Phd in ANGIO-CARDIO-THORACIC PATHOPHYSIOLOGY AND IMAGING

Thesis title: AUTOPHAGY, OXIDATIVE STRESS AND MOLECULAR SIGNALLING IN THORACIC AORTIC DISEASE

BACKGROUND: Thoracic aortic aneurysms (TAA) are segmental, full-thickness dilatations of the thoracic aorta. Their pathogenesis is multifactorial and includes complex molecular and cellular mechanisms. The present study has the aim to evaluate and describe the impact of autophagic balance in biopsies of aneurysmatic aortas harvested in patients undergoing ascending aortic surgery. In particular, we evaluated the correlation between redox state, autophagic state of these samples and the overall dilation of the aorta, stratified for population characteristics and prevalence of risks factors. As previous studies were based on animal models or in vitro studies, we propose a study conducted in vivo and on human tissue samples. METHODS: Twenty-five patients with TAA were enrolled. Autophagy and oxidative stress were evaluated in blood and aortic tissue samples through quantification of p62, ATG5, MST1, LC3 and soluble NOX2-derived peptide (sNox2-dp), Hydrogen Peroxide (H2O2), hydrogen peroxide break-down activity (HBA) respectively. Endothelial dysfunction was evaluated by serum and tissue Nitric Oxide (NO) production. Univariate analysis non-parametric tests were performed for comparisons between groups (Chi-Squared and Fisher Exact test in case of categorical variables or response rate, Mann-Whitney and Kruskal-Wallis test in case of continuous variables). Linear regression models were used in univariate analyses to assess if the presence of cardiovascular risk or oxidative stress were positively associated to autophagy. All tests were 2-sided, accepting p<0.05 as indicating a statistically significant difference and confidence intervals were calculated at 95% level. RESULTS: Our patients demonstrated decreased LC3 and increased p62 levels in aorta and free ATG5 in serum, in association with increased phosphorylation of Mst1 that can be interpreted as a global reduction in autophagic activity. Analysis of quantitative correlation between levels of Oxidative Stress and Autophagy showed an inverse relationship between the two phenomenon. We performed linear regression models in univariate analyses to assess if the presence of cardiovascular risk or oxidative stress levels were positively associated to the autophagic flux observed. Finally, we matched the presence of cardiovascular risks and the redox state encountered with variations of p62, ATG5, LC3/Actin and pMST1/MTS1 respectively. CONCLUSIONS: Our pilot study gives a molecular snapshot in a complex and changing dynamic process. Correlation between autophagy, redox state and ascending aortic aneurysm development in human is still putative and trials are particulary rare till now. Our study demonstrates a putative role of Nox2-induced autophagy in human TAA. These findings could have paramount translational implications as they could pinpoint novel treatment targets in order to prevent the development or limit the progression of TAA. We are now committed in focusing our future efforts in order to enroll more patients and parallel evaluate authopagy in healthy subjects, to extend our case and to confim our hypothesis