gal-1-deficient (Lgals1(-/-)) mice showed enhanced cardiac inflammation, characterized by increased numbers of macrophages, natural killer cells, and total T cells, but reduced frequency of regulatory T cells, leading to impaired cardiac function at baseline and impaired ventricular remodeling 7 days after nonreperfused AMI. Treatment of mice with recombinant Gal-1 attenuated cardiac damage in reperfused AMI. Taken together, our results indicate a protective role for Gal-1 in normal cardiac homeostasis and postinfarction remodeling by preventing cardiac inflammation. Thus, Gal-1 treatment represents a potential novel strategy to attenuate heart failure in AMI.

Effect of early versus late AT1 receptor blockade with losartan on postmyocardial infarction ventricular remodeling in rabbits

To characterize the temporal activation of the renin-angiotensin system after myocardial infarction (MI) in rabbits, we examined cardiac ANG II type 1 receptor (AT(1)R) expression and ANG II levels from 3 h to 35 days. The effects of losartan (12.5 mg.kg(-1).day(-1)) on functional and histomorphometric parameters when treatment was initiated early (3 h) and late (day 15) post-MI and maintained for different periods of time [short term (4 days), midterm (20 days), and long term (35 days)] were also studied. AT(1)R expression increased in the MI zone at 15 and 35 days (P < 0.05). ANG II levels increased (P < 0.05) in the non-MI zone at 24 h and in the MI zone as well as in plasma at 4 days and then progressively decreased until 35 days. The survival rate was significantly lower in untreated MI and early long-term-treated animals. Diastolic pressure-volume curves in MI at 35 and 56 days shifted to the right (P < 0.05). This shift was even more pronounced in long-term-treated groups (P < 0.05). Contractility decreased (P < 0.05 vs. sham) in the untreated and long-term-treated groups and was attenuated in the midterm-treated group. The early administration of losartan reduced RAM 11-positive macrophages from 4.15 +/- 0.05 to 3.05 +/- 0.02 cells/high-power field (HPF; P < 0.05) and CD45 RO-positive lymphocytes from 2.23 +/- 0.05 to 1.48 +/- 0.01 cells/HPF (P < 0.05) in the MI zone at 4 days. Long-term treatment reduced the scar collagen (MI: 70.50 +/- 2.35% and MI + losartan: 57.50 +/- 2.48, P < 0.05), determined the persistency of RAM 11-positive macrophages (3.02 +/- 0.13 cells/HPF) and CD45 RO-positive lymphocytes (2.77 +/- 0.58 cells/HPF, P < 0.05 vs. MI), and reduced the scar thinning ratio at 35 days (P < 0.05). Consequently, the temporal expressions of cardiac AT(1)R and ANG II post-MI in rabbits are different from those described in other species. Long-term treatment unfavorably modified post-MI remodeling, whereas midterm treatment attenuated this harmful effect. The delay in wound healing (early reduction and late persistency of inflammatory infiltrate) and adverse remodeling observed in long-term-treated animals might explain the unfavorable effect observed in rabbits.

Beneficence, Justice, and Lifelong Learning Expressed in Medical Oaths.

Introduction: The principles of justice, beneficence, and nonmaleficence are prescriptions of the Hippocratic Oath. To fulfill them, physicians are obligated morally to lifelong learning; yet, there is little evidence that the relationship of beneficence to lifelong learning or to continuing medical education (CME) is expressed in medical oaths. Methods: We analyzed 48 medical oaths written from the first century Ce through the present day, searching for a commitment to lifelong learning and for specification of a relationship to the principle of beneficence. Thirteen ancient and medieval and 35 modern and contemporary oaths were inventoried for source, such as corresponding to a medical school. They were sorted by those that mention the commitment toward lifelong learning and to determine their relationship with the principle of beneficence. Results: Of the 48 medical oaths analyzed, only 20 manifest the commitment to lifelong learning. However, most of the oaths that contain this commitment do not pertain to medical schools, with the exception of the Declaration of Geneva. Of this group, 16 also indicate the principle of beneficence. Of these 16, only 3 establish a link between both. One medical oath indicated this commitment, and none of them analyzed the relation with the principle of beneficence. Discussion: The commitment toward CME should not be absent in the present medical oaths. It is a duty and right of all physicians, and in turn, society should recognize this obligation in order to offer opportunities for the achievement of the principle of beneficence that will result in better health care.

