Impaired arterial dilation and increased NOX2 generated oxidative stress in subjects with ataxia-telangiectasia mutated (ATM) kinase

Background: Subjects with mutations in the Ataxia-Telangiectasia mutated (ATM) gene encoding for ATM kinase have a greater predisposition to develop atherosclerosis, but the mechanism behind this phenomenon is not yet understood. NADPH oxidase type 2 may play a role in this process, leading to endothelial dysfunction and an increased susceptibility to thrombosis. The purpose of this study was to assess the redox state in individuals with ATM mutations and determine its impact on endothelial function. Methods: In this cross-sectional study, twenty-seven children with ataxia telangiectasia (AT) (13 males and 14 females, mean age 15.1 +/- 7.6 years) were compared with 27 controls (13 males and 14 females, mean age 14.6 +/- 8.4 years) matched for age and gender. Additionally, 29 AT parents with heterozygous mutation of ATM (h-ATM) gene, and 29 age- and gender-matched controls were included. Endothelial function was evaluated through brachial flow-mediated dilation (FMD) and the assessment of nitric oxide (NO) bioavailability. Oxidative stress was evaluated by measuring serum activity of soluble NOX2-dp (sNOX2-dp), hydrogen peroxide (H2O2) production, and hydrogen breakdown activity (HBA). Thrombus formation was assessed through the Total Thrombus Formation Analysis System (T-TAS). Results: AT children and parents with heterozygous ATM mutations exhibited significantly lower FMD, HBA, and NO bioavailability as compared to age and gender matched controls. AT children and ATM carrier of heterozygous ATM mutations had significantly higher concentrations of sNOX2-dp and H2O2 as compared to controls. Compared to the respective controls, AT children and their parents, who carried heterozygous ATM mutation, showed an accelerated thrombus growth as revealed by reduced occlusion time. Multivariable linear regression analysis revealed that sNOX2 (standardized coefficient beta: -0.296; SE: 0.044; p = 0.002) and NO bioavailability (standardized coefficient beta: 0.224; SE: 0.065; p = 0.02) emerged as the only independent predictive variables associated with FMD (R-2: 0.44). Conclusions: This study demonstrates that individuals with ATM mutations experience endothelial dysfunction, increased oxidative stress, and elevated thrombus formation. These factors collectively contribute to the heightened susceptibility of these individuals to develop atherosclerosis.