Correlation between total nitrite/nitrate concentrations and monoamine oxidase (types A and B) and semicarbazide-sensitive amine oxidase enzymatic activities in human mesenteric arteries from non-diabetic and type 2 diabetic patients

S.F Nunes,M.C Lopes,M.M Caramona,I.V Figueiredo,J.S Pereira

doi:10.1590/s0100-879x2011007500156

Abstract

The aim of this study was to determine the correlation between total nitrite/nitrate concentrations (NOx) and the kinetic parameters of monoamine oxidase enzymes (MAO-A and MAO-B) and semicarbazide-sensitive amine oxidase (SSAO) in human mesenteric arteries. Arteries were from non-diabetic and type 2 diabetic patients with sigmoid or rectum carcinoma for whom surgery was the first option and who were not exposed to neo-adjuvant therapy. Segments of human inferior mesenteric arteries from non-diabetic (61.1 ± 8.9 years old, 7 males and 5 females, N = 12) and type 2 diabetic patients (65.8 ± 6.2 years old, 8 males and 4 females, N = 12) were used to determine NOx concentrations and the kinetic parameters of MAO-A, MAO-B and SSAO by the Griess reaction and by radiochemical assay, respectively. The NOx concentrations in arteries from diabetic patients did not differ significantly from those of the non-diabetic group (10.28 ± 4.61 vs 10.71 ± 4.32 nmol/mg protein, respectively). In the non-diabetic group, there was a positive correlation between NOx concentrations and MAO-B parameters: Km (r = 0.612, P = 0.034) and Vmax (r = 0.593, P = 0.042), and a negative correlation with the SSAO parameters: Km (r = -0.625, P = 0.029) and Vmax (r = -0.754, P = 0.005). However, in the diabetic group no correlation was found between NOx concentrations and the three kinetic parameters of the enzymes. These results suggest an important function of sympathetic nerves and vascular NOx concentrations in arteries of non-diabetic patients. Thus, these results confirm the importance of a balance between oxidants and antioxidants in the maintenance of vascular homeostasis to prevent oxidative stress.

Highlights

Increased concentrations of reactive oxygen species (ROS) have been implicated in vascular diseases as well as diabetic vascular complications
No significant difference was found between the type 2 diabetic group and the non-diabetic group regarding the levels of nitrites (3.57 ± 2.58 vs 4.47 ± 2.17 nmol/ mg protein, respectively) and nitrates (6.71 ± 3.33 vs 6.24 ± 3.44 nmol/mg protein, respectively) in homogenates of inferior mesenteric arteries
We found: 1) no significant difference for NOx concentrations in the artery homogenates between the type 2 diabetic and non-diabetic groups; 2) in the diabetic group, NOx concentrations did not correlate with MAO-A, MAO-B or sensitive amine oxidase (SSAO) enzyme activities; 3) in the non-diabetic group, NOx did not correlate with MAO-A kinetic parameters (Km and Vmax), but NOx was positively correlated with MAO-B kinetic parameters (Km and Vmax) and negatively correlated with SSAO kinetic parameters (Km and Vmax)

Summary

Introduction

Increased concentrations of reactive oxygen species (ROS) have been implicated in vascular diseases as well as diabetic vascular complications. Under electron reduction, forms superoxide anion (O2-), which serves as a progenitor for hydrogen peroxide (H2O2) and reduces bioactive nitric oxide (NO), leading to endothelial dysfunction [1]. Decreased BH4 concentrations alter the activity of endothelial NOS (eNOS) in blood vessels, cause enhanced uncoupling of eNOS, increase O2- production and decrease NO in blood vessels, favoring production of ONOO- [5]. Another isoform with a relevant role is inducible NOS (iNOS), which is expressed in macrophages and other tissues [6].

Objectives

Methods

Results

Conclusion