Biomedical subjects

Ricardo Rocha

Publications and source records attributed to Ricardo Rocha.

14 recordsLinked to original sources

PubMed2006

RepeatAround: a software tool for finding and visualizing repeats in circular genomes and its application to a human mtDNA database.

RepeatAround is a Windows based software tool designed to find "direct repeats", "inverted repeats", "mirror repeats" and "complementary repeats", from 3 to 64 bp length, in circular genomes. It processes input files directly extracted from GenBank database, providing visualisation of the repeats location in the genomic structure, so that for instance, in most mtDNAs the user can check if the repeats are located in coding or non-coding region (and in the first case in which gene), and how far apart the repeat pair(s) are. Besides the visual tool, it provides other outputs in a spreadsheet containing information on the number and location of the repeats, facilitating graphic analyses. Several genomes can be inputed simultaneously, for phylogenetic comparison purposes. Other capabilities of the software are the generation of random circular genomes, for statistical evaluation of comparison between observed repeats distributions with their shuffled counterparts, as well as the search for specific motifs, allowing an easy confirmation of repeats flanking a newly detected rearrangement. As an example of the programme's applications we analysed the Direct Repeats distribution in a large human mtDNA database. Results showed that Direct Repeats, even the larger ones, are evenly distributed among the human mtDNA haplogroups, enabling us to state that, based only on the repetitive motifs, no haplogroup is particularly more or less prone to mtDNA macrodeletions.

Computational Biology↗

PubMed2005

Effect of aldosterone and MR blockade on the brain and the kidney.

The renin-angiotensin-aldosterone system (RAAS) plays a central role in the development of hypertension and the progression of end-organ damage. Although angiotensin-I converting enzyme (ACE) inhibitors and angiotensin II (Ang II) subtype-1 (AT(1)) receptor antagonists can initially suppress plasma aldosterone, it is now well established that aldosterone escape may occur whereby aldosterone levels return to, or exceed, baseline levels. The classical effects of aldosterone relate mainly to its action on epithelial cells to regulate water and electrolyte balance. However, the presence of mineralocorticoid receptors (MR) at nonepithelial sites in the brain, heart and vasculature, is consonant with the fact that aldosterone also has direct effects in these tissues. Substantial evidence now exists that supports the action of aldosterone at non-epithelial sites which in turn provokes a number of deleterious effects on the cardiovascular system including necrosis and fibrosis of the vasculature and the heart, vascular stiffening and injury, reduced fibrinolysis, endothelial dysfunction, catecholamine release and production of cardiac arrhythmias. Several studies have now shown that vascular and target-organ protective effects of MR antagonism occurs in the absence of significant blood pressure lowering or fluid loss, which is consistent with a major role for endogenous mineralocorticoids as direct mediators of cardiovascular injury. Adverse cardiovascular effects may occur in response to aldosterone alone, activation of the RAAS or aldosterone escape during chronic ACE inhibition or AT(1) receptor antagonism. The specific blockade of aldosterone action should prove to be of great therapeutic value in the prevention of cerebral and renal vascular disease and associated end-organ damage.

Aldosterone↗

PubMed2004

Aldosterone target organ protection by eplerenone.

The classical mineralocorticoid effect of aldosterone on unidirectional transepithelial sodium transport in the kidney was long thought to be the predominant effect of this hormone. However, there is convincing evidence for additional extrarenal actions of aldosterone that are mediated via activation of mineralocorticoid receptors (MRs) in the heart, vasculature and brain. It is now postulated that many of the detrimental effects of aldosterone are mediated through MR activation in these nonclassical target organs. The selective aldosterone blocker, eplerenone (Inspra), is under development for human therapeutic use for treatment of hypertension and heart failure post-myocardial infarction (MI). Clinical and preclinical studies have linked elevated aldosterone to hypertension, left ventricular and vascular remodeling, cardiac, renal, and cerebral vascular inflammation and injury, and increased risk of mortality in heart failure patients. Multiple studies in experimental models of hypertension and heart failure demonstrate that selective blockade of aldosterone by eplerenone effectively preserves cardiac function, attenuates maladaptive left ventricular remodeling and tissue and vascular injury in part by reducing vascular inflammation in aldosterone target organs.

Aldosterone↗

PubMed2003

Estradiol and progestins differentially modulate leukocyte infiltration after vascular injury.

