Potential mechanisms involved in angiotensin II receptor type 2 (AT2R)-mediated cardioprotection in aging-associated senescence

• Grant number: 24/16044-1
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: August 01, 2025
• End date: August 31, 2028
• Field of knowledge: Biological Sciences - Physiology - Physiology of Organs and Systems
• Principal Investigator: Maria Luiza de Morais Barreto de Chaves
• Grantee: Larissa Maria Zacarias Rodrigues
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 19/17031-2 - Inflammasome in the cardiac physiopathology, AP.TEM

Abstract

Aging is one of the main risk factors for death from cardiovascular diseases (CVDs). Several biological processes related to aging can contribute to the development and progression of these CVDs: changes in intercellular communication, chronic inflammation, changes in cellular metabolism, and senescence. The Renin-Angiotensin System (RAS) corresponds to an important endocrine axis that regulates cardiovascular function and, when activated by the AT1 receptor (AT1R), leads to the activation of inflammatory pathways and cellular senescence. Although frequently associated with antagonistic actions to those of AT1R, the role of the AT2 receptor (AT2R) during cardiac aging has not yet been described, and it is in this context that this proposal fits. A previous study developed in our Master's degree (FAPESP Grant No. 2022/00057-1), using aged AT2R knockout mice, demonstrated an increase in senescence markers, fibrosis, and impaired cardiac function, indicating a potential cardioprotective effect of AT2R, also in aging. In order to continue the scientific questions that have arisen, and using the same experimental aging model, the objective is to evaluate which potential mechanisms could explain this cardioprotective effect mediated by AT2R. Furthermore, we intend to evaluate the contribution of fibroblasts, which are part of the cardiac cellular microenvironment, to this cardioprotective action, exploring mechanisms of intercellular cross-talk. For this purpose, in vivo models will be used: wild-type male mice and AT2R knockouts, young (4-5 months) or old (18-21 months of age), as well as in vitro: primary cultures of cardiac fibroblasts, isolated from mice. Experimental approaches will evaluate the intracellular pathways triggered by AT2R, its potential contribution to mechanisms associated with cardiac metabolism and inflammation, through techniques that seek to evaluate protein expression (western blotting), gene expression (RT-qPCR), the contribution of immune cells to the inflammatory profile (flow cytometry) and evaluation of mitochondrial function (respiration - oroboros - and mitochondrial membrane potential - spectrofluorimetry). Gain-of-function assays, with overexpression of AT2R (through viral transfection) in cardiac fibroblasts from elderly individuals will allow exploring potential mechanisms of paracrine action associated with the release of secretory factors associated with senescence, in cardiac tissue, during the aging phase. (AU)