A inibição da Arginase com L-Norvalina restaura os níveis de nitrito na hipertrofia cardíaca murina induzida por isoproterenol

Abstract

Introduction: Cardiac hypertrophy figures among the main causes of cardiovascular diseases, contributing to the increasing number of deaths worldwide. Allied to this, such condition may also result from some type of cardiovascular injury, promoting morphofunctional changes in the heart. In this sense, the cardioprotective role of nitric oxide (•NO) by nitric oxide synthase (NOS) activity has been shown. Nevertheless, NOS substrate, L-arginine, is also required for arginase activity, a key enzyme in the urea cycle. Thus, it has been suggested that arginase may negatively modulate changes from cardiac hypertrophy. Based upon this scenario, the present work aimed to evaluate the role of arginase and the redox balance in a murine model of isoproterenol-induced cardiac hypertrophy. Methods: C57Bl/6 male mice (12-16 weeks old) were divided into the following groups: Control (CT), Isoproterenol (ISO) Isoproterenol+Arginase Inhibitor (ISO+I). ISO and ISO+I groups received administration (s.c.) of isoproterenol (15mg.kg-1) during 7 days. At the same time, the arginase inhibitor L-norvaline was given in drinking water (1.5%; ~3 mg.kg-1) for the ISO+I group. Heart weight/body weight (HW/BW) ratio and left ventricle weight/body weight (LVW/BW) ratio were used as cardiac mass indices. Lipid peroxidation was measured by the TBARS method. Superoxide dismutase (SOD), catalase (CAT) and arginase activities were assessed both in plasma and in left ventricle, as well as nitrite levels. Results: ISO and ISO+I groups (6.1±0.12 mg.g-1 and 5.9±0.11 mg.g-1, respectively) presented a similar increase in HW/BW ratio when compared to CT group (4.8±0.05 mg.g-1). Similarly, LVW/BW ratio was also elevated, corresponding to an increase of 23 and 26% in ISO and ISO+I groups. LDH activity was significantly increased in ISO and ISO+I groups (355±20.4 U.L-1 and 358±14.3 U.L-1; respectively) compared to the CT group (267±17.7 U.L-1). Plasma lipid peroxidation was shown to be lower in ISO and ISO+I groups (0.006±0.001 [MDA] nM/[Protein] mg.mL-1 and 0.005±0.001 [MDA] nM/[Protein] mg.mL-1, respectively) compared to the CT group (0.009±0.001 [MDA] nM/[Protein] mg.mL-1). However, no difference for the left ventricle was observed. SOD activity in left ventricle was 3.3-fold higher in ISO and ISO+I groups compared to baseline, while in CT group this variation was 2.8-fold. It was also observed that cytosolic SOD was more active than mitochondrial SOD. CAT activity was found reduced in ISO and ISO+I groups (29.4±2.8 [Formaldehyde] mM/[Protein] mg.mL-1 and 36.2±5.3 [Formaldehyde] mM/[Protein] mg.mL-1, respectively) when compared to CT group (57.3±5.2 [Formaldehyde] mM/[Protein] mg·mL-1). Plasma arginase activity was shown to be reduced in ISO and ISO+I groups (2.4±0.2 [Urea] mM/[Protein] mg.mL-1 and 1.9±0.2 [Urea] mM/[Protein] mg.mL-1, respectively) when compared to CT group (3.4±0.3 [Urea] mM/[Protein] mg.mL-1). Plasma nitrite levels were lower in ISO group (1.7±0.3 μM.mL-1) compared to ISO+I and CT groups (4.0±0.9 μM.mL-1 and 4.2±0.7 μM.mL-1, respectively). No significant changes were observed in left ventricle arginase activity. Nevertheless, nitrite levels were reduced in ISO group (53.3±4.0 μM.mL-1) compared to CT group (76.6±7.9 μM.mL-1). Conclusion: Arginase inhibition using L-norvaline was not capable of reverting isoproterenol-induced cardiac hypertrophy. Furthermore, plasma lipid peroxidation was reduced, with no changes in left ventricle. SOD activity was not altered while CAT activity was shown to be reduced in left ventricle. Plasma arginase activity was also diminished, without difference in left ventricle. A reduction in plasma and left ventricle nitrite levels was observed, with this result reverted by arginase inhibition.