BACKGROUND: Inflammation plays an important role in the response to endoluminal vascular injury. Estrogen (17beta-estradiol, E2) inhibits neointima formation in animal models, and the progestin medroxyprogesterone acetate (MPA) blocks this effect. This study tested the hypothesis that E2 inhibits the migration of inflammatory cells, particularly granulocytes, into the rat carotid arteries after acute endoluminal injury and that MPA blocks this effect. METHODS AND RESULTS: Ovariectomized rats were randomly divided into subgroups and treated with E2, MPA, E2+MPA, or vehicle and subjected to balloon injury of the right carotid artery. After 1, 3, or 7 days, rats were euthanized, and carotid arteries (injured and control) were analyzed for inflammatory cells by flow cytometry. At 1 day, granulocytes (HIS48+ and CD45+), monocyte/macrophages (Mar1+ and CD45+), and T lymphocytes (CD3+ and CD45+) were increased 26-fold, 12-fold, and 3-fold, respectively, in injured compared with contralateral control arteries of vehicle-treated rats. Granulocytes and monocyte/macrophages decreased markedly by 3 days. E2 reduced the granulocyte and monocyte/macrophage populations of injured vessels by approximately 50% and increased T lymphocytes. MPA had no independent effect on inflammatory cells but completely blocked the effect of E2. Immunohistochemical examination verified these findings and localized inflammatory cells to the adventitial and periadventitial domains of injured vessels. CONCLUSIONS: E2 may limit the neointimal response to endoluminal vascular injury, at least in part, by limiting leukocyte entry from adventitial/periadventitial tissues into injured vessels early in the injury response.

Animals↗

PubMed2003

Transgenic model of aldosterone-driven cardiac hypertrophy and heart failure.

Aldosterone classically promotes unidirectional transepithelial sodium transport, thereby regulating blood volume and blood pressure. Recently, both clinical and experimental studies have suggested additional, direct roles for aldosterone in the cardiovascular system. To evaluate aldosterone activation of cardiomyocyte mineralocorticoid receptors, transgenic mice overexpressing 11beta-hydroxysteroid dehydrogenase type 2 in cardiomyocytes were generated using the mouse alpha-myosin heavy chain promoter. This enzyme converts glucocorticoids to receptor-inactive metabolites, allowing aldosterone occupancy of cardiomyocyte mineralocorticoid receptors. Transgenic mice were normotensive but spontaneously developed cardiac hypertrophy, fibrosis, and heart failure and died prematurely on a normal salt diet. Eplerenone, a selective aldosterone blocker, ameliorated this phenotype. These studies confirm the deleterious consequences of inappropriate activation of cardiomyocyte mineralocorticoid receptors by aldosterone and reveal a tonic inhibitory role of glucocorticoids in preventing such outcomes under physiological conditions. In addition, these data support the hypothesis that aldosterone blockade may provide additional therapeutic benefit in the treatment of heart failure.

11-beta-Hydroxysteroid Dehydrogenase Type 2↗

PubMed2003

Aldosterone/salt induces renal inflammation and fibrosis in hypertensive rats.

BACKGROUND: We evaluated the role of aldosterone as a mediator of renal inflammation and fibrosis in a rat model of aldosterone/salt hypertension using the selective aldosterone blocker, eplerenone. METHODS: Unnephrectomized, Sprague-Dawley rats were given 1% NaCl (salt) to drink and randomized to receive treatment for 28 days: vehicle infusion (control); 0.75 microg/hour aldosterone subcutaneous infusion; or aldosterone infusion + 100 mg/kg/day oral dose of eplerenone. Blood pressure and urinary albumin were measured and kidneys were evaluated histologically. Renal injury, inflammation, and fibrosis were assessed by immunohistochemistry, in situ hybridization, and reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: Aldosterone/salt induced severe hypertension compared to controls (220 +/- 4 mm Hg vs. 131 +/- 4 mm Hg, P < 0.05), which was partially attenuated by eplerenone (179 +/- 4 mm Hg, P < 0.05). In aldosterone/salt treated rats, renal histopathologic evaluation revealed severe vascular and glomerular sclerosis, fibrinoid necrosis and thrombosis, interstitial leukocyte infiltration, and tubular damage and regeneration. Aldosterone/salt increased circulating osteopontin (925.0 +/- 80.2 ng/mL vs. 53.6 +/- 6.3 ng/mL) and albuminuria (75.8 +/- 10.9 mg/24 hours vs. 13.2 +/- 3.0 mg/24 hours) compared to controls and increased expression of proinflammatory molecules. Treatment with eplerenone reduced systemic osteopontin (58.3 +/- 4.2 ng/mL), albuminuria (41.5 +/- 7.2 mg/24 hours), and proinflammatory gene expression: osteopontin (OPN), monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6), and interleukin-1beta (IL-1beta). CONCLUSION: These findings indicate that aldosterone/salt-induced renal injury and fibrosis has inflammatory components involving macrophage infiltration and cytokine up-regulation. Attenuation of renal damage and inflammation by eplerenone supports the protective effects of aldosterone blockade in hypertensive renal disease.