Galectin-3 is essential for early wound healing and ventricular remodeling after myocardial infarction in mice☆☆☆

Fil: Gonzalez, German Esteban. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Fisiopatologia Cardiovascular; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Houssay. Instituto de Bioquimica y Medicina Molecular; Argentina

Atrial natriuretic peptide behaviour and myocyte hypertrophic profile in combined pressure and volume-induced cardiac hypertrophy.

Objective To investigate cardiomyocyte hypertrophy and hormonal profile in cardiac hypertrophy resulting from sequentially applied overloads. Methods We studied Sprague–Dawley rats with renovascular hypertension (RV), where pressure overload predominates, or deoxycorticosterone acetate (DOCA)-salt (DS), where volume overload predominates, at 2 and 4 weeks of treatment, and the combination of both models in inverse sequence: RV 2 weeks/DS 2 weeks (RV2/DS2) and DS 2 weeks/RV 2 weeks (DS2/RV2), and their sham controls (Sh). Results Blood pressure and cardiomyocyte diameter increased to a similar extent in RV and DS at 2 and 4 weeks and in combined models. Cardiomyocyte length increased remarkably in the DS4 group. Circulating atrial natriuretic peptide (ANP) was elevated in all hypertensive groups after 2 and 4 weeks. The RV2/DS2 group showed similar plasma ANP levels to RV4, but DS2/RV2 exhibited a three-fold increase in ANP levels (P < 0.001 versus Sh4, DS2 and DS4). Atrial ANP mRNA remained unchanged in all groups. DS treatment alone or in combination with RV increased left ventricular ANP mRNA, meanwhile only RV treatment increased left ventricular B-type natriuretic peptide (BNP) mRNA. Ventricular ANP expression levels, but not circulating ANP, correlated with both cardiomyocyte diameter (r = 0.859, P < 0.01) and length (r = 0.848, P < 0.01). Renal expression of natriuretic peptide receptor C (NPR-C) was unchanged in RV4 but decreased to a similar extent in the DS4 group and both combined treatments. Conclusion Morphometric patterns seem to be more related to the paracrine function of the heart than to the secretion of ANP and the endocrine function. Plasma ANP in the DS2/RV2 group could indicate a different evolution of the remodelling process. ANP expression seems to be a more sensitive marker for volume than for pressure overload.

Oral Multicomponent DNA Vaccine Delivered by Attenuated Salmonella Elicited Immunoprotection against American Trypanosomiasis

We have reported that attenuated Salmonella (S) carrying plasmids encoding the cysteine protease cruzipain (Cz) protects against Trypanosoma cruzi infection. Here, we determined whether immunoprotection could be improved by the oral coadministration of 3 Salmonella carrying the plasmids that encode the antigens Cz, Tc52, and Tc24. SCz+STc52+STc24-immunized mice presented an increased antibody response against each antigen compared with those in the single antigen-immunized groups, as well as higher trypomastigotes antibody-mediated lyses and cell invasion inhibition compared with controls. SCz+STc52+STc24-immunized and -challenged mice rendered lower parasitemia. Weight loss after infection was detected in all mice except those in the SCz+STc52+STc24 group. Moreover, cardiomyopathy-associated enzyme activity was significantly lower in SCz+STc24+STc52-immunized mice compared with controls. Few or no abnormalities were found in muscle tissues of SCz+STc24+STc52-immunized mice, whereas controls presented with inflammatory foci, necrosis, and amastigote nests. We conclude that a multicomponent approach that targets several invasion and metabolic mechanisms improves protection compared with single-component vaccines.