de Castro Brás, Lisandra ECakir, Sirin Nazan2024-01-172023-122023-12-08December 2http://hdl.handle.net/10342/13289Worldwide, the prevalence of cardiovascular disease (CVD) is escalating, with myocardial infarction (MI) significantly contributing to the heightened rates of morbidity and mortality. Notably, one in every four MI patients progress to heart failure (HF). Following an MI, the left ventricle (LV) undergoes extensive alterations in both its structure and function, a phenomenon referred to as LV remodeling. The inflammatory response triggered by MI can exacerbate ventricular remodeling, culminating in chamber dilation, progressive dysfunction, and an elevated risk of HF. The extracellular matrix (ECM) plays a crucial role in post-MI wound healing, with proteolytically-released ECM fragments, known as matricryptins, exhibiting significant biological activity. In this dissertation, we conducted an extensive examination of the roles of a cardiac collagen matricryptin in the acute inflammatory response that follows infarction, placing a specific emphasis on how this matricryptins alters remodeling of the ECM. Previous work from our lab showed this matricryptin, p1159, significantly reduces long-term cardiac remodeling post-MI. Our objective was to determine whether p1159 beneficial effects stem from alterations to the acute inflammatory response, identifying it as a viable anti-inflammatory strategy for the treatment of cardiac remodeling. Additionally, this approach aimed to determine if exogenous delivery of p1159, as a competitive substrate of matrix metalloproteinase (MMP)-9, is sufficient to mitigate MMP-9 proteolysis of cardiac ECM post-MI. Since MMP-9 directly correlates with mortality and morbidity in MI patients, identification of a novel modulator of MMP-9 proteolytic activity could lead to a new therapeutic strategy aimed at mitigating cardiac dysfunction. In the first study presented in this thesis, we explored the impact of the collagen-derived matricryptin p1159 on the initiation, progression, and resolution of inflammation following MI, aiming to identify potential therapeutic targets to mitigate adverse LV remodeling. Utilizing a rodent model of MI, we meticulously measured various inflammatory markers, assessed the infiltration, numbers, and phenotype of leukocytes, and quantified both systemic and local levels of inflammatory cytokines and chemokines from day 3 (D3) and day 5 (D5) post-MI in both adult males and females. These time points are known for presenting peak levels of neutrophils and macrophages, respectively, post-MI in rodents. Our study showed that while matricryptin p1159 treatment does not change the number of infiltrating leukocytes into the LV post-MI, it altered both neutrophil and macrophage phenotype by reducing expression of pro-inflammatory molecules. Surprisingly, our study did not reveal sex-dependent differences. In the second study of this thesis, we aimed to understand how alterations in the substrate profile of matrix metalloproteinase-9 (MMP-9). Utilizing Terminal Amine Isotopic Labeling of Substrates (TAILS) proteomics, we compared and quantified the peptidome in mice treated with either control vehicle or the matricryptin p1159. Through this study, we sought to address three pivotal questions: 1) Is p1159 a competitive substrate of MMP-9 in vivo? By modulating MMP-9 proteolytic capacity, as opposed to inhibiting the enzyme, can we effectively reduce adverse LV remodeling post-MI?; 3) What are the molecular and cellular consequences of reducing MMP-9 activity on myocardial substrates in the immediate post-MI response? Here, we demonstrate p1159 treatment significantly reduced formation of naturally cleaved peptides, particularly at D3 post-MI, suggesting that p1159 presence decreases proteolysis of endogenous substrates. Specifically, p1159 treated LVs presented reduced formation of known MMP-9 products, showing that p1159 can act as a competitive substrate of MMP-9 in vivo. Our study opens a new research avenue for the MMP world and offers a novel approach to modulate proteases’ capacity without inhibition to preserve their beneficial roles. Furthermore, this research demonstrated how omics approaches can be applied to fundamental research questions, providing insights that can be later translated into clinical settings.application/pdfenMMP-9Left ventricle remodelingHeart FailureMyocardial InfarctionMatricryptinDoctoral Dissertation2024-01-11