Aldosterone↗

PubMed2003

Aldosterone plays a pivotal role in the pathogenesis of thrombotic microangiopathy in SHRSP.

Angiotensin-converting enzyme inhibitors and aldosterone receptor antagonists ameliorate malignant nephrosclerotic lesions of thrombotic microangiopathy in salt-loaded, stroke-prone, spontaneously hypertensive rats (SHRSP) without controlling hypertension. This suggests that angiotensin II (Ang II) and/or aldosterone (ALDO) plays a critical role in renal injury in this model. For evaluating their relative roles in the pathogenesis of thrombotic microangiopathy, SHRSP were adrenalectomized and infused with vehicle, Ang II, or ALDO or were sham-operated for adrenalectomy (SHAM). Saline-drinking rats were assigned to one of four groups: SHAM, adrenalectomy, adrenalectomy + Ang II (25 ng/min, subcutaneously), or adrenalectomy + ALDO (40 micro g/kg per d, subcutaneously). All SHRSP received dexamethasone (12 micro g/kg per d, subcutaneously). Adrenalectomy did not show changes in body weight, plasma creatinine, sodium and potassium, and daily urinary sodium and potassium excretion; did not prevent hypertension but prevented proteinuria (12 +/- 1 versus 49 +/- 3 mg/d; P < 0.01); and abrogated thrombotic microangiopathy and decreased plasma aldosterone (<16 versus 710 +/- 91 pg/ml; P < 0.001) compared with SHAM. Systolic BP in adrenalectomy + Ang II and adrenalectomy + ALDO (238 +/- 8 and 241 +/- 9 mmHg, respectively) was similar to SHAM. Despite Ang II infusion, proteinuria (17 +/- 9 mg/d) and thrombotic microangiopathy and plasma aldosterone (18 +/- 18 pg/ml) remained low but daily urinary excretion of sodium and potassium were not different from adrenalectomy + ALDO. Adrenalectomy + ALDO showed plasma aldosterone levels of 735 +/- 147 pg/ml; plasma potassium was lower; plasma creatinine and proteinuria (78 +/- 7 mg/d) were greater and thrombotic microangiopathy lesions were comparable to SHAM. These results demonstrate a pivotal role for aldosterone in the development of thrombotic microangiopathy, independent of hypertension.

Aldosterone↗

PubMed2002

The pathophysiology of aldosterone in the cardiovascular system.

Until relatively recently, the mineralocorticoid hormone aldosterone was thought to be produced uniquely in the adrenal cortex and to act exclusively on epithelia to promote sodium retention and potassium excretion. However, it is now known that aldosterone also acts on nonepithelial tissues, such as brain, heart, and blood vessels, and that enzymes required for aldosterone biosynthesis are expressed in these same tissues, which may be consistent with local aldosterone production acting in a paracrine fashion. A number of studies indicate that aldosterone exerts clearly deleterious effects when levels are inappropriate for salt status. For example, aldosterone in a high-salt environment initiates a vascular inflammation response that leads to cardiac and vascular pathologies. In experimental models of hypertension and heart failure, the nonepithelial effects of aldosterone are mediated via classical mineralocorticoid receptors, and are largely or completely abolished by administration of the selective aldosterone blocker eplerenone or by reduction of circulating aldosterone by adrenalectomy. In the present manuscript, we review some of the most recent discoveries in the field of aldosterone biology, with special emphasis on the mechanisms involved in the deleterious actions of this mineralocorticoid in cardiovascular tissues.

Aldosterone↗

PubMed2002

Structural, functional, and molecular characterization of the SHHF model of heart failure.

Heart failure is a complex multifactorial disease resulting in a myriad of progressive changes at the molecular, cellular, and physiological level. To better understand the mechanisms associated with the development of congestive heart failure, a comprehensive examination of the aging lean male spontaneously hypertensive, heart failure-prone rat (SHHF) was conducted. Myocardial function and structural integrity progressively diminished as evidenced by decreased ejection fraction and increased left ventricular volume measured using echocardiography. Functional and structural changes were accompanied by elevations in circulating inflammatory markers, including tumor necrosis factor-alpha (TNF-alpha), IL-6, and TNF receptors type 1 and 2. Increased systemic inflammatory marker levels were consistent with age-dependent changes in the expression pattern of genes that contribute to stress, inflammation, and the extracellular matrix in SHHF animals analyzed from age 4 to 18 mo. In summary, the SHHF rat shares many hallmark features of the human disease state and represents a key experimental model for the dissection of complex human heart failure pathophysiology.

