Reduced blood pressure in sickle cell disease is associated with decreased angiotensin converting enzyme (ACE) activity and is not modulated by ACE inhibition.

BACKGROUND: Sickle cell disease (SCD) incurs vaso-occlusive episodes and organ damage, including nephropathy. Despite displaying characteristics of vascular dysfunction, SCD patients tend to present relatively lower systemic blood pressure (BP), via an unknown mechanism. We investigated associations between BP and renin-angiotensin-system (RAS) components in SCD and determined whether an inhibitor of angiotensin converting enzyme (ACE; often used to slow SCD glomerulopathy) further modulates BP and RAS components in a murine model of SCD. METHODS: BP was compared in human subjects and mice with/without SCD. Plasma angiotensin II, ACE and renin were measured by immunoassay. BP was reevaluated after treating mice with enalapril (25 mg/kg, 5x/week) for 5 weeks; plasma and organs were stored for angiotensin II and ACE activity measurement, and quantitative real-time PCR. RESULTS: Diastolic BP and systolic BP were significantly lower in patients and mice with SCD, respectively, compared to controls. Reduced BP was associated with increased plasma renin and markers of kidney damage (mice) in SCD, as well as significantly decreased plasma ACE concentrations and ACE enzyme activity. As expected, enalapril administration lowered BP, plasma angiotensin II and organ ACE activity in control mice. In contrast, enalapril did not further reduce BP or organ ACE activity in SCD mice; however, plasma angiotensin II and renin levels were found to be significantly higher in enalapril-treated SCD mice than those of treated control mice. CONCLUSION: Relative hypotension was confirmed in a murine model of SCD, in association with decreased ACE concentrations in both human and murine disease. Given that ACE inhibition has an accepted role in decreasing BP, further studies should investigate mechanisms by which ACE depletion, via both Ang II-dependent and alternative pathways, could contribute to reduce BP in SCD and understand how ACE inhibition confers Ang II-independent benefits on kidney function in SCD.

Reduced plasma angiotensin II levels are reversed by hydroxyurea treatment in mice with sickle cell disease.

AIMS: Sickle cell disease (SCD) pathogenesis leads to recurrent vaso-occlusive and hemolytic processes, causing numerous clinical complications including renal damage. As vasoconstrictive mechanisms may be enhanced in SCD, due to endothelial dysfunction and vasoactive protein production, we aimed to determine whether the expression of proteins of the renin-angiotensin system (RAS) may be altered in an animal model of SCD. MAIN METHODS: Plasma angiotensin II (Ang II) was measured in C57BL/6 (WT) mice and mice with SCD by ELISA, while quantitative PCR was used to compare the expressions of the genes encoding the angiotensin-II-receptors 1 and 2 (AT1R and AT2R) and the angiotensin-converting enzymes (ACE1 and ACE2) in the kidneys, hearts, livers and brains of mice. The effects of hydroxyurea (HU; 50-75mg/kg/day, 4weeks) treatment on these parameters were also determined. KEY FINDINGS: Plasma Ang II was significantly diminished in SCD mice, compared with WT mice, in association with decreased AT1R and ACE1 expressions in SCD mice kidneys. Treatment of SCD mice with HU reduced leukocyte and platelet counts and increased plasma Ang II to levels similar to those of WT mice. HU also increased AT1R and ACE2 gene expression in the kidney and heart. SIGNIFICANCE: Results indicate an imbalanced RAS in an SCD mouse model; HU therapy may be able to restore some RAS parameters in these mice. Further investigations regarding Ang II production and the RAS in human SCD may be warranted, as such changes may reflect or contribute to renal damage and alterations in blood pressure.

Protective action of deferiprone and deferoxamine in erythrocytes isolated from patients with B-thalassemias / Ação protetora de deferiprona e desferoxamina nos eritrócitos isolados de pacientes com B-talassemias

One of the most deleterious consequences of iron overload in thalassemia is the presence of non-transferrin bound iron (NTBI), a free radical that acts as a catalyst for free oxygen radicals, in particular for hydroxyl free radicals (OH.). These radicals oxidize both membrane lipids and proteins causing irreversible damage to biologically important molecules and cellular structures. Treatment with iron chelators has been important to improve survival of these individuals. The aim of this work was the study on the effects of deferoxamine (DFO) and deferiprone (DFP) on erythrocytes under the pro-oxidative action of TBHP isolated from normal individuals and patients with β-thalassemia. The in vitro action of deferoxamine and deferiprone on the oxidative metabolism of erythrocytes from β-thalassemic patients treated at the Centro de Hematologia e Hemoterapia do Paraná (HEMEPAR), Brazil, under the pro-oxidative action of TBHP was studied. Methemoglobin concentrations, reduced glutathione (GSH), hemolysis indexes and the enzyme activities of G6-PD and GR were determined. The oxidation indexes were higher in erythrocytes of β-thalassemic individuals than those from normal individuals. Treatment of the normal and β-thalassemic erythrocytes with DFO and/or DFP protected against the formation of GSH promoted by TBHP.

Uma das maiores consequências da sobrecarga do ferro na β-talassemia é a presença de ferro não ligado à transferrina (NTBI), um radical livre que age como um catalisador do radical livre do oxigênio, particularmente radical hidroxil (OH.). Estes radicais oxidam os lipídeos e as proteínas da membrana causando danos irreversíveis às moléculas biologicamente importantes e às estruturas celulares. O tratamento com quelantes do ferro é importante para a melhoria da sobrevivência destes indivíduos. O objetivo deste trabalho foi o estudo sobre o efeito da desferoxamina (DFO) e da deferiprona (DFP) em eritrócitos isolados de indivíduos normais e de pacientes com β-talassemias, sob a ação pró-oxidativa de TBHP. Neste trabalho foi estudada a ação in vitro da desferoxamina e o deferiprona no metabolismo oxidativo dos eritrócitos de pacientes β-talassêmicos atendidos no Centro de Hematologia e Hemoterapia do Paraná (Hemepar), Brasil, sob a ação pró-oxidativa de TBHP. Concentrações de metahemoglobina glutationa reduzida, índices de hemólises, atividades das enzimas G6PD e GR foram determinadas. Os índices de oxidação analisados foram maiores nos eritrócitos de indivíduos β-talassêmicos do que nos normais. Tratamentos dos eritrócitos normais e β-talassêmicos com DFO e/ou DFP protegem contra a oxidação de GSH promovida por TBHP.