Animals↗

PubMed2002

Aldosterone induces a vascular inflammatory phenotype in the rat heart.

Vascular inflammation was examined as a potential mechanism of aldosterone-mediated myocardial injury in uninephrectomized rats receiving 1% NaCl-0.3% KCl to drink for 1, 2, or 4 wk and 1) vehicle, 2) aldosterone infusion (0.75 microg/h), or 3) aldosterone infusion (0.75 microg/h) plus the selective aldosterone blocker eplerenone (100 mg. kg(-1). day(-1)). Aldosterone induced severe hypertension at 4 wk [systolic blood pressure (SBP), 210 +/- 3 mmHg vs. vehicle, 131 +/- 2 mmHg, P < 0.001], which was partially attenuated by eplerenone (SBP, 180 +/- 7 mmHg; P < 0.001 vs. aldosterone alone and vehicle). No significant increases in myocardial interstitial collagen fraction or hydroxyproline concentration were detected throughout the study. However, histopathological analysis of the heart revealed severe coronary inflammatory lesions, which were characterized by monocyte/macrophage infiltration and resulted in focal ischemic and necrotic changes. The histological evidence of coronary lesions was preceded by and associated with the elevation of cyclooxygenase-2 (up to approximately 4-fold), macrophage chemoattractant protein-1 (up to approximately 4-fold), and osteopontin (up to approximately 13-fold) mRNA expression. Eplerenone attenuated proinflammatory molecule expression in the rat heart and subsequent vascular and myocardial damage. Thus aldosterone and salt treatment in uninephrectomized rats led to severe hypertension and the development of a vascular inflammatory phenotype in the heart, which may represent one mechanism by which aldosterone contributes to myocardial disease.

Aldosterone↗

PubMed2002

Selective aldosterone blockade prevents angiotensin II/salt-induced vascular inflammation in the rat heart.

We studied the role of aldosterone (aldo) in myocardial injury in a model of angiotensin (Ang) II-hypertension. Wistar rats were given 1% NaCl (salt) to drink and randomized into one of the following groups (n = 10; treatment, 21 d): 1) vehicle control (VEH); 2) Ang II infusion (25 ng/min, sc); 3) Ang II infusion plus the selective aldo blocker, eplerenone (epl, 100 mg/kg.d, orally); 4) Ang II infusion in adrenalectomized (ADX) rats; and 5) Ang II infusion in ADX rats with aldo treatment (20 micro g/kg.d, sc). ADX rats received also dexamethasone (12 micro g/kg.d, sc). Systolic blood pressure increased with time in all treatment groups except the VEH group (VEH, 136 +/- 6; Ang II/NaCl, 203 +/- 12; Ang II/NaCl/epl, 196 +/- 10; Ang II/NaCl/ADX, 181 +/- 7; Ang II/NaCl/ADX/aldo, 236 +/- 8 mm Hg). Despite similar levels of hypertension, epl and ADX attenuated the increase in heart weight/body weight induced by Ang II. Histological examination of the hearts evidenced myocardial and vascular injury in the Ang II/salt (7 of 10 hearts with damage, P < 0.05 vs. VEH) and Ang II/salt/ADX/aldo groups (10 of 10 hearts with damage, P < 0.05). Injury included arterial fibrinoid necrosis, perivascular inflammation (primarily macrophages), and focal infarctions. Vascular lesions were associated with expression of the inflammatory mediators cyclooxygenase 2 (COX-2) and osteopontin in the media of coronary arteries. Myocardial injury, COX-2, and osteopontin expression were markedly attenuated by epl treatment (1 of 10 hearts with damage, P < 0.05 vs. Ang II/salt) and adrenalectomy (2 of 10 hearts with damage, P < 0.05 vs. Ang II/salt). Our data indicate that aldo plays a major role in Ang II-induced vascular inflammation in the heart and implicate COX-2 and osteopontin as potential mediators of the damage.

Adrenalectomy↗

PubMed2002

Rationale for the use of aldosterone antagonists in congestive heart failure.

Traditionally, the role of aldosterone in heart failure was thought to be a result of its effects on epithelial cells where it induces sodium reabsorption and potassium excretion with subsequent haemodynamic effects from intravascular volume expansion. On this basis, spironolactone, a non-selective aldosterone antagonist, has been used for the treatment of congestive heart failure to block aldosterone-mediated effects in epithelial cells. The Randomized Aldactone Evaluation Study (RALES), in which spironolactone was added to existing therapy in patients with heart failure, showed a significant reduction in morbidity and mortality. These results suggest that the role of aldosterone in the pathophysiology of cardiovascular disease may be more complex than previously recognised. There now is extensive experimental and growing clinical evidence for an important physiological role for aldosterone in the pathology of cardiac and renal disease. Classical effects of aldosterone are mediated via its nuclear receptor. Novel non-epithelial effects of aldosterone are mediated via a second messenger system, which involves activation of the sodium/hydrogen antiporter. These effects of aldosterone have been demonstrated in the kidney, vascular smooth muscle cell and leukocytes, and in the regulation of rapid corticotropin suppression. It has been hypothesised that cardiac damage induced by aldosterone is independent of the presence of hypertension. In support of this, experimental evidence demonstrates that cardiovascular damage induced by aldosterone can be prevented by administration of a selective mineralocorticoid receptor antagonist. These findings suggest the dissociation between cardiovascular lesions and high blood pressure, and highlight the importance of aldosterone in the pathological changes.

Aldosterone↗

PubMed2002

Cardiac damage prevention by eplerenone: comparison with low sodium diet or potassium loading.

To determine the extent to which dietary sodium modulates aldosterone-induced cardiovascular damage, and to determine whether increased dietary potassium can prevent this damage, we used the Nomega-nitro-L-arginine methyl ester (L-NAME)/angiotensin II (Ang II) rat model of cardiac injury. This model is dependent on the presence of aldosterone for the occurrence of myocardial damage. Two sets of experiments were performed. In the first set, the following groups were studied: (1) 1% NaCl to drink (control group); (2) L-NAME/Ang II with water to drink (low salt group); (3) L-NAME/Ang II/1% NaCl (high salt group); (4) L-NAME/Ang II/1% NaCl/eplerenone (eplerenone group). Systolic blood pressure increased similarly in all groups compared with controls. Compared with the controls, the high salt group, but not the low salt or eplerenone groups, developed significant myocardial damage. In the second set of experiments three groups of animals were studied: (1) L-NAME/Ang II/1%NaCl (high salt group) (2) L-NAME/Ang II/1%NaCl/eplerenone (eplerenone group), and (3) L-NAME/Ang II/1%NaCl with an extra 1% KCl in food (high dietary potassium group). Eplerenone, but not dietary potassium supplementation, prevented the development of cardiac damage. Thus, mineralocorticoid receptor antagonist treatment and low sodium diet were effective in preventing cardiac damage, which suggests that a minimal level of aldosterone and a moderately high sodium diet are both required for the development of the cardiovascular damage in the L-NAME/Ang II model. The inability of potassium supplementation to reduce myocardial damage suggests that eplerenone's protective effect is not due to its potassium-sparing ability, but is rather related to some other feature of its selective aldosterone antagonism.

Aldosterone↗

PubMedDate not supplied

Aldosterone as a mediator in cardiovascular injury.

The renin-angiotensin-aldosterone system plays a central role in the development of hypertension and the progression of end-organ damage. Although angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonists can initially suppress plasma aldosterone, it is now well established that aldosterone escape may occur, whereby aldosterone levels return to or exceed baseline levels. The classic effects of aldosterone relate mainly to its action on epithelial cells to regulate water and electrolyte balance. However, blood pressure reduction or fluid loss could not account for the results of the Randomized Aldactone Evaluation Study, which showed that a low dose of spironolactone in addition to conventional therapy could decrease the overall risk of mortality by 30% among patients with severe congestive heart failure. The action of aldosterone at nonepithelial sites in the brain, heart, and vasculature is consistent with the presence of mineralocorticoid receptors in these tissues. Aldosterone has a number of deleterious effects on the cardiovascular system, including myocardial necrosis and fibrosis, vascular stiffening and injury, reduced fibrinolysis, endothelial dysfunction, catecholamine release, and production of cardiac arrhythmias. Several studies have now shown vascular and target-organ protective effects of aldosterone receptor antagonism in the absence of significant blood pressure lowering, consistent with a major role for endogenous mineralocorticoids as mediators of cardiovascular injury. The advent of selective aldosterone receptor antagonists such as eplerenone should prove of great therapeutic value in the prevention of cardiovascular disease and associated end-organ damage.

Aldosterone↗